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2014 Mid-Atlantic Severe Discussion Thread


Kmlwx

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I feel like these lines like to clear the area early tho - so that might be a good sign for it not holding off too late

Yeah, I think that's true overall. We're in a good spot. It's just so early in the season.. wouldn't be surprised if we're locked in with clouds all day etc. However, sfc heating is not super critical here.

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Mid Atlantic wedgefest 2014 incoming.

 

just kidding

 

Nah, but it all honesty there is certainly a non-zero tornado threat tomorrow across these areas although I doubt they will be "chaseable" in any sense of the term. Ian makes a good point that surface heating will not be super critical in this situation with such strong low level winds in place, this will be almost entirely dynamically driven (perhaps like the Halloween event in the OV except likely not quite on that kind of magnitude).

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We may still get 30% wind but doubtful any higher.. some people have been wondering if we might mod risk.  New SREF/NAM look a little less impressive than earlier runs IMO. 

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We may still get 30% wind but doubtful any higher.. some people have been wondering if we might mod risk. New SREF/NAM look a little less impressive than earlier runs IMO.

I'm interested in post frontal winds. Quite an airmass change and tight gradient. Exposed areas and hilltops may get some 50mph gusts. Everybody should see a period of 35+ gusts right? Howling winds and steep temp drops are always kinda fun. Makes the day interesting.

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We may still get 30% wind but doubtful any higher.. some people have been wondering if we might mod risk.  New SREF/NAM look a little less impressive than earlier runs IMO. 

Really? I have to assume the chance of that is near zero. Doesn't have the feel of a mod risk day at all. Pretty unheard of this early for us. Though I have been very wrong about these kinds of things before lol

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Ian - just took a look at the CWG I think you were referring to - 

If you look at the SPC disco from 1730z it seems more like they were talking about a bump to 30% as you replied to that person. They specifically mention a jump in probabilities rather than a jump in the categorical risk. I'm thinking under a 2% chance of us getting mod risked tomorrow. 

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Really? I have to assume the chance of that is near zero. Doesn't have the feel of a mod risk day at all. Pretty unheard of this early for us. Though I have been very wrong about these kinds of things before lol

I'm not completely sure why myself but I've seen it mentioned a few times from diff people.  I think it's partly because SPC mentioned "upgrade" in their latest day2 though I took that to mean they may upgrade to 30% wind since it's a 15% zone now. 

 

Do think there is probably fairly widespread low end wind risk if things come together right given the alignment of the 500mb vort along the frontal zone. 

 

As Bob alluded to though, the biggest winds for many may be behind the front. 

 

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I'm interested in post frontal winds. Quite an airmass change and tight gradient. Exposed areas and hilltops may get some 50mph gusts. Everybody should see a period of 35+ gusts right? Howling winds and steep temp drops are always kinda fun. Makes the day interesting.

I think many spots will gust to 40kts or so. Hilltops probably past 50kts which is severe level wind if it was in a storm. 

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18z GFS MOS has DCA sustained at 27kts from 3-12z.. and 20+ thru the day.  NAM MOS peaks out around 30kts. That's about as high as you'll ever see MOS spit out around here.

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I think many spots will gust to 40kts or so. Hilltops probably past 50kts which is severe level wind if it was in a storm.

Thawed and squishy ground might bring down some shallow rooted trees. Nothing serious or widespread but some weak ones will prob go down tomorrow night.

I have some big trees in my back yard. Not worried because they've been thinned and topped by recent severe but it's always in the back of my mind. Should be some interesting sounds in the yard regardless.

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Day 1 0600 OTLK is out -- 15 wind/5 hail/ 5 tornado

 


DAY 1 CONVECTIVE OUTLOOK    NWS STORM PREDICTION CENTER NORMAN OK  1253 AM CDT WED MAR 12 2014    VALID 121200Z - 131200Z    ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF CNTRL  APPALACHIAN MTNS AND MID-ATLANTIC STATES...     ..CNTRL APPALACHIAN MTNS/MID-ATLANTIC    AN UPPER-LEVEL TROUGH EXTENDING FROM THE UPPER GREAT LAKES SWD INTO  THE MID MS VALLEY WILL MOVE EWD ACROSS THE OH AND TN VALLEYS TODAY.  A 90 TO 100 KT MID-LEVEL JET IN THE BASE OF THE UPPER-LEVEL TROUGH  WILL MOVE EWD ACROSS THE SRN APPALACHIAN MTNS. AT THE SFC...A  DEEPENING LOW WILL TRACK INTO THE MID-ATLANTIC AS A TRAILING COLD  FRONT ADVANCES EWD ACROSS THE SRN AND CNTRL APPALACHIAN MTNS.  CONVECTION SHOULD BE ONGOING AT THE START OF THE PERIOD ALONG AND  JUST AHEAD OF THE COLD FRONT FROM SRN OH SSWWD ACROSS ERN KY AND ERN  TN. THIS CONVECTION IS FORECAST BY THE HI-RES MODELS TO MOVE EWD AND  ORGANIZE INTO A LINE...AFFECTING THE HIGHEST ELEVATIONS OF THE CNTRL  APPALACHIAN MTNS IN THE EARLY AFTERNOON AND AFFECTING THE  APPALACHIAN FOOTHILLS TO THE EAST OF THE CREST BY THE MID AFTERNOON.  IT APPEARS THAT THE LINE OF THUNDERSTORMS WILL MOVE QUICKLY EWD INTO  THE MID-ATLANTIC BY LATE AFTERNOON.    NAM FORECAST SOUNDINGS AT 21Z FROM NEAR HAGERSTOWN MD SSWWD TO NEAR  CHARLOTTESVILLE VA SHOW A STRONG WIND SHEAR ENVIRONMENT WITH VEERED  WINDS AT THE SFC AND 50 KT OF WSWLY FLOW ABOVE 850 MB. THIS ALONG  WITH A UNIDIRECTIONAL COMPONENT ABOVE THE BOUNDARY LAYER SHOULD BE  FAVORABLE FOR STRONG OUTFLOW GUSTS AS THE CONVECTIVE LINE MOVES  ACROSS THE REGION THIS AFTERNOON. THE MAIN CONCERN FOR SEVERE THREAT  COVERAGE IS DESTABILIZATION. THE WRF-HRRR DEVELOPS SOME FAIRLY  WIDESPREAD RAINFALL ACROSS CNTRL AND NRN VA EXTENDING NWD INTO SRN  PA WHICH COULD LIMIT DESTABILIZATION IN SOME AREAS. THE NAM HAS TWO  POCKETS OF INSTABILITY...THE FIRST IN WRN MD AND THE SECOND IN NRN  NC SUGGESTING LOCALIZED HEATING SHOULD BE A FACTOR IN CREATING THE  GREATEST SEVERE THREAT WITH THE LINE. AS THE LINE MOVES INTO MD AND  CNTRL VA...ENHANCEMENT FROM THE LEFT EXIT REGION OF THE MID-LEVEL  JET...STRONG LARGE-SCALE ASCENT AND IMPRESSIVE WIND FIELDS SHOULD  CREATE A WELL-DEVELOPED FINE LINE. ALTHOUGH THE MAIN THREAT SHOULD  BE DAMAGING WIND GUSTS...A FEW TORNADOES CAN NOT BE RULED OUT WITH  ROTATING CELL ELEMENTS ASSOCIATED WITH BOWING LINE SEGMENTS. THE  WIND DAMAGE THREAT MAY CONTINUE AS FAR EAST AS THE COAST OF VA AND  NJ BY EARLY EVENING. THE SRN EXTENT OF THE SEVERE THREAT IS  QUESTIONABLE AND MAY DEPEND UPON HOW MUCH LOW-LEVEL CONVERGENCE  DEVELOPS ALONG THE FRONT. A FEW DAMAGING WIND GUSTS MAY OCCUR ACROSS  NCNTRL NC IF THE LINE CAN ORGANIZE THAT FAR SOUTH.    ..BROYLES/MOSIER.. 03/12/2014  
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as noted by SPC, several HRRR runs now are showing a fairly widespread area of showers over the area from midday into the early afternoon.    It still has a break for a couple of hours during the late afternoon and forces a broken line along the cold front, but the overall thunder/severe threat would be reduced by cooling from the showers.    Radar does seem to suggest that an area of showers is building over southwest VA and moving northeast.

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as noted by SPC, several HRRR runs now are showing a fairly widespread area of showers over the area from midday into the early afternoon.    It still has a break for a couple of hours during the late afternoon and forces a broken line along the cold front, but the overall thunder/severe threat would be reduced by cooling from the showers.    Radar does seem to suggest that an area of showers is building over southwest VA and moving northeast.

Socked in with clouds the whole ride down from PA to DC.  NAM looks like it's out to lunch as is usual.

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