Wednesday, September 19, 2007

DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 191632
SWODY1
SPC AC 191630

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1130 AM CDT WED SEP 19 2007

VALID 191630Z - 201200Z

..THERE IS A SLGT RISK OF SVR TSTMS THIS AFTERNOON/EVENING ACROSS
W/NW KS...

..CENTRAL HIGH PLAINS THIS AFTERNOON/EVENING...
A MORE AMPLIFIED PATTERN IS EVOLVING OVER THE CONUS AS A DEEP MID
LEVEL LOW DIGS SWD ALONG THE NRN/CENTRAL CA COAST...AND A POSITIVE
TILT RIDGE PERSISTS FROM TX TO THE OH VALLEY. A SHORTWAVE TROUGH
AND ASSOCIATED SURFACE CYCLONE INVOF LAKE SUPERIOR WILL CONTINUE TO
ACCELERATE NEWD ACROSS ONTARIO TO WRN QUEBEC...WHILE A TRAILING COLD
FRONT MOVES SEWD ACROSS THE GREAT LAKES AND WEAKENS. THE WRN
PORTION OF THIS FRONT WILL STALL TODAY JUST S OF I-70 ACROSS
KS/MO...AND THEN BEGIN TO REFORM NWD TONIGHT ACROSS NEB/SD IN
RESPONSE TO LEE CYCLOGENESIS ACROSS THE NRN HIGH PLAINS AND THE
DEVELOPMENT OF A 50 KT SLY LLJ.

BOUNDARY LAYER DEWPOINTS IN THE MID-UPPER 60S ARE PRESENT ALONG AND
S OF THE SURFACE FRONT IN KS/OK...AND VISIBLE SATELLITE IMAGERY
SUGGESTS THAT SUBSTANTIAL SURFACE HEATING WILL OCCUR S OF THE FRONT
ACROSS SW KS. AFTERNOON SURFACE TEMPERATURES AOA 80 F WILL RESULT
IN MLCAPE VALUES OF 1500-2000 J/KG WITH MINIMAL CONVECTIVE
INHIBITION...THUS WIDELY SCATTERED THUNDERSTORMS MAY DEVELOP IN THE
ZONE OF ASCENT ALONG THE SURFACE FRONT THIS AFTERNOON/EVENING ACROSS
W/NW KS. NW KS WILL BE ON THE SERN FRINGE OF THE STRONGER MID-UPPER
SWLY FLOW...THOUGH 50+ KT FLOW IN THE 400-250 MB LAYER AND SELY
SURFACE WINDS/VEERING LOW-LEVEL PROFILES WILL RESULT IN SUFFICIENT
VERTICAL SHEAR FOR SUPERCELLS. A TORNADO CANNOT BE RULED OUT WITH
SUPERCELLS ALONG THE FRONT GIVEN THE MODEST LOW-LEVEL
MOISTURE/SHEAR...BUT LARGE HAIL AND ISOLATED DAMAGING GUSTS WILL BE
THE PRIMARY SEVERE THREAT.

..DAKOTAS LATE TONIGHT...
OVERNIGHT...A STRENGTHENING SLY LLJ WILL RESULT IN LOW-LEVEL WAA AND
MOISTURE TRANSPORT FROM KS/NEB NWD TO THE DAKOTAS. MUCAPE VALUES OF
1000-2000 J/KG WILL BE POSSIBLE OVER THE DAKOTAS FROM 06-12Z...WHEN
ELEVATED THUNDERSTORM DEVELOPMENT WILL BECOME MORE PROBABLE IN
CONJUNCTION WITH THE MOIST WAA PATTERN AND THE RIGHT ENTRANCE REGION
OF THE UPPER JET OVER MANITOBA/ONTARIO. THE DEGREE OF INSTABILITY
AND EFFECTIVE BULK SHEAR MAY SUPPORT ISOLATED LARGE HAIL FROM
06-12Z.

..N/NE FL...
THE SUBTROPICAL LOW CONTINUES TO DEVELOP OVER SW FL IN THE MID
LEVELS...WITH SEVERAL EMBEDDED LOW-LEVEL CIRCULATION CENTERS.
ENHANCED LOW-LEVEL FLOW/SHEAR ACROSS N FL...INVOF OF MID LEVEL DRY
SLOT...MAY SUPPORT A MARGINAL SUPERCELL RISK THIS AREA TODAY INTO
TONIGHT.

.THOMPSON/JEWELL.. 09/19/2007

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