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.



Tomorrow:
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.

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 well...so 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.

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.

Snow on Schedule.. Afternoon Update

I just made a brief update on Examiner.com 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 mountains...at 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.

The Skinny on the Rain and Snow This Weekend

We've already seen nearly an inch or rain (or more in some spots). The HPC rainfall update now has an additional 1-2 inches from central Maryland to the coast. This is along the lines of what I mentioned earlier this week.
The heavy rain will be here in two more parts:
Tonight through Saturday morning.
Saturday afternoon: A cold front with the chance of a thunderstorm mixed in.

Then the cold air spills in in a few waves Sunday through Tuesday. Each will have a piece of energy, short wave (or vort max), that should carry snow showers over the mountains and through central Maryland.

It has been a long day, so I am just going to post some charts below to make my case. I am using the NAM model showing the 500mb vortivity (spin), and thickness between 1000mb and 500mb. The '540' line usually represents where the snow or freezing line would set up.
Basically, I'd be surprised it we don't get snow here by Monday or Tuesday. Sunday morning, and afternoon each have a shot. The last image is Monday Evening. This one looks like a clipper type system. A bit more widespread, and the cold air will already be established. This has the best chance to coat the ground or more in the northern/western burbs... Stay tuned.

The Developing Storm and Chance of Snow

As I mentioned on Examiner.com this morning, the models and my resulting forecast changed a bit after the morning package came in yesterday. On that note, I am going to wait until I get the new data to make my post here today. Please check back. In the meantime, the HPC rainfall forecast has gone up from yesterday. I had said that a shift in speed or track may double our totals... well we are getting close to it.

I have kept the regional radar at the bottom of this post, but you can get it on my TV Graphics tab above.

Below is my model analysis, but some of the maps are not easy to read. I have cut out our region, along with highlighting Maryland in a yellow circle.

Late Morning UPDATE:
Now that the models are trickling in, I can see the development, or perhaps over excitement of cold air in the computer models. There is a ton of information to sort through, but what I try to do here is provide the best graphical display. I will try to keep this short, but sweet.
The NGM (here), shows the next development for Saturday morning. This looked heavier on the NAM model, but the rain that moves on late Friday, will be here on Saturday morning, but perhaps break into showers during the day. The arctic boundary to our west will turn rain to snow in Chicago. That white line shows the freezing line. Could be interesting football weather in Michigan mid day.
The NAM shows low pressure slowly passing overhead, and keeping steady rain around through Saturday evening. The low in the Great Lakes looks stronger here, and the band of precipitation behind the freezing line would translate to heavy snow from Chicago to South Bend, IN, and Michigan. The way this wraps up, will pull cold air farther south behind the storm. That will arrive on Sunday- and settle in on Monday.


Snow Next Week?
Here is my personal favorite- the Canadian (from Environmental Canada) showing the surface and upper level maps behind this storm on Monday. On the left, the surface map shows what is left of the Low Pressure Center, just spinning itself out. It is stacked aloft, and circulating cold air around it, while drifting east of the Great Lakes. The black line is the 'freezing' line that is well to our south and moving off of the coast. It does not guarantee freezing temperatures for us, but it supports snow development in the clouds. The image on the right, shows the upper level chart at 500mb. This is the energy needed to generate showers, and there is a lot of it. The push of arctic air moves in during the day, keeping us in the 40s, with an afternoon rain or snow shower. The X in Ohio is the second push with the core of the cold air. That will arrive on Tuesday. This is why I put rain or snow showers for Monday, but snow showers or flurries on Tuesday. Usually the best chance for this is in the hilly terrain north and west of Baltimore, I will fine tune this we get closer. Just showers- but a start and sign of the changing season.