DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 181245
SWODY1
SPC AC 181243

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0743 AM CDT FRI MAY 18 2012

VALID 181300Z - 191200Z

...NO SVR TSTM AREAS FORECAST...

...SYNOPSIS...
LOOSELY ORGANIZED WRN U.S. TROUGH...WITH NRN MEMBER REPRESENTED BY
CLOSED LOW ON THE BC-AB BORDER AND SRN MEMBER BY TROUGH OVER
NV...WILL CONTINUE EWD THROUGH EARLY SAT. DOWNSTREAM FROM THE
TROUGH...WEAK FLOW WILL PERSIST OVER TX...THE LWR MS VLY...AND THE
OH VLY...W OF SLOWLY PROGRESSIVE LOW ALONG THE CAROLINA CST.

AT LWR LVLS...MDT SLY FLOW WILL PREVAIL OVER MUCH OF THE PLNS E OF A
NNE-SSW ORIENTED LEE TROUGH. THE TROUGH WILL BE OVERTAKEN FROM N TO
S BY A REJUVENATED COLD FRONT...ASSOCIATED WITH BC/AB UPR
SYSTEM...THAT WILL MOVE E/SE ACROSS THE NRN HI PLNS/WRN DAKOTAS
LATER TODAY...AND ACROSS WRN PORTIONS OF THE CNTRL PLNS AND THE ERN
DAKOTAS TNGT/EARLY SAT. THE LEE TROUGH AND COLD FRONT WILL SERVE TO
FOCUS TSTM DEVELOPMENT THIS AFTN AND EVE. SOME OF THIS ACTIVITY
COULD BE STRONG TO SVR...ESPECIALLY OVER PARTS OF THE DAKOTAS.
MODEST MOISTURE AVAILABILITY AND MODEST DEEP SHEAR
WILL...HOWEVER...LIKELY LIMIT THE INTENSITY...DURATION...AND
COVERAGE OF SVR WEATHER.

...DAKOTAS INTO NRN MN THIS AFTN THROUGH TNGT...
CURRENT RAOB...SFC...AND BLENDED PW DATA SUGGEST THAT BOUNDARY LAYER
MOISTURE WILL REMAIN RELATIVELY LIMITED OVER THE NRN PLNS/UPR MS VLY
THIS PERIOD...WITH AVERAGE SFC DEWPOINTS THIS AFTN AND EVE EXPECTED
TO BE AOB THE MID 50S F IN WELL-MIXED AREAS AHEAD OF COLD FRONT/LEE
TROUGH. POCKETS OF HIGHER DEW POINTS MAY EXIST ALONG WARM FRONT IN
NRN MN...BUT THESE LIKELY WILL BE ASSOCIATED WITH A LESS DEEPLY
MIXED BOUNDARY LAYER ENVIRONMENT.

WHILE SPARSE MOISTURE WILL LIMIT BUOYANCY...COMBINATION OF SFC
HEATING...STEEP MID LVL LAPSE RATES...UPLIFT ALONG COLD FRONT/LEE
TROUGH...AND SLOWLY INCREASING LARGE SCALE FORCING FOR ASCENT
SHOULD OVERCOME EML CAP AND SUPPORT A BAND OF AFTN/EVE STORMS FROM
WRN SD NNEWD INTO ERN ND. AN ISOLD STORM OR TWO COULD FORM ALONG
LEE TROUGH SEGMENT IN CNTRL SD...AND A FEW STORMS ALSO COULD FORM
ALONG SHALLOW WARM FRONTAL ZONE NOW EVOLVING OVER FAR NRN MN.

GIVEN STRENGTH OF CAP AND MOISTURE AVAILABILITY...THE MOST
CONCENTRATED ACTIVITY SHOULD EVOLVE INTO MULTICELL CLUSTERS ALONG
AND ATOP ACCELERATING COLD FRONT. THESE COULD YIELD SVR HAIL AND
PERHAPS LOCALLY DMGG WIND INTO THIS EVE AS SBCAPE INCREASES TO AOA
1500 J/KG. A SUPERCELL OR TWO ALSO MAY OCCUR...MOST LIKELY ALONG
LEE TROUGH IN CNTRL SD...AND/OR ALONG WARM FRONT IN NRN MN. THESE
STORMS ALSO COULD PRODUCE SVR HAIL/WIND.

...CO/SRN WY/CNTRL HI PLNS THIS AFTN/EVE...
INVERTED-VEE THERMODYNAMIC ENVIRONMENT WILL BE CONDUCIVE FOR SCTD
HIGH-BASED STORMS WITH A RISK FOR DRY MICROBURSTS FROM PARTS OF
WY/CO AND PERHAPS ERN UT NEWD INTO WRN NEB AS SFC HEATING FURTHER
DESTABILIZES REGION OF STRENGTHENING SWLY FLOW/ASCENT AHEAD OF COLD
FRONT. SOME OF THESE STORMS COULD MERGE INTO SMALL CLUSTERS EARLY
TNGT.

...FAR S FL THIS AFTN...
HIGH LVL WLY JET MAY YIELD AN ENHANCED RISK FOR A FEW PULSE
STORMS/MULTICELLS WITH STRONG WINDS OVER FAR S FL TODAY...WHERE PW
WILL BE AOA 1.50 INCHES AND MID LVL TEMPS RELATIVELY COOL /AROUND
MINUS 10C AT 500 MB/.

..CORFIDI/COHEN.. 05/18/2012

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