SWODY1
SPC AC 241942
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0242 PM CDT WED JUN 24 2009
VALID 242000Z - 251200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM THE NRN HIGH PLAINS TO THE
MID MS VALLEY...
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE CNTRL GULF
COAST...
...NRN PLAINS/CNTRL PLAINS...
CU FIELD IS EXPANDING RAPIDLY ACROSS NERN MT/NWRN ND ALONG WRN
FRINGE OF COOLER BUBBLE HIGH. THIS ACTIVITY IS EVOLVING AS EARLIER
FORECAST AND THUNDERSTORMS WILL LIKELY DEVELOP WITHIN A FEW HOURS
ALONG STRONGEST ZONE OF LOW LEVEL CONVERGENCE NEAR THE ND BORDER.
FARTHER SOUTH...CONVECTIVE OUTFLOW HAS FORCED PRIMARY SFC BOUNDARY
SOUTH TO THE NEB/KS BORDER. A FEW THUNDERSTORMS ARE NOW DEVELOPING
ALONG THIS WIND SHIFT AND WILL LIKELY CONTINUE TO EXPAND IN AREAL
COVERAGE GIVEN THE EXTREME INSTABILITY. AS MID LEVEL FLOW VEERS
INTO THE NW AND STRENGTHENS TO AROUND 20KT THIS ACTIVITY COULD DRIFT
TOWARD I-70 ACROSS PARTS OF NERN KS/NWRN MO.
...SERN TX/LA...
PRIMARY AXIS OF HIGH PWAT...VALUES AOA 1.5 INCH...HAS BEEN FORCED SW
ACROSS THE CNTRL GULF STATES AND EXTENDS FROM SRN MS/LA INTO NERN
TX. SCATTERED THUNDERSTORMS ARE DEVELOPING WITHIN THIS ZONE OF
GREATER MOISTURE WHERE SFC TEMPERATURES HAVE WARMED TO NEAR 100F.
GIVEN THAT MID LEVEL FLOW IS ON THE ORDER OF 20KT FROM THE NE ACROSS
THIS REGION IT APPEARS THERE IS A POTENTIAL FOR AT LEAST A FEW
MULTI-CELL SEVERE STORMS CAPABLE OF GENERATING PRIMARILY DAMAGING
WINDS.
...ELSEWHERE...
ISOLATED THUNDERSTORMS HAVE DEVELOPED WITHIN VERY WARM TEMPERATURES
ACROSS MUCH OF THE COUNTRY FROM THE SRN/CNTRL ROCKIES...EAST INTO
THE LOWER OH VALLEY. ANY OF THESE STORMS COULD GENERATE A LOCALLY
DAMAGING MICRO-BURST BUT THE OVERALL ORGANIZATION SHOULD BE TOO
MARGINAL FOR A SLIGHT RISK.
..DARROW.. 06/24/2009
.PREV DISCUSSION... /ISSUED 1129 AM CDT WED JUN 24 2009/
...NRN PLAINS ACROSS THE MID MO/MID MS RIVER VALLEYS INTO THE NRN
GREAT LAKES...
SURFACE PATTERN WILL REMAIN QUITE DIFFUSE TODAY WITH RELATIVELY WEAK
LOW LEVEL FLOW PREVAILING AND RESIDUAL EFFECTS OF PRIOR MOIST
CONVECTION MUDDLING THE WARM SECTOR. HOWEVER...WLY WINDS ALOFT WILL
STRENGTHEN SOME AS FAST MOVING SHORTWAVE TROUGH FLATTENS TOP OF
RIDGE OVER THE NRN PLAINS. IN ADDITION...SURFACE FRONT/TROUGH
SHOULD BECOME BETTER DEFINED ROUGHLY N-S ACROSS THE WRN DAKOTAS THIS
AFTERNOON...WITH SURFACE THETA-E/INSTABILITY GRADIENT BECOMING
ESTABLISHED FROM NRN WI SWWD INTO SRN MN/CENTRAL SD BY LATE TODAY.
ONGOING...ELEVATED THUNDERSTORM CLUSTER OVER SRN ND/NRN SD THIS
MORNING APPEARS TO BE TIED TO FAST MOVING AREA OF ASCENT SPREADING
ENEWD TOWARDS THE RED RIVER VALLEY TODAY. TAIL END OF THIS ACTIVITY
MAY BECOME NEAR SURFACE-BASED LATER TODAY...WITH ADDITIONAL
DEVELOPMENT POSSIBLE NEAR RESIDUAL SURFACE BOUNDARIES WITHIN WARM
SECTOR AS CAP BREAKS FROM PORTIONS OF THE UP OF MI/NRN WI WSWWD INTO
THE MID MO RIVER VALLEY. DESPITE THE RELATIVELY WEAK H85
FLOW...UPSCALE EVOLUTION INTO ONE OR MORE SEVERE MCS/S CAN BE
EXPECTED THROUGH THE LATE AFTERNOON/EVENING GIVEN FEED OF EXTREME
INSTABILITY AND MODERATE WLY FLOW ALOFT. LARGE HAIL AND DAMAGING
WINDS WILL BE PRIMARY THREATS...ALTHOUGH AN ISOLATED TORNADO CANT BE
RULED OUT. MORNING MODELS SUGGEST EVOLUTION INTO ONE OR TWO SEVERE
MCS/S POSSIBLE MOVING SEWD ACROSS THE MID MS RIVER VALLEY THIS
EVENING/OVERNIGHT...WITH ANOTHER EVOLVING/PERSISTING AHEAD OF NRN
STREAM IMPULSE AND ASSOCIATED FRONT INTO THE WRN/NRN GREAT LAKES BY
25/12Z.
ROBUST DEVELOPMENT IS ALSO EXPECTED DURING THE LATE AFTERNOON ALONG
SURFACE FRONT/TROUGH OVER WRN ND/NWRN SD WITHIN AXIS OF MODERATE
INSTABILITY AHEAD OF STRONGER NRN STREAM IMPULSE
MOVING OUT OF THE NRN ROCKIES. THIS REGIME APPEARS FAVORABLE FOR
SUPERCELLS AND POSSIBLY A FEW TORNADOES THIS AFTERNOON...WITH
ADDITIONAL THREAT OF ISOLATED VERY LARGE HAIL. THESE STORMS MAY
WEAKEN DURING THE EVENING WITH EWD EXTENT AS THEY SHIFT EAST OF
FAIRLY NARROW INSTABILITY AXIS INTO CENTRAL/ERN ND.
...CENTRAL GULF COAST...
SEASONABLY STRONG NNELY FLOW ALOFT WILL REMAIN IN PLACE OVER THIS
REGION BETWEEN VERY STRONG UPPER HIGH OVER THE SRN PLAINS AND TROUGH
OFF THE EAST COAST. SURFACE FRONT NOW FROM THE SRN APPALACHIANS
INTO THE MID SOUTH SHOULD SHIFT SWD THROUGH THE DAY AND...ALONG WITH
GULF BREEZE...MAY FOCUS LATE DAY THUNDERSTORMS WITHIN VERY UNSTABLE
AIR MASS. OVERALL SETUP APPEARS FAVORABLE FOR STRONG/SEVERE
DOWNBURSTS GIVEN VERY DRY MID LEVEL AIR ATOP LARGE LOW LEVEL THETA-E
VALUES...WITH ADDITIONAL POTENTIAL FOR CLUSTERING OR LINEAR
ORGANIZATION AS ACTIVITY MOVES SSWWD THROUGH THE EVENING GIVEN
MODEST DEEP LAYER SHEAR.
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