SPC AC 090554
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1254 AM CDT THU JUL 09 2009
VALID 101200Z - 111200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM IA/MO NEWD INTO THE GREAT
LAKES...
..SYNOPSIS...
AN UPPER TROUGH IN FAR SOUTH CENTRAL CANADA IS FORECAST TO AMPLIFY
SEWD ACROSS THE NRN PLAINS AND INTO THE WRN GREAT LAKES...
WITH A VERY LARGE UPPER HIGH ANCHORED OVER TX/OK. TIGHTENING
GRADIENT ALOFT BETWEEN THESE TWO SYSTEMS WILL RESULT IN A BROAD
SWATH OF 60-80 KT MID LEVEL WINDS SPREADING EWD IN ASSOCIATION WITH
THE UPPER TROUGH. A COLD FRONT WILL MOVE SEWD AHEAD OF THE UPPER
TROUGH AND SHOULD EXTEND FROM THE WRN U.P. SWWD INTO NWRN MO/ERN KS
AND THEN WWD INTO SERN CO.
...IA/MO NEWD INTO THE GREAT LAKES...
EVOLUTION OF SEVERE THREAT HARD TO PIN-POINT ON FRI DUE TO ONE OR
TWO MCS/S LIKELY STILL ONGOING AT THE START OF THE PERIOD ACROSS THE
UPPER MIDWEST...AND POSSIBLY IN WRN MO WITHIN ZONE OF LOW LEVEL WARM
ADVECTION...WITH A THREAT FOR HAIL. HOWEVER...AREAS THAT WARM DURING
THE MORNING AND INTO THE AFTERNOON...MODERATE TO STRONG INSTABILITY
AND STRENGTHENING WINDS ALOFT/DEEP LAYER SHEAR WILL BE FAVORABLE FOR
SUPERCELLS. THE STORM DEVELOPMENT WILL BE AIDED BY LARGE SCALE
FORCING ASSOCIATED WITH INCREASING DIFFLUENCE ALOFT SPREADING INTO
THE REGION. THIS WILL PROVIDE SUFFICIENT LIFT FOR STORMS TO DEVELOP
ALONG/AHEAD OF COLD FRONT AND ALSO ALONG REMNANT OUTFLOW BOUNDARIES
FROM MORNING CONVECTION. WHILE THE STRONG INSTABILITY AND DEEP LAYER
SHEAR WILL BE MOST SUPPORTIVE OF SEVERE HAIL...THE VERY MOIST
BOUNDARY LAYER...STRONGLY CURVED HODOGRAPHS IN THE LOWER 2KM AND
PRESENCE OF BOUNDARIES SUGGEST TORNADOES ARE ALSO POSSIBLE. AFTER
DARK...THE LOW LEVEL JET IS LIKELY TO CONGEAL STORM OUTFLOWS INTO A
LINEAR SYSTEM WITH WIND DAMAGE BECOMING THE MORE LIKELY THREAT.
..CENTRAL PLAINS...
CONVECTION MAY BE ONGOING IN THE MORNING ACROSS PORTIONS OF SD/NEB
AS WEAK IMPULSE MOVES EWD ACROSS THE CENTRAL PLAINS. ONCE THESE
STORMS WEAKEN/DISSIPATE...CONVECTIVE DEVELOPMENT WILL BE HINDERED BY
SIGNIFICANT CAPPING AS 500 MB HEIGHTS RISE ABOVE 5900M.
HOWEVER...VERY HOT SURFACE CONDITIONS SOUTH OF FRONT...TEMPERATURES
102-108 DEGREES...MAY PROVIDE DEEP ENOUGH MIXING FOR A FEW STORMS TO
DEVELOP NEAR THE BOUNDARY LATE IN THE DAY. THE VERY HIGH LFC/S
INDICATE ANY STORMS THAT DEVELOP WILL BE HIGH BASED WITH A POTENTIAL
FOR STRONG WINDS.
STORMS MAY ALSO DEVELOP ACROSS PORTIONS OF ERN WY/CO AS ELY BOUNDARY
LAYER WINDS ADVECT A VERY MOIST BOUNDARY LAYER WWD. FORCING APPEARS
WEAK AT THIS TIME...BUT SHEAR/INSTABILITY WOULD SUPPORT A SEVERE
THREAT IF STORMS DEVELOP.
...FL PENINSULA...
WEAK UPPER TROUGH WILL BE LOCATED ACROSS THE AREA WITH 500 MB
TEMPERATURES BETWEEN -8 TO -10C. WLY WINDS ABOVE THE BOUNDARY LAYER
SUGGESTS WEST COAST SEA BREEZE WILL ENHANCE THUNDERSTORMS ALONG THE
ERN PENINSULA DURING THE AFTERNOON HOURS. ALTHOUGH SHEAR WILL BE
WEAK...STRONG INSTABILITY MAY SUPPORT BRIEF SEVERE WEATHER IN A FEW
STORMS.
..IMY.. 07/09/2009
CLICK TO GET WUUS02 PTSDY2 PRODUCT
NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 1730Z
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