The SPC is forecasting ...severe thunderstorms occurring over parts of the midwest and ohio valley today.... Please read the latest public statement about this event.
| Categorical Graphic |
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| Probabilistic Tornado Graphic |
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| 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. |
| Probabilistic Damaging Wind Graphic |
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| 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. |
| Probabilistic Large Hail Graphic |
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| 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. |
SPC AC 111959
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0259 PM CDT MON JUL 11 2011
VALID 112000Z - 121200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM THE NRN ROCKIES ACROSS THE
CENTRAL PLAINS...MID MS VALLEY AND INTO THE CENTRAL/SRN
APPALACHIANS...
...THERE IS A SLGT RISK OF SVR TSTMS OVER PORTIONS OF MAINE...
...OH VALLEY AND SRN APPALACHIANS...
LONG LIVED BOWED ECHO HAS TURNED SEWD IN RESPONSE TO NEW STORMS
DEVELOPING ON THE WRN FLANK OF LINEAR SYSTEM. WHILE THE LINE
CONTINUES TO INTERCEPT A VERY WARM AND EXTREMELY UNSTABLE AIR MASS
FEEDING IN FROM THE WEST...THE LINE IS EXPECTED TO CONTINUE MOVING
MOSTLY SWD DUE TO THE STRONG WLY PROPAGATIONAL VECTOR. GIVEN THE
STRONG INSTABILITY AND ORGANIZED COLD POOL...WIND DAMAGE IS LIKELY
WITH THE SYSTEM THROUGH THE REMAINDER OF THE AFTERNOON AND INTO THE
EVENING HOURS. HOWEVER...GIVEN THE MEAN FLOW PARALLEL TO THE
LINE AND ALSO STORMS MOVING INTO WEAKER FLOW ALOFT...THE WIND DAMAGE
IS NOT EXPECTED TO BE AS EXTENSIVE AS EARLIER IN THE DAY...WITH 40
TO 60 MPH WINDS MOST COMMON. HAIL IS ALSO POSSIBLE...ESPECIALLY WITH
NEWLY DEVELOPING STORMS ON THE WRN FLANK OF LINE.
...WRN TX/OK INTO WRN KS...
WV IMAGERY SHOWS THE UPPER LEVEL CIRCULATION WAS LOCATED IN THE TX
PANHANDLE AND SOME OPERATIONAL AND STORM SCALE MODELS SUGGEST STORMS
WILL DEVELOP DURING THE NEXT FEW HOURS TO THE EAST OF THE LOW. WHILE
THE SLY DEEP LAYER SHEAR IS ONLY 15-20 KT...MODERATE INSTABILITY AND
40 DEGREE TEMPERATURE/DEWPOINT SPREADS APPEAR FAVORABLE FOR STRONG
AND POSSIBLY SEVERE WIND GUSTS. LOW SEVERE WIND PROBABILITIES HAVE
BEEN ADDED TO THIS AREA.
...MID MS VALLEY...
SOME OF AREA HAS BEEN TRIMMED OUT OF SEVERE SINCE IT APPEARS THE
REGION WILL BE LOCATED BETWEEN STORM SYSTEMS TO THE WEST AND EAST.
HOWEVER...SOME HIGH RESOLUTION MODELS DO DEVELOP ISOLATED
STORMS...SO DID NOT REMOVE ENTIRE RISK AREA.
REST OF FORECAST ON TRACK WITH ONLY MINOR ADJUSTMENTS TO THUNDER
AND SEVERE THREAT TO ACCOUNT FOR RECENT TRENDS.
..IMY.. 07/11/2011
.PREV DISCUSSION... /ISSUED 1126 AM CDT MON JUL 11 2011/
...LOWER GREAT LAKES/OHIO VALLEY...
BOWING QLCS CONTINUES TO MOVE EWD AT 50 KT ACROSS SERN LOWER MI AND
EXTREME NWRN OH...WITH THE SRN END OF THE CONVECTIVE SYSTEM TRAILING
SWWD INTO NRN INDIANA. ADDITIONAL STRONG/SEVERE STORMS ARE OVER
NWRN OH IN ADVANCE OF THE BOW ECHO SYSTEM. VISIBLE SATELLITE
IMAGERY SHOWS LIMITED CLOUDS OVER MUCH OF OH INDICATING STRONG
DIABATIC HEATING/DESTABILIZATION WILL OCCUR THIS AFTERNOON...AS
STEEP LAPSE RATES /REF 12Z KILX SOUNDING/ SPREAD EWD FROM THE MIDDLE
MS VALLEY REGION WITHIN BAND OF MODERATE WESTERLY LOW-MID LEVEL
FLOW. THE BOWING QLCS IS LIKELY TO CONTINUE EWD/ESEWD AS NEW CELLS
DEVELOP ON THE SRN END. SINCE THE BOWING QLCS IS MOVING MORE
RAPIDLY THAN THE DOWNSTREAM STORMS...THERE IS SOME UNCERTAINTY
REGARDING THE STORM SCALE EVOLUTION AS IT OVERTAKES THE LEADING
CONVECTIVE STORMS...BUT STRONG DESCENDING REAR-INFLOW JET EVIDENT IN
VAD PROFILES SUGGEST SUFFICIENT WESTERLY MOMENTUM EXISTS FOR THE
SYSTEM TO CONTINUE ACROSS MUCH OF OH THIS AFTERNOON. PRIMARY THREAT
WILL REMAIN DAMAGING WIND GUSTS BUT LARGE HAIL MAY ALSO BE POSSIBLE
GIVEN THE STEEPENING LAPSE RATES.
...NRN HIGH PLAINS INTO MIDDLE MO VALLEY...
MOIST UPSLOPE LOW LEVEL FLOW IS BECOMING ESTABLISHED OVER THE HIGH
PLAINS WITH 55-60F SURFACE DEW POINTS EVIDENT FROM SERN MT INTO ERN
WY...INCREASING TO THE MID/UPPER 60S OVER NEB. CURRENT AREAS OF
CLOUDS ARE LIKELY TO DIMINISH THIS AFTERNOON WITH REGIONS OF
STRONGER HEATING CONTRIBUTING TO MODERATELY UNSTABLE CONDITIONS WITH
MLCAPE OF 1000-2000 J/KG. STORMS ARE EXPECTED TO DEVELOP OVER THE
HIGHER TERRAIN BY MID/LATE AFTERNOON AND SPREAD EWD INTO THE LOW
LEVEL MOISTURE/INSTABILITY AXIS OVER THE PLAINS. ALTHOUGH MID LEVEL
WINDS ARE ONLY FORECAST TO BE AROUND 25-30 KT...STRONG DIRECTIONAL
SHEAR WITH HEIGHT WILL ENHANCE CONVECTIVE ORGANIZATION AND INTENSITY
WITH A FEW SUPERCELLS POSSIBLE. STRONGER CELLS WILL BE CAPABLE OF
LARGE HAIL...DAMAGING WINDS...AND A FEW TORNADOES /ESPECIALLY FROM
EXTREME ERN WY/SWRN SD INTO NEB/. CONVECTION MAY GROW UPSCALE INTO
AN MCS THIS EVENING AS THE LOW LEVEL JET INTENSIFIES OVER THE
CENTRAL PLAINS...WITH SEVERE THREAT CONTINUING ACROSS PARTS OF NEB
DURING THE OVERNIGHT HOURS.
...SWRN/SOUTH CENTRAL MT...
SWLY FLOW ALOFT IS FORECAST TO INCREASE OVER THE NRN INTERMOUNTAIN
AND NRN ROCKIES REGIONS IN ADVANCE OF THE UPPER LOW MOVING SSEWD OFF
THE PACIFIC NW COAST. CURRENT WEAK CONVECTION OVER SWRN MT MAY
SERVE TO MOISTEN THE COLUMN AND RESULT IN FURTHER DESTABILIZATION
THIS AFTERNOON AND EVENING. MODELS SUGGEST A SEPARATE AREA OF
STRONG CONVECTION WILL DEVELOP LATER THIS AFTERNOON WITHIN A ZONE OF
35-40 KT DEEP LAYER SHEAR...WHICH WILL PROMOTE A FEW SEVERE STORMS
WITH LARGE HAIL AND STRONG WIND GUSTS THROUGH THE EVENING HOURS.
...NRN MAINE...
A STRONG SHORT WAVE TROUGH OVER ONTARIO IS FORECAST MOVE RAPIDLY EWD
INTO SRN QUEBEC...AS A BAND OF STRONGER WESTERLY WINDS ALOFT SPREAD
DOWNSTREAM ACROSS NRN NEW ENGLAND. 12Z CAR RAOB SHOWS MODERATELY
STEEP MID LEVEL LAPSE RATES ARE ALREADY PRESENT OVER THE AREA...AND
SUFFICIENT MOISTURE WILL RESULT IN UNSTABLE CONDITIONS WITH MLCAPE
OF 1000-1500 J/KG. STORMS ARE EXPECTED TO DEVELOP OVER PARTS OF SRN
QUEBEC LATER THIS AFTERNOON AND MOVE ACROSS NRN MAINE WITH THREAT
FOR DAMAGING WIND GUSTS AND LARGE HAIL THROUGH THE EVENING HOURS.
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