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First severe threat of 2013 in the Mid-Atlantic

While the severe weather outbreak will be more focused on the southern states, I did this write-up just for folks in the Mid-Atlantic.

A widespread strong to severe wind event appears to be unfolding over the eastern half of the U.S. Tuesday into Wednesday, with isolated tornadoes also a threat, which is mostly across parts of the Southeast. The Mid-Atlantic has some opportunity for both on Wednesday, with the main threat obviously being a line of strong to severe winds.

We will be battling marginal lapse rates and pre-frontal clouds/rain, as we normally do in these early year setups. Very strong winds aloft (50-60 kt jet at 925mb!) suggests any sort of convection will bring down strong to severe level winds. With the strong forcing associated with the cold front, I don’t see much of a problem getting those winds to the surface. The only issue would be if a stable layer at the surface can linger ahead of the front, but that appears to be just a minor problem as the lift from the front should overcome the stable layer (if there is indeed a stable layer).

With dewpoints climbing into the lower 60s ahead of the front, we should be able to see a fairly strong frontal passage with widespread strong to severe winds. The main thing I’m watching now is the potential of a secondary low formation, which the NAM has (though that can’t be relied upon at this point). The Euro also develops a secondary low, but it comes later and further north than the NAM. If this secondary low develops before the front comes through, and if it’s far enough south, it will be able to back the winds more at the surface and would provide a greater risk for tornadoes in the Mid-Atlantic.

Active week for severe weather in the Plains

Severe weather is expected every day this week in the Plains as several shortwaves work into the central U.S. and the large-scale trough pushes eastward. While some days could have problems with instability and capping, the wind profile will be at least somewhat favorable for rotating storms and severe weather in the Plains.

Here’s the SPC maps highlighting the greatest severe weather risk areas through Saturday, with the threat expected to continue into early next week.

Tornado Outbreak ongoing in the Midwest and Southeast

Multiple violent tornadoes are tracking across the Midwest to Southeast today as this High Risk event gets underway.

CLICK HERE for an animated GIF of the long-track debris ball in southern Indiana (image size 3.28 MB).

Here’s the latest SPC outlook:

UPDATE (6:45pm): Another long-lived debris ball went through West Liberty, KY. CLICK HERE for the radar loop (another large image).

UPDATE (7:45pm): Yet another long-lived debris ball… this one went through Salyersville, KY. CLICK HERE for large image goodness.

Mid-Atlantic Discussion – Feb 29, 2012

We end the last day of meteorological winter not with snow, but with severe as storms threaten the region for the second time within a week.

Currently, there are two tornado watches active in the region… one that extends into most of WV, and another that encompasses extreme southeastern WV and most of western VA.

Both watches are set to expire during the first half of the evening. The main concern with these storms is damaging wind, with isolated tornadoes possible and a low risk of severe hail. The main cluster of storms is moving through WV/VA now, but another cluster of storms is expected in the same areas in the early evening. Both of these clusters are expected to weaken as they get east of the mountains in the northern areas, but a risk for severe will continue into the overnight hours in southern VA and NC.

Mid-Atlantic Discussion – Feb 24, 2012

I can’t believe I haven’t done one of these since August… been too long.

The first real chance for severe weather in the Mid-Atlantic this year has arrived! Tomorrow’s looking increasingly promising for at least some severe wind threat in addition to an isolated tornado or two and maybe some hail. Strong post-frontal winds and brush fires are also risks with this system.

The latest models have been pushing out CAPE values of 500-1000 J/kg in parts of the Mid-Atlantic from DC down to eastern NC tomorrow afternoon, which isn’t much, but for February it’s not too shabby. The low-level jet will also be roaring in southern VA and eastern NC, which strong thunderstorms could mix down to the surface. There is enough directional shear in the low-levels for a tornado threat in southeast VA and eastern NC, which is where I plan to storm chase.

Behind the front, dropping dewpoints and strong winds gusting to 50-60+ mph will bring a risk for brush fires to the region as well, especially in the areas that were north of the recent snowfall from last Sunday.

All of this will be going on during the afternoon and evening hours tomorrow, though winds will remain somewhat gusty going into Saturday.

Here’s the latest forecast from the SPC (click the image for their discussion):

Severe weather possible in the Mid-Atlantic tonight/tomorrow

The synoptic setup is somewhat favorable for damaging winds and perhaps an isolated tornado or two tonight into early tomorrow in the southern Mid-Atlantic as storms ahead of a cold front push through the region. Poor lapse rates will likely prevent severe weather from occurring in DC, Baltimore and points north and west.

The storm system will be what we typically see for severe weather setups in the Mid-Atlantic during the winter and early spring… low CAPE/high shear. This system was looking fairly marginal for the region up to this morning due to the poor mid-level lapse rates, but it appears that the previously under-forecast dynamics will help introduce better lapse rates to the southern Mid-Atlantic. It is still fairly borderline, but with a strengthening low-level jet producing 50-60 kt. winds at 925mb it wouldn’t take much to bring those damaging winds to the surface.

925mb winds at 4am:

Forecast sounding for Richmond at 4am:

The sounding shows that there is enough directional shear for the anticipated storms to produce a tornado or two in the southern Mid-Atlantic tonight into tomorrow morning.

SPC’s outlooks for tonight into tomorrow morning:

I am mostly in agreement with them, but I would tone it down to a SEE TEXT instead of a Slight Risk north of the NC/VA border as the storms don’t look to be terribly organized, which is something you want to see for a Mid-Atlantic low CAPE/high shear system (at least for the damaging wind potential).

Severe weather outbreak likely in the Southeast/Midwest

The SPC has released their first Moderate Risk for severe weather of the season for today:

The biggest risk will be for damaging winds along a squall line that is expected to form during the late evening to early morning hours just west and along the Mississippi River from southern Illinois southward into central Mississippi. 50-55 kt. winds in the 925-950mb level could mix down to the surface as the squall line pushes through. This is also a fairly good low CAPE/high shear setup for tornadoes, which could develop along the squall line.

The one thing to keep an eye on is the somewhat stable layer of air between the surface and 950mb, which will inhibit the potential severity for most of the storms except maybe in the southernmost areas.

I think the SPC prediction for today is fairly reasonable, but I will say that the northern extent of the Slight Risk and Moderate Risk could be cut back as the low-level air is forecast to be too stable north and east of southern Illinois. If the warm front associated with this system can get advected further north than forecast, then the SPC’s risk area could be justified. I could see that happening to a degree as the models often underforecast the northern extent of the warm sector in dynamically-strong cases such as this one, but I don’t think it will be as significant as the SPC appears to think it will be.