Sep 8, 2014 1300 UTC Day 1 Convective Outlook
Updated: Mon Sep 8 12:52:24 UTC 2014 (20140908 1300Z Day 1 shapefile | 20140908 1300Z Day 1 KML)
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20140908 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
20140908 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
2 % 41,200 3,052,164 Omaha, NE...Des Moines, IA...Cedar Rapids, IA...Waterloo, IA...Iowa City, IA...
Probabilistic Damaging Wind Graphic
20140908 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 % 90,012 5,626,757 Omaha, NE...Lincoln, NE...Des Moines, IA...Cedar Rapids, IA...Peoria, IL...
Probabilistic Large Hail Graphic
20140908 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 % 73,535 4,613,064 Omaha, NE...Lincoln, NE...Des Moines, IA...Cedar Rapids, IA...Davenport, IA...
   SPC AC 081252

   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0752 AM CDT MON SEP 08 2014

   VALID 081300Z - 091200Z

   ...NO SVR TSTM AREAS FORECAST...

   ...SUMMARY...
   AT LEAST ISOLATED SEVERE THUNDERSTORMS WILL BE POSSIBLE FROM EASTERN
   NEBRASKA EASTWARD ACROSS IOWA TO NORTHWESTERN ILLINOIS. HAIL AND
   STRONG WIND GUSTS ARE EXPECTED TO BE THE PRIMARY WEATHER HAZARDS.

   ...SYNOPSIS...
   FAIRLY LOW AMPLITUDE WILL CHARACTERIZE SYNOPTIC-SALE UPPER-AIR
   PATTERN OVER CONUS THIS PERIOD.  IN NRN STREAM...SHORTWAVE TROUGHS
   NOW OVER SRN IL AND SWRN MN EACH ARE FCST TO MOVE ENEWD AND
   WEAKEN...LATTER REACHING WI BY 00Z AND LM/WRN LOWER MI AREA BY 12Z. 
   TRAILING AND LOOSELY ATTACHED VORTICITY LOBE IS EVIDENT OVER WRN
   SD...AND SHOULD MOVE TO FSD/SUX REGION BY 00Z...THEN ACROSS NRN IA
   OVERNIGHT. 

   HEIGHTS ALOFT WILL FALL ACROSS MUCH OF NRN ROCKIES AND INTERIOR NWRN
   CONUS...ESPECIALLY AFTER 00Z...IN RESPONSE TO SERIES OF SHORTWAVE
   TROUGHS PIVOTING SEWD AND EWD OVER WRN CANADA.  AS THAT
   OCCURS...MID/UPPER-LEVEL CYCLONE -- NOW EVIDENT IN MOISTURE-CHANNEL
   IMAGERY OVER CAPE MENDOCINO AREA -- SHOULD MOVE INLAND AND DEVOLVE
   TO OPEN-WAVE TROUGH...REACHING FROM NRN NV TO CENTRAL CA BY 12Z. 

   AHEAD OF AFOREMENTIONED HEIGHT FALLS...SFC COLD FRONT ANALYZED AT
   11Z FROM SERN SK ACROSS N-CENTRAL MT IS FCST TO MOVE SEWD OVER NRN
   PLAINS.  BY 12Z THIS BOUNDARY SHOULD EXTEND FROM LS LAKEHEAD REGION
   OF ONT SWWD ACROSS NRN MN...THROUGH FRONTAL-WAVE LOW INVOF BLACK
   HILLS...TO EXTREME NRN WY OR SRN MT.  RESIDUAL/QUASISTATIONARY FRONT
   WILL REMAIN NEAR PRESENT LOCATION FROM SC TO SRN LA AND S-CENTRAL
   TX...WHILE CONTINUING GRADUAL FRONTOLYSIS.

   ...MID MO VALLEY/MID TO UPPER MS VALLEY...
   ONGOING CLUSTER OF STG TSTMS ACROSS FSD/SUX REGION IS LOCATED WITHIN
   JUXTAPOSITION OF TWO REGIMES OF LARGE-SCALE ASCENT--LOW-LEVEL WAA
   AND ISENTROPIC ASCENT TO LFC NEAR NOSE OF 30-40-KT LLJ...AND COMPACT
   PLUME OF DCVA RELATED TO SWRN MN SHORTWAVE TROUGH.  THIS ACTIVITY IS
   EXPECTED TO CONTINUE SHIFTING SEWD TO ESEWD OVER NWRN IA THROUGH
   MID-LATE MORNING.  EXPECT CONVECTION TO BECOME MORE DISORGANIZED AND
   PERHAPS DISSIPATE DURING FORENOON HOURS AS LLJ WEAKENS AND
   PRIMARY/LEADING VORTICITY LOBE EJECTS AWAY FROM AREA. 
   MEANWHILE...HOWEVER...EMBEDDED CELLS MAY FLARE UP TO PRODUCE HAIL OR
   GUSTS NEAR SVR LEVELS...WHERE DOWNDRAFTS ACCELERATE THROUGH
   RELATIVELY DRY SUBCLOUD LAYER ENOUGH TO PENETRATE NEAR-SFC LAYER OF
   STG STATIC STABILITY. 

   OUTFLOW/DIFFERENTIAL-HEATING BOUNDARY FROM ONGOING MCS SHOULD
   CONTRIBUTE TO RENEWED POTENTIAL FOR STG/ISOLATED SVR TSTM
   DEVELOPMENT THIS AFTN -- WHETHER FROM REMAINS OF MORNING CONVECTION
   MOVING INTO DESTABILIZING AIR MASS OR DEVELOPMENT ANEW INVOF
   BOUNDARY.  RICHEST PW PLUME CONTAINING GULF-ORIGIN MOISTURE WILL
   REMAIN S OF THIS AREA THROUGH PERIOD.  HOWEVER...LEADING PHASE OF
   MOIST ADVECTION THROUGH WEAKENING SRN-CONUS BAROCLINIC ZONE WILL
   COMBINE WITH EVAPOTRANSPIRATION TO BOOST NEAR-SFC MOISTURE OVER THIS
   REGION THROUGHOUT TODAY.  BY LATE AFTN...60S F SFC DEW POINTS SHOULD
   APPEAR...COMBINING WITH DIURNAL HEATING ALONG AND SE OF BOUNDARY TO
   YIELD MLCAPE RANGING FROM AROUND 1000 J/KG NEAR MS RIVER TO OVER
   2000 J/KG IN ERN NEB...CONCURRENT WITH WWD STEEPENING OF MIDLEVEL
   LAPSE RATES THAT IS RELATED TO PROGRESSIVELY STRONGER EML WITH WWD
   EXTENT.  LOW-LEVEL SHEAR AND VORTICITY SHOULD BE LOCALLY MAXIMIZED
   NEAR THAT BOUNDARY ALSO...OFFERING POTENTIAL LOCALIZED FOCUS FOR
   SUPERCELL EVOLUTION.  

   GIVEN CAPPING CONCERNS AND MESOSCALE BOUNDARY UNCERTAINTIES...TIMING
   AND POSITION OF STRONGEST AFTN/EVENING DEVELOPMENT IS STILL UNCLEAR.
   RATHER FOCUSED AREA OF HIGHER UNCONDITIONAL SVR PROBABILITIES MAY
   DEVELOP WITHIN BROADER 5% SWATH ONCE THOSE SPATIAL/TIMING
   UNCERTAINTIES ARE BETTER-RESOLVED.  SHORT-LIVED MCS ALSO MAY EVOLVE
   FROM AFTN/EVENING CONVECTION AND PROCEED SEWD OVER PORTIONS
   IA...NWRN IL AND/OR NRN MO TONIGHT.

   ..EDWARDS/JIRAK.. 09/08/2014

   CLICK TO GET WUUS01 PTSDY1 PRODUCT

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