SWODY1
SPC AC 241242
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0742 AM CDT THU APR 24 2008
VALID 241300Z - 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...
...NEB/KS...
A LARGE UPPER TROUGH REMAINS OVER THE WESTERN STATES THIS
MORNING...WITH SEVERAL SHORTWAVE TROUGHS ROTATING ACROSS THE ROCKIES
INTO THE PLAINS. ONE SUCH FEATURE IS NOW DIGGING ACROSS NV AND WILL
APPROACH THE CENTRAL HIGH PLAINS BY EARLY EVENING. AHEAD OF THE
SYSTEM...SOUTHERLY LOW LEVEL WINDS WILL TRANSPORT MOISTURE NORTHWARD
AND HELP DESTABILIZE AIR MASS ACROSS PARTS OF NEB/KS. 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 AROUND THAT TIME CAPABLE OF VERY
LARGE HAIL AND A FEW TORNADOES. ACTIVITY WILL SPREAD EASTWARD INTO
THE MODERATE RISK AREA 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 BEFORE
DIMINISHING AFTER 06Z.
...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
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.
..HART/JEWELL.. 04/24/2008
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