DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 122000
SWODY1
SPC AC 121957

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0257 PM CDT FRI JUL 12 2013

VALID 122000Z - 131200Z

...THERE IS A SLGT RISK OF SVR TSTMS OVER PORTIONS OF ERN DAKOTAS
AND NWRN MN...

ONLY SIGNIFICANT CHANGE WITH THIS OUTLOOK IS TO ADD 5 PERCENT
WIND/HAIL PROBS ACROSS PORTIONS OF AZ. A SMALL COMPLEX OF TSTMS THAT
MOVED THROUGH SERN AZ THIS MORNING HAS SHOWN SOME INTENSIFICATION AS
IT MOVES GENERALLY NW. A DEEPLY MIXED BOUNDARY LAYER AND MLCAPES OF
1000-1500 J/KG SHOULD SUPPORT A CONTINUED LOCALIZED SVR WIND/HAIL
THREAT FOR THE NEXT FEW HOURS. ADDITIONAL TSTMS DEVELOPING OVER
CENTRAL AZ MAY ALSO POSE AN ISOLATED SVR THREAT.

DESTABILIZATION CONTINUES IN ADVANCE OF TSTMS OVER ERN ND AND EXPECT
EXISTING STORMS TO INTENSIFY TO SVR LEVELS...WITH ADDITIONAL
DEVELOPMENT SWD INTO ERN SD...OVER THE NEXT FEW HOURS AS REFLECTED
BY MOST SHORT-TERM HIGH-RESOLUTION GUIDANCE.

..BUNTING.. 07/12/2013

.PREV DISCUSSION... /ISSUED 1129 AM CDT FRI JUL 12 2013/

...SYNOPSIS...
STRONG...ELONGATED RIDGE WILL REMAIN IN PLACE FROM THE SRN
RCKYS/PLNS INTO THE UPR MS VLY/GRT LKS AS THE WLYS PERSIST ACROSS NE
PACIFIC...THE PACIFIC NW...AND S CNTRL CANADA. THE RIDGE SHOULD
BUILD FARTHER E/ENE THIS PERIOD AS HEIGHT RISES IN WAKE OF SHORTWAVE
TROUGH EXITING THE CANADIAN MARITIMES ENCOURAGE WV CLOSED LOW TO
RETROGRESS W/SW INTO KY.

SHORTWAVE TROUGH NOW OVER WA WILL INDUCE WEAK LEE CYCLOGENESIS OVER
MT LATER TODAY...WHILE A LWR AMPLITUDE DOWNSTREAM IMPULSE NOW OVER
MT/WY HELPS DRIVE A SFC TROUGH/WEAK COLD FRONT E/SE ACROSS THE RED
RVR VLY OF THE NORTH. TSTMS...SOME SVR...MAY FORM ALONG THE COLD
FRONT/TROUGH LATER TODAY/TNGT OVER ERN ND/WRN MN. OTHERWISE...A MORE
CONDITIONAL RISK FOR STRONG TO LOCALLY SVR STORMS WILL EXIST ALONG
THE LEE TROUGH IN MT...AND IN ASSOCIATION WITH DAYTIME HEATING OF
MOIST/CONDITIONAL UNSTABLE AIR MASS OVER PARTS OF THE SOUTH AND
EAST.

...CNTRL HIGH PLNS NEWD INTO ERN DAKOTAS/MN TODAY INTO TNGT...
LOW-LVL MOISTURE WILL CONTINUE TO INCREASE AHEAD OF PRE-FRONTAL
TROUGH OVER THE ERN DAKOTAS/WRN MN TODAY...IN RESPONSE TO BOTH
ADVECTION AND EVAPOTRANSPIRATION. AT THE SAME TIME...LOW-LVL
MOISTURE SHOULD PERSIST AHEAD OF COLD FRONT IN ERN WY/WRN NEB AS
WINDS SLACKEN AND RETURN TO WEAK SELY NEAR THE SW END OF THE TROUGH.
COUPLED WITH STRONG SFC HEATING...EXPECT SIZABLE SFC-BASED
INSTABILITY TO DEVELOP BY AFTN...WITH MLCAPE RANGING FROM 1500-2500
J/KG.

A STOUT EML CAP WILL...HOWEVER...PERSIST FROM THE CNTRL RCKYS NEWD
INTO MN...WITH 700 MB TEMPS AOA 15C EXPECTED AS FAR NE AS ABR
DELAYING STORM DEVELOPMENT. NEVERTHELESS...SFC HEATING...ASCENT WITH
DISTURBANCE SHEARING NEWD FROM MT/WY...AND UPLIFT ALONG THE
TROUGH/FRONT SHOULD BE SUFFICIENT TO OVERCOME CINH AND SUPPORT SCTD
TSTMS BY LATE AFTN.

GIVEN 40-50 KT WSWLY 500 MB FLOW ACCOMPANYING THE UPR
IMPULSE...AMPLE DEEP SHEAR WILL EXIST FOR SUSTAINED
STORMS/SUPERCELLS WITH SVR HAIL/WIND IN ND/NW MN. MODEST LOW-LVL
FLOW SHOULD LIMIT TORNADO THREAT...ALTHOUGH THE RISK WILL BE
NON-ZERO...ESPECIALLY IN THE RED RV VLY WHERE SFC WINDS ARE APT TO
REMAIN MORE SLY. THE CONVECTION SHOULD GRADE INTO MAINLY MULTICELLS
OR SMALL CLUSTERS WITH SW EXTENT...GIVEN SUBSTANTIALLY WEAKER SHEAR
EXPECTED OVER WRN NEB/SE WY. DEEPLY-MIXED BOUNDARY LAYER ENVIRONMENT
IN THIS REGION COULD...HOWEVER...PROMOTE SVR SFC GUSTS. SOME OF THE
STORMS...ESPECIALLY THOSE IN SD/NEB...COULD LINGER INTO THE NIGHT.

...NRN HIGH PLNS THIS AFTN/EVE...
STEEP LOW/MID-LVL LAPSE RATES AND GRAZING INFLUENCE OF APPROACHING
UPR IMPULSE SHOULD FOSTER ISOLD AFTN/EVE TSTM DEVELOPMENT OVER THE
NRN RCKYS...AND POSSIBLY INVOF DEVELOPING LEE LOW IN MT.
MID/HIGH-LVL SPEED SHEAR WILL INCREASE WITH TIME...YIELDING FAIRLY
LONG...NEARLY STRAIGHT HODOGRAPHS. THE WIND FIELD ALSO WILL
ENCOURAGE ENE SPREAD OF THE STORMS ACROSS THE PLNS. WHILE STATIC
INSTABILITY WILL BE GREAT...SPARSE MOISTURE /SFC DEWPOINTS IN THE
40S F/ WILL LIMIT BUOYANCY...WITH MLCAPE LIKELY TO REMAIN AOB 500
J/KG. ALTHOUGH DMGG WIND GUSTS MAY OCCUR...OVERALL SVR THREAT
SHOULD REMAIN ISOLD.

...CNTRL/SRN APPALACHIANS TO CNTRL GULF CST THIS AFTN...
SW ADVANCE OF WV UPR LOW WILL ALLOW COLDER MID-LVL TEMPS /WITH
READINGS AOB MINUS 12 C/ TO SPREAD SW ABOVE NRN FRINGE OF RICHER
BOUNDARY LAYER MOISTURE. COUPLED WITH SFC HEATING AND FORCING FOR
ASCENT/DCVA ASSOCIATED WITH THE LOW...EXPECT FAIRLY NUMEROUS STORMS
TO DEVELOP SW TOWARD THE UPR TN VLY BY MID/LATE AFTN. THESE WILL
POSE A MARGINAL/SPORADIC SVR HAIL AND WIND THREAT. FARTHER S...STORM
DEVELOPMENT...SUSTENANCE...AND SWD PROPAGATION IN THE FORM OF LINE
SEGMENTS MAY BE FOSTERED BY MODEST/DEEP NLY FLOW OVER THE CNTRL GULF
CST REGION.

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