DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 191624
SWODY1
SPC AC 191620

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1120 AM CDT MON MAY 19 2008

VALID 191630Z - 201200Z

...NO SVR TSTM AREAS FORECAST...

...CENTRAL U.S...

NWLY FLOW REGIME ACROSS CENTRAL U.S. BETWEEN COLD SERN CANADA VORTEX
AND STRONG WESTERN RIDGE. PROVIDED THERE IS SUFFICIENT MOISTURE
THIS PATTERN WOULD BE VERY FAVORABLE FOR SEVERE THUNDERSTORMS IN THE
MONTH OF MAY. HOWEVER GULF INFLOW IN THE SWLY FLOW AHEAD OF THE
SURFACE LOW CURRENTLY NWRN MO IS MEAGER. EVAPOTRANSPIRATION SHOULD
AID IN INCREASING LOW LEVEL MOISTURE IN THE EXPANDING WARM SECTOR
FROM LOWER MO TO TN VALLEYS TODAY...HOWEVER IT APPEARS THAT ALL THE
MODELS ARE TOO AGGRESSIVE WITH DEWPOINTS AOA 60F FORECASTED INTO SRN
MO/NRN AR BY LATER THIS AFTERNOON.

PREVIOUS OUTLOOK HAS A GOOD HANDLE ON THE EXPECTED SEVERE SCENARIO
WITH ONLY A MARGINAL THREAT TODAY GIVEN THE LIMITED THERMODYNAMIC
SUPPORT.

WITH THE SURFACE LOW NWRN MO TRACKING TOWARD THE LOWER OH VALLEY
40-50KT LOW LEVEL WSWLY JET WILL PROVIDE AREA OF WARM ADVECTION
ASCENT SPREADING EWD ACROSS MS RIVER INTO KY/TN LATER TODAY. WITH
AN ELEVATED MIXED LAYER OF 8C/KM LAPSE RATES AND STRONG VEERING
SHEAR PROFILES THE ONLY LIMIT ON SEVERE THUNDERSTORMS WILL BE THE
EXPECTED MARGINAL INSTABILITY. IF ADVECTION AND EVAPOTRANSPIRATION
RESULTS IN GREATER LOW LEVEL MOISTURE THAN NOW EXPECTED...AN UPGRADE
TO A SEVERE RISK MAY BE NEEDED IN AFTERNOON UPDATE. HOWEVER IF
MLCAPES REMAIN NEAR OR BELOW 500 J/KG AS NOW EXPECTED THEN SEVERE
THUNDERSTORMS SHOULD BE LIMITED WITH BEST AREA INTO TN VALLEY THIS
EVENING WHERE STRONG ASCENT WOULD BE LOCATED.

HAVE ALSO MAINTAINED TWO OTHER CENTRAL U.S. MARGINALLY SEVERE
THREATS.

STEEP LAPSE RATES AND INVERTED VEE SOUNDINGS IN NWLY FLOW CENTRAL
HIGH PLAINS SHOULD LEAD TO HIGH BASED THUNDERSTORMS BY MID/LATE
AFTERNOON WITH STRONG DAYTIME HEATING. GUSTY WINDS AND LOCALIZED
MARGINALLY SEVERE HAIL WILL BE POSSIBLE WITH THE STRONGER UPDRAFTS.
HOWEVER AGAIN MLCAPES SHOULD BE VERY LIMITED...GENERALLY LESS THAN
300 J/KG.

ANOTHER AREA OF A FEW STRONG STORMS THIS AFTERNOON WILL BE AHEAD OF
THE MID LEVEL IMPULSE AND 80KT JET MAX THAT IS DIVING SEWD THRU ERN
DAKOTAS. AGAIN THE LIMITED INSTABILITY/MOISTURE SHOULD CONFINE ANY
SEVERE THREAT TO A FEW LOW TOPPED UPDRAFTS ACCOMPANIED BY HAIL AND
GUSTY WINDS.

..HALES/GRAMS.. 05/19/2008

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