SWODY1
SPC AC 311949
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0249 PM CDT SUN AUG 31 2008
VALID 312000Z - 011200Z
...THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF THE ERN GREAT
BASIN AND INTERMOUNTAIN W...
...THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF THE N-CNTRL AND
NERN GULF COAST...
...THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF WRN AND CNTRL
ND...
...ERN GREAT BASIN AND INTERMOUNTAIN W...
WELL-DEFINED MID/UPPER-LEVEL TROUGH OVER THE PACIFIC NW INTO GREAT
BASIN WILL CONTINUE TO INTENSIFY THIS AFTERNOON AND TONIGHT AS
STRONG UPSTREAM JET STREAK ALONG THE PACIFIC NW COAST DIGS SEWD INTO
THE TROUGH BASE. ASSOCIATED COLD FRONT EXTENDING FROM LEE CYCLONE
OVER FAR WRN ND SWWD THROUGH W-CNTRL WY...NRN UT AND CNTRL NV WILL
SHIFT EWD IN ADVANCE OF STRENGTHENING UPPER SYSTEM.
TSTMS ARE SLOWLY INCREASING IN COVERAGE AND INTENSITY EARLY THIS
AFTERNOON ALONG FRONT OVER NERN NV/NWRN UT WITHIN A STEEP LAPSE RATE
ENVIRONMENT WITH MLCAPES APPROACHING 500 J/KG. STRENGTHENING
LARGE-SCALE FORCING FOR ASCENT COUPLED WITH ADDITIONAL BOUNDARY
LAYER HEATING/DESTABILIZATION SHOULD RESULT IN FURTHER STORM
INTENSIFICATION THIS AFTERNOON INTO EVENING OVER PORTIONS OF
NRN/CNTRL UT...SERN ID AND SWRN WY. REGIONAL VADS AND SHORT TERM
MODEL GUIDANCE SUGGEST THAT VERTICAL SHEAR ALONG FRONTAL ZONE SHOULD
CONTINUE TO STRENGTHEN AS MIDLEVEL JET STREAK ROUNDS TROUGH BASE
LATER TODAY INTO TONIGHT. AS SUCH...ENVIRONMENT WILL BE SUPPORTIVE
OF EMBEDDED SUPERCELL AND/OR BOWING STRUCTURES WITH THE THREAT FOR
DAMAGING WINDS AND LARGE HAIL.
...N-CNTRL THROUGH ERN GULF COAST...
PER LATEST NHC GUIDANCE...THE CENTER OF HURRICANE GUSTAV WILL MOVE
TO JUST OFF THE SERN LA COAST BY 01/12Z. THIS WILL RESULT IN A
STEADY INCREASE IN LOW-LEVEL SHEAR/SRH ALONG THE N-CNTRL AND NERN
GULF COAST...N-NE OF THE CYCLONE CENTER. WHILE THIS INCREASE IN
SHEAR WILL OCCUR DURING THE DIURNAL MINIMUM IN INSTABILITY OVER
LAND...A FEW OF THE LAND FALLING SPIRAL BANDS MAY CONTAIN SUPERCELLS
CAPABLE OF A COUPLE OF BRIEF TORNADOES.
IN THE INTERIM...REGIONAL RADAR IMAGERY INDICATES THAT A VIGOROUS
SPIRAL BAND CONTAINING A FEW SUPERCELLS IS SITUATED JUST OFF THE
W-CNTRL/SWRN PENINSULAR COASTS WITH ADDITIONAL CLUSTERS OF STORMS
PRESENT OVER THE FL PNHDL. OBSERVATIONAL DATA AND MODEL FORECASTS
SUGGEST THAT THE MOST FAVORABLE ENVIRONMENT FOR SUPERCELLS/TORNADOES
WILL REMAIN JUST OFF THE W COAST OF THE FL PENINSULA THROUGH
TONIGHT. NONETHELESS...A MARGINAL THREAT FOR A BRIEF TORNADO AND/OR
LOCALLY STRONG WIND GUSTS WILL EXIST WITH ANY MORE INTENSE STORMS
FROM THE FL PNHDL SWD ALONG THE WRN PENINSULAR COAST.
...NRN PLAINS...
LATEST MESOANALYSIS INDICATES A LEE CYCLONE OVER FAR WRN ND WITH
ATTENDANT COLD FRONT EXTENDING FROM N-CNTRL ND SWWD THROUGH THIS LOW
THROUGH N-CNTRL WY TO SECONDARY LOW PRESSURE OVER NERN NV. A LEE
TROUGH WAS ALSO ANALYZED FROM THE LOW SWD INTO ERN CO. THIS FRONT
WILL SLOWLY SHIFT EWD/SEWD THROUGH THE REMAINDER OF THE FORECAST
PERIOD...GRADUALLY OVERTAKING LEE TROUGH.
12Z SOUNDINGS INDICATED THE PRESENCE OF A WARM EML/STEEP LAPSE RATE
ENVIRONMENT...BUT ONLY A SHALLOW MOIST PROFILE. THESE DATA SUGGEST
THAT TEMPERATURES OF 95-100F WILL BE REQUIRED TO OVERCOME CAP AND
INITIATE DEEP...MOIST CONVECTION. DESPITE THE PRESENCE OF
INCREASING HIGH CLOUDINESS...CURRENT SURFACE OBSERVATIONS INDICATE
THAT TEMPERATURES HAVE ALREADY WARMED TO 90-95F E OF LEE TROUGH AND
S OF FRONT OVER THE WRN DAKOTAS. THUS...IT APPEARS THAT
SURFACE-BASED STORM DEVELOPMENT WILL BE POSSIBLE LATER THIS
AFTERNOON OR THIS EVENING. THIS INITIATION MAY PERHAPS BE AIDED BY
A WEAK...LEAD SHORT WAVE TROUGH NOW LIFTING NEWD THROUGH NWRN WY
INTO S-CNTRL MT.
PORTION OF FRONT OVER ND WILL LIKELY EXPERIENCE THE MOST FAVORABLE
COLLOCATION OF 40-50 KT OF EFFECTIVE BULK SHEAR AND MODERATE
INSTABILITY WHERE THE POTENTIAL WILL EXIST FOR ORGANIZED/ROTATING
STORMS CAPABLE OF DAMAGING WINDS AND LARGE HAIL. OTHER MORE
ISOLATED STORMS ARE POSSIBLE SWD ALONG LEE TROUGH...ESPECIALLY WITH
FRONTAL/TROUGH OCCLUSION TONIGHT. WHILE A FEW MARGINALLY SEVERE
STORMS ARE POSSIBLE...THE WEAKENING SHEAR WITH SWD EXTENT ALONG WITH
WEAKENING INSTABILITY SHOULD TEND TO LIMIT A MORE SUBSTANTIAL SEVERE
THREAT.
..MEAD.. 08/31/2008
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