Thursday, June 16, 2011

DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 161953
SWODY1
SPC AC 161952

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0252 PM CDT THU JUN 16 2011

VALID 162000Z - 171200Z

...THERE IS A SLGT RISK OF SVR TSTMS FROM OH TO PA AND INTO THE
CAROLINAS...

...THERE IS A SLGT RISK OF SVR TSTMS THIS AFTERNOON INTO TONIGHT
FROM THE GREAT BASIN TO THE PLAINS AND LOWER MS VALLEY...

...LITTLE OVERALL CHANGE TO THE PREVIOUS DAY 1 OUTLOOK...

...MS/AL...
STORMS HAVE ERUPTED NEAR THE SURFACE THETA-E AXIS OVER MS/AL WITH
MLCAPE IN EXCESS OF 3000 J/KG. ADJUSTED THE SLIGHT LINE A BIT
FARTHER E TO ACCOUNT FOR CURRENT LOCATION. STORMS SHOULD REMAIN
RELATIVELY STATIONARY BUT MAY DRIFT SWWD WITH TIME INTO VERY WEAK
SWLY LOW LEVEL FLOW.

...ERN OK...WRN AR...
A SMALL CLUSTER OF STORMS CONTINUES TO PROPAGATE SEWD ALONG AN OLD
OUTFLOW BOUNDARY. SWLY LOW LEVEL FLOW WILL CONTINUE TO FEED THIS
SYSTEM VERY UNSTABLE AIR. THE 18Z LMN SOUNDING SHOWED OVER 3000 J/KG
MLCAPE ALONG WITH VERY STEEP LAPSE RATES. DESPITE MARGINAL DEEP
LAYER SHEAR...PRESENCE OF STEEP LAPSE RATES AND OUTFLOW SHOULD HELP
THE SYSTEM MAINTAIN OR INCREASE IN INTENSITY AS IT TRAVELS SEWD.

...UT INTO NWRN CO/SRN WY EWD INTO WRN NEB...
HIGH BASED CONVECTION IS INCREASING ALONG A COLD FRONT WITH VERY
STEEP LAPSE RATE PROFILES AND WITH MODERATE DEEP SHEAR. STRONG WINDS
WILL BE THE MAIN THREAT BUT GIVEN COOL AIR ALOFT SOME MARGINALLY
SEVERE HAIL MAY OCCUR. FOR MORE INFORMATION SEE MESOSCALE DISCUSSION
1245.

OTHER STORMS ARE CURRENTLY FORMING OVER SERN WY/NERN CO AND WILL
INCREASE IN INTENSITY WITH DAMAGING WINDS LIKELY AS A FORWARD
PROPAGATING MCS DEVELOPS. HAIL IS ALSO LIKELY. SOME HAIL COULD
BECOME VERY LARGE ONCE STORMS REACH THE UPPER 50S/LOWER 60S
DEWPOINTS FARTHER E INTO CNTRL NEB...BUT THIS WILL ALSO DEPEND ON
STORM MODE...WITH ISOLATED CELLS BEING CAPABLE OF SIG HAIL. HIGH
RESOLUTION MODELS SHOW STORMS MERGING TOGETHER AND THIS SEEMS
REASONABLE GIVEN OUTFLOW POTENTIAL WHERE STORMS ARE GENERATING. SEE
MESOSCALE DISCUSSION 1246 FOR MORE DETAIL.

..JEWELL.. 06/16/2011

.PREV DISCUSSION... /ISSUED 1136 AM CDT THU JUN 16 2011/

...NW TX/OK/KS THROUGH TONIGHT...
CONVECTIVE OUTFLOW WITH A WEAKENING MCS OVER NW AR AND UPSTREAM
CONVECTION IN ERN KS HAVE REINFORCED THE EFFECTIVE FRONT FROM S
CENTRAL KS TO E CENTRAL OK. WAA WITH A 30-40 KT LLJ WILL PERSIST
TODAY ACROSS OK/SRN KS...AND COULD HELP MAINTAIN THE KS CLUSTER AS
IT MOVES SEWD INTO SE KS/NE OK WITH AN ATTENDANT RISK FOR ISOLATED
LARGE HAIL AND DAMAGING WINDS. THE OUTFLOW BOUNDARY IN THE WAKE OF
THIS CONVECTION TRAILS WWD/NWWD TO A LEE CYCLONE THAT WILL BE
MAINTAINED THROUGH TONIGHT NEAR THE SW KS/SE CO BORDER...WHILE A
DRYLINE EXTENDS SWD ACROSS THE TX PANHANDLE INTO NW TX.

A WARM EML HAS ALREADY OVERSPREAD THE SW KS/WRN OK/NW TX AREA.
LOW-LEVEL ASCENT ALONG THE BOUNDARIES AND SURFACE TEMPERATURES NEAR
100 F WILL BE NEEDED TO REMOVE CONVECTIVE INHIBITION...WITH
CONVECTIVE INITIATION EXPECTED LATE THIS AFTERNOON. THOUGH THE WARM
SECTOR DEWPOINTS WILL MIX INTO THE 50S...THE STEEP LAPSE RATES AND
VERY WARM SURFACE TEMPERATURES WILL SUPPORT MLCAPE NEAR 2000 J/KG.
ADDITIONALLY...VERTICAL SHEAR PROFILES WILL BE FAVORABLE FOR
HIGH-BASED SUPERCELLS CAPABLE OF PRODUCING DAMAGING WINDS AND LARGE
HAIL. THE EVENING STORMS COULD GROW INTO A CLUSTER OR TWO AND
PERSIST OVERNIGHT WHILE MOVING EWD ALONG THE REMNANT OUTFLOW/WARM
FRONT ACROSS SRN KS OR NRN OK.

...UT NEWD TO HIGH PLAINS...
A STRONG SHORTWAVE TROUGH OVER ID/ORE THIS MORNING WILL ROTATE ESEWD
OVER NRN NV/NRN UT/SRN ID THIS AFTERNOON AND ENEWD TO THE NRN HIGH
PLAINS LATE TONIGHT...AROUND THE SRN PERIPHERY OF THE NRN ROCKIES
CLOSED LOW. A WEAK SURFACE REFLECTION/INVERTED TROUGH WILL BE
MAINTAINED DOWNSTREAM ACROSS THE NRN HIGH PLAINS...WHILE THE
ASSOCIATED COLD FRONT MOVES SLOWLY SEWD ACROSS THE SRN GREAT BASIN.
A BROKEN BAND OF HIGH-BASED STORMS IS EXPECTED ALONG THE FRONT THIS
AFTERNOON FROM CENTRAL UT INTO NW CO...WHERE SURFACE DEWPOINTS NEAR
40 F AND AFTERNOON TEMPERATURES AOA 80 F WILL CONTRIBUTE TO SBCAPE
OF 500-1000 J/KG. EFFECTIVE BULK SHEAR IN EXCESS OF 40 KT WILL
SUPPORT ORGANIZED CLUSTERS...AND POTENTIALLY HIGH-BASED SUPERCELLS
CAPABLE OF PRODUCING A FEW SEVERE WIND GUSTS AND MARGINALLY SEVERE
HAIL.

ADDITIONAL STORM DEVELOPMENT IS EXPECTED THIS AFTERNOON IN THE AREA
OF WEAK UPSLOPE FLOW FROM NRN CO/SE WY EWD/NEWD OVER THE HIGH
PLAINS...WHERE MODEST INSTABILITY WILL COINCIDE WITH SUFFICIENT
VERTICAL SHEAR FOR SUPERCELLS. OTHER MORE ISOLATED STORMS MAY ALSO
FORM ALONG THE FRONT/INVERTED TROUGH FROM THE NEB PANHANDLE NWD INTO
SD...AND THE HIGH PLAINS CONVECTION WILL SPREAD EWD TO THE SURFACE
BOUNDARY THIS EVENING. DAMAGING WINDS AND LARGE HAIL WILL BE THE
MAIN THREATS...THOUGH A TORNADO OR TWO CANNOT BE RULED OUT.

...UPPER OH VALLEY/LEE OF THE APPALACHIANS THIS AFTERNOON...
A CLOSED MIDLEVEL LOW OVER THE MI/INDIANA BORDER WILL PROGRESS EWD
TO NRN OH THIS AFTERNOON...WHILE A WEAK LEAD SHORTWAVE TROUGH MOVES
EWD OVER THE APPALACHIANS. A WEAK SURFACE TROUGH/FRONT IS MOVING
ACROSS THE APPALACHIANS NOW...WITH SURFACE HEATING ONGOING IN CLOUD
BREAKS E OF THE BOUNDARY FROM VA INTO NC. FARTHER NW...SURFACE
HEATING AND RESIDUAL DEWPOINTS IN THE 60S HAVE SPREAD NEWD INTO OH
IMMEDIATELY IN ADVANCE OF THE MIDLEVEL LOW. EXPECT SMALL
BANDS/CLUSTERS OF STORMS TO FORM BY EARLY-MID AFTERNOON ACROSS
OH...AND THESE STORMS WILL ROTATE EWD TOWARD WRN PA LATER THIS
AFTERNOON/EVENING AS THE THICKER LOW CLOUDS ERODE SOME FROM W TO E.
COOL MIDLEVEL TEMPERATURES...MLCAPE OF 500-1000 J/KG AND EFFECTIVE
BULK SHEAR OF 30-35 KT SHOULD SUPPORT A FEW STORMS CAPABLE OF
DAMAGING GUSTS AND MARGINALLY SEVERE HAIL THROUGH THIS EVENING.

IMMEDIATELY E OF THE APPALACHIANS THIS AFTERNOON...STORM DEVELOPMENT
IS EXPECTED IN A BROKEN BAND FROM THE WRN CAROLINAS INTO VA/MD WHERE
SURFACE HEATING WILL BE STRONGER. MLCAPE IS NOT EXPECTED TO EXCEED
1000-1500 J/KG AS A RESULT OF RATHER POOR MIDLEVEL LAPSE RATES...AND
DEEP-LAYER VERTICAL SHEAR WILL NOT BE PARTICULARLY STRONG.
THUS...THE SEVERE THREAT APPEARS TO BE ON THE LOWER MARGINS FOR A
SLIGHT RISK...WITH ISOLATED STRONG/DAMAGING GUSTS AND HAIL NEAR
SEVERE LEVELS THE MAIN CONCERNS.

...AR TO NW MS/SW TN THIS AFTERNOON...
A REMNANT MCV OVER NW AR WILL MOVE ESEWD TODAY INVOF A SURFACE WARM
FRONT. SURFACE HEATING WILL WEAKEN THE CAP BY EARLY-MID AFTERNOON
AND COULD SUPPORT ADDITIONAL THUNDERSTORM DEVELOPMENT NEAR THE MCV
AND ALONG THE DIFFUSE FRONT. AFTERNOON MLCAPE OF 2500-3500
J/KG...STEEP LOW-LEVEL LAPSE RATES...AND LOCALLY ENHANCED VERTICAL
SHEAR NEAR THE MCV COULD SUPPORT A RISK FOR A FEW DAMAGING GUSTS
AND/OR LARGE HAIL THIS AFTERNOON/EVENING.

...SRN MS/AL/GA/FL THIS AFTERNOON...
OUTFLOW FROM OVERNIGHT CONVECTION HAS MOVED SWD INTO S FL AND WWD
INTO THE WRN FL PANHANDLE AND SW AL. THE ENVIRONMENT ACROSS MOST OF
FL IS MORE STABLE COMPARED TO YESTERDAY...WITH STORM COVERAGE AND
THE SEVERE STORM RISK LIKEWISE REDUCED. THE REMAINING STRONG
INSTABILITY ACROSS EXTREME SE LA/SRN MS/SW AL WILL LIKELY SUPPORT A
FEW MULTICELL STORM CLUSTERS CAPABLE OF PRODUCING ISOLATED STRONG
DOWNBURSTS THIS AFTERNOON.

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