Tornado Warning 99, NWS Tulsa, OK

EASTERN OKLAHOMA/NORTHWEST ARKANSAS FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TULSA OK
545 PM CST MON NOV 22 1999

ABOUT TO UPDATE ZONES TO INCLUDE NEW SVR TSTM WATCH CONFIGURATION.
OBJECTIVE SURFACE ANALYSIS SHOWS THE STRONGEST 3 HR PRESSURE FALLS
TAKING PLACE JUST NW OF TUL.  THEREFORE...THIS AREA WILL SEE THE
STRONGEST INCREASE IN SFC MSTR CONVERGENCE OVER THE NEXT HOUR OR
TWO.  LOW-LEVEL WINDS WILL ALSO BACK IN ADVANCE OF THE PRESSURE
FALLS AND LEAD TO STRONGER LOW-LEVEL INFLOW AND STORM RELATIVE
HELICITY.  DESPITE A SVR TSTM WATCH BEING IN EFFECT...ALL INTERESTED
PARTIES SHOULD BE READY FOR TORNADIC CONDITIONS AS SUFFICIENT SHEAR
AND INSTABILITY ARE IN PLACE.

HEAVY RAINFALL WILL ALSO BE A THREAT AS 45-55 KT MID-LEVEL WINDS RUN
PARALLEL TO THE FRONT...CURRENTLY LOCATED FROM PNC-LTS...LEADS TO
TRAINING OF CELLS.  HOWEVER...ONE-HOUR FLASH FLOOD GUIDANCE VALUES
ARE GENERALLY 2.5-3.5 INCHES AND WILL BE HARD TO BEAT.  BY
MIDNIGHT...MID-LEVEL WINDS WILL VEER SOME...CAUSING THE ACTION TO
FINALLY SHIFT EAST SOME THOUGH INCREASING THE THREAT FOR A SQUALL
LINE AND DAMAGING WIND POTENTIAL.

FCSTID = 22

.TUL...
AR...SEVERE THUNDERSTORM WATCH UNTIL 11 PM FOR ZONES
ARZ001...002...010...011...019...020...029.
OK...SEVERE THUNDERSTORM WATCH UNTIL 800 PM CST MONDAY FOR ZONES
OKZ054...OKZ059.  SEVERE THUNDERSTORM WATCH UNTIL 1100 PM CST MONDAY
FOR REMAINDER OF AREA.

ARZ001-002-010-011-019-020-029-OKZ049-053>076-231200-

EASTERN OKLAHOMA/NORTHWEST ARKANSAS HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE TULSA OK
100 PM CST MON NOV 22 1999

...A FEW SEVERE THUNDERSTORMS ARE EXPECTED ACROSS EASTERN OKLAHOMA AND
NORTHWEST ARKANSAS TONIGHT...

.SYNOPSIS...
A STATIONARY FRONT EXTENDED FROM EMPORIA TO NEAR PONCA CITY TO LUBBOCK
TEXAS EARLY THIS AFTERNOON. THIS FRONT WILL CONTINUE TO DRIFT SLOWLY
NORTH AS A WARM FRONT THROUGH THIS EVENING AS SURFACE LOW PRESSURE
INTENSIFIES OVER WEST TEXAS. A STRONG UPPER LEVEL WEATHER SYSTEM WILL
MOVE ACROSS COLORADO THIS AFTERNOON AND THEN MOVE NORTHEAST ACROSS
KANSAS AND OKLAHOMA TONIGHT.

BY MIDNIGHT...THE SURFACE LOW PRESSURE CENTER WILL BE LOCATED NEAR
BARTLESVILLE WITH A COLD FRONT EXTENDING SOUTHWESTWARD INTO CENTRAL
OKLAHOMA.

.PRIMARY HAZARD...
A FEW SEVERE THUNDERSTORMS ARE EXPECTED TONIGHT AS THE UPPER LEVEL
SYSTEM AND SURFACE LOW APPROACH FROM THE WEST. SEVERE THUNDERSTORMS ARE
POSSIBLE ACROSS ALL OF EASTERN OKLAHOMA AND NORTHWEST ARKANSAS TONIGHT.

WIND PROFILES APPEAR FAVORABLE FOR ISOLATED TORNADOES...MAINLY ACROSS
EASTERN OKLAHOMA THIS EVENING. A SQUALL LINE MAY DEVELOP ALONG THE FRONT
ACROSS CENTRAL OKLAHOMA THIS EVENING...MOVING INTO EASTERN OKLAHOMA WITH
DAMAGING WIND POTENTIAL AFTER MIDNIGHT.

.DISCUSSION...
THE LACK OF A FOCUSING BOUNDARY AND INSUFFICIENT DESTABILIZATION WILL
PRECLUDE ANY SEVERE THUNDERSTORM DEVELOPMENT ACROSS EASTERN OKLAHOMA AND
NORTHWEST ARKANSAS THIS AFTERNOON...ALTHOUGH ISOLATED THUNDERSTORMS ARE
POSSIBLE. THE BEST CHANCE FOR SUPERCELL THUNDERSTORMS WILL BE ACROSS
NORTHEAST OKLAHOMA NORTH AND WEST OF TULSA AFTER 6 PM. BACKED SURFACE
WINDS AHEAD OF THE SURFACE LOW AND NEAR THE FRONTAL BOUNDARY ALONG WITH
INCREASING JET STREAM WINDS COULD LEAD TO SUPERCELL TORNADOES. GREATER
INSTABILITY ACROSS SOUTHEAST OKLAHOMA COULD ALSO AID ERCELL
DEVELOPMENT THIS EVENING.

THE MODE OF CONVECTION OVERNIGHT WILL EVOLVE INTO BOW ECHO LINE
SEGMENTS AS UPPER LEVEL FORCING INCREASES. DAMAGING STRAIGHT LINE WINDS
WILL BE POSSIBLE AS THUNDERSTORMS BECOME NUMEROUS ACROSS THE AREA.

.SPOTTER ACTIVATION...
SPOTTER ACTIVATION MAY BE NEEDED ACROSS NORTHEAST OKLAHOMA THIS EVENING.
SPOTTERS ACROSS SOUTHEAST OKLAHOMA AND NORTHWEST ARKANSAS SHOULD BE
PREPARED FOR ACTIVATION OVERNIGHT.

@

ARZ001-002-010-011-019-020-029-OKZ049-053>076-231200-

EASTERN OKLAHOMA/NORTHWEST ARKANSAS HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE TULSA OK
100 PM CST MON NOV 22 1999

...A FEW SEVERE THUNDERSTORMS ARE EXPECTED ACROSS EASTERN OKLAHOMA AND
NORTHWEST ARKANSAS TONIGHT...

.SYNOPSIS...
A STATIONARY FRONT EXTENDED FROM EMPORIA TO NEAR PONCA CITY TO LUBBOCK
TEXAS EARLY THIS AFTERNOON. THIS FRONT WILL CONTINUE TO DRIFT SLOWLY
NORTH AS A WARM FRONT THROUGH THIS EVENING AS SURFACE LOW PRESSURE
INTENSIFIES OVER WEST TEXAS. A STRONG UPPER LEVEL WEATHER SYSTEM WILL
MOVE ACROSS COLORADO THIS AFTERNOON AND THEN MOVE NORTHEAST ACROSS
KANSAS AND OKLAHOMA TONIGHT.

BY MIDNIGHT...THE SURFACE LOW PRESSURE CENTER WILL BE LOCATED NEAR
BARTLESVILLE WITH A COLD FRONT EXTENDING SOUTHWESTWARD INTO CENTRAL
OKLAHOMA.

.PRIMARY HAZARD...
A FEW SEVERE THUNDERSTORMS ARE EXPECTED TONIGHT AS THE UPPER LEVEL
SYSTEM AND SURFACE LOW APPROACH FROM THE WEST. SEVERE THUNDERSTORMS ARE
POSSIBLE ACROSS ALL OF EASTERN OKLAHOMA AND NORTHWEST ARKANSAS TONIGHT.

WIND PROFILES APPEAR FAVORABLE FOR ISOLATED TORNADOES...MAINLY ACROSS
EASTERN OKLAHOMA THIS EVENING. A SQUALL LINE MAY DEVELOP ALONG THE FRONT
ACROSS CENTRAL OKLAHOMA THIS EVENING...MOVING INTO EASTERN OKLAHOMA WITH
DAMAGING WIND POTENTIAL AFTER MIDNIGHT.

.DISCUSSION...
THE LACK OF A FOCUSING BOUNDARY AND INSUFFICIENT DESTABILIZATION WILL
PRECLUDE ANY SEVERE THUNDERSTORM DEVELOPMENT ACROSS EASTERN OKLAHOMA AND
NORTHWEST ARKANSAS THIS AFTERNOON...ALTHOUGH ISOLATED THUNDERSTORMS ARE
POSSIBLE. THE BEST CHANCE FOR ERCELL THUNDERSTORMS WILL BE ACROSS
NORTHEAST OKLAHOMA NORTH AND WEST OF TULSA AFTER 6 PM. BACKED SURFACE
WINDS AHEAD OF THE SURFACE LOW AND NEAR THE FRONTAL BOUNDARY ALONG WITH
INCREASING JET STREAM WINDS COULD LEAD TO ERCELL TORNADOES. GREATER
INSTABILITY ACROSS SOUTHEAST OKLAHOMA COULD ALSO AID ERCELL
DEVELOPMENT THIS EVENING.

THE MODE OF CONVECTION OVERNIGHT WILL EVOLVE INTO BOW ECHO LINE
SEGMENTS AS UPPER LEVEL FORCING INCREASES. DAMAGING STRAIGHT LINE WINDS
WILL BE POSSIBLE AS THUNDERSTORMS BECOME NUMEROUS ACROSS THE AREA.

.SPOTTER ACTIVATION...
SPOTTER ACTIVATION MAY BE NEEDED ACROSS NORTHEAST OKLAHOMA THIS EVENING.
SPOTTERS ACROSS SOUTHEAST OKLAHOMA AND NORTHWEST ARKANSAS SHOULD BE
PREPARED FOR ACTIVATION OVERNIGHT.