SWODY1
SPC AC 111958
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0258 PM CDT FRI MAY 11 2007
VALID 112000Z - 121200Z
..NO SVR TSTM AREAS FORECAST...
..SRN APPALACHIANS WWD TO SRN PLAINS...
DESPITE WEAK LAPSE RATES...STRONG SURFACE HEATING WITHIN A MOIST AIR
MASS /SURFACE DEWPOINTS IN THE 60S/ STRETCHING FROM THE TN/LOWER OH
VALLEYS SWWD TO THE SRN PLAINS WILL CONTINUE TO WEAKEN ANY REMAINING
INHIBITION AND RESULT IN MODERATE INSTABILITY. ASCENT AHEAD OF
SHORT WAVE TROUGH MOVING SEWD INTO LOWER OH VALLEY AND ALSO ALONG
THE PERIPHERIES OF A COUPLE OF MID LEVEL LOWS/MCV/S ALONG THE UPPER
TX COAST AND LOWER TN VALLEY WILL CONTINUE TO SUPPORT GREATER
CONCENTRATIONS OF TSTM CLUSTERS. HOWEVER...OVERALL WEAK LOW LEVEL
CONVERGENCE AND WEAK LAPSE RATES/DEEP LAYER SHEAR WILL TEND TO LIMIT
POTENTIAL FOR MORE ROBUST UPDRAFTS AND HIGHER PROBABILITIES OF
SEVERE WEATHER. MUCH OF THIS ACTIVITY IS DIURNALLY DRIVEN AND IS
EXPECTED TO DECREASE IN AREAL COVERAGE THIS EVENING AS THE AIR MASS
STABILIZES WITH THE LOSS OF DAY TIME HEATING.
..NRN PLAINS INTO PARTS OF THE CENTRAL PLAINS...
ASIDE FROM ONGOING CUMULUS/ISOLATED TSTM DEVELOPMENT OVER MUCH OF
THE HIGHER TERRAIN FROM THE SWRN STATES NWD TO PARTS OF WY/MT AND
THE BLACK HILLS...UPPER RIDGE IS TENDING TO SUPPRESS CONVECTIVE
DEVELOPMENT SO FAR THIS AFTERNOON. OBJECTIVE ANALYSES ARE
INDICATING A DEVELOPING AXIS OF MODERATE INSTABILITY FROM WRN SD
WNWWD TO SRN MT WHERE SURFACE DEWPOINTS ARE IN THE UPPER 40S TO
LOWER 50S AND LAPSE RATES REMAIN STEEP. THE GREATEST POTENTIAL FOR
THE DEVELOPMENT OF ORGANIZED TSTMS APPEARS TO BE ACROSS SRN MT/FAR
NRN WY AROUND 00Z AS ASCENT AHEAD OF A WEAK MID LEVEL IMPULSE
APPROACHES THIS REGION FROM THE NRN GREAT BASIN. DEEP LAYER SHEAR
ALONG SRN PERIPHERY OF STRONGER FLOW ALOFT AND MODERATE INSTABILITY
WILL BE SUFFICIENT FOR ORGANIZED STORMS...BUT UNCERTAINTY IN OVERALL
STORM COVERAGE MAINTAINS LOW SEVERE PROBABILITIES.
GREATER CONFIDENCE FOR TSTM DEVELOPMENT REMAINS ACROSS CENTRAL INTO
ERN SD THIS EVENING THROUGH THE OVERNIGHT FORECAST PERIOD AS WAA
INCREASES ALONG THE NOSE OF A SSWLY LLJ EXPECTED TO STRENGTHEN FROM
THE CENTRAL HIGH PLAINS INTO CENTRAL SD. WEAK ELEVATED INSTABILITY
AND SUFFICIENT EFFECTIVE BULK SHEAR VALUES MAY SUPPORT A THREAT FOR
ISOLATED SEVERE HAIL WITH THIS OVERNIGHT ACTIVITY.
.PETERS.. 05/11/2007
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