SWODY2
SPC AC 251728
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1228 PM CDT MON AUG 25 2008
VALID 261200Z - 271200Z
...THERE IS A SLGT RISK OF SVR TSTMS FOR PARTS OF NEB/SD...
...NRN/CENTRAL PLAINS...
A STRONG MID LEVEL SHORTWAVE TROUGH NOW OVER WRN WA/ORE WILL
PROGRESS EWD OVER MT/NRN WY TOMORROW...AND THE DAKOTAS TUESDAY
NIGHT. THIS MID LEVEL WAVE WILL BE ACCOMPANIED BY A STRONG SURFACE
COLD FRONT WHICH WILL MOVE EWD ACROSS THE DAKOTAS AND SEWD ACROSS
THE CENTRAL HIGH PLAINS BY LATE TUESDAY. A PLUME OF BOUNDARY LAYER
DEWPOINTS OF 60-64F WILL CONTINUE TO SPREAD NWD FROM WRN KS/NEB TO
THE CENTRAL DAKOTAS IN ADVANCE OF THE COLD FRONT...BENEATH AN
ELEVATED MIXED LAYER PLUME FROM THE NRN ROCKIES. EXPECT MLCAPE
VALUES OF 1000-2000 J/KG IMMEDIATELY E OF THE COLD FRONT DURING THE
AFTERNOON...THOUGH A SUBSTANTIAL CAP WILL LIKELY DELAY CONVECTIVE
INITIATION UNTIL LATE AFTERNOON AND CONFINE STORMS TO THE COLD
FRONT. A BAND OF THUNDERSTORMS WILL THEN SPREAD EWD/SEWD WITH THE
COLD FRONT ACROSS THE ERN DAKOTAS/NEB INTO TUESDAY NIGHT.
THE STRONGER MID LEVEL FLOW AND ASSOCIATED DEEP LAYER VERTICAL SHEAR
ARE FORECAST TO LAG W OF THE SURFACE COLD FRONT TOMORROW AFTERNOON
ACROSS ND...WHILE THE MOISTURE/INSTABILITY CORRIDOR REMAINS NARROW
AS A RESULT OF SURFACE RIDGING ACROSS THE GREAT LAKES. ISOLATED
LARGE HAIL/DAMAGING WINDS WILL BE POSSIBLE DURING THE AFTERNOON/
EVENING...BUT THE OVERALL SEVERE STORM THREAT APPEARS TOO MARGINAL
FOR A SLIGHT RISK AT THIS TIME. FARTHER S INTO NEB...CLUSTERS OF
THUNDERSTORMS SHOULD PERSIST WELL INTO THE OVERNIGHT HOURS NEAR THE
COLD FRONT...AIDED BY MOISTURE TRANSPORT WITH A 30-40 KT LLJ.
VERTICAL SHEAR WILL BE SOMEWHAT STRONGER FROM SRN SD INTO NEB WHERE
MID-UPPER FLOW WILL BE MORE WLY/NWLY ABOVE THE SSWLY LLJ...AND
INSTABILITY SHOULD PERSIST ACROSS THIS SAME AREA DEEPER INTO THE
OVERNIGHT HOURS. A FEW SUPERCELLS COULD OCCUR EARLY AFTER STORM
INITIATION DURING THE EVENING ALONG THE COLD FRONT...TO THE NE OF
THE RESIDUAL /SWD MOVING/ LEE CYCLONE IN NE CO. OTHERWISE...EXPECT
CONVECTION TO EVOLVE INTO CLUSTERS OF ELEVATED STORMS LATE TUESDAY
INTO EARLY WEDNESDAY...WITH THE POTENTIAL FOR AT LEAST ISOLATED
LARGE HAIL AND DAMAGING WINDS.
...SRN APPALACHIANS...
THE REMNANTS OF TROPICAL DEPRESSION FAY WILL MOVE SLOWLY NEWD FROM
AL TO ERN TN BY TUESDAY NIGHT. A GRADUAL WEAKENING OF THIS SYSTEM
IS EXPECTED WITH TIME AS IT MOVES FARTHER INLAND...AND THE STRONGER
LOW-LEVEL SHEAR WILL BE OFFSET FROM THE RICHER LOW-LEVEL
MOISTURE/INSTABILITY FARTHER TO THE S. THUS...THE THREAT FOR
SUPERCELLS/TORNADOES WILL LIKEWISE DECREASE COMPARED TO THE PAST
COUPLE OF DAYS.
..THOMPSON.. 08/25/2008
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