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Feb

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.

***** IMPORTANT INFORMATION CONCERNING MONDAY’S WEATHER *****

 
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.

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!

Brush fire pictures from the Germantown, MD area

These were all taken from the same area where the power lines run north from Rt. 28 up until the end of Brandon Way Rd. in Darnestown, MD. The time I was there was approx. 1:45-2:45 pm. This was from the same area as the GIF animation in the previous post.

If you would like the full resolution, un-watermarked images, please leave a message on the Twitter page, or contact me using the e-mail address in the contact page.

UPDATE:
Here’s some pictures from Jason from the same area: http://www.weatherwarrior.net/chaserquest/bydate/2011/20110219/

Winds helping a brush fire in Germantown, MD

To add to the wind discussion in the previous post, here’s an animation of smoke from a brush fire (unconfirmed) in the Germantown, MD area:

 
There is also a brush fire near BWI in Hanover. Very dry conditions and strong winds are helping the brush fires intensify and spread quickly.

EDIT: I thought this was originally just blowing dust, but it was indeed a brush fire… I don’t really have any first-hand experiences with either.

Winds gusting to 60-70+ mph possible in the Mid-Atlantic today

Winds are already gusting to 50-60 mph across the region, and it will be getting even stronger as we head into the afternoon! Gusts of 60-70 mph are possible, and could even reach hurricane force (74+ mph)! Wind speeds of 58+ mph is the minimum reading for a thunderstorm to be considered severe. BWI has already hit wind speeds of 55 mph today, with DCA and IAD just a few mph weaker.

Here’s a crash course in how to determine the strongest wind gusts:

You can use forecast soundings if you want… I have IAD’s sounding from this morning since we’re in nowcast territory.

Here’s the sounding, with the mixing layer labeled:

 
In dry air, the mixing layer is a volume of air that has temperatures that cool dry-adiabatically (a rate of 9.8 C/km) as you go up. Air is free to mix within this layer, and it is where the wind can blow uninhibited from the top of the layer to the bottom of the layer. The strongest winds in this layer indicates the maximum wind possible. A mixing layer can either be at the surface or aloft.

The wind barbs on the right indicate the winds at certain levels… the lines and flags indicate the wind speed in knots. Winds of ~65 kts are shown at the top of the mixing layer. More information on deciphering the winds barbs: LINK

Granted, this is just the 12z (7am EST) sounding… as the sun warms the atmosphere, the mixing layer will likely go higher up and we could see those stronger winds in the mixing layer this afternoon.

Winter Storm Threat: Feb 9-10 (final call)

The precipitation shield did fill in a little bit from DC and points south on the models, but not to the degree I thought they were going to. I made some adjustments to the forecasts because of that, bringing the 1-2″ line and the 2-4″ contour over the Apps. further south. I brought the 1-2″ contour up north in southeastern NC due to the warmer temperatures.

 
It will be hard to tell how much the DC area gets due to snow sublimation in the lower levels early on, but I could see DC/MoCo getting a dusting to 1/4″ with a small chance of going higher. Areas north of MoCo up towards Frederick and Baltimore could see a dusting at best.

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