SPC AC 060556
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1256 AM CDT THU AUG 06 2009
VALID 061200Z - 071200Z
...THERE IS A SLGT RISK OF SVR TSTMS OVER A LARGE PART OF THE
CNTRL/NRN PLNS WEST TO THE NRN GRT BASIN/NRN INTERMOUNTAIN W...
...NRN GRT BASIN/INTERMOUNTAIN W...
ACTIVE WEATHER DAY IS EXPECTED ACROSS THE REGION THUR AND THUR NIGHT
AS THE STUBBORN UPR LOW OFF THE NRN CA CST FINALLY EJECTS NEWD.
COMBINATION OF RECYCLED LLVL MOISTURE AND ARRIVAL OF SUB-TROPICAL
MOISTURE WILL BOOST INSTABILITY VALUES...PARTICULARLY JUST AHEAD OF
THE CDFNT FROM SWRN MT SWWD INTO CNTRL NV /MLCAPES TO 1500 J PER
KG/. PV-ANOMALY ROUNDING THE BASE OF THE TROUGH NEAR SFO EARLY THUR
MORNING WILL EJECT INTO CNTRL NV THUR AFTN AND ID THUR NIGHT. THIS
WILL ENHANCE THE FRONT AND RESULT IN TSTM DEVELOPMENT OVER CNTRL/NRN
NV BY MID-AFTN. ACTIVITY WILL EXPAND NEWD TOWARD CNTRL ID AND SWRN
MT WITH TIME. WHILE ISOLD SUPERCELLS WILL BE POSSIBLE WITHIN 50-55
KTS OF BULK SHEAR...WITH TIME...SSWLY TROPOSPHERIC FLOW WILL
BACK...FAVORING MOSTLY LINE SEGMENTS. INITIAL CELLS WILL PRODUCE
LARGE HAIL AND PERHAPS AN ISOLD TORNADO...AND DMGG WINDS WILL BECOME
MORE OF A THREAT BY EVENING. SVR RISKS WILL EDGE EWD THUR NIGHT
TOWARD WY/NWRN UT AS THE UPR TROUGH ACCELERATES EWD.
...CNTRL/NRN PLNS...
A WEAK CONVECTIVELY-ENHANCED SHORTWAVE TROUGH WILL TRAVEL FROM ERN
CO ESE INTO KS THUR AFTN. IT IS UNCLEAR ON THE ULTIMATE OUTCOME OF
THE TSTM CLUSTERS ASSOC WITH THIS IMPULSE. MID-LVL CAP WILL LIKELY
CONTINUE TO BE A NEGATIVE TO SUPPORT SFC-BASED STORMS DOWNSTREAM...
THOUGH ELEVATED STORMS WITH HAIL WILL CERTAINLY BE POSSIBLE INTO
MOST OF CNTRL/SRN KS AND NRN OK.
PRIMARY SVR THREATS WILL EVOLVE LATE THUR AFTN INTO THUR NIGHT.
EXPECT WARM MID-LVL TEMPS WILL SURGE ACROSS THE HIGH PLNS DURING THE
DAY IN ADVANCE OF THE UPR TROUGH ACROSS THE GRT BASIN. AT THE SAME
TIME...LLVL MOISTURE WILL ADVECT NWWD WITH 60S SFC DEW POINTS COMMON
ALONG THE HIGH PLNS. COMBINATION OF UPSLOPE FLOW... ENHANCED ALONG
N SIDES OF LEE-SIDE CYCLONES OVER NERN WY AND NERN CO...MODEST LARGE
SCALE HEIGHT FALLS...AND STRONG HEATING ON THE MOUNTAINS WILL AID IN
TSTM INITIATION BY LATE AFTN FROM NERN CO TO SERN MT. DEEP LAYER
SHEAR OF 40-45 KTS AND H7-H5 LAPSE RATES IN EXCESS OF 7-7.5 DEG C
PER KM SUGGEST THAT SUPERCELLS WILL BE LIKELY WITH LARGE HAIL.
ONE OR MORE MCS/S WILL EVOLVE THUR NIGHT AS INITIAL ACTIVITY
CONGEALS AND MOVES TOWARD THE LWR PLNS. AGAIN...INHIBITION WILL BE
A NEGATIVE FACTOR...BUT ACTIVITY WILL LIKELY TRANSITION INTO
ELEVATED STORM CLUSTERS ALONG A 50-60 KT SLY LLJ. THIS APPEARS MOST
LIKELY ALONG/N OF THE MO RVR IN SRN ND AND MOST OF SD. LARGE HAIL
AND GUSTY WINDS WILL BE LIKELY WITH THIS ACTIVITY.
OTHER ELEVATED STORMS WILL PROBABLY DEVELOP FARTHER S ALONG ERN EDGE
OF THE SURGING CAP FROM ERN NEB SWD TO ERN KS/WRN MO LATE THUR
NIGHT. THIS ACTIVITY MAY ALSO CONTAIN AT LEAST ISOLD LARGE HAIL.
...LWR MS VLY TO UPR TX CST...
WEAK MID-LVL WAVE OVER AR EARLY THUR MORNING WILL MIGRATE SWD AND BE
IMPETUS FOR DIURNALLY-ENHANCED TSTMS...PROBABLY FAVORING AN OLD
FRONT SITUATED FROM THE LWR MS VLY NWWD INTO NRN LA. NNELY STEERING
FLOW AND STRONG DESTABILIZATION OF THE DOWNSTREAM BOUNDARY LAYER
WILL BE FAVORABLE FOR UPSCALE DEVELOPMENT INTO LINES/CLUSTERS
POSSIBLY PRODUCING ISOLD WET MICROBURSTS AS FAR SW AS THE UPR TX
CST/E TX.
...SERN STATES...
H5 SHORTWAVE TROUGH WILL MOVE ACROSS THE SERN STATES ON THUR AFTN
ACCOMPANIED BY AROUND MINUS 8 DEG C MID-LVL TEMPERATURES ATOP
BOUNDARY LAYER DEW POINTS AOA 68 DEG F. TSTMS WILL INTENSIFY INVOF
A WEAK SFC FRONT FROM SERN VA SWWD ACROSS THE CNTRL CAROLINAS AND
INTO SERN GA DURING THE MORNING. SFC-8KM SHEAR WILL BE MODEST AT
BEST...BUT STRONGER STORMS WILL BE CAPABLE OF ISOLD WET MICROBURSTS.
..RACY.. 08/06/2009
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