Current Surface Map

A low pressure center will move into the Great Lakes tomorrow, dragging a warm front into the area. The warm front will bring in even warmer air and possibly another round of showers as it moves through. Highs tomorrow will be in the upper 60s and approach 70 in many areas.

The low will bring a cold front through the area on Friday, bringing gusty winds and another round of showers. Behind the front, temperatures will tumble and top out in the mid to upper 40s this weekend under mostly sunny skies.

Current Surface Map

Expect partly sunny skies today and tomorrow. Highs today and tomorrow will be in the mid to upper 50s.

Southwest flow around the high pressure off the coast will continue to pump warmer air into the region on Thursday with highs approaching and possibly topping 70 degrees in most areas.

A cold front will approach and cross the region on Friday, bringing a better chance of rain and possible a rumble of thunder as it moves through. Highs Friday will be in the mid 60s before dropping back to near normal on Saturday and Sunday and into next week.

Current Surface Map

Winds will be lighter tomorrow, but we will still be under the influence of the high pressure, with sunny skies again and highs in the low to mid 50s. The high moves off the coast tomorrow night as a weak upper level disturbance moves through, bringing a slight chance of showers. There will be a series of these systems that will try to pass through the area through the week, but high pressure off the coast should keep us mostly dry. There is a slight chance of a shower Wednesday through Friday, but otherwise, expect mostly sunny skies with highs around 60 Wednesday, climbing into the mid to upper 60s on Thursday and mid 60s on Friday.

A cold front will pass through on Friday, dropping temperatures back into the 40s for next weekend.

Current Surface Map

As far as the snow, the storm will remain to our south today, any snow that falls in Maryland today may provide a dusting to a slushy inch, mainly on grassy surfaces.

This has been a tricky forecast and the storm could still surprise us and drift north a bit more than anticipated, but it looks as though SW Virginia will be the big winners with this one. It is simply too hard to get a decent snowfall here with the setup that we see with this storm.

Remember, the LWX radar is down, so do not use that to track the storm, please use the new map, along with the TBWI radar.

Here is the URL for the new map: http://www.marylandwx.com/f5data/sfcmap.php

From the NWS:

NOUS61 KCTP 172023
FTMLWX
Message Date: Feb 17 2012 20:23:30
THE DUAL POLARIZATION UPGRADE OF KLWX BEGAN AT 14Z 17 FEB 2012. KLWX WILL BE INOPERATIVE DURING THE UPGRADE PROCESS THROUGH 00Z 25 FEB 2012.

The regional radar and the TBWI radar on our Radar Data page will still be in operation.

Surface 1pm

Compare that with the 12z GFS for 18z this afternoon:

12z GFS valid 1pm today

As you can see, everything is pretty much going how the GFS said it would. The high pressure over Iowa is basically correct. The high off the Virginia/Carolina coast is correct and the low over western NY is correct.

Most importantly, the low pressure center off the Texas/Louisiana coast is correct and the precipitation extent and intensity is correct. It does have rain further north and west than what is currently falling, so that may be something to watch going forward.

If you would like to follow the progress of the storm, I have created a loop of the surface image that I posted above. It is in experimental mode right now, but should be stable enough to use.

The loop can be found at: http://www.marylandwx.com/f5data/flashsatrad.php

Current Weather Map

After watching the models shift the storm track north yesterday morning, all of the models began shifting the track back to the south through the day, and last night, shifted far enough south to miss the state completely.

Overnight, they have shifted back north again slightly, and are coming to a solution that will take the storm off the Carolina coast. This track will put us on the extreme northern edge of the precipitation and as mentioned in yesterday’s post, the northern edge has a sharp gradient where there is a few inches of snow, to nothing over about 50 miles. A wobble in the track of the storm would be the difference in whether we see accumulating snow or not.

The other issue working against snowfall here is the lack of cold air at the surface. In order for our area to get accumulating snow, we will need heavier precipitation to cool us down. It doesn’t appear that we will get into any of the heavier precipitation so surface temperatures will not cool enough to support accumulations.

At this point, it appears a slushy inch is possible across central and southern Maryland with less to the north. So it goes this winter.

Things definitely could change, and a small change could make the difference here on the northern edge. If warranted, I will update again this evening.

Current Weather Map

Now, on to the big weather story. Overnight, the models that had been showing the storm staying further south have shifted the storm north, while the models that were bringing it further north have shifted to the south. As you know with these systems, the exact track is impossible to determine at this point and any shift at all in the track has a drastic impact on the weather for our area.

What we do know at this point is that the storm system that is currently forming over the southwest will continue to move eastward along the Gulf coast. At that time, it will begin to interact with northern stream energy diving out of Canada. This will help pull the system northward and strengthen it. What we don’t know is how far north the storm will come, and when it does, how much cold air it will run into.

Here is the latest NAM solution for Sunday evening:

NAM 7pm Sunday

Here is the latest GFS solution for Sunday evening:

GFS 7pm Sunday

What you can notice on both models is how sharp the cutoff is on the northern edge of the precipitation. That will further complicate the forecast, as totals range from near a half inch of liquid to nothing over about 100 miles. Both models show between .25 and .50″ of liquid total, but again a slight jog in the track makes a huge difference:

NAM Total Precipitation

GFS Total Precipitation

In any case, this will not be a crippling snowstorm and will start as rain for most areas east of I-95. At this point, it looks as though rain will change to snow Sunday afternoon and several inches of snow are likely for the Balt/DC metro areas, with more to the NW and less to the SE.

This forecast will be updated this evening and tomorrow as more data comes in and hopefully we gain a stronger model consensus.

Current Weather Map

Overnight, the models came into better agreement regarding the storm system that looks to affect the area on Sunday.

06z GFS model for Sunday Afternoon

While confidence is increasing that this storm will affect the area, it is still too early to tell how much of an impact it will have and whether we see rain, snow or a mix. Hopefully we continue to see the agreement in the models as we move closer to the event and can begin forecasting how much rain or snow we see.

At any rate, the potential continues to exist that a significant winter storm could affect the state on Sunday.

Current Weather Map

High pressure builds in for Friday into Saturday bringing mostly sunny skies and highs around 50. The high will gradually move off the coast ahead of the next possible storm system that could affect the area on Sunday.

GFS Model for Sunday Morning

There are a lot of different variables to deal with and many different solutions depending on the timing of each. It is too early to give any specific forecast, but the pieces are in place for the first time this winter for a potential significant snowfall in the Mid-Atlantic area.

As the National Weather Service said “it is simply a waiting game” to see how it develops at this point.