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February 2011

Mid-Atlantic – The Week Ahead (Feb 27 – Mar 6)

Temperatures will be above normal today as the sun peaks through scattered clouds southerly winds push warmer air into the region. The birds are chirping this morning as spring tries to get going early in our region. Enjoy today, because tomorrow will be a different story.


After a miserable but warm start to Monday, skies should clear up a bit as temperatures climb into the upper 60s to lower 70s ahead of a rapidly approaching storm system. This system is expected produce plenty of severe weather across the region, with most of the concern centered on severe wind as storms line out, with some bowing segments. The storms should start moving across the Appalachians in the early afternoon, approaching the BWI/DC/RIC areas in the late afternoon or early evening. There is also some tornado and hail potential with these storms as a decent amount of thermal instability (CAPE of 500-1000 J/kg) and excellent wind shear fuel the thunderstorms. The SPC currently has a 30% severe risk (high-end Slight Risk) over most of the region, but I wouldn’t be terribly surprised if it got bumped to a low-end Moderate Risk somewhere in the region (central/southern WV/VA and DC/MD?). Yes it’s February, but this storm is more of an April-type system for the region, and should be taken seriously. Do not let your guard down on this one.

Following the Monday storm will be a nice break in the weather as mostly sunny and seasonal weather takes over. Tuesday through Thursday should be pretty nice as we start the month of March and meteorological spring along with it. Friday will be a bit gloomier as clouds and a few rain showers pop up over the region. This will continue into Saturday as a very complicated pattern evolves over the weekend. The models begin to SUBSTANTIALLY diverge with a late weekend storm system approaching the region from the west. The GFS currently has a storm moving through Saturday night into Sunday, while the ECMWF takes a much slower and perhaps more complicated look at this system, bringing it through much later (late next Monday). Right now I would go with a chance of rain showers Saturday and Sunday, but it is probably the most complicated system I’ve seen this season (and there’s been plenty of them), so confidence is very, very low.

Snowfall Verification for Feb 21-22

I’ve procrastinated long enough…

Overall not too shabby. The orientation and majority placement of the higher totals were generally correct, though the cut-off on the southern edge left a good amount of room for improvement. My first forecast was much better in that regard. The area of highest snowfall was off, but the idea of having the 8-12″ in western PA was certainly worth applauding despite the questionable positioning. The northern edge of the 2-4″ was also overdone.

This forecast gets a B- from me… general orientation and position of the more significant snowfall totals was good, but the southern edge and some of the northern edge of the higher totals definitely needed to be scaled back. A blend of my first and final forecasts would have probably yielded a B/B+ rating.

Thoughts on the Friday storm

Forgot to get the snowfall verification up today, but I should be able to get it up tomorrow (FRIDAY SATURDAY… fell asleep early Thursday and Friday!)… maps are saved and ready to go when I have the time. I did get some errands run today instead :)

Looking at the Friday system… still a chance for strong winds in the DC area, but severe is unlikely at this point. Southern VA could get in on some severe wind and maybe a tornado. That’s with a round of storms coming through Friday morning… there is potential for a second round of storms further north in northern VA and DC/MD as the upper-level low moves into the region. A developing dry slot is forecast to move into the area and erode the cloud cover late Friday morning into Friday afternoon. Temperatures in the 60s, along with the upper-level forcing and decent instability and moisture will bring another round of showers/storms into the area. If storms can develop and get organized Friday afternoon, we’ll have another shot at strong winds, but weaker storms and plain ol’ rain are more likely.

If the setup changes I’ll issue a revised forecast tomorrow or early Friday.

What to Watch Fore(cast) – Feb 22-28

Not doing a full discussion this week… storm tracks for Big Storm #1 and #2 will have to be monitored for their impact in the Mid-Atlantic states. The Friday storm could be frozen precipitation, heavy rain and/or strong thunderstorms for the DC area! More on that as the details get clearer. Arkansas through Pennsylvania will be a big concern for widespread flooding by the beginning of next week as both of the big storms put down significant precipitation totals in that region.


West is cold and stays cold – A strong push of cold air from western Canada will keep the West much below normal through most of the week. The Northern Plains will also get in on the very cold temperatures.

Plenty of snow in the Pacific Northwest – The cold temperatures will provide a good atmosphere for the Pacific Northwest to finally get the big snows they have been waiting all winter for.

Big storm #1 – Severe storms in the Southern Plains Thursday and in the Southeast on Friday, with snow in the Central Plains, Midwest and Northeast.

Big storm #2 – A warmer and further north system, with severe in the Central/Southern Plains Sunday moving into the Southeast and Mid-Atlantic Monday. Back-end snow for the Central Plains, Midwest and (maybe) Northeast.

Winter Storm Threat: Feb 21-22 (final call)

The morning update:

Temperatures are coming in colder than expected early across the northern half of the region as northerly winds take over. That means earlier/easier changeover to snow for many. This’ll be a fun one.

EDIT: Need to add that I also made a slight adjustment to the time constraints to better fit the storm period.

Winter Storm Threat: Feb 21-22 (only call?)

This forecast is for the second part of the two-part rain/snow event. What I have is not too different from what the models show now, save for some lesser amounts in northern MD. The changeover from rain to snow and the surface temperatures will be the biggest players in inhibiting snowfall totals. The models have probably underforecast the warmth in MD on Monday before the front makes its way through from north to south. However, once the changeover is made, moderate to heavy snowfall after a brief period of moderate sleet could lead to decent totals from DC northwards through central PA. The best combination of colder air and intense snowfall seems to be in southwestern PA, where a band of 4-8″+ is possible.

I also included a small area of 8-12″ for upsloping and cooler surface temperatures in the Appalachians in southern PA. The band of higher totals could shift north/south a bit depending on the placement of the low as it passes over the region.

EDIT: I may have to make some last minute changes to it if the temperatures stay colder in northern MD today. The 2-4″ and 4-8″ contours could creep further south!

Mid-Atlantic – The Week Ahead (Feb 20-27)

Today will be the calm before the storms as a two-part system brings rain, mixed precipitation and snow to the region Monday and Tuesday. The rain will start early tomorrow across PA and edging into northern MD as the first piece of energy pushes through. As the light/moderate rain pushes further south into northern VA, all of MD and Delmarva, a changeover to mixed precipitation and finally snow will occur on the northern edge of the precipitation. Temperatures will crash from the 60s Monday afternoon into the low to mid 30s Tuesday morning. Because of the warmer temperatures and rain to start, snow will have a hard time sticking to the ground from DC southward, if it even snows at all in the southern parts of the region. Snowfall totals of 1-2″ (and local totals of 2-4″) are possible from just north of DC to the MD/PA line, with 2-4″ (and locally 4-6″) north of the Mason-Dixon and in the western Appalachians. Most of the snow will fall early Tuesday, with some snow showers lingering past morning rush hour.

High pressure will move into the region to keep things quiet until the front edge of another system moves into the region on Thursday. Heavy rain and a maybe thunderstorms will be possible with this next system, with a possible changeover to a little snow at the back-end of the storm in the northern and western parts of the region.

After this system exits the region Friday night, there will be a brief break in the wet weather until yet another storm moves in early on Sunday, which will bring more rain and maybe some snow into the region. Next Sunday’s storm has some big snow potential to the north of the region, and it will be something to keep track of for our region as well.