SWODY1
SPC AC 280514
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1214 AM CDT SUN SEP 28 2008
VALID 281200Z - 291200Z
...NO SVR TSTM AREAS FORECAST...
...SYNOPSIS...
LARGE SCALE PATTERN WILL AMPLIFY THROUGH THE PERIOD AS UPPER RIDGE
BUILDS OVER THE INTERMOUNTAIN WEST...WITH AN UPPER TROUGH DEVELOPING
SOUTHEASTWARD OVER THE CENTRAL CANADIAN PRAIRIE AND ADJACENT
PORTIONS OF THE NORTHERN PLAINS/UPPER MIDWEST THIS
AFTERNOON/TONIGHT. FARTHER EAST...PERSISTENT UPPER LOW WILL CONTINUE
TO WEAKEN/SPREAD NORTHEASTWARD OVER THE NORTHEAST STATES TOWARD
SOUTHERN NEW ENGLAND...WHILE LATEST NHC FORECASTS SUGGEST HURRICANE
KYLE WILL RACE NORTHWARD TOWARD THE FAR EASTERN COAST OF MAINE AND
BAY OF FUNDY VICINITY BY LATE THIS AFTERNOON/EARLY EVENING.
...NEB AND ADJACENT MIDDLE MISSOURI VALLEY...
AS HEIGHT FALLS OCCUR OVER THE NORTHERN PLAINS/UPPER MIDWEST IN
ADVANCE OF THE APPROACHING UPPER TROUGH...CORRESPONDING SURFACE COLD
FRONT WILL STEADILY SPREAD EAST-SOUTHEASTWARD ACROSS THE NORTHERN
PLAINS DURING THE DAY. TSTMS SHOULD INITIATE ALONG THE COLD FRONT
/OR PERHAPS A LEADING PREFRONTAL TROUGH/...INITIALLY ACROSS THE FAR
EASTERN DAKOTAS AND WESTERN MN BY MID AFTERNOON...AND EVENTUALLY
INTO NORTHERN/WEST CENTRAL NEB BY LATE AFTERNOON/EARLY EVENING.
BENEATH A PLUME OF STEEP MID LEVEL LAPSE RATES...AMPLE HEATING /80S
F/ AND MODEST BOUNDARY LAYER MOISTURE /MAINLY 50S F DEWPOINTS/
SHOULD LEAD TO MODERATE INSTABILITY IN THE PREFRONTAL WARM
SECTOR...WITH THE POSSIBILITY OF 1000-2000 J/KG MLCAPE /MAXIMIZED
ACROSS NEB AND FAR SOUTHERN SD/. WHILE MID/UPPER TROPOSPHERIC FLOW
WILL BE STEADILY INCREASING BY EVENING ACROSS THE REGION...INITIALLY
WEAK VERTICAL SHEAR OF 25-30 KT /ALBEIT WELL-VEERED/ DURING THE LATE
AFTERNOON/EARLY EVENING SHOULD TEND TO LIMIT OVERALL TSTM
ORGANIZATION. NEVERTHELESS...SUFFICIENT INSTABILITY WITH COOL
PROFILES ALOFT/STEEP MID LEVEL LAPSE RATES AND STRONGLY VEERED WIND
PROFILES WILL SUPPORT MULTICELLS AND PERHAPS A FEW SHORT DURATION
SUPERCELLS CAPABLE OF SEVERE HAIL...WITH ISOLATED DAMAGING WIND
GUSTS ALSO A POSSIBILITY. AFOREMENTIONED STRENGTHENING FLOW ALOFT
AND AN INCREASING SOUTHWESTERLY LOW LEVEL JET/WARM AIR ADVECTION
REGIME MAY MAINTAIN AN ISOLATED/MARGINAL SEVERE HAIL RISK THROUGH
THE EVENING ACROSS EASTERN NEB/WESTERN IA.
..GUYER/JEWELL.. 09/28/2008
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