SPC AC 231706
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1206 PM CDT WED APR 23 2008
VALID 231630Z - 241200Z
...THERE IS A MDT RISK OF SVR TSTMS ARTS OF WRN OK/NWRN TX INTO
CENTRAL OK/N-CENTRAL TX...
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS A LARGE PART OF THE SRN
PLAINS/KS INTO THE CENTRAL HIGH PLAINS...
...SYNOPSIS...
LATE MORNING WV IMAGERY DEPICTS A WELL-DEFINED SHORTWAVE TROUGH
EJECTING NEWD ACROSS ERN NM AND ANOTHER SPREADING ACROSS THE GREAT
BASIN. BOTH OF THESE FEATURES ARE EXPECTED TO SUPPORT SEVERE
THUNDERSTORM POTENTIAL OVER PORTIONS OF THE GREAT PLAINS DURING THE
PERIOD. SURFACE PATTERN REMAINS COMPLEX OVER THE SRN PLAINS WITH
PRIMARY FRONT STALLED FROM IND SWWD INTO W-CENTRAL TX...WITH
ADDITIONAL WARM FRONT/REMNANT OUTFLOW BOUNDARY PERSISTING FROM
CENTRAL OK SEWD INTO THE ARKLATEX. SURFACE LEE TROUGH WILL ALSO
REMAIN PRONOUNCED TODAY FROM DEVELOPING LOW NEAR THE SD/NE/WY
TRI-STATE REGION SWD INTO WRN TX.
...SRN INTO THE CENTRAL PLAINS...
OVERALL SETUP IS QUITE MESSY THIS MORNING AS DEEP LIFTING IS ALREADY
SUPPORTING WIDESPREAD STRONG/SEVERE THUNDERSTORMS FROM SWRN TX INTO
CENTRAL KS. WITH MID/UPPER SYSTEM EJECTING NEWD ...CAP WILL
CONTINUE TO WEAKEN AND SUPPORT CONTINUED INCREASE IN THUNDERSTORM
COVERAGE AND INTENSITY THROUGH THE DAY ACROSS THIS REGION.
WIDESPREAD STORM COVERAGE AND MODEST DEEP LAYER SHEAR WILL LIKELY
SUPPORT PRIMARY MODE OF MULTICELLS...WITH EMBEDDED SUPERCELLS...FROM
NWRN TX ACROSS WRN OK/CENTRAL KS FOR MUCH OF THE DAY. APPEARS
HAIL...SOME OF WHICH COULD BE QUITE LARGE...WILL BE MOST COMMON
SEVERE EVENT TODAY AS LAPSE RATES REMAIN STEEP AND DEEP LIFT/COOLING
ALOFT OVERSPREADS THE REGION. ADDITIONAL STRONG TO SEVERE
THUNDERSTORMS SHOULD DEVELOP DURING THE AFTERNOON INVOF RESIDUAL
OUTFLOW BOUNDARY FROM CENTRAL OK TOWARDS THE ARKLATEX WITH THREAT
INCREASING AGAIN LATE IN THE PERIOD AS LLJ SHIFTS ACROSS THIS
REGION.
SHEAR WILL REMAIN STRONGEST AND MORE FAVORABLY SUPPORT LONGER-LIVED
SUPERCELLS ALONG SRN EDGE OF MORE WIDESPREAD ACTIVITY...LIKELY
EXTENDING FROM W-CENTRAL/SWRN TX ENEWD TOWARDS SWRN OK/N-CENTRAL TX
INTO THE EVENING. WITH INCREASING SLY LLJ LATE TODAY AND AXIS OF
STRONGEST WLY MID LEVEL WINDS BECOMING JUXTAPOSED OVER WRN-NWRN
TX...TORNADO POTENTIAL WILL ALSO INCREASE DURING THE AFTERNOON WITH
MORE ISOLATED TORNADO POTENTIAL SPREADING NEWD DURING THE EVENING
INTO OK AS SHEAR INCREASES.
...CENTRAL HIGH PLAINS...
AS AFOREMENTIONED SURFACE LOW DEEPENS OVER THE CENTRAL HIGH PLAINS
TODAY...SELY LOW LEVEL FLOW AND INFLUX OF NEAR 50F SURFACE DEW
POINTS IS EXPECTED TO DEVELOP INTO THIS REGION. STRONG IMPULSE NOW
OVER THE INTERMOUNTAIN REGION SHOULD SUPPORT A RISK OF SEVERE
THUNDERSTORMS...INCLUDING SUPERCELLS...LATE TODAY AND THIS EVENING
AS IT EJECTS NEWD. FORECAST SOUNDINGS INDICATE CONDITIONS SHOULD
BECOME QUITE FAVORABLE FOR ISOLATED...HIGH
BASED-SUPERCELLS...DESPITE MARGINAL LOW LEVEL MOISTURE...GIVEN VERY
STEEP MID LEVEL LAPSE RATES/COLD AIR ALOFT. THIS SHOULD INCREASE
THE POTENTIAL FOR ISOLATED VERY LARGE HAIL STONES BEFORE UPDRAFTS
WEAKEN AND BECOME MORE NUMEROUS ALONG NOSE OF LLJ AFTER DARK.
...LOWER GREAT LAKES INTO WRN NEW ENGLAND...
A PROGRESSIVE SHORTWAVE TROUGH WILL MOVE FROM THE NRN GREAT LAKES
THIS MORNING INTO NEW ENGLAND/QUEBEC OVERNIGHT. AHEAD OF ASSOCIATED
SFC COLD FRONT...DAYTIME HEATING WILL COMBINE WITH STEEP MID LEVEL
LAPSE RATES TO SUPPORT MUCAPE VALUES FROM 500-1000 J/KG FROM
PORTIONS OF VT/NH SWWD INTO WRN/CENTRAL PA BY MID-AFTERNOON.
SUFFICIENT CONVERGENCE ALONG THE FRONT COMBINED WITH WEAKENING CINH
SHOULD SUPPORT SCT TSTM DEVELOPMENT ALONG THE FRONT BETWEEN 18-20Z.
MODEST VERTICAL SHEAR /30 KTS IN THE CLOUD BEARING LAYER/ WILL
SUPPORT SOME WEAK UPDRAFT ROTATION WITH MAINLY MULTICELLULAR
CHARACTERISTICS. THEREFORE...A LOW PROBABILITY AREA WILL BE ISSUED
TO COVER ISOLATED MARGINALLY SVR HAIL/WIND WITH THE STRONGEST TSTMS.
TSTMS ARE EXPECTED TO WEAKEN/DIMINISH BY 03Z AS THEY MOVE INTO SRN
NEW ENGLAND/ERN PA AND SERN NY.
..EVANS/CROSBIE.. 04/23/2008
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