Severe Thunderstorm Warning 211, NWS Tulsa, OK

EASTERN OKLAHOMA/NORTHWEST ARKANSAS FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TULSA OK
325 PM CDT MON MAY 22 2000

TOR WATCH JUST ISSUED COVERS ALL BUT FAR WESTERN ZONES. EXPECT
DEVELOPMENT ALONG SFC TROUGH FROM NEAR VINITA TO HENRYETTA TO
NEAR MCALESTER. TEMPS WARMING INTO MID 90S JUST WEST OF THE AREA
WITH DEWPOINTS NEAR 70 EVEN BEHIND SFC TROUGH...SO COULD POP A
STORM A BIT FURTHER WEST THAN CURRENT POS OF TROUGH. LAPS STILL
SHOWING ABOUT 30 J/KG OF CAP TO OVERCOME SO WILL PLAN ON CONVECTION
REMAIN SCATTERED AND SPREAD 30-40% POPS FROM TUL/MLC EASTWARD.
CONVECTION IS EXPECTED TO DIMINISH BY MIDNIGHT.

WARMING CONTINUES IN MID LEVELS OVERNIGHT AND CAP SHOULD BE
IN PLACE BY TUE AFTERNOON. COULD SEE SOME OVERNIGHT SHOWERS DEVELOP
IN AREA OF BEST ISENTROPIC LIFT IN SE OK LATE TONIGHT WITH A MORNING
SHOWER POSSIBLE FROM FSM SOUTHWARD. NEAR RECORD HIGH TEMPS FCST
TUE AND WED AS HEAT CURRENTLY SW OF THE AREA SPREADS THIS WAY.
CONFIDENT ABOUT TMPS TUE MAINLY IN MID 90S WITH SOME UPPER 90S
POSSIBLE. MODELS ALL SAG FRONTAL BOUNDARY SOUTH INTO NE OKLAHOMA
WED. ETA IS SLOWEST IN DROPPING FRONT AND COOLING SOUTHWARD. HAVE
SEEN SIMILAR FRONTS HANG JUST NORTH OF THE AREA WITH HEAT REMAINING
OR EVEN INCREASING IN PREFRONTAL COMPRESSION AREA. H5-H7 WINDS REMAIN
PARALLEL TO BOUNDARY WITH H5 HGHTS RAISING A BIT WED MORNING. WILL
COOL NRN ZONES A FEW DEGS WED AND RAISE TEMPS IN SRN ZONES A DEG
OR TWO FROM TUE MAXES.

BOUNDARY MAY CONT TO SAG SOUTH AS PER MRF PROGS WITH CAP WEAKENING NORTH
OF IT. INSTABILTIY AND FLOW OVER STALLED SFC BOUNDARY WILL INCREASE THURS
AS UPPER FLOW BECOMES SOUTHWEST. CHC FOR CONVECTION IN NRN ZONES THURSDAY
AM NOT SURE ABOUT CHC FOR PCP FRIDAY AS BOUNDARY MAY LIFT NORTH OF
THE AREA AS SW FLOW INCREASES. MRF BRINGS SHORT WAVE THROUGH THE
AREA ON SATURDAY...SO WILL SPREAD CHC POPS OVER ALL AREAS THEN.
TEMPS WILL COOL BACK INTO 80S TO NEAR 90 IN EXTENDED.

FCSTID = 13
TUL   67  96  72  93 /  30   5   0   5
FSM   63  95  68  97 /  30  10   0   5
MLC   69  96  73  98 /  20   5   0   0
BVO   61  97  63  90 /   5   5   0   5
FYV   65  90  68  92 /  30   5   0   5
BYV   65  90  68  92 /  30   5   0   5
MIO   67  96  70  93 /  30   5   0   5
MKO   69  96  73  98 /  20   5   0   0
F10   67  96  72  93 /   5   5   0   5
HHW   70  95  74  98 /  10  10   0   0

.TUL...
AR...NONE.
OK...NONE.

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 CDT MON MAY 22 2000

...ISOLATED SEVERE THUNDERSTORMS WILL BE POSSIBLE ACROSS EASTERN
OKLAHOMA AND NORTHWEST ARKANSAS THIS AFTERNOON AND EVENING...

.SYNOPSIS...
A PRE-FRONTAL TROUGH...AHEAD OF A WEAK COLD FRONT IN KANSAS...WAS
LOCATED FROM EAST OF KANSAS CITY TO NEAR TULSA TO SOUTH OF LAWTON
EARLY THIS AFTERNOON. MODERATELY STRONG NORTHWESTERLY FLOW ALOFT WAS
ALSO PRESENT ACROSS THE CENTRAL U.S. THE PRE-FRONTAL TROUGH IS
EXPECTED TO SHIFT A LITTLE FURTHER SOUTH THIS AFTERNOON BEFORE
WASHING OUT TONIGHT.

.PRIMARY HAZARD...
ISOLATED SEVERE THUNDERSTORMS...CAPABLE OF HAIL...DAMAGING WINDS AND
DANGEROUS CLOUD-TO-GROUND LIGHTNING...WILL BE POSSIBLE THIS
AFTERNOON AND EVENING ACROSS MUCH OF EASTERN OKLAHOMA AND ALL OF
NORTHWEST ARKANSAS. PERSONS PLANNING OUTDOOR ACTIVITIES SHOULD KEEP
ABREAST OF THE LATEST WEATHER CONDITIONS AND FORECASTS. THE ACTIVITY
SHOULD DECREASE IN COVERAGE AND INTENSITY AFTER 10 PM.

.DISCUSSION...
AN AREA OF SURFACE CONVERGENCE HAS DEVELOPED NEAR AND PARALLEL TO
I-44 IN NORTHEAST OKLAHOMA...ALONG A PRE-FRONTAL TROUGH. TO THE
SOUTH OF THIS BOUNDARY WINDS WERE GENERALLY FROM THE SOUTH-SOUTHWEST
WHILE BEHIND IT... WINDS WERE FROM THE WEST-SOUTHWEST. WHILE THE LOW
LEVEL MOISTURE TO THE SOUTH OF THE TROUGH WAS SOMEWHAT SHALLOW...
SURFACE DEW POINT TEMPERATURES HAVE RISEN TO NEAR 70F...RESULTING IN
CAPE VALUES NEAR 3000 J/KG.

AN AREA OF ELEVATED CONVECTION LOCATED ACROSS EAST-CENTRAL OKLAHOMA
WILL CONTINUE TO SHIFT EAST THIS AFTERNOON. WHILE THE STORMS HAVE
REMAINED BELOW SEVERE LEVELS SO FAR...THEY HAVE THE POTENTIAL TO
BECOME SEVERE THIS AFTERNOON...ESPECIALLY IF THEY SATURATE THE LOW
AND MID LEVELS OF THE ATMOSPHERE AND/OR TAP THE HIGH INSTABILITY AT
THE SURFACE. THESE STORMS MAY PRODUCE HAIL UP TO 1 INCH AND WIND
GUSTS TO 60 MPH.

THERE IS ALSO A CHANCE THAT ADDITIONAL THUNDERSTORMS WILL DEVELOP
AFTER 4 PM ALONG THE PRE-FRONTAL TROUGH. WITH THE MODERATE TO HIGH
INSTABILITY IN PLACE AND 40 TO 50 KT NORTHWEST FLOW AT 18000
FEET...ANY SURFACE-BASED THUNDERSTORMS THAT DEVELOP WILL BE SEVERE.
HAIL UP TO 2 INCHES IN DIAMETER AND WIND GUSTS TO 70 MPH WILL BE
POSSIBLE WITH THESE STORMS. WITH NORTHWEST FLOW IN THE MID AND UPPER
LEVELS...MODERATELY-STRONG DIRECTIONAL SHEAR WILL ALSO BE PRESENT.
IF ANY STORMS DEVELOP AHEAD OF THE PRE-FRONTAL TROUGH...SUPERCELL
STORMS WILL BE POSSIBLE. STORM-RELATIVE HELICITY VALUES USING A
SOUTHEAST STORM MOTION WERE AROUND 100-150 M2/S2. NEGATIVE FACTORS
FOR SEVERE THUNDERSTORM DEVELOPMENT INCLUDE A LAYER OF WARM AIR
ACROSS CENTRAL AND SOUTHERN OKLAHOMA CAPPING THUNDERSTORM
DEVELOPMENT THIS AFTERNOON AS WELL AS SOMEWHAT WEAK CONVERGENCE
ALONG THE PRE-FRONTAL TROUGH.

ANY STORMS THAT DEVELOP ARE EXPECTED TO WEAKEN THIS EVENING AFTER 9
PM BEFORE DISSIPATING BEFORE MIDNIGHT.

.SPOTTER ACTIVATION...
SPOTTER ACTIVATION MAY BE REQUIRED THIS AFTERNOON AND EVENING ACROSS
NORTHEAST OKLAHOMA AND NORTHWEST ARKANSAS SOUTH OF I-44.

A GRAPHICAL VERSION OF THIS OUTLOOK ALONG WITH OTHER DETAILED
FORECASTS CAN BE OBTAINED AT HTTP:/WWW.NWSTULSA.NOAA.GOV/.