SPC: "...SIGNIFICANT SEVERE WEATHER EPISODE LIKELY...&

[Guest]

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1115 AM CDT WED APR 21 2004

VALID 211630Z - 221200Z

THERE IS A MDT RISK OF SVR TSTMS TO THE RIGHT OF A LINE FROM HRO 35
NW LIT HOT 25 N TXK PRX ADM GAG 40 WSW P28 BVO UMN HRO.

THERE IS A SLGT RISK OF SVR TSTMS TO THE RIGHT OF A LINE FROM 40 NNE
ART MSV DOV DCA MGW CRW 35 SW HSV MLU GGG DAL 45 SE SPS LBL 40 E LAA
50 SE GLD ICT JEF SLO HUF FWA 15 ESE APN.

GEN TSTMS ARE FCST TO THE RIGHT OF A LINE FROM 40 ESE EWN 15 ESE RWI
35 NE LYH 15 W SSU 10 ESE RMG 20 WNW LUL 25 WNW HOU 45 NW NIR 35 SSE
JCT 40 NNW MWL 15 ESE LTS 35 WNW RTN FMN 40 WNW 4HV 35 NE U31 55 N
SVE 30 S MFR 50 NNW 4BK ..CONT.. 65 NNE ISN 45 W BIS MBG 50 WNW
RWF 20 W FRM 25 NW FNB 25 S FNB MKC ALN 25 W MTO 20 SSE MTW 20 SE
ANJ.

...THERE IS A MDT RISK OF SVR TSTMS THIS AFTERNOON AND TONIGHT OVER
MUCH OF OK...WESTERN AR...AND SOUTHWEST MO...

...THERE IS A SLGT RISK OF SVR TSTMS FROM THE SOUTHERN PLAINS ACROSS
THE TN/OH VALLEYS INTO PARTS OF PA/NY...

...SIGNIFICANT SEVERE WEATHER EPISODE LIKELY TO DEVELOP THIS
AFTERNOON AND TONIGHT ACROSS PARTS OF OK/AR...

MORNING WATER VAPOR IMAGERY SHOWS A LARGE TROUGH OVER MUCH OF THE
UNITED STATES TODAY...WITH A SERIES OF SHORTWAVE TROUGHS MOVING
QUICKLY WEST TO EAST ACROSS THE CENTRAL PLAINS INTO THE OH VALLEY.
MODEL GUIDANCE SHOWS ONE FEATURE CURRENTLY OVER WEST TX...WHICH WILL
AMPLIFY AND ROTATE INTO EASTERN OK BY EVENING. THE AIRMASS OVER
THIS REGION IS MORE MOIST AT THE SURFACE THAN YESTERDAY WITH
WIDESPREAD LOW 60S DEWPOINTS IN PLACE. ALSO...MID LEVEL LAPSE RATES
ARE STEEPER AND 500MB TEMPERATURES ARE COOLER...INDICATIVE OF THE
MODERATE-STRONG INSTABILITY THAT WILL DEVELOP BY MID-LATE AFTERNOON.
POCKETS OF LOW CLOUDS SHOULD CONTINUE TO DIMINISH...RESULTING IN A
RATHER LARGE AREA OF UNCAPPED 2000-3000 J/KG MLCAPE.

CONVERGENCE ALONG WEAK/SUBTLE SURFACE BOUNDARIES ACROSS NORTHERN OK
IS EXPECTED TO RESULT IN EXPLOSIVE THUNDERSTORM DEVELOPMENT BY MID
AFTERNOON...SPREADING SOUTHEASTWARD INTO EASTERN OK BY EARLY
EVENING. CONVECTIVE MODE THROUGHOUT THIS REGION WILL LIKELY BE
SUPERCELLULAR DUE TO STRONG DEEP LAYER VERTICAL SHEAR. VERY LARGE
HAIL WILL BE LIKELY WITH STRONGEST STORMS. GREATEST TORNADO THREAT
APPEARS TO EXIST NORTH OF OLD OUTFLOW BOUNDARY WHICH WILL LIKELY
EXTEND FROM SOUTH OF END EASTWARD TOWARD FSM/MLC WHERE BACKED LOW
LEVEL WINDS WILL BE ENHANCED. ALSO...STRONGER SOUTHERLY LOW LEVEL
WINDS WILL DEVELOP BY LATE AFTERNOON OVER SOUTHEASTERN
OK...PROVIDING FAVORABLE LOW LEVEL SHEAR PARAMETERS FOR POTENTIALLY
TORNADIC SUPERCELLS. DAMAGING TORNADOES ARE POSSIBLE IN BOTH OF
THESE AREAS. STORMS WILL LIKELY MAINTAIN INTENSITY THROUGH THE
EVENING AS THEY MOVE/DEVELOP EASTWARD INTO WESTERN AR AND SOUTHWEST
MO...WITH AN INCREASING THREAT OF DAMAGING WINDS.

...SOUTHWEST KS...
SEVERE STORMS OVER OK WILL LIKELY DEVELOP WEST-NORTHWESTWARD INTO
PARTS OF SOUTHWEST KS BY EVENING. FULL SUNSHINE TODAY WILL RESULT
IN VERY STEEP LOW LEVEL LAPSE RATES AND AID IN THE DEVELOPMENT OF AT
LEAST MARGINAL INSTABILITY /MLCAPE VALUES AROUND 1000 J/KG/. THIS
ACTIVITY WILL LIKELY POSE A RISK OF LARGE HAIL THROUGH THE EVENING
BEFORE WEAKENING.

...IN/OH/MI...
BROAD PLUME OF SOUTHWEST LOW LEVEL WINDS HAVE MAINTAINED A
RELATIVELY MOIST/MARGINALLY UNSTABLE AIRMASS FROM SOUTHERN IND INTO
EASTERN LOWER MI. ALTHOUGH MUCH OF THIS AREA WILL HAVE ONLY LIMITED
DIURNAL HEATING DUE TO CLOUDS...POTENTIAL EXISTS FOR ISOLATED
THUNDERSTORM DEVELOPMENT BY EARLY AFTERNOON. STRONG WINDS ALOFT
SUGGEST A RISK OF DAMAGING WINDS IN STRONGER CELLS.

...MS/AL/TN/KY...
BAND OF SHOWERS/THUNDERSTORMS CURRENTLY EXTENDS FROM NORTHWEST MS
INTO CENTRAL KY. AIRMASS AHEAD OF THIS ACTIVITY WILL DESTABILIZE BY
AFTERNOON WITH POCKETS OF MUCAPE OVER 1500 J/KG...AND SUFFICIENT
VERTICAL SHEAR FOR THUNDERSTORM ORGANIZATION. THESE STORMS MAY
RE-INTENSIFY BY LATE AFTERNOON...WITH THE POTENTIAL FOR LARGE HAIL
AND DAMAGING WINDS IN STRONGER CELLS.

...NY/PA/MD/VA...
AIRMASS OVER THE DELMARVA REGION INTO WESTERN NY WILL DESTABILIZE
RAPIDLY TODAY DUE TO FULL SUNSHINE AND SURFACE DEWPOINTS IN THE 50S.
APPROACHING SHORTWAVE TROUGH AND TAIL END OF STRONGER SOUTHERLY LOW
LEVEL WINDS SHOULD AID IN THE DEVELOPMENT OF SCATTERED THUNDERSTORMS
BY MID/LATE AFTERNOON. FORECAST SOUNDINGS IN THIS REGION SHOW
STRONG LOW LEVEL VEERING WINDS WITH HEIGHT AND SUFFICIENT CAPE FOR
THE POSSIBILITY OF SUPERCELLS. ACTIVITY IS EXPECTED TO SPREAD
NORTHEASTWARD ACROSS NY/PA DURING THE EVENING AND SLOWLY WEAKEN.

..HART/BANACOS.. 04/21/2004

[wx247]

Here it is graphically!

[WXBUFFJIM]

Definitely a big day with widespread supercells likely from Oklahoma City and Red Rock, Oklahoma eastbound into east central Oklahoma. Hail could get up to grapefruit sized with destructive tornadoes as well.

Stay safe in Oklahoma and west central Arkansas today through tonight. It's also looking like a busy day, but to less of an extent for DC and Baltimore. Severe storms are possible in the DC and Baltimore area later today with hail and high wind the primary threat as a warm front combines with instability and veering winds with height. I cannot rule out an isolated tornado in the north central Mid Atlantic either with the turning of the winds with height. Southeast winds at the surface and southwest winds aloft. A 90 degree turning of the winds with height, perpendicular if you will can easily result in rotating supercells in spots across the north central Mid Atlantic. Something to keep an eye on throughout the day. It's 70 degrees and mostly sunny here in Baltimore with a dewpoint of 56. Dewpoints and tempertaures are rising with each hour.

Jim

[Colin]

COOL!! I'm in the slight risk area, but NWS doesn't mention more than a shower. Oh well, we'll see!

[the outbreaker]

Kind of uncanny how these incipient storms are popping in the same general location, between Lawton and OKC, as occurred on May 3 1999

http://www.srh.noaa.gov/oun/enhanced.php[/url]