Severe Thunderstorm Warning 274, NWS Tulsa, OK

EASTERN OKLAHOMA/NORTHWEST ARKANSAS FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TULSA OKLAHOMA
325 PM CDT WED SEP 18 2002

CURRENT WATER VAPOR IMAGERY ALONG WITH MORNING UPPER AIR ANALYSIS
SHOW LARGE UPPER TROUGH ENCOMPASSING THE CENTRAL U.S.  A POTENT
VORTICITY MAXIMA IS ALSO READILY VISIBLE ROTATING NEAR THE FOUR
CORNER REGION.  A STRONG UPPER JET />= 100KTS/ WAS SAMPLED OVER THE
PACIFIC NORTHWEST PROVIDING ADDITIONAL ENERGY FOR THE STRENGTHENING
SOUTHERN PORTION OF THE LONGWAVE TROUGH AXIS.  SURFACE FRONTAL
BOUNDARY IS LOCATED FROM THE CENTRAL TEXAS PANHANDLE THROUGH NORTH
CENTRAL KANSAS.  STRONG SOUTHERLY WINDS HAVE SUSTAINED ABUNDANT LOW
LEVEL MOISTURE IN SPITE OF AMPLE BOUNDARY LAYER MIXING.

THE LONG WAVE TROUGH WILL EFFECTIVELY SPLIT AS THE APPROACHING
VORT MAX AND UPPER JET ALLOWING FOR CLOSED UPPER LOW DEVELOPMENT OVER
SOUTHEAST COLORADO BY THURSDAY MORNING.  THE APPROACHING DYNAMICS
WILL COUPLE WITH THE PRESENT FRONTAL BOUNDARY TO SPARK A LARGE AREA
OF THUNDERSTORMS OVERNIGHT.  EXACT EVOLUTION OF THUNDERSTORM COMPLEX
IS TOUGH AS A STRONG CAPPING INVERSION REMAINS IN PLACE OVER MUCH OF
THE SOUTHERN PLAINS WHICH WILL TAKE TIME TO ERODE AS COOLER MID
LEVEL TEMPS APPROACH.  CURRENT THINKING HAS THUNDERSTORMS DEVELOPING
TO THE WEST...AND POSSIBLY NORTH...BY LATE EVENING AND PROGRESSING
INTO NORTHEAST OKLAHOMA BY MORNING AS FRONTAL BOUNDARY MAKES SLOW
PROGRESS EASTWARD.  ELEVATED INSTABILITY AXIS WILL BE PRESENT ALONG
WITH STRONG WIND FIELDS TO CREATE AN ENVIRONMENT FAVORABLE FOR
SEVERE WIND POTENTIAL WITH THIS LINEAR MCS.

FRONT MAKES SLOW PROGRESS EASTWARD ON THURSDAY WITH THUNDERSTORM
COMPLEX GRADUALLY WEAKENING DURING THE MORNING BEFORE STRENGTHENING
AGAIN BY AFTERNOON AS IT INGESTS MORE UNSTABLE AIR.  THE SLOW
PROGRESSION OF THE MID/UPPER TROUGH AXIS...FAVORABLE UPPER JET
DYNAMICS...AND POOLING MOISTURE ALONG THE SURFACE BOUNDARY WILL
LEAVE POTENTIAL FOR HEAVY RAINS ESPECIALLY ACROSS FAR NORTHEAST
OKLAHOMA.  THUNDERSTORM CHANCES CONTINUE ALONG FRONTAL BOUNDARY INTO
THE INITIAL PORTION OF THE THURSDAY NIGHT PERIOD.  PRECIP TAPERS OFF
BY FRIDAY MORNING HOWEVER EXPECT LOW CLOUDS TO RESIDE OVER MOST OF
THE AREA AS UPPER TROUGH AXIS BEGINS TO LIFT NORTHEAST.  AREAS MOST
LIKELY TO SEE AMPLE SUN ON FRIDAY WILL BE SOUTHWEST OF TULSA WHERE
HIGH TEMP FORECASTS ARE TOUGH.

COOL SATURDAY MORNING AS CLOUD COVER DECREASES AND WINDS GO LIGHT.
WARM UP BEGINS SLOWLY DURING THE WEEKEND WITH NEXT FRONTAL BOUNDARY
SLATED FOR NEXT TUESDAY/WEDNESDAY.  WILL CONTINUE WITH SLIGHT CHANCE
WORDING FOR THIS TIMEFRAME HOWEVER SURFACE FLOW MAY REMAIN EASTERLY
FOR MOST OF NEXT WEEK LIMITING LOW LEVEL MOISTURE RETURN.  NEXT
WEDNESDAY WILL BE INTRODUCED AS A RATHER COOL DAY AS BOTH GFS/ECMWF
AGREE ON RATHER POTENT AIRMASS POISED TO MOVE DOWN THE PLAINS BY MID
WEEK.

TUL  70  75  58  75 /  60  70  20  10
FSM  73  83  63  79 /  20  80  60  10
MLC  73  80  58  78 /  40  70  30  10
BVO  69  75  56  75 /  60  70  20  10
FYV  69  79  59  72 /  30  80  60  10
BYV  68  78  60  71 /  20  80  60  10
MIO  69  74  57  73 /  40  70  50  10
MKO  72  76  59  76 /  40  70  30  10
F10  72  76  58  77 /  40  70  20  10
HHW  73  83  63  79 /  20  70  60  10

FORECAST ID = 07

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

ARZ001-002-010-011-019-020-029-OKZ049-053>076-191100-

EASTERN OKLAHOMA/NORTHWEST ARKANSAS HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE TULSA OK
540 PM CDT WED SEP 18 2002

...THERE IS A CHANCE OF SEVERE THUNDERSTORMS OVER MUCH OF NORTHEAST
   OKLAHOMA TONIGHT...
...SEVERE THUNDERSTORMS ARE POSSIBLE ACROSS A LARGE PART OF EASTERN
   OKLAHOMA AND NORTHWEST ARKANSAS THURSDAY...

SEVERE THUNDERSTORMS DEVELOPED LATE THIS AFTERNOON OVER WESTERN
OKLAHOMA AND SOUTH CENTRAL KANSAS.  THESE ARE EXPECTED TO CONTINUE
TO DEVELOP AND MOVE TO THE EAST NORTHEAST THROUGH THE EVENING.  AT
THEIR CURRENT SPEED AND DIRECTION...SOME OF THESE THUNDERSTORMS
COULD REACH WESTERN PORTIONS OF OSAGE...PAWNEE...CREEK AND OKFUSKEE
COUNTIES AROUND MID EVENING.  A BROADER AREA OF PRECIPITATION WILL
LIKELY DEVELOP BEHIND THE COLD FRONT MOVING INTO NORTHWEST OKLAHOMA
AT THIS TIME.

.SPOTTER ACTIVATION...
SPOTTER ACTIVATION MAY BE REQUIRED THIS EVENING OVER PARTS
OF NORTHEAST OKLAHOMA TO THE WEST OF A MIAMI TO WAGONER TO HENRYETTA
LINE. SPOTTER ACTIVATION MAY BE REQUIRED OVER ALL OF EASTERN
OKLAHOMA AND NORTHWEST ARKANSAS DURING THE DAY THURSDAY.

.DISCUSSION...
THE VIGOROUS UPPER LEVEL SYSTEM WILL SWING OUT OF THE SOUTHERN
ROCKIES AND INTO THE PLAINS TONIGHT AND THURSDAY.  THE STRONG
DYNAMICS FROM THIS SYSTEM ALONG WITH THE COLD FRONT MOVING INTO
OKLAHOMA SHOULD RESULT IN CONTINUED CONVECTIVE DEVELOPMENT THROUGH
THE NIGHT.

THREAT TABLE
VALID THROUGH 1200 UTC THURSDAY

AREA 1...ALONG AND WEST OF A MIAMI TO WAGONER TO HENRYETTA LINE
THUNDERSTORM PROBABILITY...70
SEVERE PROBABILITY IF STORMS OCCUR...90
SIGNIFICANT SEVERE PROBABILITY IF STORMS OCCUR...40

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

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