SWODY1
SPC AC 271257
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0757 AM CDT WED AUG 27 2008
VALID 271300Z - 281200Z
...THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF THE CAROLINAS AND
VA...
...THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF THE MID MO AND
UPR MS VLYS...
...SYNOPSIS...
AMPLIFIED PATTERN WILL PERSIST OVER THE NRN TIER AND SRN CANADA THIS
PERIOD....WHILE WEAK TO VERY WEAK FLOW REGIME CONTINUES AT LWR
LATITUDES. INITIAL POTENT SHORTWAVE TROUGH NOW OVER MB/MN WILL
CONTINUE RAPIDLY NNE TO WRN HUDSON BAY AS A SERIES OF WEAKER
DISTURBANCES UPSTREAM ACROSS THE NRN RCKYS AND PACIFIC NW REINFORCE
BROADER CYCLONIC FLOW OVER THE NRN PLNS. FARTHER E...BLOCK OVER
QUEBEC AND CLOSED LOW S OF THE MARITIME WILL COMPLICATE THE NEWD
ADVANCE OF T.D. FAY/S REMNANTS ACROSS THE OH VLY AND SRN MID
ATLANTIC REGION.
...CAROLINAS/SRN VA/SRN WV...
MAJOR PORTION OF WHAT WAS LEFT OF THE MID TROPOSPHERIC CIRCULATION
OF T.D. FAY IS MOVING NE ACROSS WRN VA/NC ATTM. SATELLITE DATA
SUGGEST THE VORT LOBE WILL CONTINUE TO ELONGATE/WEAKEN AS IT MOVES
CLOSER TO DEVELOPING BLOCK OVER THE NERN STATES. A MID LVL WARM
POCKET EXTENDS W AND SW FROM THE VORT LOBE TO AN UPSTREAM MID
LATITUDE IMPULSE OVER MO. ALL OF THESE FEATURES EXPECTED TO
MAINTAIN WEAK CLOSED LOW OVER OH TODAY...AND MODEST SWLY MID LVL
FLOW ACROSS VA AND THE CAROLINAS. HOWEVER...AT LWR LVLS...ABOVE
SETUP LIKELY WILL SUPPORT ONLY MINIMAL FURTHER NWD ADVANCE OF SRN NC
W/E WARM FRONT.
CURRENT BAND OF STORMS OVER CNTRL AND SRN NC APPEARS TO BE
ASSOCIATED WITH LEAD VORT LOBE MENTIONED ABOVE. THE STORMS SHOULD
CONTINUE NE INTO INCREASINGLY UNSTABLE AIR ALONG AND S OF WARM FRONT
OVER ERN NC THROUGH EARLY AFTN. ALTHOUGH MAGNITUDE AND DIRECTIONAL
COMPONENT TO SHEAR IN THIS REGION IS LESS RELATIVE TO THAT WHICH
EXISTED IN RECENT DAYS IN GA AND AL...IT WILL BE SUFFICIENT TO
ENHANCE LOW LVL STORM ROTATION AND POSE A RISK FOR ISOLD TORNADOES
GIVEN EXPECTED SFC HEATING AND RICH MOISTURE INFLOW. OTHER STORMS
MAY FORM WITH SFC HEATING IN WAKE OF VORT LOBE FROM WRN/CNTRL NC
SEWD ALONG LOW LVL CONFLUENCE ZONE INTO SC. WARM MID LVL
TEMPERATURES WILL...HOWEVER...LIKELY TEMPER THE STRENGTH/LONGEVITY
OF ANY SUCH CONVECTION.
...UPPER MIDWEST/MIDDLE MISSOURI VALLEY/CENTRAL PLAINS...
AS THE LEAD SHORTWAVE TROUGH EJECTS NE INTO CANADA TODAY...
ASSOCIATED COLD FRONT SHOULD CONTINUE E/SE ACROSS MN/ERN SD AND NEB.
ONGOING STORM CLUSTERS OVER MN/IA/ERN NEB SHOULD WEAKEN LATER THIS
MORNING. ADDITIONAL TSTM DEVELOPMENT/INTENSIFICATION SEEMS LIKELY
THIS AFTN AND...ESPECIALLY...EARLY TONIGHT. ALONG WITH
MOIST/UNSTABLE AIR /WITH SBCAPE OF 1500-2500 J PER KG/...
DEVELOPMENT WILL BE FOSTERED BY ARRIVAL OF LARGE SCALE ASCENT
ASSOCIATED WITH SHORTWAVE IMPULSE NOW IN THE NRN RCKYS. APPROACH OF
THIS DISTURBANCE MAY CAUSE COLD FRONT TO TEMPORARILY STALL ACROSS
NRN NEB...SE SD...NW IA...AND SRN MN LATER TODAY...WITH THE FRONT
SERVING AS THE PRIMARY FOCUS FOR LOW LVL UPLIFT.
ALTHOUGH THE STRONGEST FLOW ALOFT WILL ONCE AGAIN EXIST N AND W OF
THE FRONT...AMPLE /35-40 KT/ DEEP WLY SHEAR WILL BE PRESENT NEAR THE
BOUNDARY FOR SUPERCELLS AND OTHER FORMS OF SUSTAINED STORMS.
OVERALL...SVR HAIL AND WIND WILL BE THE PRIMARY THREATS...ALTHOUGH
TORNADOES CANNOT BE RULED OUT DURING THE INITIAL STAGES OF
DEVELOPMENT. THE STORMS LIKELY WILL GROW INTO ONE OR MORE CLUSTERS
LATE TONIGHT/EARLY THURSDAY. THESE COULD BOTH FORWARD-PROPAGATE E
INTO WI...AND BACK-BUILD/REGENERATE ACROSS SRN SD...SRN MN...NRN IA
AND NE NEB.
...AZ/LWR CO VLY...
MODERATE MID LVL ENE FLOW ALREADY PRESENT /PER FGZ RAOB/ WILL
INCREASE TO AROUND 30 KTS OVER AZ AND THE LWR CO VLY TODAY AS UPR
RIDGE ELONGATES INTO REGION ON SRN SIDE OF NRN RCKYS TROUGH. AMPLE
HEATING/MOISTURE SHOULD EXIST TO ALLOW STORMS TO FORM ALONG THE RIM
AND CERTAINLY OVER THE SRN THIRD OF THE STATE. HOWEVER... PRESENCE
OF SLOW SE-MOVING UPR TROUGH MAY COMPLICATE PATTERN OF CONVECTIVE
DEVELOPMENT...POTENTIALLY LESSENING CHANCES OVER NRN SECTIONS. AT
ANY RATE...OVERALL SETUP SUGGESTS AN UPSWING IN ACTIVITY OVER AT
LEAST CNTRL/SRN AZ RELATIVE TO YESTERDAY. INCREASING MID LVL FLOW
WILL ENHANCE STORM PROPAGATION FROM THE RIM SW TOWARD THE LWR
DESERTS...AND THE POTENTIAL FOR DMGG OUTFLOW WINDS.
..CORFIDI/BRIGHT.. 08/27/2008
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