Severe Thunderstorm Warning 341, NWS Tulsa, OK

EASTERN OKLAHOMA/NORTHWEST ARKANSAS FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TULSA OK
1135 AM CDT FRI AUG 17 2001

...UPDATE...

TSTMS STARTING TO PROPAGATE NORTHWARD INTO SOUTHEAST OK...FROM NORTH
TEXAS MCS. THESE STORMS ARE MOVING INTO MODERATELY UNSTABLE AIRMASS
WITH LIS ALREADY IN THE -5 TO -7 DEG C RANGE.  ALSO TSTMS ARE
ALREADY STARTING TO DEVELOP NORTH OF TULSA.  WILL SEND UPDATE TO
RAISE POPS ACROSS BOTH AREAS.

...PREV DISCUSSION...

SCT AC DECK STARTING TO MOVE INTO NORTHEAST OKLAHOMA THIS MORNING IN
ASSOCIATION WITH DISSIPATING THUNDERSTORM COMPLEX. OUTFLOW BOUNDARY
FROM CONVECTION HAS MOVED INTO NORTHWEST OKLAHOMA.  ATMOSPHERE WILL
BECOME MODERATELY UNSTABLE BY LATE AFTERNOON ALONG AND SOUTH OF MAIN
CLOUD SHIELD. DIFFERENTIAL HEATING...ALONG WITH ANY RESIDUAL OUTFLOW
BOUNDARIES WILL PROVIDE A FOCUS FOR TSTM DEVELOPMENT LATE THIS
AFTERNOON INTO THE EVENING...PRIMARILY NORTH OF A TUL/FYV LINE.
WITH CAPES FORECAST IN THE 1500-2000 J/KG RANGE COMBINED WITH MODEST
DEEP LAYER SHEAR...ANY STORMS THAT DEVELOP COULD BE SEVERE WITH
LARGE HAIL/DAMAGING WINDS. 50H S/W AXIS SWINGING SOUTH AHEAD OF MAIN
UPPER LOW MAY ALSO ENHANCE THUNDERSTORM DEVELOPMENT THIS EVENING.
WITH THAT SAID CURRENT FORECAST HAS THINGS PRETTY WELL IN HAND.
WILL UPDATE TO TWEAK TEMPS UP...MAINLY ACROSS EAST-CENTRAL
OK/WEST-CENTRAL ARK WHERE CLOUD COVER WILL LIKELY REMAIN LIMITED.

FCSTID = 12

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

ARZ001-002-010-011-019-020-029-OKZ049-053>076-181100-

EASTERN OKLAHOMA/NORTHWEST ARKANSAS HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE TULSA OK
120 PM CDT FRI AUG 17 2001

...A FEW SEVERE THUNDERSTORMS ARE POSSIBLE THIS AFTERNOON THROUGH
EARLY TONIGHT ACROSS EASTERN OKLAHOMA AND NORTHWEST ARKANSAS...

A SURFACE BOUNDARY GENERATED FROM MORNING THUNDERSTORMS WILL LINGER
OVER NORTHERN AREAS TODAY AND WILL PROVIDE THE FOCUS FOR DEVELOPMENT
OF THUNDERSTORMS THROUGH THE AFTERNOON. THE BOUNDARY IS EXPECTED TO
REMAIN NORTH OF A TULSA TO FAYETTEVILLE LINE.  ADDITIONAL
THUNDERSTORMS WILL SPREAD NORTHWARD INTO SOUTHEAST OKLAHOMA WITH
OTHER ISOLATED STORMS POSSIBLY DEVELOPING DURING THE HEAT OF THE
AFTERNOON AREAWIDE. INSTABILITY WILL BE GREATEST OVER SOUTHEAST
OKLAHOMA WHICH MAY ALLOW A FEW STORMS TO BECOME SEVERE. THE BOUNDARY
IN NORTHERN AREAS WILL PROVIDE ADDITIONAL LIFT WHICH COULD GENERATE
A FEW SEVERE STORMS AS WELL. THE MAIN THREAT FROM THE STORMS WILL BE
LARGE HAIL AND STRONG DOWNBURST WINDS WITH THE GREATEST CHANCES
NORTH OF HIGHWAY 412 AND SOUTH OF I-40.  STORMS WILL MOVE EASTWARD
AT AROUND 15 MPH AND MAY ENTER NORTHWEST ARKANSAS BEFORE WEAKENING.

.SPOTTER ACTIVATION...
ACTIVATION OF STORM SPOTTERS MAY BE NECESSARY THIS AFTERNOON THROUGH
EARLY TONIGHT ACROSS EASTERN OKLAHOMA AND NORTHWEST ARKANSAS.  LAW
ENFORCEMENT AGENCIES...EMERGENCY MANAGEMENT OFFICIALS...STORM
SPOTTER GROUPS...AND OTHER INTERESTED CONCERNS SHOULD CONTINUE TO
MONITOR THE LATEST UPDATES.

.DISCUSSION...
CONVECTION WAS DEVELOPING ALONG THE OUTFLOW BOUNDARY NEAR THE KANSAS
BORDER EARLY THIS AFTERNOON AND THUNDERSTORMS WERE SPREADING
NORTHWARD INTO SOUTHEAST OKLAHOMA. LIFTED INDICES WERE BETWEEN -5
AND -8 OVER SOUTHEAST OKLAHOMA WITH CAPES BETWEEN 1500 AND 2500 J/KG.
INSTABILITY WAS NOT AS GREAT OVER NORTHERN SECTIONS HOWEVER LOW
LEVEL MOISTURE WAS INCREASING. THERE WAS LITTLE OR NO CAP LEFT OVER
MUCH OF EASTERN OKLAHOMA. THUNDERSTORMS ARE EXPECTED TO INCREASE IN
COVERAGE DURING THE AFTERNOON IN THE UNSTABLE UNCAPPED AIRMASS WITH
THE MAIN THREAT FOR SEVERE STORMS BETWEEN 2PM AND 8PM. WEAK WIND
FIELDS IN THE MID LEVELS WILL LIMIT THE SHEAR AVAILABLE BUT THE
AMOUNT OF INSTABILITY MAY ALLOW HAIL UP TO 1 INCH AND DAMAGING
DOWNBURST WINDS TO BE A THREAT. ADDITIONAL THUNDERSTORMS WILL BE
POSSIBLE OVERNIGHT...BUT WITH MINIMAL INSTABILITY ANY STORMS SHOULD
REMAIN BELOW SEVERE LEVELS.

THREAT TABLE
VALID THROUGH 1200 UTC SATURDAY
AREA 1...NORTH OF HIGHWAY 412
THUNDERSTORM PROBABILITY...100
SEVERE PROBABILITY IF STORMS OCCUR...30
SIGNIFICANT SEVERE PROBABILITY IF STORMS OCCUR...5

AREA 2...SOUTH OF I-40
THUNDERSTORM PROBABILITY...100
SEVERE PROBABILITY IF STORMS OCCUR...40
SIGNIFICANT SEVERE PROBABILITY IF STORMS OCCUR...10

AREA 3...BETWEEN I-40 AND HIGHWAY 412
THUNDERSTORM PROBABILITY...50
SEVERE PROBABILITY IF STORMS OCCUR...30
SIGNIFICANT SEVERE PROBABILITY IF STORMS OCCUR...5

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 SIZE HAIL OR LARGER.

RELATED GRAPHICAL INFORMATION CAN BE FOUND AT: WWW.SRH.NOAA.GOV/TULSA