SPC AC 061938

   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0238 PM CDT THU OCT 06 2016

   VALID 062000Z - 071200Z

   ...THERE IS AN ENH RISK OF SVR TSTMS THIS AFTERNOON AND EVENING
   ACROSS PARTS OF EASTERN KANSAS....SOUTHEASTERN NEBRASKA...
   SOUTHWESTERN IOWA...AND NORTHWESTERN MISSOURI...

   ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS SURROUNDING AREAS OF THE
   CENTRAL/SOUTHERN PLAINS AND MID/LOWER MISSOURI VALLEY...

   ...THERE IS A MRGL RISK OF SVR TSTMS AS FAR NORTH AS THE UPPER
   MIDWEST AND AS FAR SOUTH AS PARTS OF WEST TEXAS...

   ...THERE IS A MRGL RISK OF SVR TSTMS TONIGHT ACROSS CENTRAL FLORIDA
   ATLANTIC COASTAL AREAS...

   ...SUMMARY...
   SEVERE THUNDERSTORMS ARE LIKELY THIS AFTERNOON AND EVENING ACROSS
   PARTS OF THE CENTRAL PLAINS AND ADJACENT MID MISSOURI
   VALLEY...PARTICULARLY ACROSS PARTS OF EASTERN KANSAS AND
   SOUTHEASTERN NEBRASKA INTO SOUTHWESTERN IOWA AND NORTHWESTERN
   MISSOURI. ISOLATED TORNADOES...ONE OR TWO OF WHICH MAY BE
   STRONG...LARGE TO VERY LARGE HAIL...AND DAMAGING WINDS WILL ALL BE
   POSSIBLE.

   ...20Z UPDATE...
   PRIMARY CHANGE WITH THIS UPDATE IS TO INCREASE TORNADO PROBABILITIES
   ACROSS PARTS OF SERN NEB AND FAR NWRN MO INTO ERN KS. A STRONG
   TORNADO OR TWO MAY ALSO OCCUR ACROSS THIS REGION. LATEST SFC
   OBSERVATIONS AND VISIBLE SATELLITE IMAGERY SHOW AN INCREASINGLY
   MOIST AND UNSTABLE LOW-LEVEL AIRMASS AS DIURNAL HEATING BECOMES
   MAXIMIZED. A WARM FRONT EXTENDS ACROSS NERN KS/SERN NEB NEWD INTO
   S-CNTRL IA...AND AN OUTFLOW BOUNDARY FROM PRIOR CONVECTION IS
   LOCATED FROM NERN OK INTO S-CNTRL KS. EFFECTIVE SRH VALUES WILL
   LIKELY BE ENHANCED ALONG THESE BOUNDARIES THROUGH THE EARLY EVENING
   HOURS WHERE SFC WINDS ARE BACKED TO SLY/SELY. SHEAR VECTORS NEARLY
   ORTHOGONAL TO THE BOUNDARY ACROSS CNTRL/ERN KS SHOULD FAVOR AN
   INITIAL SUPERCELL MODE FOR AT LEAST A FEW HOURS THIS AFTERNOON...
   BEFORE THE LINEAR FORCING OF THE FRONT LIKELY ENCOURAGES UPSCALE
   GROWTH INTO A SQUALL LINE WITH DAMAGING WINDS BECOMING THE MAIN
   THREAT. THE 30 PERCENT WIND PROBABILITIES/ENH AREA HAVE ALSO BEEN
   EXPANDED SEWD INTO MORE OF ERN KS/WRN MO BASED ON LATEST SHORT-TERM
   MODEL GUIDANCE SUGGESTING A DAMAGING BOW MOVING THROUGH THIS REGION
   THROUGH THE EARLY EVENING.

   FOR ADDITIONAL NEAR-TERM METEOROLOGICAL DETAILS REGARDING THE SEVERE
   THREAT ACROSS THE CNTRL PLAINS INTO THE MID MO VALLEY...SEE
   MESOSCALE DISCUSSION 1766. FOR MORE DETAILS REGARDING THE THREAT
   ACROSS THE SRN PLAINS /OK AND TX/...SEE MESOSCALE DISCUSSION 1767.

   ..GLEASON/JEWELL.. 10/06/2016

   .PREV DISCUSSION... /ISSUED 1116 AM CDT THU OCT 06 2016/

   ...SYNOPSIS...
   A SIGNIFICANT SHORT WAVE IMPULSE...WITHIN LARGER-SCALE UPPER
   TROUGHING IN THE MID-LATITUDE WESTERLIES...IS IN THE PROCESS OF
   ACCELERATING NORTHEASTWARD OUT OF THE EASTERN GREAT BASIN/CENTRAL
   ROCKIES REGION.  MODELS INDICATE THAT THIS FEATURE WILL ADVANCE
   ACROSS THE NORTH CENTRAL PLAINS AND MID MISSOURI VALLEY LATER TODAY
   AND TONIGHT.  AS IT DOES...IT MAY COME INCREASINGLY IN PHASE WITH AN
   IMPULSE PIVOTING AROUND THE SOUTHERN PERIPHERY OF A CYCLONIC
   CIRCULATION NOW CENTERED NEAR THE SOUTHERN SASKATCHEWAN/MANITOBA
   BORDER AREA.  ASSOCIATED FORCING FOR ASCENT MAY CONTRIBUTE TO
   SURFACE CYCLOGENESIS ACROSS PARTS OF THE UPPER MIDWEST AND UPPER
   GREAT LAKES REGION BY LATE TONIGHT...WITH A TRAILING SURFACE COLD
   FRONT FORECAST TO SURGE SOUTH OF THE UPPER MISSISSIPPI/MID MISSOURI
   VALLEY AND CENTRAL PLAINS THROUGH MUCH OF THE SOUTH CENTRAL PLAINS
   AND MID MISSOURI VALLEY BY 12Z FRIDAY.

   WELL SOUTH OF THE STRONGER WESTERLIES...MAJOR HURRICANE MATTHEW IS
   EXPECTED TO GRADUALLY MIGRATE INTO...AND NORTHWARD ALONG...THE
   FLORIDA ATLANTIC COAST LATER TODAY THROUGH TONIGHT.

   ...CENTRAL PLAINS...MID/LOWER MISSOURI VALLEY REGION...
   A PERSISTENT AREA OF THUNDERSTORM ACTIVITY AND ASSOCIATED CLOUD
   COVER ACROSS PARTS OF THE LOWER CENTRAL PLAINS INTO LOWER MISSOURI
   VALLEY PROBABLY WILL CONTINUE TO SLOWLY WEAKEN/DIMINISH THROUGH THE
   DAY.  BUT THIS MAY NOT BE IN TIME TO ALLOW FOR SUBSTANTIVE BOUNDARY
   LAYER DESTABILIZATION ACROSS AREAS CURRENTLY IMPACTED PRIOR TO COLD
   FRONTAL PASSAGE THIS EVENING.

   HOWEVER...IN THE WAKE OF THE ONGOING ACTIVITY...AT LEAST A NARROW
   CORRIDOR OF SUBSTANTIVE DESTABILIZATION APPEARS POSSIBLE ALONG THE
   QUASI-STATIONARY FRONTAL ZONE NOW EXTENDING FROM NEAR/NORTH OF THE
   MISSOURI/IOWA BORDER INTO THE CENTRAL HIGH PLAINS.  THIS FRONT WILL
   PROVIDE THE FOCUS FOR A NORTHEASTWARD MIGRATING SURFACE WAVE OUT OF
   SOUTHWEST KANSAS ACROSS THE MID MISSOURI VALLEY THROUGH THIS
   EVENING...BEFORE MORE SUBSTANTIVE SURFACE LOW DEVELOPMENT/DEEPENING
   TAKES PLACE LATER TONIGHT ACROSS THE UPPER MIDWEST/GREAT LAKES
   REGION.

   THE PRIMARY SEVERE WEATHER POTENTIAL FOR THIS PERIOD IS EXPECTED TO
   ACCOMPANY THE SURFACE WAVE AS IT TRACKS ACROSS PARTS OF NORTH
   CENTRAL/NORTHEAST KANSAS INTO THE MID MISSOURI VALLEY LATE THIS
   AFTERNOON.  GIVEN MOISTURE NOW PRESENT IN THE WARM SECTOR...THE
   DEVELOPMENT OF MODERATELY LARGE CAPE /UP TO AROUND 2000 J PER KG/ IN
   AT LEAST A NARROW CORRIDOR ALONG THE FRONT AHEAD OF THE SURFACE WAVE
   STILL SEEMS PROBABLE WITH STEEPENING OF MID-LEVEL LAPSE RATES. 
   ALTHOUGH DEEP LAYER WIND FIELDS AND SHEAR WITHIN THE INSTABILITY
   AXIS MAY NOT BE EXTREME...IT SHOULD BE MORE THAN SUFFICIENT FOR
   ORGANIZED SEVERE STORM DEVELOPMENT GIVEN THE POTENTIAL INSTABILITY.

   FORCING ASSOCIATED WITH LOW-LEVEL WARM ADVECTION NEAR A 30-40 KT
   SOUTHERLY 850 MB JET MAY SUPPORT AT LEAST A COUPLE OF DISCRETE
   SUPERCELLS...WITH POTENTIAL FOR VERY LARGE HAIL AND TORNADOES IN
   INITIAL STORM DEVELOPMENT.  EVENTUALLY...LARGE-SCALE FORCING FOR
   ASCENT PROBABLY WILL CONTRIBUTE TO UPSCALE CONVECTIVE GROWTH
   ALONG/AHEAD OF THE FRONT...WITH DAMAGING WIND POTENTIAL BECOMING THE
   MORE PROMINENT SEVERE WEATHER THREAT.  THIS ACTIVITY WILL ATTEMPT TO
   SPREAD NORTHEASTWARD INTO PARTS OF THE UPPER MIDWEST TONIGHT...BUT
   IT REMAINS UNCLEAR WHETHER BOUNDARY LAYER DESTABILIZATION WILL
   REMAIN SUFFICIENT TO SUPPORT CONTINUING SEVERE WEATHER POTENTIAL.

   SOUTH AND SOUTHWEST OF THE SURFACE WAVE...A WINDOW OF OPPORTUNITY
   APPEARS TO EXIST ALONG THE PRE-FRONTAL TROUGH...AND PERHAPS THE COLD
   FRONT AS IT OVERTAKES THE TROUGH...FOR SEVERE STORM DEVELOPMENT
   ACROSS THE REMAINDER OF CENTRAL INTO EASTERN KANSAS AND WESTERN
   OKLAHOMA.  HOW QUICKLY THE COLD FRONT WILL UNDERCUT THIS ACTIVITY
   REMAINS IN SOME QUESTION...AND WILL DETERMINE THE EXTENT OF THE
   SEVERE HAIL/WIND POTENTIAL THROUGH THE EVENING HOURS.

   ...FLORIDA ATLANTIC COASTAL AREAS...
   GIVEN THE PROXIMITY OF MAJOR HURRICANE MATTHEW TO THE FLORIDA
   ATLANTIC COAST...AND SOME LINGERING UNCERTAINTY CONCERNING THE EXACT
   TRACK...THE DEVELOPMENT OF A RISK FOR ISOLATED TORNADOES IS NOT OUT
   OF THE QUESTION TONIGHT.  HOWEVER...BASED ON THE CURRENT FORECAST
   TRACK...THE POTENTIAL FOR APPRECIABLE INLAND BOUNDARY LAYER
   DESTABILIZATION ALLOWING FOR TORNADIC POTENTIAL STILL SEEMS LOW AT
   THE PRESENT TIME.

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