Thursday, November 19, 2009

DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 191627
SWODY1
SPC AC 191626

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1026 AM CST THU NOV 19 2009

VALID 191630Z - 201200Z

...NO SVR TSTM AREAS FORECAST...

...ERN NC TODAY/TONIGHT...
A WEAK SURFACE WAVE LOCATED OFF CAPE FEAR THIS MORNING IS FORECAST
TO GRADUALLY MIGRATE NWD OVER FAR ERN COASTAL NC TODAY AHEAD OF AN
OPENING NEGATIVELY TILTED UPPER TROUGH OVER THE OH VALLEY REGION.
ELY COMPONENT TO LOW LEVEL FLOW WILL CONTINUE ALONG/AHEAD OF THE
SURFACE LOW WITH A PLUME OF MID 60 DEWPOINTS CONTRIBUTING TO
MARGINAL POTENTIAL INSTABILITY /GENERALLY AOB 500 J/KG MLCAPE/ WHERE
CLOUD BREAKS OCCUR. WITH THE STRONGER FORCING RELEGATED TO THE
UPPER OH VALLEY/LOWER GREAT LAKES REGIONS...FORECAST SOUNDINGS
DISPLAY A WEAKNESS IN THE FLOW IN THE LOW-MID LEVELS. AS A
RESULT...THIS MAY ONLY SUPPORT A FLEETING SUPERCELL STRUCTURE OR
TWO...WITH ONLY ISOLD CONVECTIVE COVERAGE EXPECTED.

...CNTRL TX TO COASTAL PLAIN TONIGHT...
PROGRESSIVE SRN STREAM UPPER TROUGH OVER THE SRN ROCKIES/NRN MEXICO
THIS MORNING WILL MOVE EWD TODAY/TONIGHT...AS MODEST MID-LEVEL SWLY
FLOW IS MAINTAINED DOWNSTREAM OVER PARTS OF TX. IN THE LOW
LEVELS...A MODIFIED CONTINENTAL AIR MASS OVER THE WRN GULF WILL
RETURN INLAND WITH LOWER AND MID 60 DEWPOINTS SPREADING NWD INTO THE
LOWER RIO GRANDE VALLEY AND PORTIONS OF S-CNTRL TX. ALTHOUGH THE
REGION WILL BE INITIALLY CAPPED THIS AFTERNOON...STRONGER FORCING
FOR ASCENT ATTRIBUTED PRIMARILY TO APPROACHING UPPER TROUGH FROM THE
W AND STRENGTHENING CONVERGENCE INVOF LEE TROUGH OVER CNTRL TX AND
MOIST/WAA IN THE LOW LEVELS WILL LIKELY GIVE WAY TO DEVELOPING
CLUSTERS OF STORMS ACROSS CNTRL TX SEWD TO THE MID COASTAL PLAIN
RESPECTIVELY THIS EVENING AND INTO THE OVERNIGHT HOURS. DEEP LAYER
SHEAR PROFILES WILL BE ADEQUATE FOR ORGANIZED STORMS...INCLUDING
SUPERCELLS...CAPABLE PRIMARILY OF A LOW THREAT FOR LARGE HAIL ACROSS
A SIZABLE PORTION OF CNTRL/S TX. AN ISOLD TORNADO CAN NOT BE RULED
OUT...ESPECIALLY NEAR THE LOWER COASTAL PLAIN LATE TONIGHT...WHERE
SURFACE-BASED STORMS ARE MOST LIKELY AMIDST INCREASING CLOCKWISE
CURVED HODOGRAPHS.

..SMITH/KERR.. 11/19/2009

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