SPC AC 251259
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0759 AM CDT WED JUN 25 2008
VALID 251300Z - 261200Z
...THERE IS A SLGT RISK OF SVR TSTMS EXTENDS FROM ERN WY/SERN MT EWD
TO OH VALLEY/SOUTHERN GREAT LAKES...
...SYNOPSIS...
STRONGER WESTERLIES WILL BE CONFINED TO NRN STATES WITH RATHER WEAK
EMBEDDED SHORT WAVE TROUGHS. VORT MAX TRACKING ACROSS SASKATCHEWAN
INTO SRN MANITOBA WILL CONTINUE EWD WITH MUCH OF ITS ENERGY
REMAINING OVER AND N OF UPPER GREAT LAKES...WHILE ANOTHER TROUGH
MOVES INTO PAC NW TONIGHT. CONVECTIVELY ENHANCED MID LEVEL VORT MAX
IS CURRENTLY LOCATED OVER CENTRAL IA AND WILL LIKELY PROVIDE AN AREA
OF ASCENT AND STRONGER BAND OF MID LEVEL FLOW ACROSS THE OH VALLEY
AND SRN GREAT LAKES THIS AFTERNOON.
A SURFACE LOW NOW OVER NWRN MN WILL TRACK ENEWD INTO WRN ONTARIO
WITH TRAILING COLD FRONT MOVING EWD INTO THE NRN GREAT LAKES AND WRN
END STALLING OVER THE CENTRAL PLAINS. OUTFLOW BOUNDARY IS WELL
ESTABLISHED EARLY THIS MORNING EXTENDING FROM CENTRAL IL INTO
CENTRAL/NWRN MO AND ERN NEB...WHICH RAISES UNCERTAINTY ABOUT
LOCATION AND DEGREE OF MAXIMUM INSTABILITY LATER TODAY AS RETURNING
RICH GULF MOISTURE REMAINS TRAPPED BY THIS FEATURE THIS MORNING.
GIVEN THIS UNCERTAINTY...HAVE LITTLE CONFIDENCE IN IDENTIFYING AREAS
OF GREATER SEVERE PROBABILITIES ATTM. HIGHER PROBABILITIES MAY NEED
TO BE REINTRODUCED IN LATER OUTLOOKS ONCE CORRIDORS OF GREATER
SEVERE THREAT BECOME MORE EVIDENT.
...GREAT LAKES/NRN OH VALLEY...
WNC PROFILER INDICATES A BAND OF 30-40KT WINDS AT MID LEVELS
ACCOMPANYING THE REMNANTS OF THE IA MCV WHICH WILL SPREAD ACROSS
IL/IN/NRN OH/SRN MI THIS AFTERNOON. WITH HEATING...MLCAPES WILL
CLIMB TO AOA 1500 J/KG WHICH WILL BE SUFFICIENT FOR ORGANIZED
SURFACE BASED THUNDERSTORM DEVELOPMENT BY AFTERNOON. PRIMARY THREAT
WILL BE DAMAGING WINDS WITH SOME HAIL POTENTIAL. STORMS WILL LIKELY
WEAKEN AS THEY REACH UPPER OH VALLEY BY LATE AFTERNOON/EVENING WHERE
INSTABILITY SHOULD BE LESS.
ADDITIONAL DEVELOPMENT MAY OCCUR INVOF WEAK SURFACE COLD FRONT
ADVANCING INTO NRN WI/MI U.P. THIS AFTERNOON. FORECAST SOUNDINGS
INDICATE MLCAPE AROUND 1000 J/KG AND LIMITED CAP ALONG THE
FRONT/RESIDUAL OUTFLOW BOUNDARIES BY THE MID AFTERNOON. THUS AT
LEAST ISOLATED THUNDERSTORMS ARE EXPECTED...WITH 30-40 KT EFFECTIVE
SHEAR SUPPORTIVE OF SUPERCELLS AND SMALL LINES.
...SRN MN/IA REGION INTO THE CENTRAL PLAINS...
AS WEAK FRONT SETTLES SEWD AND MORNING OUTFLOW BOUNDARY LINGERS
ROUGHLY ESE-WNW ACROSS THIS REGION...MOISTURE WILL POOL WITH THE AIR
MASS BECOMING VERY UNSTABLE BY LATE AFTERNOON. DEWPOINTS IN THE
UPPER 60S/LOWER 70S...LAPSE RATES 8C/KM OR GREATER AND TEMPERATURES
NEAR 90F...WILL SUPPORT A VERY UNSTABLE AIR MASS WITH MLCAPES AOA
3000 J/KG. LITTLE IN THE WAY OF UPPER SUPPORT FOR STORM DEVELOPMENT
IS FORECAST...THUS INITIATION WILL RELY ON LOW LEVEL CONVERGENCE
NEAR BOUNDARIES BY LATE AFTERNOON. ALTHOUGH EXPECTED 20-25 KTS OF
SHEAR WILL GENERALLY BE SUPPORTIVE OF MULTICELLULAR STORMS...THE
DEGREE OF POTENTIAL INSTABILITY SUGGEST SUPERCELLS ARE POSSIBLE.
DURING THE EVENING FORWARD PROPAGATING MCS IS POSSIBLE MOVING SEWD
ACROSS IA INTO NRN IL WITH CONTINUED WIND DAMAGE POTENTIAL.
...HIGH PLAINS...
THOUGH NOT PARTICULARLY STRONG...A SELY UPSLOPE FLOW WILL PREVAIL
INTO ERN WY/SERN MT IN THE WAKE OF WEAK COLD FRONT ACROSS THE
N-CENTRAL PLAINS. ACTIVITY WILL INITIATE OVER THE HIGHER ELEVATIONS
LATE TODAY AND MOVE EWD THROUGH THE EVENING WHERE AXIS OF MODERATE
MLCAPE WILL BE IN PLACE. VEERING WIND PROFILES UNDER 30 KT 500MB
FLOW PROVIDES A FAVORABLE ENVIRONMENT FOR SEVERE THUNDERSTORM
DEVELOPMENT INCLUDING SUPERCELLS. THE LIMITING PARAMETER FOR
SIGNIFICANT SEVERE IS THE MOISTURE. HOWEVER...WITH STEEP LAPSE
RATES AND MODEST SHEAR...DAMAGING WINDS AND HAIL ARE LIKELY WITH
STRONGER STORMS.
..EVANS/SMITH.. 06/25/2008
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NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1630Z
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