SPC AC 131223
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0723 AM CDT MON JUL 13 2009
VALID 131300Z - 141200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM THE NRN/CENTRAL HIGH
PLAINS AHEAD ACROSS THE DAKOTAS/NEB...
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE SRN AND
CNTRL PLAINS...OZARKS AND TN VALLEY...
...THERE IS A SLGT RISK OF SVR TSTMS OVER CENTRAL/ERN NC...
...HIGH PLAINS EWD ACROSS THE NRN/CENTRAL PLAINS...
UNSEASONABLY STRONG SHORTWAVE TROUGH DRIVING EWD INTO THE NRN
ROCKIES THIS MORNING WILL SHIFT STRONG MID LEVEL HEIGHT FALLS INTO
THE NRN/CENTRAL PLAINS THROUGH TONIGHT AHEAD OF IT. ATTENDANT 50-60
KT SWLY MID LEVEL JET WILL LIKEWISE OVERSPREAD THE NRN HIGH PLAINS
THIS AFTERNOON. THIS WILL OCCUR ATOP TIGHTENING LOW LEVEL GRADIENT
BETWEEN APPROACHING COLD FRONT AND STOUT HIGH PRESSURE HOLDING OVER
THE UPPER MS RIVER VALLEY/GREAT LAKES...WITH STRONG SELY LLJ
DEVELOPING BY LATE IN THE DAY ACROSS THE WRN DAKOTAS. SEVERAL
ROUNDS OF SLIGHTLY ELEVATED STORMS ARE EXPECTED TO PERSIST AND SHIFT
ESEWD ACROSS THE NRN PLAINS TODAY AHEAD OF THIS IMPULSE...WITH
ISOLATED SEVERE AS DEEP LAYER SHEAR SUPPORTS ORGANIZED ACTIVITY.
PRIMARY THREAT IS EXPECTED TO OCCUR IN WAKE OF THIS ACTIVITY OVER
PORTIONS OF MT ESEWD INTO THE CENTRAL HIGH PLAINS LATER TODAY.
SETUP WILL BECOME QUITE FAVORABLE FOR SEVERE THUNDERSTORMS ACROSS
THIS REGION THROUGH THE EVENING GIVEN INTENSE UPPER SYSTEM AND
SUBSTANTIAL SHEAR. ATTM...UNCERTAINTIES REGARDING COVERAGE/INTENSITY
OF EARLY DAY STORMS/CLOUDS WARRANTS LEAVING OUTLOOK AS A SLGT.
HOWEVER...UPGRADE TO MDT MAY BE NEEDED IN LATER OUTLOOKS SHOULD IT
BECOME MORE APPARENT SUFFICIENT INSTABILITY WILL MATERIALIZE FOR A
WIDESPREAD EVENT. REGARDLESS...FORECAST SOUNDINGS REMAIN VERY
FAVORABLE FOR SUPERCELLS AND POSSIBLE BOWING COMPLEXES...INCLUDING
THE POTENTIAL FOR TORNADIC SUPERCELLS ESPECIALLY NEAR SURFACE LOW
FORECAST TO OVERSPREAD NWRN SD. LARGE HAIL...SOME
SIGNIFICANT...WILL LIKELY BE PRIMARY SEVERE THREAT THROUGH THE
PERIOD WITH ELEVATED COMPLEXES SPREADING EWD ALONG VEERING LLJ
ACROSS THE NRN PLAINS TONIGHT. IN ADDITION...SEWD MOVING BOW ECHO
SYSTEMS MIGHT EVOLVE DURING THE EVENING AND PERSIST OVERNIGHT ALONG
GRADIENT OF STEEP LOW LEVEL LAPSE RATES/INVOF WARM FRONT TOWARDS THE
CENTRAL PLAINS.
...SRN KS/NRN OK INTO THE CENTRAL GULF COAST STATES...
OUTLOOK ACROSS THIS REGION REMAINS QUITE MESSY THIS MORNING WITH
EXTENSIVE ACTIVITY PERSISTING FROM THE OZARK PLATEAU SEWD INTO THE
CENTRAL AL. THIS SHOULD SUPPORT A SLIGHT SSWWD PUSH TO EFFECTIVE
SURFACE COLD FRONT AS COMPARED TO THE PAST FEW DAYS...ALTHOUGH WRN
END OVER NWRN OK/SWRN KS MIGHT BE SHIFTED SLIGHTLY NWD ONCE AGAIN BY
EXCESSIVE HEATING OVER THE SRN PLAINS. SEVERE THREAT FROM THE MID
SOUTH SEWD CAN BE EXPECTED WITH POCKETS OF HEATING INCREASING LOW
LEVEL LAPSE RATES AHEAD OF SEMI-ORGANIZED CONVECTIVE CLUSTERS
SHIFTING SSEWD THROUGH THE DAY. SOME UNCERTAINTY REMAINS REGARDING
DIURNAL DEVELOPMENT OVER WRN PORTION OF THIS FRONT...ALTHOUGH HIGH
RES AND OPERATIONAL WRF INDICATE AT LEAST ISOLATED SEVERE THREAT
COULD DEVELOP BY THE EARLY EVENING.
...NC...
WV IMAGERY INDICATES SHORTWAVE TROUGH APPROACHING THE ERN CAROLINAS
ALREADY THIS MORNING...SUPPORTING CLUSTER OF STRONG TO SEVERE TSTMS
ACROSS CENTRAL NC AT DAYBREAK. HEATING THIS MORNING SHOULD BE
HINDERED BY EARLY CLOUDS...HOWEVER SUFFICIENT HEATING FOR MODEST
SURFACE-BASED INSTABILITY SHOULD DEVELOP AND INCREASE THE POTENTIAL
FOR DAMAGING WINDS/HAIL. DEEP LAYER SHEAR FROM 35-45 KT MAY SUSTAIN
LINEAR COMPLEX ALREADY UNDERWAY EWD ACROSS ERN NC THROUGH THE EARLY
AFTERNOON...WITH POTENTIAL FOR ADDITIONAL DEVELOPMENT POSSIBLE AHEAD
OF APPROACHING SHORTWAVE TROUGH.
...SOUTHEAST...
A FEW SEVERE STORMS WILL BE POSSIBLE ACROSS PORTIONS OF GA AND SC
WHERE STRONG INSTABILITY AND ABUNDANT LOW-LEVEL MOISTURE WILL BE IN
PLACE AHEAD OF SWD SAGGING SURFACE COLD FRONT. HOWEVER...THE
POTENTIAL SEVERE THREAT SHOULD REMAIN MARGINAL DUE TO WEAKER
VERTICAL SHEAR IN THIS AREA.
...ME...
MOSTLY CLEAR SKIES SHOULD SUPPORT MARGINAL INSTABILITY TODAY UNDER
POCKET OF COLD MID LEVEL TEMPERATURES FORECAST TO OVERSPREAD
PORTIONS OF ME. SURFACE CONVERGENCE WILL BE WEAK...ALTHOUGH WIDELY
SCATTERED LOW-TOPPED TSTM DEVELOPMENT SHOULD OCCUR WITH POTENTIAL
FOR MARGINALLY SEVERE HAIL AND STRONG WINDS WITH THE STRONGER CORES.
..EVANS/HURLBUT.. 07/13/2009
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NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1630Z
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