SPC Tornado Probablities
SREF Significant Tornado Index >3 effective 10 p.m.
SREF Significant Tornado Index >3 effective at 1 a.m.
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1020 AM CST TUE DEC 08 2009
VALID 081630Z - 091200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE LOWER MS VALLEY/MID
SOUTH INTO CENTRAL...
...LOWER MS VALLEY...
POWERFUL S/WV AND ASSOCIATED 150KT POLAR JET WILL RAPIDLY TRAVERSE
THE CENTRAL U.S. THIS FORECAST PERIOD MOVING FROM CURRENT LOCATION
SRN ROCKIES TO OH VALLEY BY WED AM. THE DEEP SURFACE LOW OVER
CENTRAL ROCKIES WILL QUICKLY REDEVELOP INTO LOWER MO VALLEY THIS
EVENING. THE STRONG ASCENT AND VERY FAVORABLE SHEAR PROFILES WILL
QUICKLY DEVELOP EWD ACROSS SRN/CENTRAL PLAINS INTO LOWER MS VALLEY
BY LATER THIS AFTERNOON AND EVENING.
THE AIR MASS STILL REMAINS A LIMITING FACTOR FOR UPGRADING THE RISK
OVER SRN MS VALLEY...HOWEVER WITH THE LOW LEVEL JET INCREASING TO
50PLUS KT THIS AFTERNOON AND RAPID PRES FALLS AHEAD OF DEVELOPING
SURFACE LOW ACROSS LWR MO VALLEY...NOW EXPECT AT LEAST MID 60S
DEWPOINTS TO MOVE INLAND TO AT LEAST CENTRAL MS/AL BY LATER THIS
AFTERNOON AND EVENING.
40-50KT OF SFC-1KM SHEAR COUPLED WITH DEVELOPMENT OF LARGE
HODOGRAPHS WITH APPROACH OF THE INTENSE S/W AND ITS JET MAX WILL
PROVIDE MORE THAN SUFFICIENT KINEMATICS TO SUPPORT DEVELOPMENT OF
SUPERCELLS AND POSSIBLE TORNADOES.
GIVEN THE UNCERTAINTY OF DEVELOPMENT OF CAPE NO GREATER THAN 1000
J/KG IN WARM SECTOR AT THIS TIME WILL INCREASE PROBABILITIES OF
ISOLATED STRONG TORNADOES...MOST LIKELY IN THE ENHANCED SURFACE
CONVERGENCE VICINITY OF THE WARM FRONT MOVING INLAND SRN MS AND INTO
SRN AL BY THIS EVENING...BUT WITHHOLD UPGRADING THE RISK.
...COASTAL CAROLINAS INTO SERN VA...
OVERALL TRANSITION TO SSWLY FLOW FROM THE SRN/CENTRAL APPALACHIANS
EWD DURING LATTER HALF OF PERIOD SHOULD ALLOW MODIFIED BOUNDARY
LAYER TO OVERSPREAD THIS AREA OVERNIGHT. WHILE THE GREATER AIR MASS
DESTABILIZATION IS FORECAST TO REMAIN CONFINED TO THE COASTS...IT
DOES APPEAR THAT SUFFICIENT INSTABILITY MAY BE PRESENT TO SUPPORT
THE DEVELOPMENT OF ISOLATED/SCATTERED NOCTURNAL STORMS WITHIN
STRENGTHENING WAA REGIME...ESPECIALLY INVOF AND EAST OF COASTAL
FRONT. ALTHOUGH LOW AND DEEP LAYER SHEAR WILL BECOME QUITE
STRONG...OVERALL INSTABILITY REMAINS WEAK AT BEST WITH NEAR MOIST
ADIABATIC LAPSE RATES EVIDENT ON FORECAST SOUNDINGS. EXPECT A FEW
ROTATING UPDRAFTS WILL EVOLVE OVERNIGHT WITH AT LEAST LOW
PROBABILITY THREATS OF STRONG/DAMAGING WINDS AND POSSIBLY A BRIEF
TORNADO. HOWEVER...QUESTIONABLE INSTABILITY MAY TEND TO LIMIT
OVERALL SEVERE THREAT.
..HALES.. 12/08/2009
CLICK TO GET WUUS01 PTSDY1 PRODUCT
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