SPC AC 220551
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1251 AM CDT TUE MAY 22 2007
VALID 231200Z - 241200Z
...THERE IS A SLGT RISK OF SVR TSTMS WED/WED NIGHT ACROSS PARTS OF
THE SRN/CNTRL PLAINS INTO THE MID/LWR MO VALLEY....
...SYNOPSIS...
MODELS CONTINUE TO SUGGEST THAT AT LEAST A COUPLE OF SIGNIFICANT
IMPULSES...COMPRISING AMPLIFIED POLAR TROUGH WHICH HAS EVOLVED OVER
THE INTERMOUNTAIN WEST/ROCKIES REGION...WILL LIFT NORTHEAST OF THE
ROCKIES LATER TODAY THROUGH WEDNESDAY/WEDNESDAY NIGHT. HOWEVER...IT
APPEARS THAT THIS MAY OCCUR A BIT SLOWER AND FARTHER TO THE
NORTH/WEST THAN INDICATED BY PRIOR RUNS...LIKELY DUE TO THE
INFLUENCE OF STRONG RIDGING NOW IN THE PROCESS OF BUILDING ACROSS
MUCH OF THE EASTERN STATES INTO THE EASTERN CANADIAN PROVINCES.
AN ELONGATED CIRCULATION...EXPECTED TO LIFT INTO THE NORTH CENTRAL
HIGH PLAINS BY LATE THIS AFTERNOON...NOW IS GENERALLY PROGGED TO
TAKE A MORE NORTHERLY TREK INTO MANITOBA BY LATE WEDNESDAY
AFTERNOON. THE MOST SIGNIFICANT TRAILING IMPULSE IS THEN PROGGED TO
ACCELERATE NORTHEAST OF THE CENTRAL ROCKIES...THROUGH THE CENTRAL
PLAINS/MID MISSOURI VALLEY REGION LATE WEDNESDAY/WEDNESDAY NIGHT.
IN THE WAKE OF THE LATTER FEATURE...A COUPLE OF DIGGING SHORT WAVE
IMPULSES ARE FORECAST TO MAINTAIN BROADER SCALE TROUGHING ACROSS
MUCH OF THE WESTERN STATES.
...CENTRAL STATES...
DUE TO THE UNCERTAINTIES IN MODEL FORECASTS OF THE COMPLEX UPPER
FLOW EVOLUTION...DETAILS OF THE SEVERE POTENTIAL WEDNESDAY ACROSS
THE PLAINS/UPPER MISSISSIPPI VALLEY REGION REMAIN UNCLEAR. THIS IS
EXACERBATED BY A SLOW MOISTURE RECOVERY AND RETURN FLOW FROM THE
WESTERN GULF OF MEXICO...AND UNCERTAIN DETRIMENTAL INFLUENCE OF
ONGOING CONVECTIVE CLUSTERS...AND ADDITIONAL STORM CLUSTERS EXPECTED
LATER TODAY/TONIGHT.
HOWEVER...UPPER 60S/NEAR 70F DEW POINTS ARE NOW FINALLY BEGINNING TO
RETURN INLAND ACROSS SOUTHEAST TEXAS...AND THIS MOISTURE SEEMS
LIKELY TO WORK ITS WAY NORTHWARD INTO PARTS OF THE CENTRAL PLAINS BY
EARLY WEDNESDAY. A WARM MID-LEVEL ENVIRONMENT ASSOCIATED WITH AN
ELEVATED MIXED LAYER MAY LIMIT CONVECTION TO THE NORTHEAST OF THE
SOUTHERN HIGH PLAINS THROUGH EARLY WEDNESDAY. THIS SEEMS LIKELY TO
ALLOW FOR THE DEVELOPMENT OF AT LEAST MODERATE INSTABILITY AHEAD OF
A SLOW MOVING COLD FRONT...OR CONGLOMERATE PRE-FRONTAL
OUTFLOW...ACROSS MUCH OF OKLAHOMA AND CENTRAL/EASTERN KANSAS BY
WEDNESDAY AFTERNOON. THIS IS WHERE MODELS HAVE BEEN MOST CONSISTENT
IN FOCUSING STRONGEST DESTABILIZATION.
MIXED LAYER CAPE EXCEEDING 2000 J/KG BY PEAK HEATING IS EXPECTED TO
SUPPORT THE INITIATION OF VIGOROUS STORMS...AS A JET STREAK
ASSOCIATED WITH MID-LEVEL IMPULSE SHIFTS ACROSS THE SOUTH CENTRAL
HIGH PLAINS BY 24/00Z. WITH MODELS INDICATING A WEST SOUTHWESTERLY
500 MB SPEED MAXIMUM IN EXCESS OF 50 KT...CONFIDENCE IS GROWING THAT
DEEP LAYER SHEAR WILL BE SUFFICIENT FOR SUPERCELLS WITH AT LEAST
INITIAL ACTIVITY. THIS CURRENTLY SEEMS MOST LIKELY ACROSS PARTS OF
NORTHWEST OKLAHOMA INTO CENTRAL KANSAS...WHERE MODERATE SOUTHERLY
LOW-LEVEL FLOW WILL CONTRIBUTE TO SIZABLE LOW-LEVEL HODOGRAPHS...AND
POTENTIAL FOR TORNADOES...IN ADDITION TO VERY LARGE HAIL/DAMAGING
WIND GUSTS.
STRONGLY DIFLUENT/DIVERGENT UPPER FIELD...JUST AHEAD OF THE BASE OF
THE MID-LEVEL TROUGH WILL ENHANCE CONVECTIVE DEVELOPMENT INTO
WEDNESDAY EVENING. IT CURRENTLY SEEMS MOST PROBABLE THAT FORCING
WILL SUPPORT AN UPSCALE EVOLUTION INTO A LARGE MESOSCALE CONVECTIVE
SYSTEM. HOWEVER...IF MID-LEVEL CAPPING AHEAD OF SURFACE
FRONT/PRE-FRONTAL CONVECTIVE BOUNDARIES WEAKENS SUFFICIENTLY FOR
DISCRETE STORM DEVELOPMENT...TORNADO POTENTIAL MAY BE A BIT GREATER
THAN CURRENTLY INDICATED.
..KERR.. 05/22/2007
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NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 1730Z
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