SPC AC 010544
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1244 AM CDT FRI MAY 01 2009
VALID 011200Z - 021200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS A LARGE PART OF THE SRN
PLNS EWD INTO THE MID-SOUTH AND OH/TN VLYS...
...SYNOPSIS...
UPR TROUGH WILL DEEPEN SLIGHTLY ACROSS THE MIDWEST...GREAT LAKES AND
NERN STATES ON FRIDAY AS THE HUDSON BAY VORTEX REPOSITIONS SWD. A
SEPARATE BELT OF MODEST FLOW WILL EXIST ACROSS THE SRN PLNS INTO THE
MID-ATLANTIC REGION. EMBEDDED CONVECTIVELY ENHANCED DISTURBANCES
WILL EXIST WITHIN THIS JET. NEXT MID-LVL SHORTWAVE TROUGH...NOW
OVER THE ERN PACIFIC BASIN...WILL QUICKLY TRANSLATE EWD...ARRIVING
INTO CA BY EARLY SATURDAY.
IN THE LWR LEVELS...SYNOPTIC CDFNT TIED TO THE AMPLIFYING NRN STREAM
UPR WAVE WILL SETTLE SEWD...REACHING NEW ENGLAND...THE OH VLY...AND
SRN PLNS STATES BY FRIDAY NIGHT. A MYRIAD OF PRE-FRONTAL OUTFLOW
BOUNDARIES WILL LIKELY EXIST THROUGHOUT THE OH/TN/LWR MS VLYS AND
SRN PLNS. A DRYLINE WILL MIX EWD INTO NWRN TX AND THE ERN EDWARDS
PLATEAU.
...SRN PLNS INTO THE MID-SOUTH...
SEVERAL TSTM CLUSTERS ARE EXPECTED TO BE ONGOING FRIDAY MORNING
ACROSS THE OZARKS AND ERN OK ALONG THE NOSE OF A VEERING LLJ.
STORMS MAY ALREADY BE PRODUCING LARGE HAIL AND GUSTY WINDS. AIR
MASS DOWNSTREAM ACROSS THE MID-SOUTH WILL LIKELY HEAT SIMILAR TO
THURSDAY AND MAY BE COMPARATIVELY MORE UNSTABLE OWING TO STEEPER
MID-LVL LAPSE RATES WITH MLCAPES OF 1500-2000 J/KG EXPECTED. THE
FLOW ALOFT WILL BE SOMEWHAT WEAK...WELL REMOVED FROM THE PRIMARY
TROUGH ACROSS THE MIDWEST. HOWEVER...CORRIDORS OF STRONGER FLOW MAY
EVOLVE WITH ANY MCV THAT MAY DEVELOP...AND GIVEN AT LEAST MODEST
BUOYANCY...MULTICELL STORMS MAY PRODUCE SPORADIC DMGG WIND AND LARGE
HAIL.
HIGHER SVR PROBABILITIES WILL DEVELOP UPSTREAM BY LATE FRIDAY AFTN
AND EVENING. TRAILING OUTFLOW FROM OVERNIGHT STORMS WILL LIKELY
STALL ACROSS SRN OK AND ADJOIN WITH A TRIPLE POINT OVER FAR SW
OK/WRN N TX. STRONG HEATING IN COMBINATION WITH MID-UPR 60S SFC DEW
POINTS AND 8-8.5 C/KM MID-LVL LAPSE RATES WILL CONTRIBUTE TO AN
EXTREME UNSTABLE ENVIRONMENT OVER SRN OK/NRN TX WITH MLCAPES OF
3000-4000 J/KG. AS SBCINH WEAKENS...INGREDIENTS WILL BE FAVORABLE
FOR RAPID TSTM INITIATION INVOF THE TRIPLE POINT AND POINTS EWD
ALONG/N OF THE OUTFLOW BOUNDARY. BULK SHEAR OF 30-35 KTS AND
EXTREME INSTABILITY WILL RESULT IN SUPERCELLS WITH VERY LARGE HAIL.
A FEW TORNADOES WILL BE POSSIBLE WITH MATURING DISCRETE CELLS ACROSS
EXTREME SWRN OK AND WRN N TX THROUGH EARLY EVENING. ANY SUPERCELL
SPLITS WILL MOVE NWD...POSSIBLY INTO CNTRL OK DURING THE EVE WITH A
LARGE HAIL THREAT.
WNWLY H5 FLOW OF 30-35 KTS AND PERSISTENT MOIST BOUNDARY LAYER
INFLOW DURING THE EVENING ALONG WITH GROWING COLD POOLS MAY LEAD TO
A FORWARD PROPAGATING MCS /BOW ECHO/ THAT DEVELOPS ACROSS SRN OK AND
N TX...WITH THE APEX FAVORING THE EVENTUAL RESTING PLACE OF THE
OUTFLOW BOUNDARY...PROBABLY INVOF THE RED RIVER FRIDAY EVENING.
DMGG WINDS AND LARGE HAIL WILL BE LIKELY. TAIL-END OF THE MCS MAY
CONTINUE TO BACKBUILD SEWD TOWARD I-20 AND MAINTAIN CYCLIC SUPERCELL
CHARACTER INTO LATE EVE WITH DMGG WINDS/LARGE HAIL AND ISOLD
TORNADOES.
ONCE THE FINAL LATITUDINAL PLACEMENTS OF THE AFOREMENTIONED
BOUNDARIES ARE BETTER KNOWN...PARTS OF THE REGION MAY NEED AN
UPGRADE TO A MDT RISK.
...OH/TN VLYS...
AN MCV IS LIKELY TO BE BORN OUT OF UPSTREAM NOCTURNAL TSTMS OVER THE
OZARKS THAT WILL TRANSLATE ENE INTO THE OH/TN VLYS FRIDAY AFTN.
DOWNSTREAM CLOUDS WILL LIKELY MITIGATE STRONG HEATING...BUT POCKETS
OF MLCAPE APCHG 750-1000 J/KG COMBINED WITH CLOSE PROXIMITY TO
STRONGER HIGH LEVEL FLOW ACROSS THE MIDWEST MAY YIELD ONE OR TWO SVR
STORMS WITH HAIL AND/OR DMGG WIND GUSTS.
...MID-ATLANTIC REGION...
MCV NOW MOVING EWD ACROSS CNTRL KY WILL ACCELERATE ENE AND SKIRT THE
MID-ATLANTIC REGION DURING PEAK HEATING. IF SUFFICIENT HEATING CAN
OCCUR...AXIS OF INSTABILITY CHARACTERIZED BY MLCAPES NEAR 500 J/KG
AND WLY BULK SHEAR AOA 35 KTS COULD BE SUFFICIENT FOR AN ISOLD SVR
STORM WITH DMGG WIND GUSTS/HAIL.
..RACY/HURLBUT.. 05/01/2009
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