DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 181945
SWODY1
SPC AC 181943

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0243 PM CDT FRI MAY 18 2012

VALID 182000Z - 191200Z

...THERE IS A SLGT RISK OF SVR TSTMS PARTS OF ERN UT/SWRN WY/NWRN
CO...

...FAR ERN UT/SWRN WY/NWRN CO...
THE STRENGTH OF THE UPPER SYSTEM CROSSING THE INTERMOUNTAIN WEST HAS
RESULTED IN EARLIER EXPANSION OF STORM COVERAGE THAN INITIALLY
ANTICIPATED...WHICH IN MANY AREAS WILL HINDER MIXING OF THE BOUNDARY
LAYER -- AND SUBSEQUENTLY THE POTENTIAL FOR EVAPORATIVELY DRIVEN
DAMAGING GUSTS. STILL HOWEVER...THREAT FOR LOCAL GUSTS APPEARS
SUBSTANTIAL ENOUGH TO WARRANT CONTINUATION OF THE SLIGHT RISK ACROSS
THIS AREA THROUGH THE REMAINDER OF THE AFTERNOON.

...ELSEWHERE...
LOW BOUNDARY LAYER DEWPOINTS -- AND THUS LIMITED INSTABILITY --
SHOULD CONTINUE TO PREVAIL ACROSS THE DAKOTAS AND VICINITY. DESPITE
THE PRESENCE OF THE NE-SW LOW-LEVEL BAROCLINIC ZONE BISECTING THE
DAKOTAS THIS AFTERNOON...MODEST WARM SECTOR CAPE...LIMITED
SHEAR...AND LIKELIHOOD THAT MOST CONVECTION WILL REMAIN TO THE COOL
SIDE OF THE FRONT SUGGESTS THAT SLIGHT RISK UPGRADE REMAINS
UNNECESSARY ACROSS THIS REGION.

DIURNALLY DRIVEN CONVECTION IS ALSO ONGOING ACROSS PARTS OF THE
SOUTHEAST AS AN UPPER LOW LINGERS INVOF THE CAROLINA COAST...BUT
ASIDE FROM S FL -- WHERE MODESTLY ENHANCED FLOW ALOFT IS SUPPORTING
A FEW MARGINALLY SEVERE CELLS...SEVERE THREAT SHOULD REMAIN MINIMAL.

..GOSS.. 05/18/2012

.PREV DISCUSSION... /ISSUED 1127 AM CDT FRI MAY 18 2012/

...ERN UT/SWRN WY INTO WRN CO...
WATER VAPOR IMAGERY SHOWS A STRONG UPPER TROUGH MOVING EWD ACROSS
THE GREAT BASIN THIS MORNING...ASSOCIATED WITH 70-100 M HEIGHT FALLS
AND -18C TEMPERATURE AT 500 MB. DYNAMIC FORCING FOR LARGE SCALE
ASCENT AHEAD OF THE TROUGH COUPLED WITH FRONTAL LIFT ALONG AN
ADVANCING COLD FRONT HAS RESULTED IN A BAND OF TSTMS FROM THE SERN
ID/SWRN WY BORDER SSWWD INTO CENTRAL UT. ENVIRONMENT DOWNSTREAM
FROM THE CONVECTIVE BAND IS CHARACTERIZED BY A DEEP SFC-BASED MIXED
LAYER AND AMPLE MID LEVEL MOISTURE. VISIBLE IMAGERY SHOWS LIMITED
CLOUDS FROM PARTS OF ERN UT INTO SWRN WY...WITH CLOUDS EXPECTED TO
DIMINISH FROM THE WEST OVER WRN CO THIS AFTERNOON. THIS WILL
PROMOTE STRONG DIABATIC HEATING THIS AFTERNOON AND EVENING...FURTHER
STEEPENING LAPSE RATES AND CONTRIBUTING TO DEVELOPMENT OF MUCAPE OF
500-1000 J/KG. THE PRESENCE OF A DEEP MIXED LAYER WILL ALSO RESULT
IN LARGE VALUES OF DCAPE...INDICATING POTENTIAL FOR STRONG
DOWNDRAFTS ENHANCED BY EVAPORATIVE COOLING AND DRY ADIABATIC LAPSE
RATES. THIS WILL RESULT IN A THREAT FOR STRONG/SEVERE WIND GUSTS AS
STORMS SPREAD/DEVELOP EWD THIS AFTERNOON AND EVENING.

...ERN WY INTO THE DAKOTAS...
A FRONTAL BOUNDARY WILL CONSOLIDATE FROM NERN ND SWWD INTO SERN WY
THIS AFTERNOON AS THE PRIMARY COLD FRONT MOVES EWD ACROSS ERN MT AND
NERN WY. LOW LEVEL MOISTURE WILL CONTINUE TO BE A LIMITING FACTOR
WITH SURFACE DEW POINTS LIKELY REMAINING AOB 55F...BUT STEEP LAPSE
RATES WILL COMPENSATE TO SOME EXTENT ALLOWING MUCAPE TO REACH
1000-1500 J/KG. LARGE SCALE FORCING FOR ASCENT ASSOCIATED WITH AN
UPSTREAM NRN TROUGH CURRENTLY OVER THE BC/ALTA REGION IS EXPECTED TO
LAG WELL WEST OF THE FRONTAL LOCATION...WITH MESOSCALE LIFT AND
SUBSEQUENT CONVECTIVE DEVELOPMENT MOST CONCENTRATED ALONG/WEST OF
THE SURFACE BOUNDARY. THE STEEP LAPSE RATES AND LOW LEVEL MIXED
LAYER MAY SUPPORT HAIL AND A FEW STRONG WIND GUSTS WITH ISOLATED
CONVECTIVE CELLS...BUT OVERALL SEVERE THREAT IS EXPECTED TO BE
LIMITED.

...FAR S FL THIS AFTN...
HIGH LVL WLY JET MAY YIELD AN ENHANCED 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/.

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