The SPC is forecasting ...severe thunderstorms expected over a broad swath of the southern and central plains today through tonight.... Please read the latest public statement about this event.
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| Probabilistic Large Hail Graphic |
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SPC AC 261959
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0259 PM CDT SUN APR 26 2009
VALID 262000Z - 271200Z
...THERE IS A HIGH RISK OF SVR TSTMS ACROSS PARTS OF WRN OK AND SRN
KS...
...THERE IS A MDT RISK OF SVR TSTMS ACROSS PARTS OF KS...OK...AND
TX...
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE SRN AND
CNTRL PLAINS...UPPER MIDWEST AND LOWER OH VALLEY...
...CURRENT THINKING ACROSS THE MODERATE AND HIGH RISK AREAS...
THE LARGE MCS FROM NW OK EXTENDING NNEWD ACROSS KS INTO NEB AND IA
IS ORGANIZING INTO A LINEAR MCS AND WILL CONTINUE TO HAVE A
WIDESPREAD SEVERE THREAT LATE THIS AFTERNOON INTO THE MID-EVENING.
RUC ANALYZED INSTABILITY AND VERTICAL SHEAR FIELDS APPEAR FAVORABLE
FOR AN EXTENSIVE SEVERE THREAT COVERAGE. LARGE HAIL AND WIND DAMAGE
SHOULD ACCOMPANY THE STRONGER CELLS IN THE SQUALL-LINE EWD ACROSS
THE REMAINDER OF KS INTO NW MO AND SRN IA. A FEW TORNADOES SHOULD
OCCUR WITH SUPERCELLS EMBEDDED IN THE LINE OR AHEAD OF THE LINE
THROUGH EARLY TO MID-EVENING.
FURTHER SOUTHWEST ACROSS THE HIGH RISK AREA...THE LATEST SHORT-TERM
THUNDERSTORM GUIDANCE SUGGESTS A SHORT LULL IN CONVECTIVE
DEVELOPMENT SHOULD OCCUR LATE THIS AFTERNOON AS THE SRN EDGE OF A
LARGE MCS EXITS TO THE NORTHEAST. THEN THE NEW RUC AND NAM FORECASTS
SUGGEST REPEAT INITIATION WILL OCCUR NORTH TO SOUTH ALONG MOST OF
THE DRYLINE IN THE 23Z TO 01Z TIMEFRAME. THE RUC ALSO SUGGESTS THE
STRONGER VERTICAL SHEAR PROFILES OF 50 TO 60 KT STILL LOCATED JUST
WEST OF THE HIGH RISK AREA WILL MOVE EWD INTO WRN OK BY EARLY
EVENING. THIS WILL STRENGTHEN VERTICAL SHEAR PROFILES WITH THE
LOW-LEVEL JET ALSO INCREASING ATTM HELPING STORMS THAT INITIATE TO
RAPIDLY OBTAIN SUPERCELL STRUCTURES CAPABLE OF PRODUCING LARGE HAIL
AND TORNADOES. THE THREAT FOR STRONG TORNADOES AND VERY LARGE HAIL
APPEARS TO BE THE GREATEST FROM AROUND WOODWARD OK SWD TO ABOUT
WICHITA FALLS TX WHERE AN AXIS OF LOW LCL HEIGHTS CURRENTLY EXISTS.
CONFIDENCE IS STILL HIGH THAT A CLUSTER OF TORNADIC SUPERCELLS
SHOULD ORGANIZE ALONG THIS CORRIDOR THIS EVENING.
...CHANGES TO THE OUTLOOK...
NO AREAL CHANGES TO THE OUTLOOK FOR THE 20Z ISSUANCE.
..BROYLES.. 04/26/2009
.PREV DISCUSSION... /ISSUED 1125 AM CDT SUN APR 26 2009/
A COMPLICATED...YET SIGNIFICANT SEVERE WEATHER EVENT APPEARS TO BE
DEVELOPING OVER PARTS OF THE CENTRAL AND SOUTHERN PLAINS TODAY.
WATER VAPOR IMAGERY CONTINUES TO SHOW A PRONOUNCED SHORTWAVE TROUGH
ADVANCING EASTWARD ACROSS EASTERN NM. THIS FEATURE WILL MOVE INTO
THE TX PANHANDLE BY THIS AFTERNOON...WITH LARGE SCALE ASCENT
OVERSPREADING MUCH OF NORTH TX/OK/KS. THE RESULT WILL BE A LARGE
AREA OF CONCERN FOR SCATTERED INTENSE THUNDERSTORMS. THE GREATEST
CONCENTRATION WILL LIKELY BE ALONG THE SURFACE DRYLINE/ COLD FRONT
FROM CENTRAL KS...ACROSS WESTERN OK...INTO WESTERN NORTH TX.
HOWEVER...POTENTIAL FOR SIGNIFICANT SEVERE WILL BE PRESENT OVER A
MUCH LARGER AREA.
...KS/NEB/IA...
MORNING THUNDERSTORMS CONTINUE TO INTENSIFY AND EXPAND IN COVERAGE
ACROSS PARTS OF EASTERN KS/SOUTHEAST NEB/MUCH OF IA IN REGION OF
STRONG LOW LEVEL WARM ADVECTION AND LIFT. AIRMASS IS RECOVERING
QUICKLY IN THIS REGION...WITH SUFFICIENT INSTABILITY FOR A RISK OF
LARGE HAIL AND DAMAGING WINDS. RADAR TRENDS AND MODEL GUIDANCE
SUGGEST THE POTENTIAL FOR MULTIPLE EPISODES OF STRONG CONVECTION IN
THIS AREA TODAY.
...SOUTH CENTRAL KS/WESTERN OK/EASTERN TX PANHANDLE...
A VOLATILE ENVIRONMENT IS EXPECTED TO DEVELOP BY MID AFTERNOON
ACROSS THIS REGION WITH MLCAPE VALUES OF 2000+ J/KG AND DEWPOINTS IN
THE MID 60S. MORNING RAOBS AND MODEL FORECAST SOUNDINGS SHOW A
RATHER WEAK CAPPING INVERSION OVER THIS AREA...ALLOWING SHOWERS AND
THUNDERSTORMS TO DEVELOP THIS MORNING. MORE INTENSE STORMS WILL
OCCUR LATER THIS AFTERNOON ALONG THE DRYLINE OVER THE EASTERN TX
PANHANDLE AS SHORTWAVE TROUGH OVER NM APPROACHES. GIVEN THE WEAK
CAP...IT APPEARS THAT BROKEN CLOUD COVER AND SCATTERED SHOWERS WILL
HELP TO LIMIT THE NUMBER OF STORMS AND REDUCE VERTICAL MIXING OF LOW
LEVEL MOISTURE. THIS WILL LEAD TO A VERY FAVORABLE THERMODYNAMIC
ENVIRONMENT FOR SUPERCELLS CAPABLE OF VERY LARGE HAIL AND TORNADOES.
KINEMATIC FIELDS WILL ALSO BE VERY FAVORABLE WITH LARGE...CURVED
HODOGRAPHS AND EFFECTIVE HELICITY VALUES OVER 500 M2/S2. MODEL
GUIDANCE IS VERY INCONSISTENT IN TIMING AND EVOLUTION OF CONVECTIVE
ACTIVITY. HOWEVER...THE COMBINATION OF A POTENT
ENVIRONMENT...APPROACHING UPPER TROUGH...AMPLE MOISTURE IN
PLACE...AND MULTIPLE OBJECTIVE GUIDANCE MEASURES INDICATING A
WIDESPREAD RISK OF SIGNIFICANT TORNADOES...FEEL THERE IS SUFFICIENT
CONFIDENCE TO UPGRADE TO HIGH RISK FROM SOUTH CENTRAL KS INTO
WESTERN OK.
...WEST TX...
STRONG HEATING AND A VERY UNSTABLE AIRMASS WILL BE PRESENT THIS
AFTERNOON AND EVENING ALONG THE DRYLINE FROM WESTERN NORTH TX INTO
SOUTHWEST TX. SCATTERED SUPERCELLS ARE EXPECTED TO DEVELOP ALONG
THIS AXIS WITH A RISK OF VERY LARGE HAIL...ISOLATED TORNADOES...AND
LOCALLY DAMAGING WINDS.
CLICK TO GET WUUS01 PTSDY1 PRODUCT
NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0100Z