DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 030546
SWODY1
SPC AC 030544

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1244 AM CDT MON SEP 03 2012

VALID 031200Z - 041200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE GULF COAST
STATES...

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE CNTRL
PLAINS AND MID MO VALLEY...

...GULF COAST STATES...
AN UPPER-LEVEL TROUGH WILL MOVE SLOWLY SEWD ACROSS THE OH AND TN
VALLEY TODAY. AT THE SFC...A PRONOUNCED CORRIDOR OF LOW-LEVEL
MOISTURE SHOULD BE IN PLACE FROM THE CNTRL GULF COAST EXTENDING NWD
ACROSS THE TN VALLEY WHERE SFC DEWPOINTS SHOULD AGAIN BE IN THE
LOWER TO MID 70S F. THE MOIST AIRMASS WILL CONTRIBUTE TO STRONG
DESTABILIZATION BY THIS AFTERNOON WITH THE MODELS FORECASTING MLCAPE
VALUES ACROSS THE CNTRL GULF COAST IN THE 2000 TO 3000 J/KG RANGE.
THIS ALONG WITH LARGE-SCALE ASCENT ASSOCIATED WITH THE UPPER-LEVEL
TROUGH SHOULD ENABLE FOR THE INITIATION OF NUMEROUS THUNDERSTORMS
ACROSS THE SLIGHT RISK AREA WITH MCS DEVELOPMENT POSSIBLE THIS
EVENING ACROSS THE REGION.

FORECAST SOUNDINGS AT 00Z/TUE ALONG THE INSTABILITY AXIS FROM ERN MS
EWD ACROSS CNTRL AL SHOW 0-6 KM SHEAR IN THE 30 TO 40 KT RANGE WITH
SOME DIRECTIONAL SHEAR BELOW 700 MB. THE SHEAR ENVIRONMENT ALONG
WITH STEEP LOW-LEVEL LAPSE RATES AND A VERY MOIST BOUNDARY LAYER
WITH PRECIPITABLE WATER VALUES OF 2.0 TO 2.5 INCHES SHOULD SUPPORT A
THREAT FOR WET DOWNBURSTS. THE THREAT MAY BE LOCALLY ENHANCED WITH
LINE SEGMENTS THAT HAVE ACCESS TO THE STRONGEST INSTABILITY.
SUPERCELL DEVELOPMENT WILL ALSO BE POSSIBLE BUT THE WARM AIR ALOFT
IS EXPECTED TO LIMIT THE HAIL THREAT.

...MID MO VALLEY/NRN AND CNTRL PLAINS...
A SUBTLE UPPER-LEVEL TROUGH WILL MOVE ACROSS THE NRN AND CNTRL
PLAINS TODAY. AT THE SFC...A COLD FRONT WILL ADVANCE SEWD ACROSS THE
DAKOTAS AND NEB. AHEAD OF THE FRONT...SFC DEWPOINTS SHOULD BE IN THE
LOWER TO MID 60S F FROM MID MO VALLEY EXTENDING NEWD ACROSS THE
UPPER MS VALLEY WHERE THE MODELS DEVELOP MODERATE INSTABILITY THIS
AFTERNOON. THUNDERSTORM DEVELOPMENT WILL BE POSSIBLE ALONG THE
INSTABILITY AXIS FROM SE NEB EXTENDING NEWD ACROSS IA INTO SRN WI
LATE THIS AFTERNOON AND ALSO ALONG THE FRONT FROM SE SD SWD INTO
NCNTRL NEB.

FORECAST SOUNDINGS AT 00Z/TUE AT OMAHA AND DES MOINES NEAR THE
GREATEST INSTABILITY SHOW 0-6 KM SHEAR IN THE 40 TO 50 KT RANGE DUE
TO SUBSTANTIAL DIRECTIONAL SHEAR BELOW 850 MB AND STRONG SPEED SHEAR
IN THE MID-LEVELS. THIS COULD SUPPORT SUPERCELL DEVELOPMENT WITH A
THREAT FOR LARGE HAIL POSSIBLE IN AREAS THAT DESTABILIZE THE MOST. A
WIND DAMAGE THREAT MAY ALSO DEVELOP AS THE CELLS MOVE SEWD ACROSS
THE SLIGHT RISK AREA EARLY THIS EVENING.

FURTHER WEST ACROSS ECNTRL NEB...A STRONG CAP IS FORECAST TO BE IN
PLACE MUCH OF THE AFTERNOON. DUE TO THE CAP...THE MAIN CONVECTIVE
FOCUS SHOULD BE ALONG THE COLD FRONT. IF STORMS CAN INITIATE ALONG
THE FRONT AND MOVE SEWD INTO ECNTRL NEB DURING THE EVENING...THEN
THE SHEAR ENVIRONMENT AND LARGE TEMP-DEWPOINTS SPREADS COULD SUPPORT
AN ISOLATED WIND DAMAGE THREAT.

...SOUTH FLORIDA...
AN UPPER-LEVEL LOW WILL APPROACH SRN FL TODAY FROM THE SOUTHEAST.
AHEAD OF THE UPPER-LEVEL LOW...MODERATE INSTABILITY IS FORECAST
ACROSS SOUTH FL WITH SFC DEWPOINTS IN LOWER 70S F. THE MOIST AND
UNSTABLE AIRMASS ALONG WITH 30 KT OF FLOW IN THE MID-LEVELS COULD BE
ENOUGH FOR A MARGINAL SEVERE THREAT AS STORMS INITIATE THIS
AFTERNOON. STEEP LOW-LEVEL LAPSE RATES MAY SUPPORT A MARGINAL THREAT
FOR DAMAGING WIND GUSTS. THE STRONGER UPDRAFTS MAY ALSO BE CAPABLE
OF PRODUCING HAIL DUE TO THE COLD TEMPS ALOFT ASSOCIATED WITH THE
UPPER-LEVEL LOW.

..BROYLES/MOSIER.. 09/03/2012

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