SPC AC 211245
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0745 AM CDT TUE OCT 21 2008
VALID 211300Z - 221200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PORTIONS OF THE
CNTRL/SRN PLNS...
...SYNOPSIS...
THE UPR TROUGH MOVING INTO THE NRN INTERMOUNTAIN WEST THIS MORNING
IS EXPECTED TO SIGNIFICANTLY AMPLIFY AS IT MOVES ACROSS THE ROCKIES
AND INTO THE CNTRL/NRN PLNS BY TONIGHT. LEE CYCLOGENESIS OCCURRING
OVER SE MT WILL INTENSIFY THIS AFTN WITH THE LOW DEVELOPING SEWD
ALONG THE HIGH PLNS. AN ATTENDANT CDFNT WILL STRENGTHEN AND SURGE
SEWD THROUGH THE PLNS...REACHING THE CNTRL DAKS...CNTRL NEB AND SERN
CO BY EARLY EVENING. MEANWHILE...A WEAKER FRONT SITUATED FROM THE
OZARKS TO THE TX PNHDL WILL REDEVELOP NWD INTO KS BY EARLY TONIGHT.
...CNTRL/SRN PLNS...
12Z SOUNDINGS/GOES PWAT SENSORS SUGGEST THAT A MODESTLY MOIST AIR
MASS /SFC DEW POINTS IN THE LWR 50S AND PWATS OF 3/4-1 INCH/ WAS IN
PLACE ALONG/S OF THE SRN PLNS FRONT. STRENGTHENING SLY FLOW IN
ADVANCE OF THE APCHG ROCKIES SYSTEM WILL TRANSPORT THIS MOISTURE NWD
BENEATH THE ERN FRINGE OF STEEP MID-TROPOSPHERIC LAPSE RATES
EMANATING FROM THE SRN PLATEAU. THE RESULT WILL BE FOR A MODEST
DESTABILIZATION OF THE COLUMN WITH MLCAPES OF 500-1000 J PER KG FROM
SWRN NEB SWD INTO THE TX PNHDL BY MID-AFTN.
RAPID MASS ADJUSTMENTS WILL LIKELY COMMENCE BY MID-AFTN AS STRONGLY
DIVERGENT UPR JET EXIT REGION DIGS INTO THE CNTRL HIGH PLNS.
LOW/MID-LVL FRONTOGENETIC RESPONSE AND AFOREMENTIONED INSTABILITY
WILL CONTRIBUTE TO VIGOROUS TSTM DEVELOPMENT BY LATE AFTN/EARLY EVE
ALONG THE CDFNT OVER THE CNTRL HIGH PLNS. FCST SOUNDINGS EXHIBIT A
LARGELY ANAFRONTAL TYPE OF AIRFLOW WHICH SHOULD RESULT IN A LARGER
SCALE CONVECTIVE BAND NEAR/SLIGHTLY IN WAKE OF THE FRONT. STRONG
ISALLOBARIC FORCING AND LIKELY GROWING STORM-SCALE COLD POOLS WILL
BOOST RISKS FOR DMGG WIND GUSTS ALONG WITH THE THREAT FOR HAIL. SVR
THREATS WILL CONTINUE SEWD THROUGH WRN/CNTRL KS INTO THE TX/OK
PNHDLS AND THE WRN HALF OF OK OVERNIGHT.
ANOTHER CLUSTER OF TSTMS WILL LIKELY INCREASE TODAY FARTHER TO THE E
OVER PORTIONS OF KS/OK. SATL DEPICTS A WEAKER SUBTROPICAL IMPULSE
MIGRATING TOWARD THE TX PNHDL/OK THIS MORNING. STORMS DEVELOPING IN
ASSOCIATION WITH THIS FEATURE WILL LIKELY FOCUS ALONG/N OF THE
RETREATING BOUNDARY AND EXPAND ACROSS THE LWR MO VLY TONIGHT ALONG
THE STRENGTHENING AND BROAD SLY LLJ AXIS. MID-LVL LAPSE RATES WILL
BE COMPARATIVELY WEAKER THAN FARTHER TO THE W...REDUCING THE RISK
FOR WIDESPREAD SVR WEATHER. HOWEVER....LOW-LVL SHEAR INVOF THE
RETREATING BOUNDARY AND SOME INCREASE IN DEEPER LAYER SHEAR WILL
INCREASE THE RISK FOR EMBEDDED SUPERCELL STRUCTURES WITH HAIL...DMGG
WIND GUSTS AND PERHAPS A BRIEF TORNADO ACROSS NRN OK/SRN KS LATE
AFTN/EARLY EVE. OTHERWISE...ACTIVITY THAT DEVELOPS NEWD TOWARD THE
LWR MO VLY WOULD MOSTLY BE AN ISOLD HAIL/GUSTY WIND THREAT.
..RACY/HURLBUT.. 10/21/2008
CLICK TO GET WUUS01 PTSDY1 PRODUCT
NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1630Z
|
