DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 191953
SWODY1
SPC AC 191951

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0251 PM CDT FRI JUL 19 2013

VALID 192000Z - 201200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE GREAT
LAKES...OH VALLEY...NRN APPALACHIAN MTNS AND NEW ENGLAND...

NO CHANGES ARE MADE TO THE OUTLOOK FOR THIS ISSUANCE.

..BROYLES.. 07/19/2013

.PREV DISCUSSION... /ISSUED 1130 AM CDT FRI JUL 19 2013/

...LOWER MI AND VICINITY THIS AFTERNOON INTO TONIGHT...
A LEAD SHORTWAVE TROUGH OVER NW WI/WRN UPPER MI WILL PROGRESS EWD
OVER NRN LOWER MI TODAY...AS THE PRIMARY UPSTREAM TROUGH OVER NE
MANITOBA DIGS SEWD OVER ONTARIO. ASSOCIATED CYCLOGENESIS ACROSS
QUEBEC /JUST E OF JAMES BAY/ WILL HELP DRIVE A COLD FRONT SEWD
ACROSS THE CENTRAL PLAINS...UPPER MS VALLEY...AND UPPER GREAT LAKES
BY TONIGHT.

A BROKEN BAND OF CONVECTION HAS CROSSED NRN LOWER MI AS OF MID
MORNING IN ADVANCE OF THE LEAD SHORTWAVE TROUGH...WHILE A SECOND
BAND IS ONGOING OVER WRN UPPER MI AND FAR NRN WI ALONG THE SURFACE
COLD FRONT. THE STRONGEST SURFACE HEATING AND GREATEST
DESTABILIZATION WILL OCCUR TODAY ALONG AND SE OF THE PRE-FRONTAL
CONVECTIVE BAND FROM NRN IL TO LOWER MI...WHERE AFTERNOON SURFACE
TEMPERATURES IN THE UPPER 80 TO LOWER 90S WILL REMOVE CONVECTIVE
INHIBITION AND CONTRIBUTE TO MLCAPE OF 1500-2500 J/KG.
UNIDIRECTIONAL WIND PROFILES WITH 35-45 KT MEAN WLY LOW-MIDLEVEL
FLOW WILL COMBINE WITH THE MODERATE BUOYANCY AND STEEPENING
LOW-LEVEL LAPSE RATES TO RESULT IN A RISK FOR DAMAGING WINDS WITH
THE STRONGER EMBEDDED STORMS/LINE SEGMENTS.

THERE ARE SOME CONCERNS REGARDING THE MAGNITUDE AND COVERAGE OF THE
DAMAGING WIND RISK THIS AFTERNOON. LOW-LEVEL CONVERGENCE IS WEAK AT
BEST WITHIN THE PRE-FRONTAL BAND FROM NRN IL TO LOWER MI WHICH
BRINGS INTO QUESTION THE ORGANIZATION AND COVERAGE OF STORMS.
ALSO...THE STRONGEST LOW-MIDLEVEL FLOW AND POTENTIAL FOR MOMENTUM
TRANSFER WILL RESIDE FARTHER N ACROSS NRN LOWER MI WHERE STORMS THIS
MORNING HAVE INTERRUPTED THE DIURNAL CYCLE OF DESTABILIZATION. THE
NET RESULT IS SOMEWHAT QUESTIONABLE PHASING OF THE STRONGER FLOW
FIELDS AND LARGER-SCALE ASCENT WITH THE MORE UNSTABLE WARM SECTOR.
STILL...WILL MAINTAIN THE RISK FOR A FEW DAMAGING GUSTS GIVEN THE
ONGOING STORMS IN LOWER MI...AND SOME POTENTIAL FOR INTENSIFICATION
LATER THIS AFTERNOON OF THE CONVECTION ALONG THE COLD FRONT.

...WRN/NRN NY INTO NRN NEW ENGLAND THROUGH TONIGHT...
AN INITIAL CLUSTER OF STORMS HAS WEAKENED OVER MAINE AS OF LATE
MORNING...WITH SURFACE HEATING/DESTABILIZATION UNDERWAY S-W OF THE
DIFFERENTIAL HEATING ZONE/WARM FRONT ACROSS SRN/CENTRAL MAINE. IT
APPEARS THAT CONVECTIVE INITIATION THIS AFTERNOON WILL RELY ON LOCAL
TERRAIN CIRCULATIONS OR WEAK LAKE BREEZES TO THE LEE OF ERIE AND
ONTARIO. THE MORE ORGANIZED STORMS FROM NRN LAKE HURON TO EXTREME
SW QUEBEC ARE EXPECTED TO REACH NRN NY AND WRN MAINE PERHAPS AS
EARLY AS 22-23Z...NEAR THE END OF THE DIURNAL HEATING CYCLE.
THUS...THE RISK FOR DAMAGING WINDS/LARGE HAIL THROUGH THE AFTERNOON
SHOULD REMAIN RATHER MODEST WITH WIDELY SCATTERED STORMS ON THE SE
FRINGE OF THE STRONGER MIDLEVEL FLOW...WITH AN INCREASE IN THE
DAMAGING WIND POTENTIAL LATE THIS AFTERNOON/EVENING WITH THE
APPROACH OF THE ONTARIO/QUEBEC STORMS. OTHERWISE...ANY RISK FOR A
SUPERCELL/TORNADO WILL BE CONFINED TO THE ZONE OF STRONGER LOW-LEVEL
SHEAR FROM EXTREME NRN NY INTO MAINE...THOUGH STORM COVERAGE SHOULD
REMAIN ISOLATED AT BEST.


...ERN WY/WRN NEB AND SD THIS AFTERNOON INTO TONIGHT...
A WEAK POST-FRONTAL UPSLOPE FLOW REGIME IS DEVELOPING ACROSS THE
CENTRAL/NRN HIGH PLAINS. ONGOING CONVECTION WILL SLOWLY CLEAR FROM
WNW TO ESE...ALLOWING STRONGER SURFACE HEATING BY MIDDAY ACROSS ERN
WY. EXPECT NEW CONVECTION TO FORM LATE THIS AFTERNOON IN THE CASPER
TO SHERIDAN CORRIDOR AND THEN MOVE EWD OVER THE HIGH PLAINS THIS
EVENING. INSTABILITY WILL NOT BE PARTICULARLY LARGE...BUT VERTICAL
SHEAR WILL BE SUFFICIENT FOR SOMEWHAT HIGH-BASED SUPERCELLS WITH A
MARGINAL HAIL/WIND RISK. SOME CONVECTION COULD PERSIST FARTHER E
AND OVERNIGHT INTO WRN SD IN CONJUNCTION WITH LOW-LEVEL WAA AND A
25-30 KT LLJ.

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