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Monday, December 31, 2007

Icy Morning, Mild End of 2007

At 2:30 this morning, some snow showed up on our regional radar. Only snow on the ground was north of Shrewsbury, PA. So if you took my map from yesterday and shifted it north about 20 miles, it fits. Otherwise, it was just wet.
This morning- ICY ROADS- became a problem after 5am. That's when temps dropped near freezing, and the JFX proved itself as an ice rink.
Since most of I-83 (JFX) is elevated, it is more susceptible to freezing, like many bridges and ramps.

One of the most frequent winter questions I get is about this. "Why do bridges and overpasses freeze first"? This is primarily due to cold air passing both above and below the road surface. So there is no insulating from the ground. Add in some moisture from a wet road evaporating, and this will further cool down the surface. As a result, even when the air is just above freezing, elevated surfaces and freeze.

We should have a sunny day, with a finish in the upper 40s. Not much to say about New Year's night as next weather system approaches. We should cloud up, but be in the mid 30s at midnight. Light snow or rain will move in by daybreak, so late party folk may want to think twice. My forecast maps are available on the TV Graphics page. I left my computer at home- with my snow records on it... so I will post the 1990s on New Years Day for you to view while surfing Bowl games.

Saturday, December 29, 2007

Our Very Own Snow. For Real!

I am postponing the Snowfall Records until tomorrow so I can spend my limited weekend time on tonight's snow. My former radio partner Tony Pann tried convincing me on Friday- but I did not buy it. If you see the TV Graphics page, my outlook map for Sunday (from Friday) showed a chance of rain late... I thought there was a chance that this might even miss us to the south. The snow I had on the map, was back in the mountains. But things change.

Here is the proven NAM model showing the '540' line by this evening. There will be enough moisture as the freezing line catches up to drop some snow. Another shot appears to want to move in New Year's Day. That was my original forecast early last week, and I was talked out of it by Thursday. Well, it's back.
As of this morning, there did not seem to be much grid model support for local snow. This was due to temps being too warm, and the precip departing before was have a chance. However, I do believe we will get cloud temps to cool down enough, but with wet ground and marginal surface temps, here is what I expect locally. If you are local then I will be back on ABC2 Monday morning with the latest. It is a sign of the pattern turning more favorable for us in January. Although it make take until the 2nd week of the month for us to truly make to turn to colder weather for a longer duration.

Snowfall Records- 1980s

As we look at the 1980s snowfall in Baltimore, the decade is on target with the past 30 year average. But a few outliers are clearly seen. This was a clear El Nino/La Nina decade.

First, '80-'81 and '88-'89 both had less than 10 inches of snow. A La Nina occurred in '88-'89. Yet the '82-'83' season and '86-'87 both had about 35" of snow. These two big seasons were during El Nino. The '82-83' was a very strong El Nino that led to billions of dollars in damage in CA, and instigated the current research and government funding for satellites and buoys. The '86-'87 El Nino was just developing.

Friday, December 28, 2007

Snowfall Records- 1960s and 1970s

Since I am off today, bot much to say about the next two events. My forecast maps are on the TV Graphics Page. Basically, rain tonight and tomorrow morning. The Sunday system will be a close call, just south and perhaps some snow mixed in Sunday night. I will touch on that tomorrow.
Snowfall Records below: These are the two decades that get interesting. For those of you in your 40s and 50s (age) who say it snowed a lot more when you were a kid, you were right! The 1960s was the snowiest decade in Baltimore during the last century. The average of 32.4" was an increase of about 50% above the long time average. Clearly an anomaly that was followed along much of the east. It was this aberration that lead to many climate scientists to believe that we were heading for another ice age. Compare that to the 1950s (yesterday's post) which was 25% below the long time average.
Below you will see the 1970s dropped back to below average. So if you are in your 30s, well it might not be that impressive. Unless you focus on '77-'79. The last two years of the 1970s made up for the decade shortfall, below the chart see what I find most interesting....
We often use not just long term average since 1883, but the 30 year average. Yes, our 30 year comparison has dropped below the long term average, but it is all relative, and how you break up the decades. If you use the 50s, 60s, and 70s, the average is 21.6". Almost exactly on par with the long term. Yet two of those decades were well below normal. Tomorrow, I'll show the 1980s and 1990s. While part of the last 30 year comparison, it also includes the #1 snow year on record.

Thursday, December 27, 2007

Snowfall Records- 1940s and 1950s

I have had a few emails mentioning that they are having issues posting comments. It is a Microsoft Internet Explorer issue. Many web pages have problems, but not all address it. Again, the link at the right to Firefox is will work best. It is free and safe. If you can not download it and have problems, you copy and paste this link in a new browser window:

Snowfall in the 40s and 50s does reach some of your childhoods. You can see below that the 1940s in Baltimore were fairly consistent and slightly above the average. In 1949-1950, less than 1 inch of snow fell. No one blamed Global Warming then....
In fact the 1950's is an outlier decade since it averaged nearly 7 inches below normal. One standout is the monster year of '57-'58 with 43 inches. I will examine some of the reasons a little deeper after this series is done.

Wednesday, December 26, 2007

Snowfall Records- 1920s and 1930s

A potent storm off of the Carolina coast will provide rain today. Follow the maps in the TV Graphics Radars and Maps Tabs. Today I continue my series on snowfall records by the decades. I often hear people saying it snowed so much more in the past than it does today. Christmas just passed with sunny skies and dry ground. It should be noted that we average a white Christmas once every five years, and our last one was back in 2002. We are running about normal.
Below are the snowfall records for the 1930s and 1940s. You'll notice the '20s had some big years (ending in '22- 44.4", and ending in '24- 33.6"), but the decade was nearly 2 inches below the average since 1883.
Snowfall did go up a bit in the 1930s. This is my favorite decade of comparison for current weather. This was the dust bowl era! For the decade, they had about 1 inch above the average. You will see quite a few snowy winters. Also two winters with less than 10 inches of snow! The hottest year on record in the US was 1934, yet one of the top snowiest years was 1934 with 47.9". This is quite similar to 2002-2003. We had one of the top 5 hottest years, and the #2 season with 58.1" of snow.

Tuesday, December 25, 2007

Christmas Day

Due to the holiday and slow traffic, I will resume the seasonal snow history tomorrow. Today's lack of morning clouds was no a complete miss. This visible satellite shows the clouds line along the vort lobe I showed yesterday- just a little farther south. I expect the cirrus and alto stratus to return later today as developing low pressure near the Gulf coast heads northeast. Tomorrow is a tough call as the NGM has a complete miss off the coast, but the NAM has us with rain. I am playing safe with clouds and showers. If the NAM is right, then we may be left with cooler temps and more showers instead of sun on Thursday as well.

Monday, December 24, 2007

Snowfall Records- 1900s and 1910s

Since this is Christmas Eve I should note the most snow on Christmas Eve Day was 8.4" in 1966. When I get to the '60s in you will see a distinct jump in the snowfall. However, there is a small chance of some snow flurries for us Christmas Day. Here is the NAM 500mb map for Christmas Day. The vort maxes are highlighted with an X. These are areas of upper level support of clouds and showers - even when void of surface features. The colored area over MD is what separates us from High Pressure moving in. It is left over energy wrapped around the recent storm. If we have NW winds continue, then instability clouds will form to our west, and perhaps some flurries. Its not much, but it is something.

How often have you heard, "It snowed a lot more when I was a kid" or "My parents had to walk to school in 20 inches of snow. Uphill. Both Ways"?
This is the beginning of my look at snowfall in Baltimore, by season and decade. You will see the first two decades of the 1900s. While there are some outstanding years both high and low in snowfall, the average for each decade nearly matches the 124 year average:

Sunday, December 23, 2007

Severe Weather, Christmas Outlook

Rain, Thunderstorms, and strong winds. Another round of rough weather, unbecoming of winter. Well, actually it is.. except the storm track is well to our west, so we get the warm side . You can follow along on the TV Graphics- Radars and Stuff Page. Basically, we have a fog advisory, wind advisory, bay coastal flood watch, oh and the chance of thunderstorms. I am on nights this week, starting tonight. So I will update graphics this evening.
SNOW: Yesterday I began working on compiling some snow data for Baltimore. Rather than overload the circuits on this topic, I am going to do a series this week on Baltimore Snowfall by the decades. While many people say, "It used to snow a lot more", you might be surprised by some of the data. Since it is a holiday week, that will be my main focus in this weeks posts.

Our hopes for a White Christmas

While it will likely remain mild after this storm passes, there is still a shortwave that could produce showers on Christmas- despite your Weather Channel forecast not showing it. I continue to put a small chance for Tuesday/ More tomorrow. On average, we have about a 20% chance of a snow on the ground in Baltimore for Christmas. That's about 1 in every 5 years.

Saturday, December 22, 2007

It's Here! Oh, yeah - Winter that is.

I am working on some stats and stuff, so please check back later today.

Friday, December 21, 2007

Warm Wet Weekend. Christmas Snow?

This morning's national radar seen here (3am to 5am) is a little bit of job security. No, I will never claim perfection-nor should any forecaster. Yet I did beat the computers on this one. Yesterday I mentioned the prospect of this southern storm being a little closer to us, and worth mentioning. This morning, while the surface low was chugging through GA and SC, the shield of rain was on our doorstep. While it was just patchy drizzle and flurries here, it helped to moisten up the atmosphere and set the stage for more today. Combine the east wind, and more drizzle and fog will form throughout the day, in fact into the weekend. Not 100% on my end, but I did mention the chance yesterday, while there was no support from NWS or the mid range models.

As for this weekend, I am sticking with the Canadian here, which show a chance of getting over 1 inch of rain. Here you can see the 500mb level (on the right) energy I marked with an X. That is the support for a second area of low pressure to form along the front to enhance the rain. That's a good soaker on a holiday weekend! The push of warm air will continue all day Sunday, so my forecast of 54F may actually occur at night.

Here again is the Canadian 500mb (roughly 18,000Ft) map. I've highlighted the troughs with an X to show the energy that will keep us active for the end of 2007. The one over Maryland is the support for flurries or light snow. It looked a little more yesterday on the surface prog maps, but there still is hope for the flakes. The system in New Mexico will reach us with rain or snow by next Friday. The Pacific NW trough will likely affect us after that, but the traditional La Nina pattern with storms riding the Great Lakes and giving us rain, is likely to continue for the next 2-3 weeks.

Thursday, December 20, 2007

Split Decision

Today, a normal day for late December. This is essentially the shortest day of the year, well daylight for those who want to get technical. The Winter Solstice is over the weekend, but the change in daylight from today to Saturday is only a difference of 7 seconds. So today being the sunny one, enjoy it!
We have cold air (35F-40F) in here for tomorrow, but that will also push this current system to our south. That gives us the clouds, but no snow. The winds around the Canadian High Pressure will be from the northeast. That could add some moisture for an evening snow shower or freezing drizzle in spots..but it does not look like a big deal now. Not much model support, but I have been watching the radar all morning, showing a hint at the precipitation shifting a little farther north. It may be worth watching on our southern fringe.

The weekend storm, which is now in the Rockies, will take a track into the Great Lakes. There is our split. South and west, we keep missing our mark. That will certainly draw in warmer air and bring us plain old rain. Two questions arise, how much rain, and how warm. The GFS model I followed last week, is bringing a front in a weakened for Sunday Evening, while my trusty Canadian model is much more wet. For the purpose of impact, I am showing that Canadian here. An inch of rain would help our drought, and could be the cast, if this model verifies a wave of Low Pressure riding up the front. Behind that, I see an upper level disturbance with the cold air on Christmas day. This may provide some holiday flurries.

Tuesday, December 18, 2007

La Nina Update

On schedule, today's weak system is passing to our north. The outlook for our next storm is to pass to our south off of the South Carolina coastline on Friday. You can see my outlook on my TV Graphics page (tab above-main web site). Unfortunately for snow lovers the next big storm will be on Sunday- again passing to our west keeping us on the warm side. I'll have more tomorrow.

This winter weather pattern was expected to be governed by La Nina. That is the sister part of El Nino Pacific and water near South America have cooled down to about 2C below normal. This heat is the energy source for the storm track, and net result - the natural warming and cooling of the tropical Pacific Ocean. The animations here show the past month of ocean temperatures, and anomalies (compared to normal), with the Pacific in the center. Clearly a moderate La Nina with the tropical easterlies pushing the warm water to Southeast Asia with temps near or slightly above normal. While the equatorial jetstream for North America. The expectation is on track and you can see the Winter Outlooks through the link at the right. But that is only part of the story. While Pacific storms will crash into the Western US over the next 7-10 days, that would often bring a mild winter for the eastern half of the nation. We can thank the build up of snow in the heartland and central Canada for battling that and keeping us near normal as this happened. The source of our cold- the Polar Vortex is sliding over the pole to Eurasia, but the North Atlantic Oscillation does show modest negative (cold numbers). I will show that tomorrow, but no clear indication with opposing forces over the next few weeks. Just an average end to December.. but storm track currently does not favor much snow for us.
US and Canada Snowpack:

Back To Normal...

You know that feeling- after the holidays? The foods been eaten, the family is gone, oh and the presents have been opened... and then there is the lull back of normal. It's like that box was not a Wii, but a dozen pairs of socks. So, there is no snow on the ground to look at, and the results of my latest poll show the disappointment, but expected average of a low B with my last forecast. OK, so it's back to work! Our weather has undergone some drama with the chill and especially the wind. I was just going through some of the reports from the weekend and saw the peak wind at Anne Arundel Community College in Glen Burnie hit 63mph on Sunday. Now with calm winds, and a chilly morning, it's just waiting for the temps to rebound. Last year we set our record high on this date with 72F. This afternoon we will just barely get back into the 40s. You can see the Almanac on the TV Weather Graphics page.
If you click over the Radars and Stuff page, you'll see general pattern is passing to our north. This may provide some clouds tomorrow. The following system might just miss us to south. The models have been in and out on this. Here is the Canadian (my personal favorite), showing the southern branch storm. This is not what you might think. No chance of this turning up the coast- just shooting out to sea. However, the chance of us getting clipped on the northern fringe with flurries or light snow. I should note that this is one of the more aggressive models, while most are keeping us dry. I just want to keep the hope alive for many of you who are searching for something. It also gives me something to talk about. beyond this, the weekend storm looks like another Great Lakes Track. that would be a rainmaker for us, but still 6 days out.
TOMORROW: Current La Nina Animations

Monday, December 17, 2007

Day Off

I have today off, so if you notice some TV graphics on the web site have not been updated, that is why. You can continue to rate my forecast with the poll at the right. As of 10am, the average seems to fall in my own range of "low B". There is a hint that we may have another shot of snow or ice at the end of the week. I will dive into that tomorrow, and try even harder to hit it.

Sunday, December 16, 2007

Report Card: A Whole Lot of Nothing?

Here is the verified surface weather map for Sunday morning. The same time frame I was using with the GFS model all week. Overall, I think it did a good job with positioning. The major problem was the delay in the initial precipitation. Since it began for most of us between 7pm-9pm, the atmosphere had a chance to warm up a little and not produce the snow or sleet expected. That would have helped to hold the temps down longer, and result in more ice. I did notice many spots did have some icing north and west of the beltway. Even ABC2 was down below freezing until midnight, so some ice did build up, but not much.
Here was what I woke up to: I live north in 'hill country' and did not break to 33F until 4am. This begs the question: Does it count if you slept through it? I've often wondered that. That goes along the same lines as you hearing a forecast for snow, but it's not in front of you house. So if it happened, but not for your area, is that a busted forecast?
This brings up another poll questions I have posted at the right.
I may be hard or easy on my own forecast, but how would you rate it? If you have not been following all week, you can scroll down for all of the previous blog posts. I held off on early snow maps, but even when I put out about 1 inch, it did not happen. We got ice, but later, and less than expected. If you see my map below, the purely rain area, including Baltimore City and BWI were on target. So how did I do? I give my forecast a B/B-. Not exact, but not bad. Am I being too hard or too nice? I am polling just straight letter grades for simplicity. You 2ns Guess poll results show most of you caught on to the rain winning...
The final part of this storm will be the wind. We do have Wind Advisory for this afternoon and tonight. While we may see a snow shower- especially north and west... we should all have winds gusting between 40 and 50 mph.
If you can watch the Patriot Game in New England. They will be dealing with the heart of this storm. On the edge of ice and snow, could make for near white out conditions....

Saturday, December 15, 2007

Major Ice for Some, Others Get None

Fellow weather geeks that have followed the models have seen the trend. The poll at the right reflects the shift to a track farther west. Is all lost? The arctic air has not truly built in here, and the tropical feed into this system will have dramatic warming on the east side. Again, for simplicity, I have been comparing just one model - the GFS - all week to show how elements can change. This also proves my point from earlier this week with that ridiculous snowcast on Tuesday. There are so many models to look at and decipher, many layers of the atmosphere, and text extractions (that won't look pretty here). If I showed it all I would run out of room on this blog- and bore half of you out of here. So let's stick with the basics and continue with the GFS which in fact I think is doing the best job. If you want to discuss other models, you can shoot me an e-mail. I'll try to get back with all of you (but it is the weekend). Here you can see the primary Low still dominant Sunday morning, and slower development of the secondary low. That second low is too close to us, and not off of the coast- which allows the warm flow to dominate. Some areas will get hammered! North/Central PA through central New England will get a major ICE STORM. This may include parts of central MD- but warm air will scream in here Sunday morning. The 'vertical velocities' and tropical support from Olga will produce heavy rain rates and likely thunderstorms... especially for the Eastern Shore. Where the cold air holds longer, moderate icing of 1/2" or more is possible. I think that will be confined west of us.
Even though some sun and warming have taken place today, keep this in mind:

  • Low dewpoints will allow for evaporational cooling. The initial precipitation evaporates and drops the temperature to the Wet Bulb level. So when it starts, it will get cooler. At noon BWI was 35F with a dewpoint temp of 19F. That gives a wet bulb near 26F. I don't see us dropping that low, but it should go back below freezing when 'stuff' begins between 4pm and 7pm.
  • NE winds will lock in that cold air longer farther west and in valleys. While I have a general forecast map, elevation will play a role in ice- in this case, lower levels get more as warm air reaches hill tops first.
  • Sunday morning potential for temperatures near 50F with heavy rain in the cities. The may be a sharp boundary with the cold air's last stand. Depending on the actual time and position of 2nd Low, will determine when the wind shifts and cold air filters back in.
  • Sunday afternoon: A brief period of snow may be enough to coat the ground, or an inch or so. It's the quick drop in temps that would cause a quick freeze of anything wet.
  • Sunday Night's Winds 30-50mph may drop trees and power lines

Snow Poll 2nd Guess

Here are the results of the 1st Guess Snow Poll. With 98 people voting you can see the expectation was for a modest amount. The winning vote is for 1"-2", but a close second are hopefuls for more. Not sure if I swayed the vote with my forecast, or the vagueness of the ice and rain mixed in. For simplicity purposes I have posted a 2nd Guess Snow Poll right here. I will have my analysis and final call just after noon...

Friday, December 14, 2007

My First Call- Updated and fixed diagram

Before I get into my 1st call, a reminder that a new Snow Poll is at the right side here. That is your 1st call for total snow at BWI. This includes beginning and end of storm, by Sunday night.
Also, a lot of questions on freezing rain. Here is a great animation explaining winter precipitation. As warm air works in to a storm, it often rides above the ground first, while cold air which is more dense stays at the surface. Depending on how thick the layer of warm air is, and how warm it is will determine:

  1. If snowflakes from the clouds melt.
  2. If there is a chance to refreeze before reaching the ground.
  • Sleet- Melts then refreezes
  • Freezing Rain: Falls as rain, freezes on the ground.
The most extreme I have seen was in Danbury, CT with rain at 19F. A few years ago we have drizzle at 21F in front of ABC2 Studios.

Being my day off, this will be brief... The models have been all over the place. There general idea I see is slower with the development of the coastal Low. This will make for a longer duration event. Considering the Coastal Low synopsis, it also means a better chance that we have an ice storm. Calling total snow will be tough since I still think we will see it on the bookends - both beginning and end of the storm Sunday evening. All snow line will be well to the north - highlighted in white. Most likely we get between 1/2 and 3 inches (north) of snow then change to sleet/freezing rain quickly after dark. This coastal Low during Sunday should bring us back to snow around noon. Depending on the strength and position we could pick up a few inches on the back side before ending. There is model support for the warm air to get in with temps in the upper 40s Sunday morning. I don't fully agree with that. Cold air damming usually is tough to break west of the bay. That is why I-95 or the bay often ends up as the dividing line. The cold air gets banked up just east of the mountains. Its possible that Frederick and Carroll counties have much more ice than Frostburg which will likely turn to rain closer to the primary low. Again this is 'roughly' what I see right now. It could all change with just a shift 50-100 miles on tonight's models. One thing to look out for is how cold it gets tonight. If we end up low to mid 20s before the clouds roll in, it will hold us lower at the onset. Updated at 3:30pm: It should be noted that storms like to set footprints for themselves. In this case the snow or ice pack can lock in the freezing air. But something that should not get left out is the wind on the back side of this storm..GALE FORCE in the metro areas throughout the region. That means if there is ice on trees, etc., it will be a major problem. Still thinking just north and west - as typical.
I'll get back Saturday morning. This whole event will also determine if I have to get back to work myself this weekend, so I have a personal investment here.

Thursday, December 13, 2007

You win! The Early Snowmap and another model.

The 1st Snow Poll is now closed. I was surprised at the response to not show the early map, yet then final surge just barely won 54 to 50. 20 of you would rather wait until after the storm. Well, here it is, but small enough for those of you who don't want to see it. THIS IS NOT MY FORECAST! I don't know this forecaster, but it came from an Accuweather forecaster on Tuesday. It shows Baltimore in the 3"-6" range. I'm curious to see if he has changed his outlook since then. Again, if you click the image, you may have trouble backing up here. Copy URL and paste back in browser - sorry.
I am off work on Friday I will make my first call here during lunch time. I have posted a new Snow Poll at the right. Here you can share you're best 1st guess of total snow (not including ice, etc) for the Baltimore area. This does not include the northern snow-burbs, but the official report at the airport on Sunday night. I'll run another one on Saturday as well to see if you change your mind.

More Model Support. Here is a 75 Hr forecast from the SREF my buddy Tony Pann sent me. This is for Sunday afternoon and holds the morning GFS idea. Notices the coastal Low over DE, and MD is on the back side. This looks like the primary, with no occlusion or transfer. This would be in response to a strong block to our north. I'm sure the message boards are lit up this evening with renewed hope.

ICE-olated Mid Day

One of my gripes with perceived warming is due to bad weather stations. At 11am, I noticed a lot of 'weatherbug' stations ranging from 31F-34F. BWI was 37F, and stuck there all morning. That site has had issues in the past, so I called the NWS office. They compared to weather underground, and thought it was fine. Well sure enough, at noon, it dropped to 34F. Much more in line with the region, but what if I did not call???
Snow lovers, this is actually a good sign. The front early in the week was projected to move north, but did not and temps stayed colder. Today's damming is keeping us colder- and a better chance of ice that I did not believe this morning. So the trend of colder may be due to the model's lack of data up north, and lack of credit to cold air. The trend this morning with the weekend storm is colder and more ice/snow. And that may be biased. The Snow Poll ends soon, so if I post the map, it will be this evening. I am off of work tomorrow, but will blog by noon when the morning models are in. That is when I will put my first snow cast out.


Note: There is a blogger problem with clicking for a full image today. You may not be able to get back to the blog, so copy URL and re paste if needed.
This is the advisory I woke up to. Ice will be isolated, but I have to report it. As of 4am, I could not find any temperatures in the metro Baltimore area below freezing. At 6am, it was ranging from 31F to 34F in Central Baltimore County. Sure the first round of precip may drop the temp a degree or two from evaporational cooling, so there may be some 'isolated' icy spots, but today's problems will be to our north in central PA to NYC metro. Locally, between 31F and 35F, and any ice would be just during the morning ride - North of the beltway! However, wet roads, and ice build up on 'other stuff' is possible. Mainly the valleys hold on to the cold. The hills just warmer with tis set up.
The Snow Poll has a few more hours, but I am surprised that most of you do not want to feed the sensational machine with early snow forecasts. A few hours left, but again I will act on the results.
As we shift out attention to the weekend storm, here is the latest from the GFS model for Sunday. Honestly, with it's tendency to flip and flop, this is not too bad. It's back to where it was two days ago with a coastal Low off of the DE coast. This could be the perfect set up for the NW 'burbs and southern PA, but any fluctuation would prove a bust. There is so much to consider with this storm, first of which is the current storm passing through. That wraps ups off of the Canadian coast and sets up the cold block. The exact position on Saturday of this block will determine how far south the cold air gets, and resulting path of the next storm.
Here is the Canadian Model showing Saturday evening. The High in Ontario is the result of that block, but also look at the intrusion of Olga from the Caribbean. That would not only inject tropical moisture, but warm air into the system.

The Canadian's solution on Sunday is an initial Low in Ohio, occluding (closing off in late stage of development) and sending it's energy to a developing system overhead or just south. That's not good for snow, but ice or rain turn over. This Low is about 100 west of the GFS, and would make all the difference in how much we get. At this point, I can say that there will be enough moisture to result in 1-3 inches of liquid. But will that include ice, or snow? Then how much of each? Central PA/NY and New England a foot plus a good possibility. But for the big I-95 cities it is that classic meandering mix. Either way, it should end as snow as it pulls away from us on Sunday. Whatever happens Saturday night is still 'up in the air', but Sunday morning through mid day should be our snow time.

Wednesday, December 12, 2007

Wednesday's Waiting Game

First- a reminder of the Snow Poll on the right. I will act on the results. Comments should be fixed, so please share your thoughts...
Today: The warm up. It was expected to be the warmest day, but huge bust potential as any sunshine could jump temps into the 70s. Since we were at 52F at 5am, I am conservatively going 60F-65F. Just waiting on the front just west which could slide in before evening with rain.
Tomorrow: Rain ending as snow? Always waiting for the next model run, but based on my morning forecast, here you can see the NGM 'slow with the low'. Based on this projection, the final wave along this old front will be to our southwest on Thursday evening. Cold air will spill in, but not allow the freezing line to catch up and for us to turn over to end as snow.

Here however is the NAM model for the same time. You can see the low has passed to our south 'east'. That would allow the north wind to drag down colder air. There is one problem here. Notice the yellow line- that is the famed '540 line'. A thickness measured that often relates to the rain/snow line in storms. It is too far north, but not the only ingredient. There is a lot of information to decipher, but here is the 850mb Temperature map. This is an idea of where the freezing line might set up at cloud level (roughly 4,000Ft). What's difficult here is that surface temps may be above freezing while it's cold enough aloft. I see this an an elevation thing at best. Which means Hereford Zone and up near the PA line has the best chance, but lower elevations will not allow any clouds flakes to survive the trip. Locally, just a near miss for most of us.
As for this weekend storm, remember when I said it was too early to get excited? There has been a lot of talk about the potential for this coastal bomb, and you will likely see fluctuations in the models. The GFS model I have been showing demonstrates this often. It has a warm bias with coastals, and can shift a rain snow line 100 miles with each run. Here you can see it is 200 miles north of yesterday's position for Sunday morning. It could very well shift back with the next output, but a sign of how fickle the chaotic atmosphere is. To plot a specific time, place, snow line and amount too far out is nearly impossible. Surely the potential for a big east coast storm is safe, but not who gets what. I've seen it too many times, and don't want to get myself excited, nor scare the viewers. Should I also mention that there is also a chance that energy from Olga gets pulled into the east coast trough? I will, if it holds tomorrow. Again, a waiting game. We wait for the next model to see if the trend is faster and farther, slower or closer. Snow, ice, rain, or a bust. Please vote in the 'Snow Poll' and Stay tuned...