SWODY2
SPC AC 091723
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1223 PM CDT THU SEP 09 2010
VALID 101200Z - 111200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE LOWER MO VALLEY AND
SOUTH CENTRAL PLAINS FRIDAY AFTERNOON AND EVENING...
...SYNOPSIS...
LATE MORNING WATER VAPOR IMAGERY SHOWED A COUPLE OF SHORTWAVE
TROUGHS EMBEDDED WITHIN THE WRN TROUGH...1/ MOVING NEWD THROUGH NRN
GREAT BASIN...AND 2/ MOVING SEWD THROUGH ORE. DURING DAY 2...THE
LEAD SHORTWAVE TROUGH WILL LIFT NNEWD INTO CENTRAL CANADA EARLY IN
THE PERIOD...WHILE THE ORE SHORTWAVE TRACKS ENEWD FROM THE NRN GREAT
BASIN TO THE DAKOTAS BY 11/00Z AND INTO THE UPPER MS VALLEY BY 12Z
SATURDAY...AIDING IN THE EWD ADVANCEMENT OF THE WRN LONGWAVE TROUGH.
AN ASSOCIATED EAST-SOUTHEAST ADVANCING COLD FRONT ACROSS THE PLAINS
WILL PROVIDE A FOCUS FOR STRONG TO SEVERE TSTM DEVELOPMENT...MAINLY
ACROSS PORTIONS OF THE LOWER MO VALLEY/LOWER PORTIONS OF THE
SOUTH-CENTRAL PLAINS. MEANWHILE...A SURFACE BOUNDARY EXTENDING EWD
FROM AN AREA OF LOW PRESSURE IN WRN KS INTO CENTRAL MO TO LOWER TN
VALLEY WILL SHIFT NWD INTO LOWER MO VALLEY BY FRIDAY AFTERNOON
PROVIDING FOCUS FOR ADDITIONAL STORMS.
...LOWER MO VALLEY/SOUTH-CENTRAL PLAINS...
STRONGEST HEIGHT FALLS ARE EXPECTED ACROSS THE NRN PLAINS TO UPPER
MS VALLEY THIS FORECAST PERIOD...WITH WEAKER FALLS /30-40 METER PER
12 HR AT 500 MB/ OCCURRING FARTHER S ACROSS THE LOWER MO VALLEY
AFTER 11/00Z. EXTENSIVE CLOUD COVER IS EXPECTED ON THE COOL SIDE /E
AND N/ OF THE AFOREMENTIONED SURFACE BOUNDARIES FROM THE MID MO TO
MID MS VALLEYS. THIS FACTOR WILL TEND TO LIMIT THE NWD MOVEMENT OF
THE WARM FRONT WITH STRONGEST SURFACE HEATING LIKELY OCCURRING
ACROSS THE ERN KS/SWRN MO PORTION OF THE SLIGHT RISK AREA.
INCREASING LOW LEVEL MOISTURE /SURFACE DEWPOINTS IN THE LOWER 70S/
ACROSS THE WARM SECTOR WILL SUPPORT MODERATE-STRONG INSTABILITY
/MLCAPE 2000-3000 J PER KG/.
A DRY LINE EXTENDING SWD FROM THE KS LOW AND THE SEWD ADVANCING COLD
FRONT WILL PROVIDE THE FOCI FOR CONVECTION/TSTMS FRIDAY
AFTERNOON...ESPECIALLY AS THE COLD FRONT MERGES WITH/OVERTAKES THE
DRY LINE. THIS PROCESS SHOULD OCCUR INITIALLY OVER NERN-ERN KS AT
THE TRIPLE POINT...AND THEN SSWWD INTO OK FRIDAY EVENING/ NIGHT.
ADDITIONAL STORMS WILL BE POSSIBLE WITHIN LOW LEVEL WAA REGIME ALONG
WARM FRONT IN MO. ALTHOUGH STRONGER MID-UPPER LEVEL WINDS ARE
EXPECTED TO LAG THE COLD FRONT...SOME INCREASE IN WSWLY MIDLEVEL
WINDS ACROSS THE SLIGHT RISK AREA COMBINED WITH VERTICALLY VEERING
WIND PROFILES SUGGESTS EFFECTIVE BULK SHEAR WILL BE AROUND 40 KT.
THIS IS FAVORABLE FOR SUPERCELLS WITH A THREAT FOR STRONG/DAMAGING
WINDS...HAIL AND A TORNADO OR TWO... ESPECIALLY WITH THE INITIAL
ACTIVITY. MODELS SUGGEST STORMS COULD EVOLVE INTO A LINEAR MCS INTO
THE EVENING AS GREATER HEIGHT FALLS SPREAD INTO THE LOWER MO
VALLEY...AND ACTIVITY BACKBUILDS SSWWD INTO OK. THE SLIGHT RISK
AREA HAS BEEN EXPANDED SWD INTO NRN OK...WHERE STRONG INSTABILITY
WILL PROMOTE THE POTENTIAL FOR SEVERE STORMS AS THE COLD FRONT
ADVANCES SEWD INTO THAT REGION BY EARLY EVENING...PRIOR TO THE ONSET
OF BOUNDARY LAYER STABILIZATION.
...ERN DAKOTAS/MIDDLE MO VALLEY/UPPER MIDWEST...
A CONSIDERABLY LESSER OPPORTUNITY/DEGREE OF DESTABILIZATION IS
ANTICIPATED IN VICINITY OF THE NORTH-SOUTH ORIENTED OCCLUDING
FRONTAL ZONE...WHERE MOISTURE CORRIDOR SHOULD BE RATHER NARROW AND
LOCATED INVOF THE FRONT. NONETHELESS...A FEW EARLY DAY ELEVATED
TSTMS COULD POSE A SEVERE HAIL THREAT. ADDITIONAL STRONG/PERHAPS
SEVERE TSTM DEVELOPMENT /CAPABLE OF HAIL AND WIND/ MAY OCCUR ALONG
THE FRONT DURING THE AFTERNOON ACROSS THE ERN DAKOTAS AS STRONGER
FORCING FOR ASCENT SPREADS INTO THIS REGION WITH THE APPROACH OF NRN
GREAT BASIN SHORTWAVE TROUGH. GIVEN WEAK INSTABILITY...OVERALL
SEVERE WEATHER THREAT CONTINUES TO APPEAR TOO ISOLATED TO WARRANT
THE INCLUSION OF A CATEGORICAL SLIGHT RISK AREA. STORMS THAT DO
FORM SHOULD TEND TO BE LINE SEGMENTS...GIVEN EFFECTIVE BULK SHEAR UP
TO 40 KT ORIENTED NEARLY PARALLEL TO THE OCCLUDING FRONT.
..PETERS.. 09/09/2010
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