SPC AC 161732
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1132 AM CST SAT NOV 16 2013
VALID 171200Z - 181200Z
...THERE IS A MDT RISK OF SVR TSTMS OVER PARTS OF ERN IL...EXTREME
SERN WI...SRN LOWER MI...OH...INDIANA...AND NRN KY...
...THERE IS A SLGT RISK OF SVR TSTMS FROM THE MID-SOUTH/TN VALLEY
INTO THE GREAT LAKES REGION...
...POTENTIAL EXISTS FOR A WIDESPREAD DAMAGING WIND EVENT AND SEVERAL
TORNADOES /SOME POSSIBLY STRONG/ SUNDAY AFTERNOON AND NIGHT ACROSS
PARTS OF THE OH VALLEY AND GREAT LAKES...
...SYNOPSIS...
LONGWAVE TROUGH CURRENTLY OVER THE WRN US IS FORECAST TO INTENSIFY
THROUGH SUNDAY AS A VERY STRONG MID-LEVEL JET STREAK DIGS SEWD
ACROSS THE GREAT BASIN AND CENTRAL ROCKIES BEFORE PROGRESSING EWD
ACROSS THE CENTRAL PLAINS/MID MS VALLEY DURING THE AFTERNOON. THE
UPPER TROUGH IS FORECAST TO BECOME NEGATIVELY-TILTED AS IT LIFTS
NEWD ACROSS THE GREAT LAKES REGION DURING THE SECOND HALF OF THE
PERIOD.
AT THE SURFACE...AN INTENSE DEEPENING LOW IS FORECAST TO MOVE FROM
IA TOWARD ERN LAKE SUPERIOR DURING THE DAY AND PROGRESS INTO ERN
ONTARIO AND WRN QUEBEC AT NIGHT. A STRONG COLD FRONT WILL ARC SWD
FROM THE LOW WITH THE NRN PART OF THE FRONT ACCELERATING ACROSS THE
GREAT LAKES REGION. THE SRN PART OF THE FRONT IS EXPECTED TO LAG
SWWD...REACHING AN ERN LOWER MI/SRN INDIANA/CENTRAL AR/NRN TX LINE
BY 18/00Z...AND ERN NY/NRN VA/WRN NC/NRN GA AND LOWER MS VALLEY BY
THE END OF THE PERIOD.
...OH VALLEY INTO THE SRN GREAT LAKES...
OVERNIGHT STORMS MAY BE CONTINUING FROM PARTS OF THE OH VALLEY SWWD
ACROSS THE MID-SOUTH/TN VALLEY IN ASSOCIATION WITH A WEAK SHORTWAVE
TROUGH AND LOW LEVEL WARM ADVECTION. THIS ACTIVITY MAY CONTAIN A
MORE LIMITED SEVERE THREAT FOR HAIL AND STRONG/SEVERE WIND GUSTS AS
IT SHIFTS EWD/NEWD WITH TIME. ALTHOUGH DYNAMIC FORCING FOR LARGE
SCALE ASCENT IS EXPECTED TO REMAIN PRIMARILY NORTH OF THIS
AREA...SUFFICIENT DEEP LAYER SHEAR WILL SUPPORT ORGANIZED STORM
STRUCTURES INCLUDING POTENTIAL FOR ISOLATED SUPERCELLS.
THE PRIMARY SEVERE THREAT IS EXPECTED TO DEVELOP DURING THE LATE
MORNING INTO EARLY/MID AFTERNOON FROM ERN IA INTO PARTS OF
NRN/CENTRAL IL...THEN SPREAD EWD THROUGH THE OVERNIGHT HOURS ACROSS
THE GREAT LAKES AND OH VALLEY. STRONG SSWLY LOW LEVEL WINDS WILL
CONTINUE TO ADVECT MOISTURE NWD TOWARD THE DEEPENING SURFACE LOW
WITH 60-65F DEW POINTS REACHING AS FAR NORTH AS NRN PARTS OF IL AND
INDIANA. A PLUME OF STEEPER MID LEVEL LAPSE RATES IS FORECAST TO
EXTEND EWD FROM THE CENTRAL PLAINS TOWARD THE SRN GREAT LAKES AND
WILL CONTRIBUTE TO INCREASED INSTABILITY WITH CAPE OF 1000-1500 J/KG
FORECAST ACROSS PARTS OF IL AND INDIANA. STRONG/SEVERE STORMS MAY
DEVELOP AS EARLY AS MID/LATE MORNING OVER PARTS OF ERN IA NEAR THE
SURFACE LOW AND ADVANCING COLD FRONT...THEN INCREASE IN COVERAGE
INTO NRN/CENTRAL IL DURING THE AFTERNOON AS STRONG DYNAMIC FORCING
WITHIN THE LEFT EXIT REGION OF THE MID/UPPER LEVEL JET STREAK
OVERSPREADS THE LOW LEVEL MOISTURE/INSTABILITY AXIS.
FORECAST SOUNDINGS INDICATE DEVELOPMENT OF CLOCKWISE TURNING
LOW-LEVEL HODOGRAPH STRUCTURES IN ASSOCIATION WITH STRONG VEERING
WIND PROFILES. SEVERAL 12Z CONVECTION-ALLOWING MODELS /ESPECIALLY
THE 4 KM WRF-NSSL AND 1.3 KM NAM FIRE NEST/ INDICATE DEVELOPMENT OF
SUPERCELLS ALONG/AHEAD OF THE COLD FRONT ACROSS PARTS OF IL/INDIANA
AND SRN LOWER MI ALONG/AHEAD OF THE STRONGEST EWD SURGE OF THE COLD
FRONT. THESE WILL HAVE A WINDOW OF OPPORTUNITY FROM MID-LATE
AFTERNOON INTO THE EARLY EVENING TO PRODUCE SWATHS OF DAMAGING WIND
GUSTS...SEVERE HAIL AND POSSIBLY SEVERAL TORNADOES /SOME STRONG/.
WITH TIME...CONVECTION IS EXPECTED TO DEVELOP INTO BOWING LINEAR
STRUCTURES AND SPREAD RAPIDLY EWD/NEWD ACROSS THE LOWER GREAT
LAKES/UPPER OH VALLEY WITH THE PRIMARY SEVERE THREAT TRANSITIONING
TO POTENTIALLY WIDESPREAD DAMAGING WIND GUSTS. THE FAST-MOVING
LINES WILL MOVE PROGRESSIVELY INTO LESSER INSTABILITY...HOWEVER
VERTICAL TRANSFER OF STRONG HORIZONTAL MOMENTUM TO THE SURFACE MAY
MAINTAIN A THREAT FOR WIND DAMAGE THROUGH MUCH OF THE OVERNIGHT
HOURS.
..WEISS.. 11/16/2013
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