Sep 18, 2014 2000 UTC Day 1 Convective Outlook
Updated: Thu Sep 18 19:50:14 UTC 2014 (20140918 2000Z Day 1 shapefile | 20140918 2000Z Day 1 KML)
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20140918 2000 UTC Day 1 Outlook Graphic
Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
No Risk Areas Forecast
Probabilistic Tornado Graphic
20140918 2000 UTC Day 1 Tornado Probabilities Graphic
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.
Tornado Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
No Risk Areas Forecast
Probabilistic Damaging Wind Graphic
20140918 2000 UTC Day 1 Damaging Wind Probabilities 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.
Wind Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
5 % 109,913 2,257,151 Billings, MT...Ogden, UT...Layton, UT...Idaho Falls, ID...Pocatello, ID...
Probabilistic Large Hail Graphic
20140918 2000 UTC Day 1 Large Hail Probabilities 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.
Hail Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
5 % 84,766 1,475,437 Billings, MT...Ogden, UT...Layton, UT...Idaho Falls, ID...Pocatello, ID...
   SPC AC 181950

   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0250 PM CDT THU SEP 18 2014

   VALID 182000Z - 191200Z

   ...NO SVR TSTM AREAS FORECAST...

   ...SUMMARY...
   ISOLATED DAMAGING WINDS AND LARGE HAIL WILL BE POSSIBLE THIS
   AFTERNOON FROM NORTHEAST NEVADA TO SOUTH CENTRAL MONTANA.  OTHER
   MARGINALLY SEVERE STORMS WITH GUSTY WINDS CAN BE EXPECTED THIS
   AFTERNOON ALONG THE SOUTH CAROLINA COAST...AS WELL AS ACROSS
   SOUTHEAST ARKANSAS AND ADJACENT AREAS OF NORTHWEST MISSISSIPPI AND
   NORTHEAST LOUISIANA.

   ...NRN NV INTO SWRN MT...
   CELLS SHOULD CONTINUE TO INCREASE IN COVERAGE AND INTENSITY THIS
   AFTERNOON FROM NERN NV ACROSS ERN ID AND INTO SWRN MT AS HEATING
   PERSISTS. SHEAR WILL CONTINUE TO FAVOR CELLULAR ACTIVITY AND A FEW
   SMALL BOWS CAPABLE OF WIND AND HAIL. FOR MORE INFORMATION SEE MCD
   1729. 

   ...SRN AR INTO CNTRL MS...
   STORMS CONTINUE TO FORM ALONG THE OLD OUTFLOW BOUNDARY...AND WHERE
   MODERATE INSTABILITY HAS DEVELOPED. SHEAR IS WEAK BUT NWLY FLOW
   ALOFT COULD RESULT IN A FEW SEWD-PROPAGATING CLUSTERS CAPABLE OF
   LOCALLY SEVERE WIND GUSTS.

   ...COASTAL SC...
   CONDITIONS DO NOT APPEAR TO BE AS FAVORABLE AS PREVIOUS DAY...WITH
   WEAKENING AND FLOW ALOFT...SOME WARNING ALOFT AND LESS OF A SURFACE
   TROUGH. THEREFORE...HAVE REMOVED LOW END SEVERE PROBABILITIES.

   ..JEWELL.. 09/18/2014

   .PREV DISCUSSION... /ISSUED 1130 AM CDT THU SEP 18 2014/

   ...NE NV TO SRN MT THIS AFTERNOON...
   A MIDLEVEL TROUGH IS MOVING SLOWLY INLAND OVER THE PAC COAST...WITH
   A BAND OF ENHANCED MID-UPPER SWLY FLOW PRECEDING THE TROUGH FROM THE
   NW GREAT BASIN TO THE NRN ROCKIES.  SOME LOW-LEVEL MOISTURE IS BEING
   DRAWN NWD ACROSS CENTRAL/ERN NV IN ADVANCE OF THE MIDLEVEL TROUGH
   AND BAROCLINIC ZONE.  LINGERING CLOUDS WITH ONGOING CONVECTION FROM
   ID INTO SRN MT COULD SLOW SURFACE HEATING...WHILE MODIFIED 12Z
   SOUNDINGS FROM SLC AND LKN SHOW THE POTENTIAL FOR SBCAPE OF 300-500
   J/KG WITH SURFACE TEMPERATURES NEAR 80 F AND DEWPOINTS IN THE MID
   40S.  THOUGH BUOYANCY WILL BE LIMITED...DEEP-LAYER SHEAR WILL BE
   FAVORABLE FOR ORGANIZED STORMS /INCLUDING SUPERCELLS/...SO WILL
   MAINTAIN LOW PROBABILITIES FOR DAMAGING WINDS/LARGE HAIL.

   ...SC/GA COAST THIS AFTERNOON...
   A WEAK SURFACE LOW AND REMNANT FRONTAL ZONE...ALONG WITH LOCAL SEA
   BREEZE CIRCULATIONS...WILL HELP FOCUS THUNDERSTORM DEVELOPMENT THIS
   AFTERNOON ALONG THE GA/SC COAST.  MLCAPE OF 1500-2000 J/KG AND
   EFFECTIVE BULK SHEAR NEAR 30 KT WILL SUPPORT THE RISK FOR
   SEMI-ORGANIZED CELLS WITH THE POTENTIAL TO PRODUCE ISOLATED STRONG
   OUTFLOW GUSTS WITH WET MICROBURSTS.

   ...SE KS/ERN OK TO THE ARKLAMISS THIS AFTERNOON...
   SEVERAL FACTORS ARE COMBINING TO REDUCE THE RISK FOR ISOLATED
   DAMAGING WINDS AND HAIL TODAY.  AN EXTENSIVE COLD POOL WITH ONGOING
   CONVECTION CONTINUES TO SURGE SWWD INTO WRN AND SRN OK...LOOSELY IN
   ASSOCIATION WITH A SUBTLE SHORTWAVE TROUGH MOVING SEWD OVER NE OK. 
   THOUGH CONVECTION HAS WEAKENED IN OK SINCE EARLIER THIS
   MORNING...LINGERING CLOUDS AND THE STABILIZING INFLUENCE OF THE COLD
   POOL WILL ACT TO REDUCE BUOYANCY THROUGH THE AFTERNOON.  THE
   STRONGER VERTICAL SHEAR WILL TEND TO REMAIN WELL ON THE COOL SIDE OF
   THE OUTFLOW BOUNDARY...SUCH THAT ORGANIZED SEVERE STORMS APPEAR
   UNLIKELY ALONG THE OUTFLOW ITSELF.  FARTHER S ALONG THE REMNANT
   FRONT FROM NRN LA TO NE TX...VERTICAL SHEAR WILL REMAIN WEAK AND
   EXTENSIVE HIGH CLOUDS /EMANATING FROM THE REMAINS OF TC ODILE/ WILL
   TEND TO SLOW SURFACE HEATING AND LIMIT BUOYANCY.  ALL THINGS
   CONSIDERED...THE RISK FOR DAMAGING WINDS AND LARGE HAIL APPEARS TO
   BE TOO SMALL TO WARRANT KEEPING AN OUTLOOK AREA. 
   OTHERWISE...SOMEWHAT STRONGER BUOYANCY IS EXPECTED ALONG THE FRONT
   FROM SE AR INTO NW MS WHERE STRONG SURFACE HEATING IS OCCURRING. 
   THERE WILL BE SOME POTENTIAL FOR GUSTY OUTFLOW WINDS WITH STORMS
   EXPECTED TO FORM ALONG THE FRONT BY EARLY AFTERNOON.

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