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Saturday, November 29, 2008

The evening got away from me

Working on a Saturday night is not the norm for me. While adjusting to this schedule (for one day), I got a little behind schedule. So I made a post on, and will forgo my update here.
Basically I see some sleet and snow at the start, but a turn over to all rain during the morning on Sunday. It will be wet and stormy up and down I-95 for the big ride home. Still a chance of snow showers Monday evening and Tuesday morning.

Sunday Storm Update

I will be working Saturday evening, and will make a post on the storm then...

Friday, November 28, 2008

Sunday Storm More Likely

First, give it up for Larry Cosgrove. I posted his outlook for the storm on Monday- yet it was his forecast from last weekend. The models have had a hard time picking it up until yesterday, and now as expected there is a wide range of possibilities.
So I want to wait until the morning package arrives before make my full forecast. However, here is the GFS that came on board two days ago. Here you can see the expected transition of energy to a second Low Pressure that will be the main storm up the coast. This is pretty much a given, but the position of this transition, as well as the timing and push of cold air will all play into what we see here. This classic set up also shows the face of a cold air dam. The is the white arrow I drew to highlight the cold air sliding south from High Pressure in New England. Because of all of the variables, and the first time this season for this type of storm, I really want to hold off for my call until I see more data. the resolution of the models improves dramatically when we get within 60 hours. That would make this morning's computer models that much more important for Sunday night and Monday's possibilities. So check back later for more. Right now, just plan for a mix, and likely heavy rain then ending with some snow

Wednesday, November 26, 2008

Fire and Rain= Mudslides. My Winter Outlook Snow Forecast

Standing Wave Clouds
This is the visible satellite image from 9:30am. It shows the distinct result of cold air rolling down from the hills and mountains to our west, and drying out. the ripples are the result of the air rolling up and down over the terrain. The more 'down' the air flows, the clouds thin out and eventually fall apart. The clouds appear to look like waves or ripples in a pond. While it was clear at Baltimore's Inner Harbor, half of our sky was covered in clouds, and just 15 miles west it was overcast. As the sun warms, mixes and destabilizes the air, more clouds will develop east of this line, and appear to shift it over the city. There still may be a flurry west of the city.

The National Weather Map shows two distinct problems, while the rest of the country catches a break.
Great Lakes snow will continue, even after throwing a stray flurry nearby today.
California has taken it on the chin this month. Record heat, wild fires, and now heavy rain. The result is a formula for mudslides. The ground can not handle the rain. The steep terrain and run off will cause problems today, but improve tomorrow.
A little piece of this will move east, but our next storm does not look impressive. In fact, I am going to jump past any flurry chance today and the light showers on Friday. The back end of the holiday could get interesting. A few days ago, I mentioned Larry Cosgrove's forecast for a coastal storm early next week. The GFS model did not have it, but it is not the best long range forecaster. However, it is what most of you see in one form or another in your long range forecasts. It did catch on to it last night. Below are just a few samples of what may happen from a few different views.
The Navy NOGAPS model does have a coast storm strengthen after passing north of Maryland Monday morning. The blue line would be the snow line, and is still too far west. This represents the cold air NOT catching up with the precipitation. The storm will dump heavy snow in New England, but NOGAPS has us with Sunday night rain, ending Monday morning, with maybe a flurry Monday evening, then clearing out.

The ECMWF or European model here shows Sunday nights map. The Low in the Great Lakes will shift energy to a developing low along the 'triple point' as it occludes. That basically means the cold air cuts off the circulation and a new storm forms. This secondary storm would not take form until Monday and after it has a chance to pass us by. Again, a near miss for us...
My trusted Canadian model does not show it either... Here is that same Great Lakes Low Sunday night into Monday.
so what to do, what to do?
There has been a tendency this season for the cold air to build farther south, and the timing of this systems mid range to be off.

So far, I have not seen much support for much of anything next week. Then the dark horse gallops back into the picture... The GFS..
Here is Sunday night's transfer of energy to the developing coastal. It may be hard to see, but the GFS has it farther south and east than any other model. Here is the low east of Ocean City, with the famed 540 thickness line (snow line in white) near I-95. That is contrary to what I showed above. The cold air DOES catch up to the precipitation. That would be a change over from rain to snow- but it looks light for now. This happens because it takes the cold air all the way down to the Gulf Coast, and allows the jet stream to buckle. This gets the cold air in here, while keeping the system closer to us.
Behind it is yet another, but strong storm off the coast. This is Monday night, along a very strong conveyor belt of energy and moisture aligned with the Gulf Stream. This might be too far away, but holding on to Larry Cosgrove's notion of something impressive.
I have cut out most of the technical stuff, and just tried to show the basic idea of what many of the models are doing or not doing. There is still a small glimmer of hope for snow lovers, and enough of a chance to warrant some attention on the holiday weekend. I thought I would take a little break- even though I have to work through Saturday. So if I see anything interesting pop up, I'll post it. Otherwise, it's just a matter of watching how this might unfold. The first order would be to gauge the Friday system. While it weakens, it should set up the next round of cold air. Depending on how that air mass builds south, could determine how the rest of the dominoes fall. Stay tuned....
{More Later}

Tuesday, November 25, 2008

Morning High Thanks To Upper Level Low

Today's temperature forecast is one of the hardest to pinpoint. We were at 45F at midnight, and remained nearly steady into the morning. The cold front moving through will allow a wind shift and new cold air mass to move in. The wind direction from the west, will modify the cold air as it rides down the mountains, so steady or falling temperatures is what I expect this afternoon.

Snow Showers:
This is all based on the upper level support. As the upper level low spins over northern Pennsylvania, it will keep the atmosphere unstable. Here is the evening map, showing all of the energy overhead. That means, even if you see some clearing this morning, the clouds will fill back in, and a few showers will develop afternoon. The best chance will be west and north of the city, and the colder air will allow for flurries to fall. Even a potent snow shower possible.

The same NAM model here with a higher resolution, shows the upper level Low drifting in Canada. The primary energy will be locked up around Lakes Erie and Ontario. I've highlighted one potential plume from Lake Erie into northern Virginia. This would happen Wednesday afternoon, and might bring the better chance of flurries for DC rather than Baltimore.

Monday, November 24, 2008

Modifying Thanksgiving and then a December 1st storm?

I lost track of time this weekend, and never got around to posting Sunday. today, I'm back with a look at how this pattern will develop this week. We can't stay cold forever, and while another shot will arrive for a few days, Thanksgiving is looking better for us. The big question may be what will happen next week. More on that later... I'm working on it now....

Before that... what will happen when this front passes tomorrow morning. I see a wide range of solutions, but I have to stick with my gut. Here the NAM for Wednesday morning, shows the stacked upper level and surface Low stuck near Lake Ontario. This will open up the great lakes, and spin some energy our way for the second half of Tuesday and Wednesday. The upper level temps are cold enough, and this unstable pattern will produce afternoon snow showers. Especially Wednesday. This Low is expected to retrograde, or drift back to the west, but at this stage, I don't think anyone has a good handle on it. Either way, plan on rain overnight, but the return to colder temps tomorrow afternoon.
As of 11:30am- I see some support for a wind shift by Wednesday evening. that wind direction is the most important thing for central Maryland. The forecasted 'West' wind is a down slope and shower killer for us. Any indication of more of a north-west component, and the chance of snow showers will go way up. However, the chance if always higher in western Howard, Carroll, and Baltimore Counties. One thing I have noticed lately, is that Harford and Cecil Counties in northeastern MD get ignored. That north west wind flow has a tendency to carry some showers your way, and sometimes bypass Baltimore. So- you will be in my thoughts as well....
So far, depending on how this thing behaves, we have a chance to clear out and warm up with a dry westerly wind for Thanksgiving. If the upper level low hangs closer, then all bets may be off.

Larry Cosgrove already did work in his last newsletter. He sees big potential for a big storm for us.
Rather than go into all of his details... I just wanted to show some support with a few models already:

The Japanese Meteorological Agency shows a coastal storm passing into Long Island, NY on Monday morning. This would linger some wrap around snow showers in Maryland. This is a 192 hour forecast, and the JMA does like to develop these coastal storms way out for us....

Saturday, November 22, 2008

Nov 21st Snow in Southern PA

Did you get any? Just wanted to share some scenes around the north side with 1 inch of new fluff. So if you did not get any at your place, it sill snowed. I was expecting a little more widespread coating. More may be on the way next week with a cold, staled upper low. More on that tomorrow.

Friday, November 21, 2008

Afternoon Update 2pm: MESO LOW means more snow

I was on the road and unable to make a full model post. This was the image from 11:30am- now fixed.
This is a strong fort max that looks like a mesoscale Low Pressure. One band in central PA and the tail back through PIT and OH. This spin should ride the upper level flow and pass south mid afternoon and may provide that burst of snow that could drop some accumulation. Timing this is between 3pm and 6pm.

This image from 1:50pm shows it dropping south and east... but not as fast as I thought. However, the spin is pretty evident on and radar loop. Check it out in my TV Graphics tab above- and click on Radars and Stuff...
If this holds up and arrives a little later.. then it could be an evening event. Since any snow falling near or after dark will stick, we could get the maximum punch out of this. It is hard to say how much, since the models are not tracking this I will stick with my initial 1-2 inches from TV this morning. But heck, you could get more if it plays out right.

This was what I was greeted to when I got home... a fresh cover of snow (yes I live a bit north of Baltimore partly for this reason). I wasn't going to show my whole place for 'security' reasons, but it was pretty. That little snowman is our 18" measuring post... and we just put it out. Last year, we got snow within 2 days of putting him out as well... How about that.
I hope you all get the some later on.

Wednesday, November 19, 2008

Winter Outlook Part 3: Larry Cosgrove

I have a great deal of respect for Larry Cosgrove of Weather America. While we never met in person, we shared a weather center in Philadelphia. I worked at WPHL on a freelance basis in 2001, and again in 2003. Larry was there much longer, before he moved up to New England. Tony Pann and I had him on our radio show Weather Talk as a frequent guest, and I enjoy his in depth analysis of the atmosphere. Below is his disection of the winter of 2008-2009. It is long, but worth the read:

Transient +PNA and -AO with recurrent NAO make for a very wintry Midwest and Eastern Seaboard!


Using persistence, climatology, and comparisons with analogue years that showed certain similarities to trends seen in weather so far in 2008, a forecast for the upcoming winter season was compiled showing expectations for temperature and precipitation in North America, the European Union, and Asia. Special emphasis was placed on potential for extreme conditions (cold vs. warmth, heavy snow or ice risk, and excessive against minimal precipitation accumulation).

October Synoptic Pattern

There have been prevailing patterns around North America which, through persistence, may offer clues to the trends of synoptic systems that will occur during the winter months. If we count the two tropical storms (Hanna and Kyle), there have been no less than six storms paralleling the Atlantic coastline since early September. Deep tropical moisture connections are evident in all cases, so if such disturbances were to occur in winter, the prospects for snow and/or ice along the Eastern Seaboard will be higher than usual.

It should also be pointed out that, despite the variability of cold to warm conditions over the West, strong ridging routinely occurred at higher latitudes over the previous six weeks. You can see this signature in the 500MB longwave pattern graphic further down the page. Any ongoing tendency of high latitude ridging over the Northwest territories and Nunavut AR must be treated as a feature favoring drainage of Arctic air into the eastern two-thirds of the U.S. during the low sun period.

Possible Influence Of ENSO And PDO

For much of the summer and fall of 2008, the El Nino/Southern Oscillation signature has been in the neutral categories, between a warm (+ENSO or El Nino) episode and a cold (-ENSO or La Nina) phase. Most forecasts maintain this neutral position through the upcoming winter (although the most recent CFS outlook suggests a return to a weak La Nina), which seems a viable idea as most important changes in oceanic temperatures across the equatorial Pacific Basin will occur between spring and autumn. ONI measures are at zero, which, in the lack of any other forcing variable, should imply that simple climatology would have an edge in the seasonal forecast. One x-factor: we have seen two strong Kelvin waves progress out of the equatorial Indian Ocean since mid-September. These impulses could very well warm the neutral character of the waters between the Philippines and Hawaii, creating a window for a neutral/positive or even weak El Nino episode at some point late in the winter.

One possible factor in play for this winter is the Pacific Decadal Oscillation (PDO), based on the measure of SSTs in the Gulf of Alaska. If waters are colder than normal, a moderating or zonal influence is sometimes evident over North America. Should sea temperatures warm to above normal below the farthest north state, correlations exist that favor -EPO or +PNA ridge formation (often a warm condition in the western states versus colder air to the right of the Rocky Mountains. While a -PDO value has been in place for much of the past year, there has been some rightward flex from much warmer seas to the west and south, clearly evident on the October 20 chart. It should also be said that there are cases (such as January 1961) where a repeated negative height anomaly over the Gulf of Alaska was simultaneous with extreme cold and snow over the eastern half of the U.S. For this reason, I feel that the modifying influence of this signature may be muted during the coming months.

MJO And Kelvin Wave Signatures

Any discussion of possible contribution of the Madden-Julian Oscillation to winter weather over North America must be tempered by these facts: one, that the processes of the MJO and its effects are still not well understood (teleconnections). Secondly, that forecasts for the various phases of the oscillation are still quite poor. Thirdly, any estimation as to the position and strength of the MJO is virtually impossible beyond the traditional 15 day period.

There have been two major Kelvin wave ejections from the area between Sri Lanka and Sumatra since September 1. Both of these impulses seemed to have the effect of amplifying the polar westerlies upon emergence into the equatorial Pacific Ocean (a case that was seen many times during the previous winter). keep in mind that after passage of these waves, waters tend to warm. This is an argument against the formation of a La Nina signature (while supporting continued neutral character of the western and central ENSO sectors). On the idea that we may speculate on the same or slightly increased activity with the MJO over the December - March period, at least six large winter storms and cPk/cA advection events may occur.

Analogue Years

There are three criteria used here for a comparison to apparent weather during the upcoming winter. One is the ONI signature for autumn, which characterizes the ENSO configuration immediately precedent to the winter season. Next is similarity in synoptic pattern, a way of how weather during 2008 looks went placed against previous years. Lastly, similarity in tropical season: how did incidence of warm-core cyclogenesis rank against previous years?

This fall has seen an almost purely neutral ENSO, with ONI measure of zero and an increasingly homogenous look to all sectors of the equatorial Pacific Ocean. Previous autumns with this reading are 1960, 1966, 1980, and 2001. So the winters of 1960-61, 1966-67, 1980-81, and 2001-02 are added to the analogue list. An additional year, 1973 is also added as its Multivariate ENSO Index (MEI) values closely follow those seen in the past few months; therefore the 1973-74 low sun period is considered for this study.

The spring and fall of 2008 bore uncanny parallels to that of 1993: multiple cases of heavy rainfall and severe thunderstorms across the Corn Belt with heat and drought an issue for much of the Eastern Seaboard. With this reflection in mind, the 1993-1994 DJFM period is included.

Possible comparisons exist with years where tropical cyclone output was more or less equal (+/- 1) between the Atlantic Basin and Eastern Equatorial Pacific Ocean, where the number of storms exceeded seasonal climatology. This caveat is significant, because there is an indication of a higher rate of interaction between the tropics and higher latitudes. Therefore, the winter seasons of 1954-55, 1959-60, 1961-62, 1988-89 and 2002-03 were added to the analogue group.

Character Of The Stratosphere, 250MB Jet Stream, And 500MB Features

In recent years, efforts to forecast stratospheric temperature have been made as an aid to surface weather forecasting. Typically, a warmer 30MB reading will correspond to colder surface values which, in cases where advection mechanisms are present, will impact lower latitudes about a week to two weeks after the foundation of the high-level ridge complex. The strongest intrusions of cold air come when the stratosphere warms suddenly above a vast ice and snow field. This was the case last year, when the mean positive thermal anomaly formed in February and was accompanied by near-record cold in some parts of the Great Lakes region.

Forecasting the development of these warm pools in the highest elevations of the atmosphere is still not easily accomplished, so the use of past-year analogues may not be helpful here. The presence and size of the polar cold core, however, might be a parameter worth watching, as the warmer alignment of temperatures will rotate below this feature. If so, this could mean an extensive period of cold across much of the U.S. in December, when the warmer banding over northern Asia works eastward. Suggested reading for this phenomenon include The Stratospheric Sudden Warming Website and Monitoring of the Stratospheric Circulation.

There are two important synoptic features seen in late September and October which stand out in relation to the coming winter. One is the character of the jet stream, which has been split over and about North America. The semizonal velocity maximum at 250MB has remained over the western and central Pacific Ocean, while the resumption of unified flow aloft tends to occur just to the right of the Grand Banks. If the upper level wind fields were to be strong and un-amplified across the northern U.S., then at least the start of the December through March time frame would be mild and dry. But the broken appearance of the wind fields, and the recurrence of above normal 500MB heights in Arctic Canada (-AO) would seem to suggest that potential for cyclogenesis and cold air advection is fairly high in areas east of the Continental Divide. Add to this what appears in analogue years as a high rate of occurrence for a negative phase of the North Atlantic Oscillation and transient examples of a +PNA flow configuration, and chances for advection of cold air into lower latitudes seem to be higher than average.

Temperature Forecast

Note that snow cover across the Northern Hemisphere has been increasing, approaching the seasonal normal for late October. Extensive snow fields are important for generation of cold temperatures, and with acreage of snow and ice over the northern portions of the continent now filling in (especially into QB, Nunavut AR and the Northwest Territories), a case can be made that building of high pressure into the U.S. and southern Canada will be accompanied by meaningful displays of cAk (coldest Arctic) air masses.

On the whole, I expect colder temperatures to dominate much of the lower 48 states. Core negative anomalies will be over the lower Great Lakes and St. Lawrence Valley, as well as central Canada. A tendency for Alberta Clipper type storms and flexed +PNA signatures will probably allow for cA intrusions to reach into the Mid-South and Eastern Seaboard. Occasional digging of shortwaves into Colorado (precedent to Colorado/Trinidad storm development) may allow for a secondary region of colder values in the Salt Lake Valley and central Front Range.

The tendency for ridge formation over the Pacific Northwest and Continental Divide may allow for relatively mild conditions in much of the Intermountain Region and the High Plains. It should be noted that if the -PDO environment strengthens, then this area of warmth would be compressed or perhaps eliminated. The tendency for ridging to develop in the Southeast, as noted in many of the analogue years for the period after January 15, favors the highest temperature profiles from the Gulf Coast into Florida and Georgia.

Month - To - Month Breakdown
Here is the forecast for the upcoming winter temperature trend, month by month. Notice that January is, by area and temperature deviation, the coldest month (while December chill impacts the Eastern Seaboard). A key issue with winters with a -PDO (coldness of Gulf of Alaska waters) is a recurrent ridge over the Southeast. I believe that as spring approaches, a tight gradient may emerge from the Ohio Valley into the Mid-Atlantic states. Think of the transition as a battleground between the entrenched colder regime associated with the transient +PNA and -AO related ridging , in concurrence with -NAO aligned blocking near Baffin Island or Greenland. This boundary could be a conduit for storms, with late-season snow and ice events across the Great lakes and Northeast. Colorado cyclones which undercut transient +PNA ridging may stimulate colder temperatures in parts of the Intermountain Region through the winter, while the unstable positive height anomalies over the Pacific Northwest keep mPk frontal structures off of the Gulf of Alaska from making frequent passages.


Repeated cold intrusions from the Upper Midwest into the Eastern Seaboard. Generally warmer across the Intermountain Region and Great Plains, with area from Utah and Colorado into Missouri and Arkansas a buffer zone between returning warmth along the western Gulf Coast and a mild regime parallel and west of the Continental Divide. Some potential for occasional occurrence of colder values in the heartland of the U.S. due to Colorado/Trinidad "A" storms with increasing snow. Greatest threat for major winter storm will be over the major cities along the Interstate 95 corridor.


Widespread cold except for the West Coast and the Southeast. Active storm track from western Gulf of Mexico up along the Atlantic shoreline will create ice and snow hazards over the eastern third of the U.S. Lake effect snows may be crippling in Cleveland OH and Buffalo NY metro areas, with occasional issues from snowfall in Chicago IL, Indianapolis IN, Cincinnati OH and Pittsburgh PA. Ice storm risk may be higher through the interior of Dixie and along the Eastern Seaboard.


While cold strengthens its grip over much of Canada and the Midwest, I suspect that ridging will be an increased presence over the Southeast (see the analogue mean 500MB composite anomaly above for insight into this possibility). Very active procession of both Alberta Clippers and Colorado/Trinidad "A" cyclones along gradient between FL-GA positive height anomaly and cAk intrusions that will reach as far south as Texas and Appalachia (some spillover into the Northeast as well).


Very similar to February scenario except that flat subtropical high may make inroads into the entirety of the Deep South (creating some warmth from Texas into the Carolinas). Extended winter for the Midwest as a whole; some risk present for late season surprise ice or snow event in the Northeast with a cold air damming scenario (i.e. backdoor cold front and overrunning).

Storm Track Scenarios

The tendency for storms over the western Atlantic Ocean and adjacent coastline stands out as we head into the colder months. Since stronger features tend to regress and deepen during winter, the lows which have formed near or east of Bermuda may instead pass closer to the Eastern Seaboard. Likewise, some potential exists for Piedmont cyclones, originating in the Deep South and passing west of the Interstate 95 corridor. The most likely options for track scenarios are for Colorado/Trinidad "A" cyclones and Hatteras (Nor'easter) Lows, as examples of these systems have already occurred, and will be favored to develop again under a transient +/- PNA configuration. Alberta Clippers may take shape in middle and late winter, precedent to cAk intrusions; Piedmont storms and Galveston Bay Spin-Up cyclones are also a strong possibility, with ridging over the Sargasso Sea setting up against digging energy from the High Plains.
Precipitation, Ice, And Snowfall
A very clear pattern emerges with the averaging the 11 seasons used as analogues: the best risk of precipitation is over the Pacific Northwest and the Old South. If the overall synoptic pattern verifies, the presence of high moisture advection against incoming shallow cold air sends all kinds of alarm bells out for the possibility of major ice storm formation around Appalachia and the Piedmont (including the markets of Birmingham AL; Atlanta GA; Charlotte NC; Raleigh NC; and Richmond VA).

Rather than attempt a calculation of total snowfall or probability of snow for the season, I felt that the best option was to match the possible synoptic signature against the mean temperature pattern set for the analogue years. This comparison could help to determine possible situations for snow vs. ice/mix vs. rain, envisioning the storm track types mentioned above. The way to read the map is fairly simple: the dark blue would be the farthest south demarcation of where snow is likely to occur; the electric blue where accumulations of snowfall are possible. Snow events that could cause moderate impacts on travel and utilities are marked in light blue, whereas disruptive or heavy snow threats are most probable in the gray zone. Where marked white are locations where memorable snowstorms could occur. The Black Hills vicinity are almost always hit by blizzards or mammoth snows in late winter and spring. But the area from WV and VA into SE ON represents a synoptic system in the heart of winter; I feel that middle Appalachia and the lower Great Lakes will be the area to watch this winter for a critical snowmaking cyclone, with lake-related additions after passage.

One point which should be made: the area seeing the best overall potential for precipitation has been affected by long term drought, with a lack of consistent water accumulation during the past two years. There should be ample potential to erode the water deficit during the upcoming winter.


Confidence in this forecast is about average. Complications which could deter verification are stratospheric temperature anomalies (somewhat cooler over North America this fall when compared to last autumn); the possible effects of a -PDO measure; the repeated presence of mid-latitude cyclones across much of the western Atlantic Ocean (which, if these storms do not retrogress as expected, would lead to a colder score across the eastern third of the nation. And the evolution of the ENSO signature across the Pacific Basin, which as of this writing was solidly neutral.

In general, placement of polar and Arctic regimes will be somewhat further south and east than last year. The average of analogue years strongly supports development of a subtropical high near the southeastern U.S. during February and March, which could begin to offset cold advection and lead to much-above-normal average temperatures in about the state of Florida.

A strong case is made for abundant precipitation, much of it frozen, over the Old South, Appalachia, the Great Lakes and the Eastern Seaboard. Ice storms may prove to be an ongoing hazard in the Piedmont and lower Appalachian Mountains. Overall threats for major snow events are higher, with chief risk for a critically high snow and wind situation over the lower Great Lakes and upper Ohio Valley.

Prepared by Meteorologist LARRY COSGROVE on
Thursday, October 30, 2008 at 4:20 P.M. CT

The previous statements are my opinions only, and should not be construed as definitive fact. Links provided on this newsletter are not affiliated with WEATHERAmerica and the publisher is not responsible for content posted or associated with those sites.

Copyright 2008 by Larry Cosgrove

Winter Comes Early..Winter Outlook Later Today

I just posted a condensed version on Since it is a long article, it will take some time to get all of the images loaded on Blogger. Please check back later.
In the meantime, I have also posted a recap of the recent snow along with Chesapeake Bay Effect and 21 inch snow pictures from Snowshoe, WV on

Tuesday, November 18, 2008

If you missed the snow last evening, we could still get more

OK, not real snow, but snow showers. This morning I was a little disappointed that the ground was not white, but I only expected a coating to 1/2 inch. While there was some north and west, it did melt as soon as it stopped. So the lack of precipitation overnight was my bad- otherwise, we are still on target.
At 6:30 am, I noticed the flare up of snow just south of Richmond, VA. That is the vort max I was showing yesterday. This is a sign of the energy shift and new development off of the coast. Not the caliber I had hinted at last night- at least not now. But it will generate strong wind this afternoon, and the chance of more flurries or snow showers.
The image below will update every 10-15 minutes, so you can follow the developing snow. You can also see it on my TV Graphics Tab above.

Monday, November 17, 2008

Snow on Schedule.. Afternoon Update

I just made a brief update on with the 4pm observation. The only thing I wanted to add here was the 18Z (mid afternoon) NAM model update.
I think this is looking a lot like the December 5th event last year. The track, the timing, the strength, and the models not fully seeing it. There is a Winter Storm Warning in the pink on this map... for the mountains of western MD into West Virginia. The forecast is for 6-12 inches of snow. That is giving the terrain credit for uplift, but the track of this low with the strong upper level support trying to catch it may enhance it east of the least as it reaches the coast.

This 500mb (upper level map), shows the vorticity or 'spin' near Indianapolis. I've highlighted that with a white X.
That is still west of the mountains, and just behind the surface low. A smaller piece in the southern Delmarva can be seen in yellow. That will be responsible for our overnight showers, but this shows that there is more to come our way by daybreak.

Jumping ahead to Tuesday afternoon at 3pm, that vort max is now stronger (orange), while rounding the base of the trough in North Carolina. If anything, this might be a little too far south, but the trough axis and support linger into southern MD. This increase in vertical velocity or rising air is a sign of strength. The outlook did have low pressure developing rapidly off of the coast, but I think if might be a little sooner and closer. That will lick our winds up to 30-40mph from the north in the afternoon, and bring the question of how long the snow will last. This may not be a clean solid band of precipitation, but any showers may be able to drop some surprising accumulation. Again, at this point, I don't see an exact repeat of the Dec. 5th, 2007 event when we had almost 5 inches of snow in Baltimore, but some places getting an inch or two looks possible now.

First Flakes=Stickage

Watch the snow here. This image will update every 15 minutes- but you may need to reload the page.I coined the phrase stickage many years ago. I think it's self explanatory, but I will elaborate below. You may have had a snow shower Sunday afternoon at your place, but all of us get a shot later today through tomorrow. I have a sense of pride, since I first called this last week, and now everyone else is hopping on board. No, this will not be a major event, but an early arrival of winter is exciting. I have learned a long time ago not to blow anything out of proportion, since it will get exaggerated on TV. That being said, our first snow is on the way.
Here is the overnight NAM model for this afternoon with a cold front type passage of an upper level trough. I've highlighted this with the purple hashed line, and the snow turn over in white. While the surface temperatures will likely make it into the 40s, it will fall, and drop to near or below freezing tonight. But it's the cloud level temps that will determine when the flakes fall. Plan for showers this afternoon that will start as rain, and then turn over. Once it gets dark, and the colder air spills in, light snow becomes more widespread.

Tuesday morning's 500mb map, shows the vort max (red X) in the prime spot to our south. This will maximize the potential, and may enhance what I am already seeing. The light snow will be around early, and linger with flurries or snow showers into the afternoon. This may turn out to be something explosive off of the coast. I have seen this a few times in the past month... and is exactly what happened with that October snowstorm just before Halloween. The atmosphere tends to hold memory, and repeat itself, so hold on it could be more that even what I am saying.

I am waiting for the morning computer models to see how this might evolve, but here is the expected precipitation with a range of .01 to .05" inches. That is enough to drop a half an inch or more in the colder spots. While I am focusing on the grassy areas, some roads will get covered overnight as the cold air spills in. Stay tuned, and enjoy!

There has also been some buzz about a large coastal storm for next Sunday and Monday. The latest GFS has this a little farther west or inland-which would be more rain for us. It's still far out, and we have to see how this cold air establishes itself over the next few days. I'll watch this each day to see how each run treats it, but can't take it seriously until Wednesday or Thursday.