SWODY1
SPC AC 241545
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1045 AM CDT THU APR 24 2008
VALID 241630Z - 251200Z
...THERE IS A MDT RISK OF SVR TSTMS OVER PORTIONS OF SOUTHERN NEB
AND CENTRAL KS...
...THERE IS A SLGT RISK OF SVR TSTMS FROM WESTERN OK INTO PARTS OF
SD/MN/IA...
...SYNOPSIS...
WIDESPREAD CONVECTION PAST 24 HOURS ASSOCIATED WITH WEAKENING S/WV
TROUGH NOW LIFTING NEWD TOWARD GREAT LAKES/OH VALLEY. IN ITS WAKE
LOW LEVEL SLY FLOW HAS TEMPORARILY WEAKENED AND VEERED ACROSS THE
PLAINS. MUCH STRONGER TROUGH NOW CROSSING INTERMOUNTAIN REGION WILL
SPREAD STRONG UPWARD MOTION AND ASSOCIATED JET DYNAMICS INTO CENTRAL
HIGH PLAINS BY THIS EVENING. SURFACE LOW WILL DEEPEN ERN CO LATER
THIS AFTERNOON AND THEN MOVE ACROSS KS TONIGHT WITH A STRONG COLD
FRONT NOW CENTRAL WY/WRN CO MOVING EWD ACROSS CENTRAL PLAINS
TONIGHT. LOW LEVEL JET WILL RESPOND TO DEEPENING PROCESS AND
INCREASE TO 30-40KT SRN/CENTRAL PLAINS BY THIS EVENING ADVECTING
DEEPER LOW LEVEL MOISTURE NWD AHEAD OF SURFACE LOW.
...NEB/NRN KS...
WITH STEEP MID LEVEL LAPSE RATES IN PLACE...STRONG DAYTIME HEATING
WILL LEAD TO STEEP LOW LEVEL LAPSE RATES AND AFTERNOON MLCAPE VALUES
OVER 2000 J/KG. FORCING MAY NOT ARRIVE OVER INSTABILITY AXIS UNTIL
NEAR 00Z. HOWEVER...SCATTERED SUPERCELL THUNDERSTORMS ARE LIKELY TO
FORM NEAR TIME OF MAX HEATING BY LATER AFTERNOON CAPABLE OF VERY
LARGE HAIL AND A FEW TORNADOES. ACTIVITY WILL SPREAD EASTWARD INTO
THE MODERATE RISK AREA BY THIS EVENING WHERE RICHER LOW LEVEL
MOISTURE WILL MAINTAIN RISK OF VERY LARGE HAIL AND TORNADOES WELL
AFTER DARK. ACTIVITY MAY ORGANIZE INTO AN MCS OVER CENTRAL KS/SOUTH
CENTRAL NEB WITH AN ENHANCED WIND DAMAGE POTENTIAL AFTER 00Z.
...SRN KS/OK...
CONSIDERABLE UNCERTAINTY EXISTS IN COVERAGE OF SEVERE STORMS ALONG
DRYLINE FROM I-70 SOUTHWARD ACROSS KS INTO OK. OPERATIONAL AND
EXPERIMENTAL MODELS AGREE THAT CYCLONIC UPPER FLOW...WEAK MID LEVEL
HEIGHT FALLS...AND SOME COOLING ALOFT WILL OCCUR ATOP SURFACE
DRYLINE THIS AFTERNOON. VERY WARM/MOIST CONDITIONS WILL LEAD TO
MLCAPE VALUES OVER 3500 J/KG ALONG DRYLINE WITH MINIMAL CAP. DESPITE
THESE POSITIVES...VERY FEW MODELS INDICATE CONVECTIVE
INITIATION TODAY. THEREFORE...OUTLOOK OVER THIS AREA IS HIGHLY
CONDITIONAL. IF STORMS CAN DEVELOP...FORECAST SOUNDINGS INDICATE
EFFECTIVE HELICITY OF 150-300 M2/S2 AND EFFECTIVE SHEAR VALUES OF
35-40 KNOTS...WHICH WOULD STRONGLY FAVOR SUPERCELLS CAPABLE OF VERY
LARGE HAIL AND TORNADOES.
...TX...
A VERY MOIST AND UNSTABLE AIR MASS IS IN PLACE THIS MORNING OVER
CENTRAL/SOUTH TX WITH DEWPOINTS NEAR 70F AND 12Z SOUNDINGS SHOWING
CONSIDERABLE CAPE. STRONG HEATING WILL HELP TO WEAKEN CAP
TODAY...WHILE SOUTHERN STREAM IMPULSE NOTED OVER NORTHERN MEXICO
APPROACHES REGION. ISOLATED AFTERNOON THUNDERSTORMS MAY DEVELOP
ALONG INSTABILITY AXIS ROUGHLY FROM DFW-SAT-LRD. ANY STORMS THAT
FORM WILL POSE A THREAT OF HAIL AND ISOLATED TORNADOES. WILL
MAINTAIN ONLY LOW SEVERE PROBABILITIES DUE TO UNCERTAINTY IN
CONVECTIVE INITIATION.
...MO VALLEY...
A BROAD REGION OF LOW LEVEL WARM ADVECTION WILL BE MAINTAINED
IN AXIS OF 30-40KT 850 SLY JET THROUGH MUCH OF THE DAY TODAY FROM
SOUTHERN MN/IA INTO EASTERN OK/AR. WIDESPREAD SHOWERS AND ISOLATED
THUNDERSTORMS ARE LIKELY IN THIS REGION...WITH THE POTENTIAL FOR
HAIL IN STRONGER CELLS. AT THIS TIME...ACTIVITY IS ANTICIPATED TO
REMAIN RATHER DISORGANIZED GIVEN THE WEAKER LAPSE RATES AND MARGINAL
DEEP LAYER SHEAR.
..HALES/CROSBIE.. 04/24/2008
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