Severe Thunderstorm Warning 328, NWS Tulsa, OK

EASTERN OKLAHOMA/NORTHWEST ARKANSAS FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TULSA OK
310 PM CDT SAT AUG 11 2001

OUTFLOW BOUNDARY HAS SHIFTED A LITTLE S THIS AFTERNOON AND IS NOW
SITUATED FROM SRN LE FLORE INTO CNTRL PUSHMATAHA AND CHOCTAW
COUNTIES IN SE OK.  LOOKING LIKE BEST CHANCES OF SVR MAY BE A LITTLE
FARTHER S THAN EARLIER THOUGHT...GENERALLY ALONG AND S OF THE RED
RIVER.  HAVE SEEN EARLIER CONVECTION OVER NCNTRL OK MOVE INTO NE
OK...WITH ADDITIONAL ISOLATED CONVECTION DEVELOPING IN NW AR.

PLAN ON CARRYING CHANCE POPS THRU THE EVENING FOR ABOUT THE NRN 1/2
OF THE FORECAST AREA...AND WILL KEEP POPS IN ALL NIGHT FOR THE SRN
ZONES.

OUTFLOW BOUNDARY WILL BE OUT OF THE PICTURE BY SUNDAY...ALTHO
MESOETA/AVN SUGGEST A WEAK SFC BOUNDARY FROM NW AR INTO WCNTRL AR
FOR TOMORROW AFTERNOON.  WILL LIMIT LOW POPS TO SE OK/WCNTRL
AR...WITH DRIER LOW-LEVEL AIR PROGGD TO MOVE INTO NE OK.

TEMP GUIDANCE LOOKS REASONABLE...AND DIDNT STRAY TOO FAR. SHUD HAVE
COMFORTABLE OVERNIGHT LOWS IN MOST LOCATIONS SUN AND MON NIGHT.

AVN MAINTAINS DRY LOW-LEVELS FOR MON THRU WED.  NEXT FRONT FORECAST
INTO CNTRL KS BY WED AFTERNOON...ABOUT 6-12 HRS FASTER THAN 00Z
MRF.  WILL KEEP MON THRU WED DRY FOR NOW...WITH POPS IN THE THUR THRU
SAT TIMEFRAME.  IF MRF IS CORRECT...BEST CHANCES OF PRECIP WILL FALL
ON FRI.

FCSTID = 18

PRELIM NUMBERS...
TUL   72  92  70  92 /  30  10  10  10
FSM   71  94  70  94 /  30  20  20  10
MLC   71  95  69  95 /  30  20  20  10
BVO   68  92  66  92 /  30  10  10  10
FYV   66  90  65  90 /  30  10  10  10
BYV   66  90  65  90 /  30  10  10  10
MIO   68  91  66  91 /  30  10  10  10
MKO   72  92  70  92 /  30  10  10  10
F10   72  92  70  92 /  30  10  10  10
HHW   72  96  70  96 /  40  30  20  10

.TSA...
AR...NONE.
OK...NONE.

ARZ001-002-010-011-019-020-029-OKZ049-053>076-121100-

EASTERN OKLAHOMA/NORTHWEST ARKANSAS HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE TULSA OK
100 PM CDT SAT AUG 11 2001

...ISOLATED SEVERE THUNDERSTORMS POSSIBLE THIS AFTERNOON AND EARLY
THIS EVENING ACROSS SOUTHEAST OKLAHOMA AND WEST CENTRAL ARKANSAS...

EARLY THIS AFTERNOON AN OUTFLOW BOUNDARY EXTENDED ACROSS SOUTHERN
OKLAHOMA...JUST NORTH OF THE RED RIVER VALLEY INTO LE FLORE COUNTY
AND SOUTHWEST ARKANSAS. THIS AREA HAS REMAINED MOSTLY SUNNY THROUGH
THE MORNING HOURS AND THE AIRMASS HAS BECOME UNSTABLE. SCATTERED
SHOWERS AND THUNDERSTORMS ARE EXPECTED TO FORM ALONG THE BOUNDARY.
ISOLATED SEVERE STORMS REMAIN POSSIBLE...MAINLY AFTER 3 PM UNTIL
AROUND SUNSET. THE BEST CHANCE FOR ANY SEVERE THUNDERSTORMS WILL BE
NEAR THE OUTFLOW BOUNDARY...OR GENERALLY SOUTH OF A LINE FROM
MCALESTER TO FORT SMITH.

ONGOING SHOWERS AND THUNDERSTORMS ACROSS NORTH CENTRAL OKLAHOMA WILL
AFFECT PORTIONS OF NORTHEAST OKLAHOMA THIS AFTERNOON...BUT THESE
STORMS SHOULD REMAIN BELOW SEVERE LIMITS. ISOLATED SHOWERS WERE ALSO
DEVELOPING ACROSS NORTHEAST OKLAHOMA...AHEAD OF THE MAIN AREA OF
CONVECTION TO THE WEST.

.SPOTTER ACTIVATION...
ORGANIZED SEVERE WEATHER IS STILL NOT EXPECTED TODAY.
HOWEVER...SPOTTER ACTIVATION MAY BE NEEDED IN A FEW AREAS OF
SOUTHEAST OKLAHOMA OR WEST CENTRAL ARKANSAS THIS AFTERNOON OR
EVENING. SPOTTERS SHOULD MONITOR THE LATEST WEATHER CONDITIONS AND
BE READY FOR ACTION IF WARNINGS ARE ISSUED.

.DISCUSSION...
THE AIRMASS IN THE THREAT AREA HAS BECOME UNSTABLE...WITH ESTIMATED
LIFTED INDEX VALUES BETWEEN -4 AND -6C...AND SURFACE BASED CAPES OF
AROUND 3000 J/KG. IN ADDITION...THERE IS THE OUTFLOW BOUNDARY IN THE
AREA TO HELP FOCUS CONVECTION. UPPER LEVEL WIND FIELDS ARE
WEAK...AND THIS WILL INHIBIT WIDESPREAD SEVERE THUNDERSTORM
DEVELOPMENT...AND ANY SEVERE STORMS WHICH DO DEVELOP MAY BE SHORT
LIVED.

HOWEVER...THE MAIN THREAT FROM ANY SEVERE STORMS IS DAMAGING
DOWNBURST WINDS. LARGE HAIL IS A SECONDARY THREAT...BUT FREEZING
LEVELS ARE RELATIVELY HIGH...SO LARGE HAIL SHOULD BE ISOLATED.

ELSEWHERE IN NORTHEAST OKLAHOMA AND NORTHWEST ARKANSAS...WIDELY
SCATTERED AFTERNOON THUNDERSTORMS WILL DEVELOP THIS AFTERNOON. MOST
AREAS NORTH OF THE OUTFLOW BOUNDARY HAVE HAD EXTENSIVE CLOUD COVER
THIS MORNING...AND HAVE NOT BECOME AS UNSTABLE AS IN THE
SOUTHEAST.

THREAT TABLE
VALID THROUGH 1100 UTC SUN AUG 12

THREAT AREA 1...SOUTH OF A LINE FROM MCALESTER TO OZARK
THUNDERSTORM PROBABILITY...90
SEVERE WEATHER PROBABILITY IF STORMS OCCUR...25
SIGNIFICANT SEVERE WEATHER PROBABILITY IF STORMS OCCUR...15

THREAT AREAS DEFINE THE GREATEST RISK. PROBABILITIES ARE IN PERCENT.
SIGNIFICANT SEVERE IS DEFINED AS F1 OR GREATER WIND/TORNADO DAMAGE
AND/OR GOLF BALL OR LARGER SIZE HAIL.

.OTHER HAZARDS...
EXCESSIVE RAINS WILL BE POSSIBLE IN AREAS NEAR SLOW-MOVING
THUNDERSTORMS.

DETAILED FORECASTS AS WELL AS A GRAPHICAL VERSION OF THIS OUTLOOK
CAN BE FOUND AT: WWW.SRH.NOAA.GOV/TULSA

SJT