SWODY2
SPC AC 031718
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1218 PM CDT WED SEP 03 2008
VALID 041200Z - 051200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE MID MS/LOWER OH
VALLEYS...
...SYNOPSIS...
MODELS REMAIN IN GENERAL AGREEMENT WITH THE EVOLUTION OF UPPER FLOW
PATTERN THROUGH THURSDAY...SHOWING A BROAD LONG WAVE TROUGH
DEVELOPING FROM THE INTERMOUNTAIN WEST TO THE MS VALLEY/GREAT LAKES
REGION. A PAIR OF SHORT WAVE TROUGHS MOVING THROUGH ALBERTA AND THE
NRN HIGH PLAINS TODAY WILL PROGRESS ENEWD INTO THE UPPER MS
VALLEY/MANITOBA ON DAY 2...WHILE ANOTHER IMPULSE DIGS SEWD REACHING
THE CENTRAL ROCKIES BY 12Z FRIDAY.
...MIDDLE/LOWER MISSISSIPPI VALLEY AND LOWER OHIO VALLEY...
THERE REMAINS SOME DIFFERENCES WITH TIMING OF THE REMNANTS OF GUSTAV
AS IT BECOMES MORE EXTRATROPICAL DURING DAY 2 PERIOD... TRACKING
NEWD ALONG ERN PERIPHERY OF THE DEVELOPING CENTRAL U.S. LONG WAVE
TROUGH. DESPITE THESE TIMING DIFFERENCES...EVEN THE SLOWER UKMET
INDICATED A SSWLY LLJ /40-50 KT/ AND SWLY MID LEVEL WINDS OF 40 KT
SPREADING ACROSS THE MID MS/LOWER OH VALLEYS THURSDAY
AFTERNOON/EVENING. AHEAD OF THE REMNANT GUSTAV CYCLONE...A STALLED
FRONTAL BOUNDARY INITIALLY LOCATED NEAR THE OH RIVER VALLEY AT 12Z
THURSDAY SHOULD MOVE NWD ACROSS IL/IND/OH. THE PRESENCE OF THIS
EFFECTIVE WARM FRONT...STRONG LOW LEVEL FLOW/ SRH AHEAD OF
GUSTAV...COMBINED WITH A MOIST AIRMASS /UPPER 60S TO LOWER 70S F
SURFACE DEWPOINTS/...SUPPORT THE GREATEST RISK FOR ISOLATED
TORNADOES AND CONVECTIVELY ENHANCED WIND DAMAGE ACROSS THE MID
MS/LOWER OH VALLEYS. THIS SHOULD ESPECIALLY BE POSSIBLE DURING THE
DAYLIGHT HOURS AS INSOLATION BOOSTS NEAR-SURFACE CAPE/PARCEL
ACCELERATIONS. ALTHOUGH LOW LEVEL FLOW/SRH WILL GRADUALLY BE
WEAKENING WITH SWD EXTENT DURING THE DAY ACROSS THE MID-SOUTH/LOWER
MS VALLEY...A RISK FOR ISOLATED TORNADOES/WIND DAMAGE WILL
NEVERTHELESS CONTINUE DURING DAY 2 PERIOD.
...CENTRAL HIGH PLAINS...
HEIGHT FALLS ARE EXPECTED AHEAD OF A SHORTWAVE TROUGH APPROACHING
THE CENTRAL ROCKIES. IN RESPONSE TO THIS SYSTEM...LEE CYCLOGENESIS
WITH AN INCREASING LOW LEVEL/MOIST UPSLOPE REGIME SHOULD RESULT IN
AN UPSWING OF TSTMS ACROSS THE CENTRAL HIGH PLAINS THURSDAY
AFTERNOON/EARLY EVENING. WHILE BOUNDARY LAYER MOISTURE WILL
INITIALLY BE LIMITED GIVEN THE EARLY-STAGE UPSLOPE...INCREASING
WINDS ALOFT/VERTICAL SHEAR AND STEEP MID LEVEL LAPSE RATES WILL
SUPPORT A RISK FOR SOME SUPERCELLS WITH SEVERE HAIL AND STRONG WIND
GUSTS...ESPECIALLY ACROSS PORTIONS OF EASTERN CO/NORTHEAST NM. A
STRENGTHENING SLY LLJ/WAA REGIME EXTENDING INTO WRN KS THURSDAY
NIGHT IS EXPECTED TO RESULT IN ELEVATED TSTMS SPREADING EWD INTO WRN
KS AND PART OF THE OK/TX PANHANDLES. THE EXISTENCE OF STEEP MID
LEVEL LAPSE RATES AND A FURTHER INCREASE IN EFFECTIVE BULK SHEAR AS
A 50 KT WLY MID LEVEL JET REACHES THIS REGION LATE IN THE PERIOD
SHOULD SUPPORT A THREAT FOR ISOLATED HAIL WITH THE STRONGER
ACTIVITY.
...SOUTHEAST STATES COAST...
LATEST NHC GUIDANCE SUGGESTS A SLOWER NWWD TRACK OF TROPICAL STORM
HANNA AND SLIGHTLY EAST OF PREVIOUS FORECASTS. GIVEN THIS NEW NHC
GUIDANCE...THE FRONT RIGHT QUADRANT OF HANNA IS EXPECTED TO REMAIN
OFFSHORE OF THE SRN ATLANTIC COAST THROUGH THE DAY 2 PERIOD. FOR
THIS REASON...THE LOW SEVERE WEATHER PROBABILITIES HAVE BEEN REMOVED
FROM THIS OUTLOOK.
..PETERS.. 09/03/2008
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