SPC AC 010554

   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   1254 AM CDT MON SEP 01 2014

   VALID 011200Z - 021200Z

   ...THERE IS A SLGT RISK OF SVR TSTMS FROM LOWER MI AND SERN WI
   THROUGH THE MIDWEST...MID MS VALLEY TO ERN KS AND FAR NERN OK...

   ...SUMMARY...
   ISOLATED TO SCATTERED SEVERE THUNDERSTORMS SHOULD DEVELOP ALONG AND
   AHEAD OF A WEAK COLD FRONT FROM PARTS OF THE SOUTHERN GREAT LAKES
   REGION SOUTHWESTWARD ACROSS INDIANA...ILLINOIS...MISSOURI INTO
   EASTERN KANSAS AND FAR NORTHEAST OKLAHOMA.  DAMAGING WINDS AND LARGE
   HAIL WILL BE POSSIBLE WITH THE STRONGEST STORMS...WHILE A TORNADO
   CANNOT BE RULED OUT ACROSS THE SOUTHWESTERN EXTENT OF THE SLIGHT
   RISK AREA. A FEW STRONG WIND GUSTS WILL BE POSSIBLE THIS AFTERNOON
   ACROSS FAR EASTERN WYOMING INTO PARTS OF SOUTHERN SOUTH DAKOTA AND
   NORTHERN NEBRASKA.

   ...LOWER MI/SERN WI TO MID MS VALLEY TO SERN KS/NERN OK... 
   A PROGRESSIVE SHORTWAVE TROUGH IS EXPECTED TO TRACK NEWD FROM THE
   UPPER MS VALLEY THROUGH THE UPPER GREAT LAKES EARLY IN THE FORECAST
   PERIOD...REACHING ONTARIO AND WRN QUEBEC BY LATE AFTERNOON/EARLY
   EVENING.  ALTHOUGH THE STRONGEST 500-MB HEIGHT FALLS /60-90 M/ ARE
   FORECAST TO SPREAD THROUGH THE NRN EXTENT OF THE UPPER GREAT
   LAKES...30-60 METER FALLS SHOULD OCCUR ACROSS THE ERN WI AND LOWER
   MI PORTION OF THE SLIGHT RISK AREA.  MEANWHILE...AN UPSTREAM
   SHORTWAVE TROUGH AND ATTENDANT SPEED MAX ARE EXPECTED TO MOVE FROM
   THE CENTRAL ROCKIES THROUGH THE CENTRAL PLAINS THIS AFTERNOON TO THE
   MIDWEST AND SRN GREAT LAKES LATER MONDAY NIGHT.

   A COLD FRONT ASSOCIATED WITH THE LEAD SHORTWAVE TROUGH IS EXPECTED
   TO EXTEND FROM WRN LAKE SUPERIOR SSWWD THROUGH CENTRAL IA INTO
   CENTRAL KS AT 12Z.  THIS BOUNDARY WILL ADVANCE TO A POSITION FROM
   ERN UPPER MI THROUGH SERN IA INTO SERN KS AND NORTH CENTRAL OK TO
   THE TX PANHANDLE BY LATE AFTERNOON.  FRONTAL CONVECTION WILL LIKELY
   BE ONGOING AT THE BEGINNING OF THE PERIOD...ENHANCED PRIMARILY BY
   ASCENT AHEAD OF THE UPPER MS VALLEY SHORTWAVE TROUGH.  ADDITIONAL
   STORMS MAY ALSO BE ONGOING AT DAYBREAK ACROSS ERN KS INTO CENTRAL/
   SRN MO WITHIN A LOW-LEVEL WAA REGIME. GUSTY WINDS AND ISOLATED HAIL
   MAY OCCUR WITH THE EARLY MORNING ACTIVITY...THOUGH GREATER TSTM
   COVERAGE AND SEVERE WEATHER THREAT WILL BE POSSIBLE ACROSS THE
   SLIGHT RISK AREA LATER TODAY.

   STRONGEST BOUNDARY-LAYER HEATING SHOULD OCCUR ACROSS SERN KS/SWRN MO
   AND OK WHERE SURFACE TEMPERATURES WILL WARM INTO THE 90S.  AS A
   RESULT...INSTABILITY IS EXPECTED TO BE GREATEST ALONG THE TRAILING
   PORTIONS OF THE FRONT WHERE THE ERN EXTENT OF STEEP LAPSE RATES WILL
   CONTRIBUTE TO MODERATE-STRONG INSTABILITY /MLCAPE 2000-3000 J PER
   KG/.  DESPITE WEAKER MIDLEVEL LAPSE RATES AND SOME UNCERTAINTY IN
   DEGREE OF SURFACE HEATING...DUE IN PART TO EARLY DAY CONVECTIVE
   DEBRIS...MODERATE INSTABILITY SHOULD ALSO DEVELOP ENEWD FROM MO TO
   LOWER MI.

   NEW TSTM DEVELOPMENT SHOULD OCCUR FROM SERN WI INTO LOWER MI AND ERN
   IA TO INDIANA FROM LATE MORNING INTO THE AFTERNOON IN VICINITY OF
   THE COLD FRONT AND ANY DIFFERENTIAL HEATING BOUNDARIES ATTENDANT TO
   EARLY MORNING CONVECTION.  A 50-60 KT SWLY MIDLEVEL JET ACCOMPANYING
   THE LEAD TROUGH WILL RESULT IN STRENGTHENING BULK SHEAR FOR THE
   POTENTIAL FOR ORGANIZED STORMS PRODUCING DAMAGING WINDS AND HAIL. 
   MEANWHILE...TSTMS ARE EXPECTED TO BACK-BUILD SWWD THROUGH MO TO SERN
   KS DURING THE MID-LATE AFTERNOON AS THE CAP WEAKENS.  LOW-LEVEL
   WINDS WILL REMAIN BACKED TO SLY INTO SERN KS...NERN OK AND SWRN MO
   ENHANCING CONVERGENCE INTO THE COLD FRONT AND POTENTIAL OUTFLOW
   BOUNDARY FROM EARLY MORNING STORMS.  STRENGTHENING WLY MIDLEVEL
   WINDS ACROSS KS/MO BY LATE AFTERNOON WILL RESULT IN STRONG BULK
   SHEAR FOR ORGANIZED STORMS INCLUDING SUPERCELLS WITH THE STRONG
   INSTABILITY SUPPORTING THE POTENTIAL FOR VERY LARGE HAIL AND STRONG
   WIND GUSTS.  THE AFOREMENTIONED ZONE OF BACKED LOW-LEVEL WINDS WILL
   ENHANCE LOW-LEVEL SHEAR FOR A TORNADO THREAT INTO THE EARLY EVENING.

   ...ERN WY/SWRN SD AND WRN/CENTRAL NEB...
   A FAST-MOVING MIDLEVEL IMPULSE IS EXPECTED TO TRACK ESEWD FROM THE
   NRN ROCKIES TO THIS DISCUSSION AREA BY LATE THIS AFTERNOON.  DESPITE
   SURFACE DEW POINTS IN THE 40S...STEEP LAPSE RATES...WITH 500-MB
   TEMPERATURES AROUND -15 C ACCOMPANYING THE IMPULSE...WILL RESULT IN
   MARGINAL INSTABILITY /MLCAPE 500-1000 J PER KG/ THIS AFTERNOON. 
   TSTMS ARE EXPECTED TO DEVELOP WITHIN THIS NORTHWEST FLOW REGIME WITH
   LOCALLY STRONG WIND GUSTS BEING THE PRIMARY THREAT.

   ..PETERS/DEAN.. 09/01/2014

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