SPC AC 171719
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1219 PM CDT SUN SEP 17 2006
VALID 181200Z - 191200Z
...NO SVR TSTM AREAS FORECAST...
...SYNOPSIS...
DEEP UPPER TROUGH/LOW ACROSS THE NATION/S MID-SECTION IS EXPECTED TO
GRADUALLY SHIFT EWD ON MONDAY AS A NEW TROUGH MOVES TOWARD THE PAC
NW COAST. SEVERAL IMPULSES /INCLUDING REMNANTS OF PAC HRCN LANE/
WILL BECOME ABSORBED INTO THE TROUGH AND EJECT NEWD THROUGH THE LWR
MS VLY. SFC FRONT FROM THE GRTLKS TO TX HAS BECOME ENTRENCHED IN
PARALLEL SWLY FLOW ALOFT AND WILL MOVE SLOWLY EWD TO LIE FROM LK ONT
SWWD THROUGH THE APPALACHIANS TO THE LWR MS VLY BY 12Z TUE.
...UPPER TX COAST NEWD TO THE OH VLY...
FETCH OF RICH MOISTURE WILL CONTINUE TO ADVECT NWD ALONG/AHEAD OF
THE COLD FRONT FROM THE TROPICAL PAC TO THE TN/OH VLYS THROUGH
MONDAY. THUS...CLOUDS AND WIDESPREAD CONVECTION CAN BE EXPECTED THE
LENGTH OF THE APPROACHING SLOW-MOVING COLD FRONT. GIVEN THE
EXPECTED LIMITED HEATING AND TROPICAL CHARACTERISTICS OF THE AIR
MASS...TROPOSPHERIC LAPSE RATES WILL BECOME RATHER WEAK. POCKETS OF
LOCAL HEATING MAY BOOST INSTABILITY ACROSS THE WRN/CNTRL GULF
COASTAL AREA...BUT EVEN HERE MLCAPES SHOULD BE AOB 1000 J/KG.
PRIND THAT MULTIPLE BANDS OF CONVECTION/TSTMS WILL ACCOMPANY THE
FRONT AND PRE-FRONTAL OUTFLOWS/CONFLUENCE ZONES MONDAY AND MONDAY
NIGHT. MODEST SWLY FLOW ALOFT WILL BOOST VERTICAL SHEAR TO SUPPORT
ORGANIZED STORMS...BUT THE AFOREMENTIONED LOW INSTABILITY/WEAK LAPSE
RATE ENVIRONMENT WILL TEND TO LIMIT THE SEVERE RISKS TO ISOLD
EVENTS. THERE MAY BE A SLIGHTLY HIGHER RISK OF ISOLD TORNADOES
ACROSS PORTIONS OF THE LWR MS VLY ALONG THE TRACK OF HRCN LANE/S
MID-LEVEL REFLECTION. LATEST NAM HAS TRENDED STRONGER WITH THIS
FEATURE AND ASSOCD LOW-LEVEL WIND FIELDS. THIS RESULTS IN A
STRONGER SFC CYCLONE ALONG THE FRONT. HOWEVER...GIVEN THAT THIS IS
A RECENT DEVELOPMENT AND GFS ONLY WEAKLY SUPPORTS SUCH A
SOLUTION...WILL REFRAIN FROM UPGRADING TO A SLGT RISK ATTM.
..RACY.. 09/17/2006
CLICK TO GET WUUS02 PTSDY2 PRODUCT
NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 0800Z
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