Probability of a tornado within 25 miles of a point. Hatched Area: 10% or greater probability of EF2 - EF5 tornadoes within 25 miles of a point.
Day 1 Tornado Risk
Area (sq. mi.)
Area Pop.
Some Larger Population Centers in Risk Area
No Risk Areas Forecast
Probabilistic Damaging Wind Graphic
Probability of damaging thunderstorm winds or wind gusts of 50 knots or higher within 25 miles of a point. Hatched Area: 10% of greater probability of wind gusts 65 knots or greater within 25 miles of a point.
Day 1 Wind Risk
Area (sq. mi.)
Area Pop.
Some Larger Population Centers in Risk Area
No Risk Areas Forecast
Probabilistic Large Hail Graphic
Probability of hail 1" or larger within 25 miles of a point. Hatched Area: 10% or greater probability of hail 2" or larger within 25 miles of a point.
Day 1 Hail Risk
Area (sq. mi.)
Area Pop.
Some Larger Population Centers in Risk Area
No Risk Areas Forecast
SPC AC 241252
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0752 AM CDT MON AUG 24 2015
VALID 241300Z - 251200Z
...NO SVR TSTM AREAS FORECAST...
...SUMMARY...
SEVERAL AREAS OF THUNDERSTORMS ARE POSSIBLE TODAY IN A BROAD ARC
FROM THE NORTHEASTERN U.S. THROUGH THE SOUTHEAST...THEN ACROSS THE
GULF COAST STATES TO PARTS OF THE DESERT SOUTHWEST AND ROCKY
MOUNTAIN STATES. A FEW THUNDERSTORMS WITH GUSTY WINDS ALSO MAY
AFFECT PARTS OF THE INTERIOR NORTHWEST.
...SYNOPSIS...
CONUS PORTION OF LARGE-SCALE/UPPER-AIR PATTERN WILL FEATURE
1. RIDGING OVER ROCKIES...ACCOMPANYING STRENGTHENING ANTICYCLONE
OVER 4 CORNERS...AND
2. ERN TROUGHING...ANCHORED BY PRONOUNCED CYCLONE NOW CENTERED OVER
ONT NEAR NRN LAKEHEAD REGION OF LS. AS SEVERAL MESOSCALE VORTICITY
MAXIMA PIVOT AROUND THAT VORTEX...NET CENTROID SHOULD SHIFT ESEWD
ACROSS NRN ONT TO JUST N OF LH BY END OF PERIOD. ASSOCIATED
TROUGHING BY THEN WILL EXTEND SWD ACROSS OH AND SRN
APPALACHIANS...PHASING AT LEAST LOOSELY WITH ANTECEDENT WEAKNESS IN
500-MB HEIGHT FIELD OVER ERN GULF AND NWRN CARIBBEAN.
AT SFC...COLD FRONT RELATED TO ONT CYCLONE WAS ANALYZED AT 11Z FROM
SRN ONT ACROSS WRN PA...WV...ERN TN...SRN AR...THROUGH WEAK
FRONTAL-WAVE LOW NEAR DFW METROPLEX...TO LOWER PECOS VALLEY AREA. BY
00Z BOUNDARY SHOULD MOVE TO ERN NY..CENTRAL MD...WRN CAROLINAS...SRN
AL...AND SW TX...LOSING DEFINITION FARTHER W ACROSS W TX AND ERN NM.
BY 12Z...DECELERATING FRONT SHOULD REACH WRN NEW ENGLAND...LOWER
CHESAPEAKE/TIDEWATER AREA...SRN GA AND MS RIVER MOUTH.
...NERN CONUS...
NARROW BAND OF CONVECTION...INCLUDING WIDELY SCATTERED
TSTMS...SHOULD DEVELOP TODAY FROM CENTRAL NY TO NRN/CENTRAL VA.
ACTIVITY SHOULD FORM INVOF SFC COLD FRONT AS IT IMPINGES UPON
CORRIDOR OF DIABATICALLY DESTABILIZED AIR AND LOW-LEVEL MOIST
ADVECTION/TRANSPORT. FRONTAL CONVERGENCE AND WILL BE LIMITED BY
LACK OF MORE SUBSTANTIAL NEAR-SFC WINDS...AS WILL LOW-LEVEL SHEAR.
HOWEVER...GIVEN WEAK CINH...SUFFICIENT LIFT SHOULD EXIST FOR GRADUAL
CONVECTIVE DEVELOPMENT FROM MIDDAY THROUGH LATE AFTN...WITH NET NEWD
MOTION OF CELLS AND EWD SHIFT OF CONVECTIVE BAND TOWARD ERN NY...ERN
PA AND CENTRAL MD. ACTIVITY SHOULD DISSIPATE AS IT SHIFTS CLOSER TO
MID ATLC COAST AND NEW ENGLAND THIS EVENING...WITH SFC DIABATIC
COOLING STRIPPING AWAY BUOYANCY BY THE HOUR.
PREFRONTAL/FRONT-PARALLEL PLUME OF 500-1200 J/KG MLCAPE MAY DEVELOP
BY MID AFTN WITH SFC DEW POINTS RANGING FROM MID-UPPER 50S F UNDER
COOLER AIR ALOFT ON N END...TO MID/UPPER 60S OVER SOME PARTS OF VA.
HOWEVER...RELATIVE DRY POCKET NOTED IN MORNING SFC ANALYSIS OVER
PORTIONS ERN VA MAY ADVECT NWD INTO SOME PREFRONTAL INFLOW PARCELS
AND REDUCE CAPE.
WHILE AN ISOLATED STG GUST CANNOT BE RULED OUT FROM MOST
SUSTAINED/INTENSE CELLS...KEY FACTORS PRECLUDE ADDITION OF
MRGL-UNCONDITIONAL SVR AREA ATTM...
1. WEAK MEAN LAPSE RATES IN LOW-MIDDLE LEVELS...AS EVIDENT IN 12Z
PIT/BUF/ALB RAOBS THAT SAMPLED WARM NOSES ALOFT. WARMTH ALOFT MAY
MODERATE SLIGHTLY AMIDST GRADUAL HEIGHT FALLS AHEAD OF ONT
CYCLONE...BUT APPRECIABLE DCVA/COOLING ALOFT REMAINS BEHIND SFC
FRONT IN PROGS.
2. WEAK LOW-MIDDLE LEVEL FLOW...LIMITING NOT ONLY LOW-LEVEL
CONVERGENCE/SHEAR BUT DEEP SHEAR ALSO. MOST FCST SOUNDINGS SHOW
EFFECTIVE-SHEAR MAGNITUDES BELOW 30 KT.
...NWRN CONUS...
ISOLATED TSTMS SHOULD DEVELOP TODAY OVER CORRIDOR FROM NWRN CA TO
SERN WA...INITIALLY OVER DIABATICALLY HEATED HIGHER TERRAIN...THEN
SPREADING/MOVING OVER DEEP/WELL-MIXED BOUNDARY LAYERS EXHIBITING
INVERTED-V CHARACTERISTICS ON FCST SOUNDINGS. PW AROUND .75 INCH
AND 100-400 J/KG MLCAPE MAY LOFT SUFFICIENT UPDRAFT-WATER MASS TO
YIELD A FEW STG DOWNDRAFT GUSTS...ESPECIALLY WHEN FACTORING IN
POTENTIAL FOR MOMENTUM TRANSFER IN RELATIVELY FAST-MOVING CELLS.
ATTM LACK OF MORE ROBUST BUOYANCY AND NEBULOUS MID/UPPER-LEVEL
SUPPORT PRECLUDE UNCONDITIONAL SVR PROBABILITIES. RELATED DRY-TSTM
FIRE HAZARD ALSO EXISTS ACROSS THIS AREA...REF SPC OUTLOOK FOR
RELATED DETAILS ON FIRE WEATHER.
..EDWARDS/COOK.. 08/24/2015
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