SWODY1
SPC AC 091943
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0243 PM CDT FRI JUL 09 2010
VALID 092000Z - 101200Z
...NO SVR TSTM AREAS FORECAST...
THE ONLY CHANGE FOR THE 20Z OUTLOOK IS TO ADD A 2 PERCENT TORNADO
PROBABILITY OVER NE TX FROM THE DALLAS/FORT WORTH METROPLEX NWD TO
THE RED RIVER. THE WSR-88D VWP FROM FORT WORTH SHOWS SUBSTANTIAL
DIRECTIONAL TURNING BELOW 3 KM WITH BACKED SFC WINDS NORTH OF A EAST
TO WEST BOUNDARY. THIS COMBINED WITH LOW LCL HEIGHTS FROM 500 TO 750
METERS AS SHOWN BY OBJECTIVE ANALYSIS MAY BE ENOUGH FOR A MARGINAL
TORNADO THREAT WITH THE MORE PERSISTENT ROTATING STORMS LATE THIS
AFTERNOON.
..BROYLES.. 07/09/2010
.PREV DISCUSSION... /ISSUED 1118 AM CDT FRI JUL 09 2010/
...CO FRONT RANGE AND ADJACENT HIGH PLAINS...
A SLOW EWD PROGRESSION OF SURFACE HIGH PRESSURE IS FORECAST TODAY
WHICH WILL SUSTAIN SLY/SELY LOW-LEVEL TRAJECTORIES BENEATH GRADUALLY
STRENGTHENING MIDLEVEL FLOW...AND A STRONG ZONAL UPPER JET. THE
COMBINATION OF DAYTIME HEATING...BOUNDARY LAYER DEWPOINTS OF 45-55
F...AND SLIGHT COOLING ALOFT /BASED ON EXTRAPOLATION OF 12Z
UPPER-AIR DATA/ SHOULD SUPPORT MODEST DESTABILIZATION WITH AFTERNOON
MLCAPE OF 500-1000 J/KG.
TSTMS ARE EXPECTED TO DEVELOP ALONG THE FRONT RANGE BY LATE
AFTERNOON/EARLY EVENING WITH ACTIVITY MOVING/DEVELOPING SEWD INTO
THE HIGH PLAINS. THE PRESENCE OF STEEP LOW- TO MIDLEVEL LAPSE
RATES...MODEST CONVECTIVE INSTABILITY AND DEEP-LAYER SHEAR
STRENGTHENING TO 30-35 KT WILL BE SUPPORTIVE OF A FEW
STRONGER/ROTATING STORMS CAPABLE OF HAIL AND LOCALLY STRONG WIND
GUSTS THROUGH THIS EVENING.
...LOWER GREAT LAKES/NRN NEW ENGLAND INTO THE CNTRL/SRN
APPALACHIANS...CUMBERLAND PLATEAU AND ADJACENT PIEDMONT...
SURFACE COLD FRONT WILL PROGRESS EWD ACROSS REGION TODAY IN
CONJUNCTION WITH PRIMARY MIDLEVEL TROUGH MOVING ACROSS THE GREAT
LAKES...AND WEAKER ATTENDING IMPULSES PROGRESSING EWD THROUGH THE OH
VALLEY INTO MID ATLANTIC STATES. 12Z OBSERVED SOUNDINGS...GPS PW
DATA AND VISIBLE SATELLITE IMAGERY INDICATE THAT A MOIST PRE-FRONTAL
AIR MASS /I.E. DEWPOINTS IN THE 60S TO LOWER 70S AND PW VALUES OF
1.50-1.75 INCHES/ WILL COMBINE WITH STRONG DIABATIC HEATING TO
PROMOTE A MODERATELY UNSTABLE AIR MASS BY AFTERNOON WITH MLCAPE OF
1000-2000 J/KG.
FORCING FOR ASCENT ASSOCIATED WITH MIDLEVEL TROUGH IN CONCERT WITH
FRONTAL CONVERGENCE AND LOCAL TERRAIN EFFECTS ARE EXPECTED TO FOSTER
CLUSTERS AND/OR BANDS OF TSTMS THIS AFTERNOON INTO EVENING WITHIN
DESTABILIZING AIR MASS. WEAK VERTICAL SHEAR AND POOR MIDLEVEL LAPSE
RATES WILL TEND TO LIMIT THE POTENTIAL FOR AN ORGANIZED SEVERE
WEATHER THREAT. NONETHELESS...THE THREAT WILL EXIST FOR LOCALLY
STRONG WIND GUSTS WITH ANY LONGER-LIVED STORM COMPLEXES THAT MAY
DEVELOP.
...CNTRL/ERN CAROLINAS...
DEEP-LAYER CYCLONE CURRENTLY LOCATED JUST OFF THE NC COAST WILL
SHIFT EWD TODAY IN RESPONSE TO APPROACH OF GREAT LAKES/OH VALLEY
MIDLEVEL TROUGH FROM THE W. AS SUCH...STRONGER BACKGROUND ASCENT
MAY BE COMPARATIVELY LESS THAN THAT SEEN ON THURSDAY. HOWEVER...AIR
MASS REMAINS QUITE MOIST WITH DEWPOINTS IN THE UPPER 60S TO LOWER
70S. AND WHEN COUPLED WITH STRONG DIABATIC HEATING...ENVIRONMENT IS
EXPECTED TO BECOME MODERATELY UNSTABLE BY AFTERNOON WITH MLCAPE OF
1500-2500 J/KG.
CONVECTIVE EVOLUTION REMAINS UNCERTAIN DUE TO THE ABOVE-MENTIONED
FACTORS. HOWEVER...THE DEVELOPMENT/INTENSIFICATION OF A LEE TROUGH
AND RESIDUAL OUTFLOW BOUNDARIES ATTENDANT TO DISSIPATING...NOCTURNAL
TSTM COMPLEX MAY SERVE AS THE FOCI FOR STRONG...DIURNAL STORM
DEVELOPMENT. THE STRONGEST DEEP-LAYER NNWLY SHEAR WILL RESIDE ALONG
THE COASTAL PLAINS...GENERALLY DECREASING WITH WWD EXTENT. GIVEN
THE MODERATE INSTABILITY...POTENTIAL WILL EXIST FOR A FEW MARGINALLY
SEVERE STORMS THROUGH THIS EVENING WITH THE PRIMARY HAZARD BEING
LOCALLY DAMAGING WIND GUSTS.
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