DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 181259
SWODY1
SPC AC 181257

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0757 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 LOW LVL 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 RAOBS...SFC OBS...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.

...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 THE RISK FOR A FEW PULSE
STORMS 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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