Sep 19, 2014 1300 UTC Day 1 Convective Outlook
Updated: Fri Sep 19 12:58:31 UTC 2014 (20140919 1300Z Day 1 shapefile | 20140919 1300Z Day 1 KML)
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20140919 1300 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
20140919 1300 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
20140919 1300 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 % 69,334 4,147,416 Omaha, NE...Lincoln, NE...Des Moines, IA...Sioux Falls, SD...Rochester, MN...
Probabilistic Large Hail Graphic
20140919 1300 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 % 184,746 9,989,889 Omaha, NE...Lincoln, NE...Madison, WI...Des Moines, IA...Sioux Falls, SD...
   SPC AC 191258

   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0758 AM CDT FRI SEP 19 2014

   VALID 191300Z - 201200Z

   ...NO SVR TSTM AREAS FORECAST...

   ...SUMMARY...
   A FEW THUNDERSTORMS MAY BECOME MARGINALLY SEVERE THIS EVENING AND
   TONIGHT FROM EASTERN NEBRASKA INTO PARTS OF MICHIGAN...AND OVER
   NORTHERN MINNESOTA.

   ...SYNOPSIS...
   GENERAL DAY-1 UPPER-AIR PATTERN OVER CONUS WILL BE DOMINATED BY
   THREE PRINCIPAL REGIMES--
   1. SLOWLY RISING HEIGHTS OVER 4-CORNERS REGION SWD OVER NWRN MEX...
   2. HIGH-AMPLITUDE SHORTWAVE TROUGH -- NOW EVIDENT IN
   MOISTURE-CHANNEL IMAGERY FROM SERN ORE ACROSS NRN/CENTRAL CA AND
   ADJOINING PAC WATERS--FCST TO EVOLVE INTO CLOSED AND TEMPORARILY
   CUT-OFF LOW OFFSHORE SRN CA...AND
   3. PROGRESSIVE/LOW-AMPLITUDE SHORTWAVES TRAVERSING NRN STREAM NEAR
   CANADIAN BORDER.

   WITHIN THAT NRN BRANCH...SHORTWAVE TROUGH THAT HAD BEEN PHASED WITH
   CA SYSTEM IS BREAKING EWD AND WILL CROSS NRN PLAINS TODAY...BEFORE
   REACHING MN/IA AROUND END OF PERIOD.  THIS FEATURE SHOULD START TO
   ACCELERATE EWD LATE IN PERIOD AS UPSTREAM PERTURBATION -- CURRENTLY
   EVIDENT OVER NRN BC -- TURNS SEWD ACROSS NRN AB AND
   AMPLIFIES...REACHING CENTRAL/SRN SK BY 12Z. 

   11Z SFC ANALYSIS SHOWED COLD FRONT ASSOCIATED WITH LEADING
   NRN-STREAM PERTURBATION FROM SRN MB SWWD ACROSS CENTRAL
   ND...W-CENTRAL/SWRN SD...AND CENTRAL WY.  FRONT IS FCST TO MOVE EWD
   ACROSS NRN PLAINS AND UPPER MIDWEST REGION THROUGH
   PERIOD....REACHING NWRN MN...E-CENTRAL SD...SWRN NEB AND CO/WY
   BORDER AROUND 00Z.  BY 12Z...FRONT SHOULD REACH CENTRAL/WRN LS...WRN
   WI...ERN NEB...AND E-CENTRAL/NERN CO.

   ...UPPER MIDWEST TO CENTRAL PLAINS...
   ALTHOUGH CONDITIONAL SEVERE THREAT WILL BEGIN DURING LATE
   AFTN...MORE CERTAIN CONVECTIVE POTENTIAL IS EXPECTED TO DEVELOP
   AFTER DARK ALONG/AHEAD OF SFC COLD FRONT...WITH ISOLATED LARGE HAIL
   AND DAMAGING GUSTS POSSIBLE.  

   LLJ NOW EXTENDING FROM CENTRAL PLAINS TO SRN MN IS EXPECTED TO SHIFT
   EWD ACROSS UPPER MIDWEST AND UPPER MS VALLEY.  DURING TIME FRAME
   FROM ABOUT 23-02Z...FAVORABLY LLJ-ENLARGED HODOGRAPHS ARE EXPECTED
   TO BECOME JUXTAPOSED WITH RELATIVELY MINIMIZED MLCINH AND PLUME OF
   60S F PREFRONTAL SFC DEW POINTS...PRIMARILY FROM SRN MN ACROSS MUCH
   OF IA.  MODIFIED FCST SOUNDINGS SUPPORT FAVORABLE PARAMETER SPACE
   FOR SUPERCELLS OR BOWS...AS THOSE FACTORS COMBINED WITH END-STAGE
   AFTN BOUNDARY-LAYER WARMTH WILL YIELD UP TO 1500-2000 J/KG
   MLCAPE...40-50 KT EFFECTIVE-SHEAR MAGNITUDES...AND 350-500 J/KG
   EFFECTIVE SRH.  HOWEVER...SUBSTANTIAL/SFC-BASED TSTM DEVELOPMENT IS
   VERY UNCERTAIN...GIVEN STG MLCINH EXPECTED TO DEVELOP THROUGH TODAY
   RELATED TO EML ADVECTING OVER AREA.  

   MIDLEVEL HEIGHT FALLS...APCHG COOLING ALOFT AHEAD OF LEADING
   SHORTWAVE TROUGH...CONVERGENCE NEAR FRONT...AND WAA/ISENTROPIC
   LIFT...SHOULD CONTRIBUTE TO GREATER UNCONDITIONAL TSTM POTENTIAL
   THIS EVENING INTO OVERNIGHT HOURS...SHIFTING EWD ACROSS MRGL-SVR
   PROBABILITY AREAS.  ELEVATED MUCAPE MAY EXCEED 2000 J/KG...WITH
   ISOLATED LARGE HAIL BEING PRIMARY CONCERN TONIGHT. 

   SEPARATE AREA OF ISOLATED TO WIDELY SCATTERED TSTMS MAY DEVELOP LATE
   AFTN INTO EVENING OVER NRN MN AND NERN ND...IN WAKE OF
   ONGOING/MORNING CONVECTION.  ELEVATED MUCAPE 1000-1500 J/KG AND
   35-45 KT EFFECTIVE-SHEAR MAGNITUDES MAY SUPPORT SPORADIC HAIL...SOME
   OF WHICH COULD REACH SVR LIMITS.

   ..EDWARDS/MARSH.. 09/19/2014

   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1630Z