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2023 Mid-Atlantic Severe Wx Thread (General Discussion)


Kmlwx
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18 minutes ago, Kmlwx said:

in fact...GFS wind gust product has 60-65mph gusts Saturday afternoon. If we can't get severe that would be a heck of a wind event...

Bingo.

Knowing the region though and our history w/ synoptic winds w/ a southerly component... my expectations are definitely in check... for now. :lol:

But seriously though, the sounding got my attention for sure and I'm keeping at least one eye on it. One can dream.

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32 minutes ago, George BM said:

Bingo.

Knowing the region though and our history w/ synoptic winds w/ a southerly component... my expectations are definitely in check... for now. :lol:

But seriously though, the sounding got my attention for sure and I'm keeping at least one eye on it. One can dream.

It can definitely get breezy with southerly winds - but yeah...our BIG winds are those NW wind events behind big storm systems typically in the fall/winter/spring. 

EC is more in check with their gusts showing in the lower 50s. If there is a synoptic wind event, I'm guessing it'll be pretty "typical" with widespread wind advisories and then perhaps high wind warnings for the ridgetops. 

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5 hours ago, George BM said:

Not convective severe but... what else stands out to you about this skew-t profile?

485271605_gfs_2023032806_fh108_sounding_77.78W76.45W38.56N39_53N.thumb.png.6d24818eb37b789ba7b82881c4bde6bf.png

It’ll be interesting to see if we can maximize the wind.  There is a disconnect right now between the best boundary layer setup (afternoon, such as in your sounding) and the best wind direction (downslope NW) which occurs more toward the evening.

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1 hour ago, yoda said:

Pretty rare for a Day 8 mention, yes?

@Kmlwx @high risk @George BM

We do actually get mentioned occasionally for Day 8. Far out, as you well know. But Leitman's explanation about storms from Day 7 moving into the Mid-Atlantic region w/ the risk of cloud debris and how it dictates what occurs in this region Day 8 definitely makes sense in my eyes. 

If nothing else, we're getting closer to the time of year where we may not have to wait weeks between convective threats. 

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On 3/29/2023 at 10:09 AM, Kmlwx said:

I don't want to start the whole global warming conversation - but I could see our severe season getting extended with a warmer/more humid climate. Late March could become a more fruitful severe producing time of year. 

      Interesting thought.    In my mind, the severe season here doesn't really kick in on average until around May 10 (yes, there are exceptions), so moving that start up to late March would be a big jump.    How about if we try a smaller increment and the severe season in mid to late April instead?

       I could also see an introduction of a fall season (aside from tropical events).      We usually end up just a bit cool for those dynamic autumn systems.

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1 minute ago, Kmlwx said:

The 6z NAM nest is high wind warning criteria gusts for most of the metro area tomorrow afternoon. 55kts shown IMBY. That's an increase over prior runs. It even has some 40kt gusts TONIGHT for our area. 

 

12 minutes ago, Eskimo Joe said:

Yea. 06z NAM has a nice 55-60kt streak at 925 mb moving smack dab over the DC metro region at 00z Sunday. 

 

2 minutes ago, MN Transplant said:

If the event ends up looking like the NAM above, we are going to see massive severe thunderstorm warning boxes accompanying that line for wind.

From the March disco obs thread

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Snippet from Mount Holly morning AFD-

A robust cold front is expected to push southeastward through our region on Saturday evening. It should bring another round of showers with thunderstorms. Mixed layer CAPE values are expected to be marginally unstable, mainly in the 250 to 500 J/Kg range. However, it will be a fairly dynamic system and any thunderstorms have the potential to easily mix down some locally damaging wind gusts.

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High wind watch in effect

Map of Forecast Area

...HIGH WIND WATCH IN EFFECT FROM SATURDAY AFTERNOON THROUGH
SATURDAY EVENING...

* WHAT...West winds 25 to 40 mph with gusts up to 60 mph
  possible.

* WHERE...Portions of central and northern Maryland, The District
  of Columbia, and northern Virginia.

* WHEN...From Saturday afternoon through Saturday evening.

* IMPACTS...Damaging winds could blow down trees and power
  lines. Widespread power outages are possible. Travel could be
  difficult, especially for high profile vehicles.

* ADDITIONAL DETAILS...The strongest winds are most likely late
  Saturday afternoon through mid Saturday evening.
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I've been split on where to post - I guess we can do the synoptic discussion in the obs thread since it's not technically "severe" and if a line DOES materialize we can do that in here. 

Tough with these early season events sometimes. I do like having the severe stuff under one "roof" because it's fun to go back and read in a single thread sometimes after an event (even years later)

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RGENT - WEATHER MESSAGE
National Weather Service Baltimore MD/Washington DC
229 PM EDT Fri Mar 31 2023


District of Columbia-Frederick MD-Carroll-Northern Baltimore-
Southern Baltimore-Prince Georges-Anne Arundel-
Northwest Montgomery-Central and Southeast Montgomery-
Northwest Howard-Central and Southeast Howard-Rappahannock-
Fairfax-Arlington/Falls Church/Alexandria-Northern Fauquier-
Western Loudoun-Eastern Loudoun-Northwest Prince William-
Central and Southeast Prince William/Manassas/Manassas Park-
Including the cities of Washington, Frederick, Ballenger Creek,
Eldersburg, Westminster, Reisterstown, Cockeysville, Baltimore,
Bowie, Suitland-Silver Hill, Clinton, College Park, Greenbelt,
Laurel, Camp Springs, Glen Burnie, Annapolis, Severn, South Gate,
Severna Park, Arnold, Odenton, Germantown, Damascus, Bethesda,
Rockville, Gaithersburg, Silver Spring, Lisbon, Columbia,
Ellicott City, Reston, Herndon, Annandale, Centreville,
Chantilly, McLean, Franconia, Arlington, Alexandria,
Falls Church, Warrenton, Purcellville, Leesburg, Ashburn,
Sterling, Haymarket, Dale City, Manassas, Woodbridge, Lake Ridge,
and Montclair
229 PM EDT Fri Mar 31 2023

...HIGH WIND WARNING IN EFFECT FROM NOON SATURDAY TO MIDNIGHT EDT
SATURDAY NIGHT...

* WHAT...Southwest winds 20 to 30 mph with gusts up to 50 mph
  Saturday afternoon, becoming northwest 25 to 35 mph with gusts
  up to 60 mph Saturday evening.

* WHERE...Portions of central and northern Maryland, The District
  of Columbia, and northern Virginia.

* WHEN...From noon Saturday to midnight EDT Saturday night. The
  strongest winds are expected Saturday evening.

* IMPACTS...Damaging winds will blow down trees and power lines.
  Widespread power outages are expected. Travel will be difficult,
  especially for high profile vehicles.

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2 minutes ago, high risk said:

     (Should this discussion be in the SVR subforum?)      What changed in the 18Z NAM Nest is that it now backs the sfc winds in the afternoon which allows low-level dew points to ramp up before the front arrives.    This creates a thermodynamic and kinematic profiles that support supercells.    it's quite a change from the earlier runs which had sfc winds veering by midday and low level dew points lowering significantly in the afternoon.     I need to see this idea show up in the 00Z cycle and see it in other models before buying in.

Moving this over here.  The 18z NAM is more aggressive on the potential for severe due to the low-level moisture.  Check out the difference between 12z and 18z.

download.png.39cac0446ebf9379ee01fa1ce81ee283.png560151479_download(1).png.1793ca0c653d6676f5ceac59d2658cae.png

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From Mount Holly-

While the sunshine Saturday afternoon may seem like a good sign of improving weather, it will actually only provide a false sense of security. We are expecting sufficient daytime heating in the afternoon to then result in convective development along and just ahead of the trailing cold front that is expected to sweep through late Saturday afternoon and early evening. Furthermore, severe weather parameters are looking favorable as convection develops. Abundant shear and sufficient instability along with favorable lapse rates will overlap across the region, leading to a risk for severe thunderstorms. At the moment, the greatest threat remains damaging winds within a thunderstorm as heavy rain within the line of storms will mix down the strong low-level winds, creating a line of strong winds as the front moves through. Forecast soundings also suggest a brief window of time when wind profiles will veer ahead of the frontal boundary, thus an isolated embedded supercell or a tornado or two is certainly possible across the area.

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Latest models are more tame on the wind, and keep any severe threat mainly to the east of most of us. @CAPE - you're in a good spot to see some rough weather today IMO. I think the vast majority of us are just too far west. Hopefully I can see some good gusts!

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