SPC AC 041227
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0727 AM CDT SAT JUL 04 2009
VALID 041300Z - 051200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE LWR OH/MID MS VLY
WWD INTO THE SRN PLNS...
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE CENTRAL/NRN HIGH
PLAINS...
...MO/AR OZARKS EWD INTO THE LWR OH VALLEY...
MDT WNWLY FLOW EXTENDS FROM UPPER RIDGE POSITION PAC NW TO ACROSS
THE ROCKIES AND CENTRAL PLAINS TO MID ATLANTIC STATES AS TROUGH OVER
NERN STATES MOVES OUT TO SEA.
COMPOSITE FRONTAL/CONVECTIVE OUTFLOW BOUNDARY FROM OVERNIGHT
THUNDERSTORM ACTIVITY HAS PUSHED EWD ACROSS MID MS VALLEY EXTENDING
WSWWD ACROSS SRN MO INTO NRN OK/NERN NM.
THE 40-50KT WSWLY LOW LEVEL JET SRN PLAINS TO LWR MO VALLEY HAS
MAINTAINED THE MOIST WARM ADVECTION FOR THE EXPANSIVE AREA OF
ELEVATED CONVECTION ONGOING ALONG AND N OF SURFACE BOUNDARY FROM SRN
KS/NRN OK EWD ACROSS THE MID MS RIVER VALLEY.
WHILE WEAKENING SOME THE LOW LEVEL JET SHIFTS EWD THIS AFTERNOON
ACROSS LOWER MO INTO LOWER OH/WRN TN VALLEYS WHICH COUPLED WITH THE
50KT MID LEVEL FLOW PROVIDES ENVIRONMENT FOR A RENEWED THREAT OF
SEVERE THUNDERSTORMS. ONCE STRONG HEATING OF WARM SECTOR CAN WEAKEN
CINH AND PROVIDE MLCAPES AOA 2000 J/KG OR GREATER STORMS SHOULD
QUICKLY DEVELOP VICINITY OF SURFACE BOUNDARIES
THE PRIMARY STORM MODE ONCE INITIATION OF SURFACE CONVECTION OCCURS
WILL TRANSITION QUICKLY INTO LINEAR GIVEN THE DOMINANT WESTERLY
COMPONENT AT ALL LEVELS. WITH INITIAL DEVELOPMENT OF SURFACE BASED
STORMS...SUPERCELLS ARE POSSIBLE GIVEN THE SHEAR AND AMOUNT OF
INSTABILITY THAT WILL BE AVAILABLE. THUS EARLY IN THE SEVERE THREAT
THERE WILL BE A POTENTIAL OF ISOLATED TORNADOS WITH ANY SUPERCELL.
HOWEVER EXPECT STORMS TO CONTINUE DEVELOPING UPSCALE WITH GENERATION
OF COLD POOLS LEADING TO AN INCREASING THREAT OF DAMAGING WINDS
ACROSS MID MS VALLEY BY LATE THIS AFTERNOON. THE WIND PROBABILITIES
WERE ACCORDINGLY RAISED THIS AREA FOR THIS POTENTIAL.
...SRN PLAINS...
STRONG HEATING IS EXPECTED ALONG/S OF ADVANCING CDFNT AND OUTFLOW
BOUNDARIES TODAY. SFC DEW POINTS UPR 60S/LWR 70S COMBINED
WITH VERY HOT TEMPERATURES WILL PRODUCE MLCAPES 2000 J/KG FROM THE
TX S PLNS EWD INTO OK. SUSTAINED LOW LVL CONVERGENCE INVOF THE
BOUNDARIES WILL YIELD WDLY SCT ROBUST TSTM DEVELOPMENT...INITIALLY
ALONG OUTFLOW BOUNDARIES IN CNTRL/ERN OK...THEN ALONG THE CDFNT FROM
WRN OK/TX S PLNS LATER. THOUGH DEEP LAYER SHEAR WILL BE
COMPARATIVELY LESS ACROSS THE REGION THAN AT POINTS FARTHER
E...INVERTED-V SUB-CLOUD THERMODYNAMIC PROFILES AND MID-LVL DRY AIR
WILL AUGMENT DOWNDRAFTS RESULTING IN DMGG WIND GUSTS. THE STRONGEST
OF STORMS MAY ALSO PRODUCE LARGE HAIL...THOUGH TROPOSPHERIC
TEMPERATURES WILL BE RATHER WARM. SVR THREATS WILL CONTINUE SWD
INVOF BOUNDARIES DURING THE EVENING.
...UPSLOPE AREAS OF CENTRAL AND NRN ROCKIES...
WEAK BOUNDARY LAYER EASTERLYS/UPSLOPE WILL PREVAIL TO LEE OF ROCKIES
AS SURFACE RIDGE SHIFTS EWD ACROSS THE PLAINS. THIS MAINTAINS LOW
LEVEL MOISTURE IN PLACE AND FAVORABLE DEEP LAYER SHEAR FOR REPEAT OF
DIURNAL THUNDERSTORM DEVELOPMENT THIS AFTERNOON. VEERING LOW LEVEL
WIND PROFILES RESULT IN SFC-6KM SHEAR OF 30-40KT ERN WY/ERN
CO...MORE THAN SUFFICIENT FOR A FEW ROTATING STORMS. PRIMARY THREAT
WILL BE LARGE HAIL AND LOCAL WET MICROBURSTS WITH GREATEST POTENTIAL
ASSOCIATED WITH ANY SUPERCELL DEVELOPMENT.
STORMS WILL MOVE ONLY SLOWLY EWD AWAY FROM HIGHER TERRAIN AS AIR
MASS EWD ACROSS HIGH PLAINS WILL CONTAIN SOMEWHAT LESS INSTABILITY
AND LESS FAVORABLE LOW LEVEL SHEAR.
..HALES/GARNER.. 07/04/2009
NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1630Z
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