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Feb 24 2016 severe weather outbreak


Ian

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Tomorrow's a tough one in several ways. If it was a month later or April I'd be fairly pumped. Still, heavily meridional trough which is generally a negative in going big. Signs are it's going to be pretty hard to destabilize properly. I don't think this is necessarily a case where a little CAPE works wonders. We need enough instability for updrafts not to get sheared apart.

 

Generally agree with SPC outlook still. One thing to watch perhaps is the NAM idea of a low popping along the Blue Ridge and riding north through the region. That enhances the backing which may increase the risk of a spinup somewhere.  Getting tor this far north this early is pretty unusual. Same in general for wind really.

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4km NMM 12z run brings a very healthy looking complex through around 02z tomorrow night. ARW is sort of similar I suppose. I'm not in until Ian is in. Which could be never. 

We've seen warm fronts get hung up too many times like 50 miles south of DC...still would love to get a sneaky SVR event with decent downpours.

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We've seen warm fronts get hung up too many times like 50 miles south of DC...still would love to get a sneaky SVR event with decent downpours.

 

Yeah - I'd assume this will happen as usual. I'd feel semi more confident if it was showing the warm pushing more north. It's pretty close on the models for DCA so I'd assume it'll be a good bit south of where it's modeled. 

Too bad it's not April or May like Ian said. :(

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Decent little event for Deep South today, looks like a spin up tossed a few twigs around just west of the NOLA Airport.  Hopefully we can at least manage a few gully washers tomorrow.

 

Uh huh

SEVERE WEATHER STATEMENT  NATIONAL WEATHER SERVICE NEW ORLEANS LA  1248 PM CST TUE FEB 23 2016    LAC063-091-105-231915-  /O.CON.KLIX.TO.W.0024.000000T0000Z-160223T1915Z/  TANGIPAHOA LA-LIVINGSTON LA-ST. HELENA LA-  1248 PM CST TUE FEB 23 2016    ...A TORNADO WARNING REMAINS IN EFFECT UNTIL 115 PM CST FOR WEST  CENTRAL TANGIPAHOA...NORTH CENTRAL LIVINGSTON AND SOUTHEASTERN ST.  HELENA PARISHES...            AT 1248 PM CST...A CONFIRMED LARGE AND EXTREMELY DANGEROUS TORNADO  WAS LOCATED OVER LIVINGSTON...OR 14 MILES EAST OF DENHAM SPRINGS...  MOVING NORTHEAST AT 30 MPH.    THIS IS A PARTICULARLY DANGEROUS SITUATION.    HAZARD...DAMAGING TORNADO.     SOURCE...RADAR CONFIRMED TORNADO
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Not too shabby: 2 PM CST outlook update from SPC: "an upgrade to High Risk may be warranted at a later update for a small portion of the Moderate Risk."

Kinda confusing but they are a lot better at small area threats than in past.
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  Kinda hard to ignore that the NAM now shows about 1000 j/kg of sfc-based cape to go along with the crazy low-level shear.   We rarely get significant severe here in low cape / high shear environments, and I was thinking that would be our setup for tomorrow evening, but 1000 j/kg would make this a different ball game if it's right.     I am, however, somewhat skeptical of the NAM's evolution in the soundings shown by Yoda, as the low-level lapse rates sharpen awfully dramatically between 00 and 03z.   The sounding at 00z would likely not support robust convection, despite having some cape due to an absence of instability in the low levels which would limit parcel acceleration.   The forecast sounding at 03z, however, would likely support severe and potentially significant severe.

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I find it interesting that the 4km NAM gives us the bulk of the activity and doesn't really do much in the NC area. I'm not sure it'll play out that way ;)

There's several pieces of guidance that seemingly shaft that NC "butter zone" and send a lot of activity into the DC area. I'll believe it when I see it but it's fun to look at. 

Ian seems on the verge of being in over on Twitter. 

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Models underdo CAD most of the time and with the cold ocean temps it's going to be hard to get the surface to heat.  That's why we will get a squall line like we always do.

 

It looks a lot worse than it did  along the gulf coast for NC and south central VA. wonder if SPC updates the risk?

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Slight risk expanded well north to the Poconos with the new SWODY1:

 

post-1389-0-74519800-1456320094_thumb.pn

 

Discussion for posterity:

 

 

 

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0700 AM CST WED FEB 24 2016

VALID 241300Z - 251200Z

...THERE IS A MDT RISK OF SVR TSTMS ACROSS PORTIONS OF EASTERN NORTH
CAROLINA AND INTO SOUTHEAST VIRGINIA...

...THERE IS AN ENH RISK OF SVR TSTMS FROM NERN SC NWD TO THE
CHESAPEAKE BAY AREA...

...THERE IS A SLGT RISK OF SVR TSTMS ALONG MUCH OF THE ERN SEABOARD
FROM FL NWD THROUGH THE MID-ATLANTIC REGION...

...THERE IS A MRGL RISK OF SVR TSTMS ACROSS MUCH OF THE REGION ALONG
AND E OF THE APPALACHIANS WITH THE EXCEPTION OF NRN AND ERN NEW
ENGLAND...

...SUMMARY...
STRONG TO SEVERE THUNDERSTORMS CAPABLE OF DAMAGING WINDS AND
TORNADOES ARE FORECAST FROM THE MID-ATLANTIC STATES SOUTHWARD
THROUGH THE CAROLINAS AND INTO FLORIDA TODAY. THE HIGHEST THREAT FOR
SEVERE WEATHER WILL BE FROM CENTRAL NORTH CAROLINA NORTHEASTWARD
INTO FAR SOUTHEAST VIRGINIA.

...SYNOPSIS...
A DEEP MID- AND UPPER-LEVEL LOW MOVING NEWD ACROSS THE MID SOUTH
ATTM WILL LIFT SLOWLY NNEWD INTO THE GREAT LAKES THROUGH THE
PERIOD...WHILE VERY STRONG FLOW ALOFT /110-PLUS KT MID-LEVEL JET/
ROUNDS THE BASE OF THE LOW AND SHIFTS ACROSS THE E COAST STATES.
THIS LOW IS EMBEDDED WITHIN A MUCH LARGER/BROADER TROUGH WHICH WILL
COVER MOST OF THE ERN 2/3 OF THE COUNTRY THROUGH THE PERIOD.

AT THE SURFACE...A DEEP LOW INVOF THE TN VALLEY IS FORECAST TO MOVE
STEADILY NEWD WITH TIME...CROSSING PA AND NY THIS EVENING/OVERNIGHT.
WHILE A TRAILING COLD FRONT ADVANCES STEADILY EWD ACROSS THE
APPALACHIANS TOWARD THE COAST...GRADUAL EROSION OF A COLD AIR DAM E
OF THE MOUNTAINS IS EXPECTED IN A ZONE OF STRONG LOW-LEVEL WARM
ADVECTION E OF THE SURFACE LOW. WEAK DESTABILIZATION WHERE THE
DAMMING AIRMASS CAN ERODE COUPLED WITH VERY STRONG LOWER- AND MID-
TROPOSPHERIC FLOW...PLUS STRONG ASCENT...WILL SUPPORT
WIDESPREAD/POTENTIALLY SUBSTANTIAL SEVERE RISK ACROSS PARTS OF THE
ATLANTIC COAST STATES.

...ERN SEABOARD FROM SERN NY SWD TO FL...
A BAND OF STRONG/ISOLATED SEVERE STORMS IS MOVING ACROSS ERN SC/SERN
GA/NRN AND WRN FL ATTM...AHEAD OF AN ADVANCING COLD FRONT S OF THE
DEEP TN VALLEY LOW. SHOWERY PRECIPITATION IS ALSO ONGOING ACROSS
PARTS OF THE CAROLINAS/VA...IN ZONE OF WARM ADVECTION ATOP A STOUT
WEDGE OF COLD AIR STILL IN PLACE.

STRONG LOW-LEVEL WARM ADVECTION WILL ACT TO GRADUALLY ERODE THE
DAMMING AIRMASS FROM SE-NW TODAY...AS THE COLD FRONT ADVANCES FROM
THE W. WHERE LOW-LEVEL WARMING/MOISTENING CAN OCCUR...MODEST
DESTABILIZATION WILL SUPPORT DEVELOPMENT OF SHOWERS AND
THUNDERSTORMS -- POSSIBLY WITHIN...BUT LIKELY IN THE WAKE OF THE
ONGOING SHOWER ACTIVITY SHIFTING NNEWD ACROSS THE AREA. WITH A VERY
INTENSE WIND FIELD SPREADING ACROSS THE AREA...STORMS WILL RAPIDLY
STRENGTHEN/ORGANIZE -- INTO BOTH SUPERCELLS AND BOWING LINE
SEGMENTS. THE GREATEST RISK/HIGHEST COVERAGE OF SIGNIFICANT SEVERE
WEATHER APPEARS TO EXIST ACROSS ERN NC INTO SERN VA...WHERE THE
DAMMING AIRMASS IS MORE LIKELY TO ERODE MOST FULLY AND MOST QUICKLY.
HERE...ISOLATED/POSSIBLY STRONG TORNADOES WILL BE POSSIBLE...ALONG
WITH DAMAGING WINDS.

FARTHER N...SEVERE PROBABILITIES HAVE BEEN EXPANDED ACROSS PA AND
INTO THE CATSKILLS. LATE THIS AFTERNOON AND EVENING...BANDS OF
INCREASINGLY ORGANIZED CONVECTION APPEAR LIKELY TO EVOLVE. WHILE
INSTABILITY SHOULD REMAIN WEAK -- AND POSSIBLY SLIGHTLY ELEVATED
ABOVE A SHALLOW COOLER BOUNDARY LAYER...STRENGTH OF THE WIND FIELD
SUGGESTS THAT WINDS APPROACHING OR EXCEEDING SEVERE LEVELS WILL
OCCUR AT LEAST LOCALLY. THE THREAT ACROSS THE ENTIRE AREA WILL END
FROM W TO E THIS EVENING/OVERNIGHT AS THE FRONT MOVES OFF THE COAST.

..GOSS/ROGERS.. 02/24/2016

 

 

 

 

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