DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 271944
SWODY1
SPC AC 271942

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0242 PM CDT FRI JUL 27 2012

VALID 272000Z - 281200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS MUCH OF THE OH VALLEY
INTO LOWER MI...

...THERE IS A SLGT RISK OF SVR TSTMS FROM THE MID ATLANTIC SWWD INTO
NRN GA AND AL...

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE BLACK HILLS
REGION...

...LOWER MI...
EXPANDED SLIGHT RISK INTO SERN LOWER MI TO ACCOUNT FOR MARGINAL HAIL
THREAT WITH CURRENT DEVELOPMENT AS IT TRAVELS EWD ACROSS THE STATE.

...BLACK HILLS/WRN SD AREA...
STORMS ARE EXPECTED TO DEVELOP ACROSS ERN WY LATER TODAY...AND WILL
PROPAGATE EWD INTO A WARM AND DEEPLY MIXED ENVIRONMENT. STRONG DEEP
LAYER SHEAR AND STEEP LAPSE RATES ALOFT SHOULD HELP TO PROMOTE FAST
STORMS MOTIONS AND OUTFLOW PRODUCTION...WITH SEVERE WINDS. THE HAIL
WILL BE LIMITED BY MOISTURE AVAILABILITY...BUT MARGINAL HAIL MAY
OCCUR. GIVEN THE DRY LOW LEVELS...HAVE REMOVED TORNADO
PROBABILITIES...AND ALSO REDUCED EXPECTED HAIL COVERAGE.

...SERN MO...
EXPANDED THE SLIGHT RISK AREA SWWD A BIT INTO SERN MO WHERE STORMS
WERE FORMING NEAR FMN ALONG THE WIND SHIFT. STRONG HEATING WILL
CONTINUE...AND NWLY FLOW ALOFT MAY ALLOW STORMS TO PROPAGATE SEWD
THIS AFTERNOON.

..JEWELL.. 07/27/2012

.PREV DISCUSSION... /ISSUED 1131 AM CDT FRI JUL 27 2012/

...SYNOPSIS...
DOMINANT CNTRL RCKYS/HIGH PLNS RIDGE EXPECTED TO SHIFT E AND
SLIGHTLY AMPLIFY THIS PERIOD AS BROAD TROUGH NOW OVER THE GRT
LKS/MID MS VLY SOMEWHAT AMPLIFIES UPON CONTINUING ESE INTO THE OH
VLY.

THE AMPLIFICATION OF THE GRT LKS TROUGH WILL BE ACCOMPLISHED IN
LARGE PART BY JET STREAK/DISTURBANCE NOW OVER THE ERN DAKOTAS. THIS
FEATURE SHOULD MOVE SE INTO IL EARLY SAT AS LEAD IMPULSE NOW OVER LK
MI/NRN IL CONTINUES ESE INTO NRN OH.

FARTHER DOWNSTREAM...ON SRN EDGE OF LARGER SCALE TROUGH...MODERATE
WSW FLOW EXPECTED TO PERSIST FROM OH/WV TO THE MID ATLANTIC/SRN NEW
ENGLAND CST. NO OBVIOUS SHORTWAVE DISTURBANCES ARE APPARENT IN
SATELLITE OR OBJECTIVE ANALYSES...BUT AT LEAST WEAK LARGE SCALE
ASCENT WILL BE PRESENT OVER PARTS OF THE REGION GIVEN GRADUAL
AMPLIFICATION OF BROAD-SCALE TROUGH.

IN THE WEST...MODERATE WSW TO WLY FLOW WILL PREVAIL FROM THE NRN GRT
BASIN TO THE NRN PLNS. THREE DISTURBANCES IN THIS FLOW...ONE NOW
OVER SW MT/WRN WY...ANOTHER NOW ENTERING WRN NV...AND A THIRD
NEARING SEATTLE...LIKELY WILL AFFECT DIURNALLY-ENHANCED STORMS OVER
INTERIOR PARTS OF THE NORTHWEST AND THE NRN PLNS LATER TODAY/TNGT.

AT LWR LVLS...WEAK SFC LOW NOW NEAR CHICAGO SHOULD TRACK ESE INTO
WRN OH BY EVE AS TRAILING COLD FRONT ADVANCES SE INTO SRN MO/FAR SRN
IL. THE LOW AND COLD FRONT SHOULD SERVE TO FOCUS STRONG TO POSSIBLY
SVR TSTM DEVELOPMENT LATER TODAY INTO TNGT. OTHERWISE...WEAK
OUTFLOW/DIFFERENTIAL HEATING BOUNDARIES...AND LEE TROUGH ALONG THE
MID ATLANTIC CST...EXPECTED TO SERVE AS FOCI FOR AFTN STORMS FROM
THE LWR MS AND TN VLYS NEWD INTO SRN NEW ENGLAND.

...OH VLY /MIDWEST THIS AFTN INTO TNGT...
POTENTIAL WILL EXIST FOR STRONG TO SVR TSTMS...MAINLY THOSE WITH
DMGG WIND...THIS AFTN INTO TNGT OVER A PARTS OF THE MID/LWR OH VLY
AND PERHAPS ADJACENT LWR MI/LK ERIE. THIS ACTIVITY WILL BE FOSTERED
BY /1/ ASCENT WITH LEAD UPR IMPULSE NOW NEAR CHICAGO...AND /2/ LATER
TODAY INTO TNGT...BY UPSTREAM DISTURBANCE NOW IN ERN SD.

RECENT CONFIGURATION OF UPR AIR PATTERN HAS NOT FAVORED ADVECTION OF
A MARKED EML INTO THE OH VLY REGION. BUT MID LVL LAPSE RATES IN SLGT
RISK AREA SHOULD BE SUFFICIENT TO SUPPORT SUSTAINED STORMS GIVEN
LIKELIHOOD FOR STRONG SFC HEATING/STEEP LOW LVL LAPSE
RATES...PRESENCE OF AFOREMENTIONED COLD FRONT/LOW...LARGE SCALE
ASCENT...AND SUFFICIENT MOISTURE /PW AROUND 1.25-1.50 INCHES/.
COUPLED WITH MODERATE DEEP WLY FLOW /30-40KT W TO WNWLY DEEP
SHEAR/...SETUP SHOULD YIELD A COUPLE BANDS OR SMALL CLUSTERS OF
STORMS CAPABLE OF DMGG WIND AND PERHAPS HAIL.

THE STORMS MAY EVOLVE INTO BOWING LINE OR TWO...WITH MOVEMENT SE
TOWARD/ACROSS THE OH RVR BY EVE. SOME POTENTIAL ALSO WILL EXIST FOR
CONTINUED STORM DEVELOPMENT ON THE SW EDGE OF STRONGER FORCING FOR
ASCENT...I.E. OVER FAR SRN IL/SE MO/WRN KY...INTO TNGT. CLOSER TO
TRACK OF SFC WAVE...A CONDITIONAL/LOW PROBABILISTIC THREAT FOR A
BRIEF TORNADO MAY DEVELOP.

...MID ATLANTIC/SRN NEW ENGLAND THIS AFTN/EVE...
SEASONABLY STRONG...UNIDIRECTIONAL WLY FLOW NOW ACROSS REGION WILL
SOMEWHAT SUBSIDE TODAY...BUT REMAIN AMPLE FOR SUSTAINED/ORGANIZED
STORMS. AREA SOUNDINGS AND CURRENT VIS SATELLITE DATA SUGGEST
RELATIVELY MODEST MID LVL LAPSE RATES ACROSS REGION...IN ADDITION TO
A LOW LVL INVERSION.

NEVERTHELESS...SUBSTANTIAL LOW LVL HEATING/DESTABILIZATION WILL
OCCUR OVER PARTS OF THE REGION TODAY...ESPECIALLY ALONG LEE TROUGH
FROM NJ SW INTO CNTRL NC. THIS ENVIRONMENT MAY FOSTER EVENTUAL
DEVELOPMENT OF A LONG...BROKEN BAND OF STORMS ALONG THE TROUGH.
LOCALIZED STRONGER STORMS WITH THE BAND COULD YIELD DMGG WIND GIVEN
ENHANCED ENVIRONMENTAL FLOW AND HIGH PW /AROUND 2 INCHES/ PRESENT
ACROSS REGION.

...NRN HIGH PLNS/INTERIOR NORTHWEST...
LOW LVL MOISTURE WILL INCREASE OVER THE NRN HIGH PLNS TODAY INTO
TNGT AS LEE TROUGH BECOMES BETTER DEFINED WITH THE APPROACH OF MT/WY
UPR IMPULSE AND WITH THE CONTINUED SE MOVEMENT OF ERN SD JET STREAK.
MOISTURE WILL...HOWEVER...REMAIN RELATIVELY LIMITED THROUGH THE
PERIOD...WITH PW EXPECTED TO REMAIN AOB 1.00 UNTIL LATE TNGT.

DIFFERENTIAL SFC HEATING...MOISTURE RETURN...AND ASCENT WITH MT/WY
TROUGH SHOULD SUPPORT SCTD STORM DEVELOPMENT OVER NRN/ERN WY/SRN MT
AND WRN SD BY LATE AFTN. THESE STORMS SHOULD MOVE E TO NE INTO THE
LWR PLNS THIS EVE/EARLY SAT. WITH SFC DEWPOINTS AROUND 50 F...STEEP
MID LVL LAPSE RATES...AND AMPLE DEEP SHEAR FOR ORGANIZED
UPDRAFTS...EXPECT MAINLY HIGH BASED STORMS WITH A THREAT FOR LOCALLY
DMGG WIND.

WAA/WARM FRONTOGENESIS WILL INCREASE OVER WRN/CNTRL SD TNGT...ON
TAIL END OF COLD FRONT MOVING SE INTO OH VLY. ANY SUSTAINED STORMS
THAT PERSIST AND OR REFORM OVER THAT AREA COULD BECOME A
SUPERCELL...WITH A POTENTIAL FOR HAIL AND ISOLD DMGG WIND. A SMALL
MCS ALSO MAY DEVELOP...BUT OVERALL SVR THREAT SHOULD REMAIN FAIRLY
MARGINAL GIVEN MODEST MOISTURE/LIMITED CAPE.

...LWR MS VLY/SOUTH...
POCKETS OF STRONG INSTABILITY/HIGH PW WILL EXIST FROM THE SRN
APPALACHIANS WSW INTO THE LWR MS VLY/SRN PLNS....AREAS LARGELY
REMOVED FROM STRONGER FLOW ALOFT. WHILE WDLY SCTD WET
MICROBURSTS MAY OCCUR...POTENTIAL FOR ORGANIZED/CONCENTRATED
ACTIVITY APPEARS LOW.

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