Today’s Severe Weather Targets the Southeast & the Northeast U.S.


Today, the severe storms will form in the south from Atlanta WSW-ward to Austin, Texas. Even areas around New York City & Philadelphia could see some severe weather. Regular storms, a few may be marginally severe will surround the severe weather risk area. And the areas would include Memphis, Little Rock & Oklahoma City later tonight. Here is what the Storm Prediction Center has to say on this.

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1123 AM CDT WED APR 20 2011

VALID 201630Z – 211200Z

…THERE IS A SLGT RISK OF SVR TSTMS FROM PARTS OF TX EWD ACROSS THE
GULF COAST STATES…

…THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE
NORTHEAST…

…CNTRL/ERN TX EWD TO GA…

12Z REGIONAL SOUNDINGS SHOWED THAT AN EML/STEEP MIDLEVEL LAPSE RATE
ENVIRONMENT REMAINS IN PLACE ACROSS A MOIST WARM SECTOR
CHARACTERIZED BY BOUNDARY LAYER DEWPOINTS IN THE UPPER 60S TO LOWER
70S. DAYTIME HEATING ALONG THE SRN FRINGE OF CONVECTIVE DEBRIS
ASSOCIATED WITH NOCTURNAL TSTM ACTIVITY SHOULD ALLOW TEMPERATURES TO
WARM INTO THE 80S AND 90S. WHEN COUPLED WITH THE HIGH MOISTURE
CONTENT AND STEEP LAPSE RATES…AIR MASS IS EXPECTED TO BECOME
MODERATELY TO STRONGLY UNSTABLE THIS AFTERNOON WITH MLCAPE VALUES
INCREASING TO 2000-4000 J/KG.

MIDLEVEL HEIGHTS ARE FORECAST TO REBOUND SLIGHTLY TODAY WITH THE
PASSAGE OF UPPER TROUGH AXIS TO THE NE. AS SUCH…TROPOSPHERIC WIND
FIELD AND LARGE-SCALE FOR ASCENT WILL CORRESPONDINGLY DIMINISH.
NONETHELESS…THE PRESENCE OF THE SYNOPTIC COLD FRONT AND
PRE-FRONTAL OUTFLOW BOUNDARIES ASSOCIATED WITH DECAYED OR ONGOING
STORMS WILL SERVE AS THE FOCUS FOR DIURNAL TSTM DEVELOPMENT. GIVEN
THE DEGREE OF INSTABILITY AND AROUND 30 KT OF DEEP WLY SHEAR…SETUP
WILL FAVOR THE DEVELOPMENT OF ORGANIZED MULTICELL CLUSTERS CAPABLE
OF DAMAGING WINDS AND HAIL. THIS THREAT WILL LIKELY CONTINUE
THROUGH THE EVENING BEFORE DIMINISHING LATER TONIGHT WITH THE LOSS
OF DAYTIME HEATING.

…NORTHEAST/MID ATLANTIC…

SHORTWAVE TROUGH AND ASSOCIATED CORRIDOR OF 12-HR HEIGHT FALLS
EXCEEDING 100-150 M AT 500 MB WILL TRANSLATE FROM THE GREAT LAKES
AND OH VALLEY NEWD THROUGH NEW ENGLAND AND THE ST. LAWRENCE VALLEY
TODAY. ASSOCIATED SURFACE LOW OVER SWRN ONTARIO AS OF 16Z WILL
CONCURRENTLY DEVELOP NEWD INTO FAR SRN QUEBEC BY 21/00Z WITH
TRAILING COLD FRONT MOVING INTO THE HUDSON AND DE RIVER VALLEYS BY
THIS TIME. WARM FRONT IS EXPECTED TO LIFT NWD THROUGH AT LEAST THE
LOWER HUDSON VALLEY BY LATE AFTERNOON/EARLY EVENING.

MORNING VISIBLE SATELLITE IMAGERY INDICATES BREAKS IN THE CLOUDS
AHEAD OF THE COLD FRONT ACROSS NY/PA WHICH SHOULD ALLOW FOR STRONGER
DIABATIC HEATING. WHEN COUPLED WITH BOUNDARY LAYER DEWPOINTS IN THE
50S…EXPECT AFTERNOON MLCAPE OF 500-1000 J/KG. LATEST MESOSCALE
AND CONVECTION-ALLOWING MODEL GUIDANCE SUGGEST THAT WEAK CONVERGENCE
ALONG THE COLD FRONT MAY LIMIT STORM COVERAGE THIS AFTERNOON INTO
EVENING. GIVEN THE STRONG WLY WIND FIELD IN PLACE…ANY STORMS THAT
CAN DEVELOP WILL BE CAPABLE OF DAMAGING WIND GUSTS AND PERHAPS A
BRIEF TORNADO.

…OK…

THE DEVELOPMENT OF A NOCTURNAL LLJ WILL SERVE TO ENHANCE LIFT AND
MOISTURE FLUX TO THE N OF SURFACE FRONT OVERNIGHT WITHIN A STEEP
MIDLEVEL LAPSE RATE ENVIRONMENT…SUPPORTING MUCAPE OF 1000-1500
J/KG. ANY TSTMS THAT CAN DEVELOP WITHIN STRENGTHENING
WAA/ISENTROPIC ASCENT REGIME WILL BE CAPABLE OF HAIL…SOME OF WHICH
MAY EXCEED SEVERE CRITERIA

Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s