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8/21 Severe Threat - Obs/Discussion


Kmlwx

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How about following some of your own forum rules and providing something other than lame one line replies with no support Ian. This is a discussion man.

I don't think it would be PDS because it's not a PDS situation. Better?

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485

ACUS11 KWNS 211555

SWOMCD

SPC MCD 211554

NYZ000-MAZ000-CTZ000-NJZ000-PAZ000-DEZ000-MDZ000-VAZ000-DCZ000-WVZ000-211800-

MESOSCALE DISCUSSION 2030

NWS STORM PREDICTION CENTER NORMAN OK

1054 AM CDT SUN AUG 21 2011

AREAS AFFECTED...PARTS OF NRN VA...THE DELMARVA...SRN AND ERN

PA...NJ...INTO THE LWR HUDSON VALLEY

CONCERNING...SEVERE POTENTIAL...WATCH LIKELY

VALID 211554Z - 211800Z

TRENDS ARE BEING MONITORED FOR AN INCREASING SEVERE THREAT THAT

COULD REQUIRE ONE OR MORE WATCHES DURING THE 17-19Z TIME FRAME.

BENEATH DIFLUENT UPPER FLOW DOWNSTREAM OF A VIGOROUS SHORT WAVE

TROUGH NOW TURNING EASTWARD THROUGH THE GREAT LAKES REGION...

SCATTERED THUNDERSTORM ACTIVITY IS ONGOING THROUGH MUCH OF THE

NORTHEAST. ASSOCIATED CLOUD COVER AND PRECIPITATION ARE SLOWING

BOUNDARY LAYER DESTABILIZATION IN BROAD POCKETS...COMPLICATING THE

SEVERE WEATHER POTENTIAL...WITH SOUTHWESTERLY DEEP LAYER MEAN FLOW

AND SHEAR STILL SOMEWHAT MODEST ACROSS MUCH OF THE REGION.

IT DOES APPEAR ONE AREA OF FORCING FOR ASCENT ASSOCIATED WITH A

SMALLER SCALE IMPULSE/WEAK AREA OF MID-LEVEL HEIGHT FALLS IS

BEGINNING TO SHIFT EAST NORTHEAST OF THE CENTRAL APPALACHIANS. THIS

COULD SUPPORT INCREASING STORM DEVELOPMENT WITHIN THE NEXT FEW HOURS

ACROSS NORTHERN VIRGINIA INTO PARTS OF SOUTH CENTRAL/ SOUTHEAST

PENNSYLVANIA...WHERE STRONGEST SURFACE HEATING IS OCCURRING. LATEST

RUC GUIDANCE SUGGESTS INHIBITION FOR MOIST BOUNDARY LAYER PARCELS

CHARACTERIZED BY 70F+ SURFACE DEW POINTS IS DIMINISHING...AND MIXED

LAYER CAPE COULD EXCEED 2000 J/KG TOWARD THE 18-20Z.

THEREAFTER...THE SEVERE WEATHER POTENTIAL...INCLUDING THE RISK FOR

ISOLATED SUPERCELLS AND ORGANIZED STORM CLUSTERS...APPEARS LIKELY TO

GRADUALLY INCREASE THROUGH THE REMAINDER OF THE AFTERNOON. THIS

PROBABLY WILL INCLUDE AREAS FROM THE LEE OF THE LOWER GREAT LAKES

EASTWARD INTO NEW ENGLAND...BUT IT REMAINS UNCLEAR WHETHER THE

THREAT WILL BECOME WIDESPREAD...OR REMAIN RELATIVELY LOCALIZED

ACROSS THESE AREAS.

..KERR.. 08/21/2011

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...BOX...OKX...ALY...PHI...BGM...AKQ...CTP...LWX...

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For future reference:

"The "particularly dangerous situation" wording is used in rare situations when long-lived, strong and violent tornadoes are possible. This enhanced wording may also accompany severe thunderstorm watches for exceptionally intense and well organized convective wind storms. PDS watches are issued, when in the opinion of the forecaster, the likelihood of significant events is boosted by very volatile atmospheric conditions. Usually this decision is based on a number of atmospheric clues and parameters, so the decision to issue a PDS watch is subjective. There is no hard threshold or criteria. In high risk outlooks PDS watches are issued most often."

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SPC seems as clueless as us to what will occur and where

When all modes are possible but none is dominant kinda gotta wait to see what fires up. Good setup but not our best for torn etc.

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For future reference:

"The "particularly dangerous situation" wording is used in rare situations when long-lived, strong and violent tornadoes are possible. This enhanced wording may also accompany severe thunderstorm watches for exceptionally intense and well organized convective wind storms. PDS watches are issued, when in the opinion of the forecaster, the likelihood of significant events is boosted by very volatile atmospheric conditions. Usually this decision is based on a number of atmospheric clues and parameters, so the decision to issue a PDS watch is subjective. There is no hard threshold or criteria. In high risk outlooks PDS watches are issued most often."

Probably should bold some of this.

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I am going to make the call.. hatched wind at 1630

Hard to say - as Ian noted it might be fairly isolated to specific cells. But still, LWX and SPC are likely talking and were talking when the morning discussion was issued so it's possible I suppose.

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Hard to say - as Ian noted it might be fairly isolated to specific cells. But still, LWX and SPC are likely talking and were talking when the morning discussion was issued so it's possible I suppose.

Go bold or go home! :P

Could be the same... but the way LWX said in the AFD, who knows

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For future reference:

"The "particularly dangerous situation" wording is used in rare situations when long-lived, strong and violent tornadoes are possible. This enhanced wording may also accompany severe thunderstorm watches for exceptionally intense and well organized convective wind storms. PDS watches are issued, when in the opinion of the forecaster, the likelihood of significant events is boosted by very volatile atmospheric conditions. Usually this decision is based on a number of atmospheric clues and parameters, so the decision to issue a PDS watch is subjective. There is no hard threshold or criteria. In high risk outlooks PDS watches are issued most often."

Probably should bold some of this.

Fair enough...

the changes of either of those occurring is negligible.

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There were at least 4-5 PDS Severe Thunderstorm Watches issued in last year or two. Not sure why this Chris guy is acting like its only a tornado driven event.

And those are for serial derechoes producing 80+ mph winds along a line usually exceeding 100+ miles...you will not see a PDS STW for localized wet microbursts.

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Just woke up and caught up to the thread...

LOL @ MoD thinking PDS Watch... the line of discussion should have dictated that, while enhanced, the overall threat is not nearly significant enough for a PDS Watch.

More pre-frontal stuff than I was expecting this morning... changing my target to NE MD for now. Jason had similar thoughts with NE MD, and it looks like we'll be chasing together today (he's calling back soon with the yay/nay).

Waiting for SPC update, watching the latest info. and should be in the road before 1:00 :thumbsup:

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