SPC AC 190101
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0801 PM CDT THU JUN 18 2009
VALID 190100Z - 191200Z
...THERE IS A MDT RISK OF SVR TSTMS FROM SRN MN...WRN AND SRN WI AND
EXTREME NERN IA...
...THERE IS A SLGT RISK OF SVR TSTMS FROM A PORTION OF THE SRN HIGH
PLAINS...CNTRL AND NRN PLAINS INTO THE UPPER MS VALLEY AND A PORTION
OF THE SERN STATES...
...NRN PLAINS THROUGH UPPER MS VALLEY REGION...
EARLY THIS EVENING A CONVECTIVELY ENHANCED BOUNDARY EXTENDS FROM W
CNTRL MN SWWD THROUGH CNTRL SD. CONVECTION DEVELOPING ALONG THIS
FEATURE IS IN ASSOCIATION WITH A VORT MAX MOVING EWD THROUGH THE NRN
PLAINS. A WARM FRONT EXTENDS FROM CNTRL WI WWD THROUGH S CNTRL MN.
FARTHER SOUTH A WEAKENING HYBRID OUTFLOW BOUNDARY/WARM FRONT EXTENDS
FROM N CNTRL IL WNWWD THROUGH CNTRL IA. A RESERVOIR OF VERY UNSTABLE
AIR EXISTS SOUTH OF THIS BOUNDARY FROM SRN MN THROUGH IA INTO CNTRL
IL WITH 3000-4000 J/KG MLCAPE. HOWEVER...A CAPPING INVERSION BASED
AROUND 850 MB WAS EVIDENT ON THE 00Z DAVENPORT RAOB WHICH HAS
PREVENTED THE DEVELOPMENT OF DEEP CONVECTION SO FAR. SOME POTENTIAL
STILL EXISTS FOR EXPLOSIVE SUPERCELL DEVELOPMENT CLOSER TO THE MORE
UNSTABLE BOUNDARY LAYER FROM NRN IA INTO SRN MN WHERE A ZONE OF
PERSISTENT FORCING FOR ASCENT EXISTS WHERE THE LOW LEVEL JET
INTERSECTS THE WEAKENING LOW LEVEL BAROCLINIC ZONE. SHOULD STORMS
DEVELOP THIS EVENING IN THIS REGION...THEY WOULD POSE A RISK OF VERY
LARGE HAIL AND TORNADOES. HAVE SHIFTED MODERATE RISK NWD SINCE
OVERALL CONFIDENCE IN INITIATION IS LOWER WITH SWD EXTENT INTO IA
DUE TO CAPPING INVERSION AND ONSET OF NOCTURNAL COOLING.
OTHER STORMS DEVELOPING FARTHER WEST OVER ERN SD/WRN MN ALONG
CONVECTIVE OUTFLOW BOUNDARY ACROSS ERN SD MAY EVENTUALLY EVOLVE INTO
AN MCS WITH AN INCREASING THREAT OF DAMAGING WIND AS THEY MOVE EWD
TOWARD THE MORE UNSTABLE BOUNDARY LAYER.
...SERN STATES...
SMALL CLUSTER OF SUPERCELLS ACROSS ERN VA WILL CONTINUE TO POSE A
RISK OF MAINLY ISOLATED LARGE HAIL AND DAMAGING WIND AS THEY MOVE
SEWD TOWARD NERN NC NEXT FEW HOURS. OTHER MULTICELL CLUSTERS FROM SC
SWD THROUGH VA WILL REMAIN CAPABLE OF PRODUCING ISOLATED DAMAGING
WIND NEXT COUPLE HOURS...BUT ACTIVITY SHOULD DIMINISH WITH LOSS OF
DIABATIC HEATING.
...WRN TX...
ISOLATED STRONG WIND GUSTS WILL REMAIN POSSIBLE WITH HIGH BASED
STORMS ACROSS WRN TX NEXT FEW HOURS...BUT THREAT SHOULD BEGIN TO
WANE BY LATE EVENING AS THE BOUNDARY LAYER STABILIZES.
..DIAL.. 06/19/2009
CLICK TO GET WUUS01 PTSDY1 PRODUCT
NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0600Z
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