Severe Thunderstorm Warning 418, NWS Norman, OK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORMAN OK
812 PM CDT WED MAY 29 2013

.UPDATE...
ADJUSTED ALL ELEMENTS FOR THE REST OF TONIGHT...ESPECIALLY
TO DECREASE STORM CHANCES OVER WESTERN NORTH TEXAS AND
FAR SOUTHWESTERN OKLAHOMA AND TO INCREASE THEM OVER
NORTHERN OKLAHOMA AND EAST OF I-35.

&&

.DISCUSSION...
THE RISK FOR SEVERE THUNDERSTORMS CONTINUES MAINLY
NORTH OF I-40 AND EAST OF I-35 THROUGH MIDNIGHT TONIGHT.
THERE MAY A SLIGHTLY ENHANCED RISK FOR TORNADOES OVER
BECKHAM...WASHITA...AND CUSTER COUNTIES OVER THE NEXT
TWO HOURS.

WILL CLOSELY MONITOR CURRENT STORMS OVER BECKHAM COUNTY THAT WILL
AFFECT LOCATIONS NEAR A ELK CITY TO PONCA CITY LINE OVER THE NEXT
SEVERAL HOURS. THESE STORMS APPEAR TO BE INGESTING THE BEST
INSTABILITY FROM AN INCREASING LOW LEVEL JET. THERE IS A LOW
CHANCE FOR TORNADOES NEAR AN ELK CITY TO CORDELL TO WEATHERFORD
LINE OVER THE NEXT HOUR OR TWO...ESPECIALLY AS LOW LEVEL WINDS
INCREASE. HEAVY RAINFALL OF 1 TO 3 INCHES AND LOCALIZED FLOODING
WITH TRAINING CELLS MAY OCCUR IN THESE AREAS AS WELL.

AT THIS TIME...ADDITIONAL SEVERE STORMS SEEM UNLIKELY FOR
MUCH OF THE OKLAHOMA CITY METRO AREA...EXCEPT FOR THE POSSIBLE
EXCEPTION OF LOCATIONS NORTHWEST OF AN EL RENO TO GUTHRIE LINE.

ADDITIONAL SHOWERS AND STORMS WILL CONTINUE ACROSS SOUTHERN
OKLAHOMA...EAST OF I-35 AS WELL. DUE TO WEAKER SHEAR...THESE
STORMS MAY REMAIN LESS ORGANIZED AND HAVE A LESS CHANCE OF
BEING SEVERE.

STRONG CAPPING WILL LIKELY NOT ALLOW FOR ANY STORM
DEVELOPMENT ACROSS WESTERN NORTH TEXAS AND FAR SOUTHWESTERN
OKLAHOMA FOR THE REMAINDER OF TONIGHT. KEPT A 20 PERCENT
CHANCE FOR STORMS IN THESE AREAS.

AFTER MIDNIGHT TONIGHT...SEVERE STORMS REMAIN UNLIKELY WITH
THE BEST RAIN CHANCES EAST OF I-35.

MBS

&&

.PREV DISCUSSION... /ISSUED 648 PM CDT WED MAY 29 2013/

DISCUSSION...
PLEASE SEE THE 00Z AVIATION DISCUSSION BELOW.

AVIATION...
SHOWERS AND THUNDERSTORMS CONTINUE ACROSS OK EARLY THIS EVENING.
ONE LINE OF STORMS WAS LOCATED FROM JUST SOUTH OF PNC THROUGH OUN.
ANOTHER LINE WAS LOCATED EAST OF WWR TO WEST OF CSM. HAVE INCLUDED
TEMPOS TO REFLECT THESE LINES...WITH A MAIN THREAT OF SEVERE WIND
GUSTS EXCEEDING 50 KT. AFTER THE TSRA DIMINISHES LATE
TONIGHT...MVFR CIGS ARE EXPECTED AGAIN AND SOUTH WINDS NEAR 20 KT
WILL CONTINUE TO IMPACT MOST OF THE TERMINALS. AN AWW WAS ISSUED
FOR OKC...BUT HAS JUST EXPIRED AS THE LINE OF STORMS MOVES OUT OF
THE AREA.

PREV DISCUSSION... /ISSUED 327 PM CDT WED MAY 29 2013/

DISCUSSION...
CURRENTLY...A LINE OF SEVERE CONVECTION REMAINS FOCUSED ALONG THE
DRY LINE ACROSS THE TX PANHANDLE. AHEAD OF THE DRY LINE...IN THE
WARM SECTOR...A SCATTERED LINE OF SUB SEVERE THUNDERSTORMS
CONTINUE TO DEVELOP ACROSS FAR SWRN OK AND WRN N TX. THERE REMAINS
A DECENT CAPPING INVERSION ACROSS CENTRAL AND NRN OK.
HOWEVER...WITH THE RECENT DEVELOPMENT ACROSS SWRN OK AND WRN N
TX...THUNDERSTORM DEVELOPMENT WILL LIKELY CONTINUE THROUGH THE
EVENING ACROSS WRN OK...AND EVENTUALLY INTO CENTRAL OK. THE
PRIMARY SEVERE THREAT WILL BE ACROSS FAR WRN/NWRN OK AS THE DRY
LINE SLOWLY PUSHES EASTWARD THIS AFTERNOON...NEAR THE OK/TX
BORDER. SCATTERED CONVECTION WILL LIKELY SPREAD INTO THE METRO
AFTER 6 PM...WITH FREQUENT LIGHTNING...SEVERE HAIL...AND WIND
GUSTS OF 50 TO 60 MPH ALL POSSIBLE. THE TORNADO THREAT FOR THE OKC
METRO REMAINS LOW THROUGH THE EVENING HOURS.

TONIGHT...
THE LARGE SCALE MID-TROPOSPHERIC TROUGH WILL REMAIN NEGATIVELY
TILTED OVERNIGHT THROUGH THURSDAY MORNING...WITH THE 500MB TROUGH
AXIS ORIENTED FROM SRN ALBERTA THROUGH THE SRN PLAINS. WITH THE
PRIMARY SFC LOW LIFTING N/NE ACROSS SRN KS OVERNIGHT...SHOWER AND
THUNDERSTORMS WILL LIKELY PERSIST THROUGH THU MORNING. AS
INDIVIDUAL STORMS MOVE OFF THE DRY LINE LATER THIS EVENING AND
ACTIVITY INCREASES ACROSS WRN OK...EXPECT THESE STORMS TO MERGE
INTO A LINE AS THEY APPROACH THE CENTRAL OK/OKC METRO. THIS WILL
LESSEN THE OVERALL TORNADO THREAT THIS EVENING FOR THE METRO.
HOWEVER...THE DAMAGING WIND THREAT AND LARGE HAIL POTENTIAL WILL
CONTINUE AS THIS AREA OF STORMS MOVE EAST THROUGH THE EVENING.

THURSDAY...
THE MAIN FORECAST CONCERN WILL BE FOCUSED ON THUNDERSTORM CHANCES FOR
THU AFTN. THE PRIMARY 500MB TROUGH WILL REMAIN NEGATIVELY TILTED
AND FOCUSED ACROSS THE WRN CONUS...FROM THE PAC NW THROUGH THE SRN
PLAINS. IN RESPONSE... ANOTHER SHORTWAVE RIDING THE LARGER TROUGH
WILL SWEEP OFF SERN CO...WITH THE DRY LINE MAKING A SURGE
EASTWARD...THIS TIME INTO WRN/N CENTRAL OK. AGREEMENT FROM SHORT
RANGE GUIDANCE WOULD PLACE IT SOMEWHERE JUST SHY OF AN ENID TO
WEATHERFORD TO CROWELL TX LINE. BUFR SOUNDINGS FOR NWRN/N CENTRAL
OK SHOW VERY STEEP LAPSE RATES AND FAVORABLE HODOGRAPHS THROUGH
THE LATE AFTN/EARLY EVENING. WITH BACKING SFC WINDS NEAR THE SFC
LOW THROUGH 00Z FRI...0-1 AND 0-3KM HELICITIES WILL INCREASE.
OVERALL...WITH THE SURGING DRY LINE FOR FOCUSED LIFT AND DECENT
DYNAMICS...THE POTENTIAL FOR SUPERCELLS WITH LARGE HAIL...
DAMAGING WINDS... AND TORNADOES LOOKS DECENT THU AFTN ACROSS N
CENTRAL OK THROUGH SWRN OK AND FAR WRN N TX BEFORE THE DRY LINE
RETREATS BACK TO THE WEST OVERNIGHT. AT THE MOMENT...THE BEST
POTENTIAL FOR TORNADOES WILL BE NEAR THE SFC LOW TRACK AND THE
BEST SURGE IN THE DRY LINE...WHICH WILL BE ACROSS N CENTRAL OK
THROUGH W CENTRAL OK. ELSEWHERE...ACROSS CENTRAL OK AND THE OKC
METRO...THE DRY LINE WILL LIKELY STALL JUST WEST OF THE
METRO...NEAR EL RENO. HOWEVER...ANY STORMS THAT MOVE OFF THE DRY
LINE AND EASTWARD...WILL BE CAPABLE OF TORNADOES...LARGE HAIL AND
DAMAGING WINDS. THROUGH THE EVENING...STORMS WILL LIKELY FORM INTO
A LINE...SHIFTING EASTWARD THROUGH THE EVENING AND OVERNIGHT AS
THE SFC LOW LIFTS E/NE ONCE AGAIN.

FRIDAY...
SEVERE WEATHER POTENTIAL WILL CONTINUE FRIDAY AS ANOTHER SHORT WAVE
RIDES SEWRD AROUND THE PRIMARY 500MB TROUGH AS IT FINALLY BEGINS
TO TRANSITION OVER THE CENTRAL PLAINS. WITH THE SFC LOW TAKING A
MORE SOUTHWARD TRACK DURING THE DAY FRIDAY...THIS WILL BRING THE
WARM FRONT INTO PLAY ACROSS NRN AND NWRN OK...DROPPING SWRD
THROUGH THE AFTN JUST NORTH OF THE OKC METRO. WHILE OUT WEST...THE
DRY LINE MAKES ANOTHER PUSH EASTWARD ACROSS WRN N TX AND S/SWRN
OK. IN RESPONSE TO THE SFC LOW/WARM FRONT/DRY LINE COMBINATION...
SFC WINDS WILL ONCE AGAIN BACK THROUGH THE AFTERNOON... RESULTING
IN INCREASED O-1KM AND 0-3KM HELICITIES THROUGH. MID-LEVEL LAPSE
RATES WILL REMAIN STEEP FROM CENTRAL OK THROUGH WRN N TX...AND
DEEP LAYER SHEAR WILL REMAIN SUFFICIENT FOR SUSTAINED UPDRAFTS AND
SUPERCELLS. AT THE MOMENT...THE GREATEST THREATS WILL BE
LARGE DAMAGING HAIL... DAMAGING WIND GUSTS... AND TORNADOES FROM
NORTH CENTRAL OK THROUGH WRN N TX.

NOT TO BE LEFT OUT...FLOODING AND FLASH FLOODING COULD BE POSSIBLE
FRIDAY AS MID-RANGE GUIDANCE SHOWS PERSISTENT SHOWER AND
THUNDERSTORM DEVELOPMENT ALONG THE WARM FRONT ACROSS NRN OK.

FOR THE WEEKEND...
SHOWERS AND THUNDERSTORMS WILL LIKELY PERSIST EARLY...EXITING TO
THE SE THROUGH THE AFTERNOON. BROAD HIGH PRESSURE WILL SET UP OVER
THE CENTRAL PLAINS...WITH DRY CONDITIONS FOR SUNDAY INTO MONDAY.

KURTZ

&&

.OUN WATCHES/WARNINGS/ADVISORIES...
OK...NONE.
TX...NONE.
&&

17/03

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