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000
ACUS02 KWNS 211706
SWODY2
SPC AC 211705

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1205 PM CDT TUE MAY 21 2013

VALID 221200Z - 231200Z

...THERE IS A SLGT RISK OF SVR TSTMS FROM THE LOWER GREAT LAKES INTO
THE OH/TN VALLEYS...

...SYNOPSIS...
HIGH AMPLITUDE BLOCKING PATTERN IS FORECAST TO CONTINUE ON WEDNESDAY
AS AN UPPER LOW CURRENTLY OVER THE UPPER MIDWEST MOVES SLOWLY EWD
AND BEGINS TO PHASE WITH A NRN STREAM SHORT WAVE TROUGH MOVING SEWD
FROM THE HUDSON BAY REGION.  IN THE WEST...A COLD UPPER LOW JUST OFF
THE PACIFIC NW COAST IS EXPECTED TO MOVE SLOWLY ONSHORE...AS A
DOWNSTREAM RIDGE DEVELOPS OVER THE SRN HIGH PLAINS.

AT THE SURFACE...A LOW INITIALLY OVER SRN LAKE MI IS FORECAST TO
DEVELOP EWD ACROSS SRN LOWER MI DURING THE AFTERNOON BEFORE LIFTING
NEWD TOWARD SWRN QUE BY THE END OF THE PERIOD.  A COLD FRONT
EXTENDING SWWD FROM THIS LOW IS FORECAST TO MOVE SLOWLY SEWD ACROSS
THE MIDDLE OH VALLEY AND MID-SOUTH. THE WRN PART OF THE FRONT WILL
CURVE WWD/NWWD ACROSS OK AND INTO CO.

...LOWER GREAT LAKES INTO THE OH/TN VALLEYS...
STRONG/SEVERE THUNDERSTORMS DURING THE DAY 1 OVERNIGHT PERIOD ARE
EXPECTED TO BE WEAKENING OVER PARTS OF THE OH/TN VALLEYS BY 22/12Z.
LINGERING CLOUDS AND SCATTERED AREAS OF PRECIPITATION ARE LIKELY TO
INHIBIT WIDESPREAD DIABATIC HEATING AND SUBSEQUENT STRONG
DESTABILIZATION INTO THE AFTERNOON.  HOWEVER...BREAKS IN CLOUD COVER
ARE EXPECTED TO BE PRESENT AND WILL FOSTER LOCALIZED REGIONS OF
STRONGER HEATING.  WITH AMPLE LOW LEVEL MOISTURE IN PLACE /SURFACE
DEW POINTS IN THE 65-70F RANGE/ POCKETS OF STRONGER INSTABILITY WITH
SBCAPE OF 1000-1500 J/KG ARE EXPECTED TO DEVELOP.

SEVERAL BANDS OF THUNDERSTORMS ARE EXPECTED TO INCREASE DURING THE
AFTERNOON...POSSIBLY AIDED BY REMNANT OUTFLOW BOUNDARIES FROM
OVERNIGHT/MORNING CONVECTION AHEAD OF THE COLD FRONT.  KINEMATIC
GUIDANCE FROM NWP MODELS IS CONSISTENT SHOWING STRENGTHENING SSWLY
WINDS ALOFT ABOVE THE GROUND SPREADING ACROSS THE OH VALLEY AND
LOWER GREAT LAKES DURING THE AFTERNOON...WITH UNIDIRECTIONAL 40-50
KT FLOW ABOVE 1-2 KM.  THIS WIND PROFILE WILL ENHANCE STORM
ORGANIZATION WITH POTENTIAL FOR A FEW BOWING LINE SEGMENTS AND
POSSIBLY SMALL SUPERCELLS TO DEVELOP...ESPECIALLY OVER PARTS OF OH
AND EXTREME SERN LOWER MI WHERE HIGHER SEVERE PROBABILITY VALUES
HAVE BEEN INTRODUCED.  DAMAGING WIND GUSTS...MARGINALLY SEVERE
HAIL...AND POSSIBLY A TORNADO OR TWO WILL BE POSSIBLE WITH STRONGER
STORMS INTO THE EVENING HOURS.

OTHER STORMS ARE LIKELY TO DEVELOP FARTHER EAST OVER PARTS OF NY/PA
WHERE STRONGER DIURNAL HEATING IS EXPECTED WITHIN A WEAKLY CAPPED
UNSTABLE ENVIRONMENT.  ALTHOUGH VERTICAL WIND SHEAR WILL BE WEAKER
IN THIS AREA...A FEW MULTICELLULAR STORM CLUSTERS ARE EXPECTED TO
DEVELOP WITH POTENTIAL TO PRODUCE DAMAGING WIND GUSTS AND HAIL.

...LOWER MS VALLEY INTO SERN TX...
OVERNIGHT CONVECTION IS EXPECTED TO BE CONTINUING FROM WRN AL/MS
INTO SERN TX DURING THE MORNING...WITH ASSOCIATED CLOUD COVER LIKELY
INHIBITING STRONGER DESTABILIZATION IMMEDIATELY AHEAD OF THE STORMS.
 ACTIVITY IS LIKELY TO SLOWLY SPREAD EWD/SEWD DURING THE DAY WITH
POTENTIAL FOR ISOLATED SEVERE STORMS PRODUCING WET MICROBURSTS OR
MARGINAL HAIL.  WEAKENING FLOW ALOFT/VERTICAL SHEAR IS EXPECTED TO
LIMIT THE OVERALL SEVERE THREAT.

..WEISS.. 05/21/2013