Severe Thunderstorm Warning 508, NWS Norman, OK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORMAN OK
328 PM CDT THU AUG 23 2001

12Z ETA AND AVN RUNS SHOW UPPER LOW CENTERED OVER EASTERN COLORADO
MOVING EAST-NORTHEAST INTO SOUTHWEST NEBRASKA WITH AVN FARTHER
SOUTH.  BIG DIFFERENCES APPEAR IN OVERALL SURFACE PATTERN WITH AVN
DEVELOPING STRONGER SURFACE LOW ACROSS NORTHEAST KANSAS BY 12Z
FRIDAY...WHILE ETA HAS WEAKER LOW ACROSS EASTERN TEXAS PANHANDLE.
INITIAL THOUGHTS ARE THAT ETA MAY BE CLOSER TO WHAT WILL EVENTUALLY
HAPPEN SO WILL FOLLOW MORE OF ETA SOLUTION IN THE SHORT TERM.

AS LOW MOVES INTO CENTRAL PLAINS THIS AFTERNOON WIND PROFILES ACROSS
NORTHERN PARTS OF CWA (CLOSER TO FRONT) BACK WHICH WILL SET-UP MORE
FAVORABLE SHEAR PROFILE FOR STORMS THAT FORM.  ETA HAS CAPES RANGING
FROM 2000 J ACROSS SOUTHWEST OKLAHOMA TO OVER 3K AROUND ICT BY 00Z
THIS AFTERNOON.  AS LLJ DEVELOPS LATER TONIGHT...GOOD LOW TO MID
LEVEL THETA-E ADVECTION IS MAXIMIZED ACROSS NORTH CENTRAL ZONES SO
BEST CHANCE FOR STORMS DURING THE OVERNIGHT APPEARS TO BE ACROSS
NORTH CENTRAL ZONES.  LOCALLY HEAVY RAINFALL WILL ALSO BE A THREAT
WHERE SURFACE/LOW LEVEL BOUNDARY INTERSECTS LLJ.

GOING INTO FORECAST FOR FRIDAY AND FUTURE TIMES WILL BE DEPENDENT
ON WHAT OCCURS THIS AFTERNOON AND TONIGHT.  OUTFLOW BOUNDARIES FROM
CONVECTION OVERNIGHT WILL LIKELY BE A FOCUS FOR MORE STORMS FRIDAY AFTERNOON
ALONG WITH SYNOPTIC FRONT.  UPPER LOW OVER CENTRAL PLAINS WILL BE SLOW
TO MOVE EAST AS IT RUNS INTO MID AND UPPER RIDGE ALONG WITH THE FACT
THAT THE STRONGER WESTERLIES WILL BE FARTHER NORTH.

BIG DIFFERENCES IN FRONTAL POSITION FOR SATURDAY WITH AVN BEING FARTHER
SOUTH AND ETA HOLDING FRONT ACROSS CENTRAL OKLAHOMA.  FOR NOW WILL
MAINTAIN CURRENT POPS FOR SATURDAY WITH TOO MANY UNCERTAINTIES.

GOING INTO THE EXTENDED PORTION OF FORECAST...MRF AND ECMWF PUSH FRONTAL
BOUNDARY SOUTH OF CWA WITH SURFACE HIGH BUILDING ACROSS THE AREA.  UPSLOPE
FLOW ALONG HIGH PLAINS ALONG WITH NORTHWEST FLOW ALOFT SHOULD GIVE
WESTERN PARTS OF FA BEST CHANCE OF RAIN DURING THE EARLY TO MID PART
OF NEXT WEEK.

FCSTID = 6
OKC   72  96  70  93 /  30  30  30  30
HBR   73  99  71  96 /  30  20  30  30
SPS   75 100  73  99 /  20  20  20  20
GAG   69  94  65  91 /  50  20  30  20
PNC   73  93  70  90 /  50  30  30  30
DUA   74  96  73  95 /  30  20  20  30

.OUN...
OK...NONE.
TX...NONE.

OKZ004>048-050>052-TXZ083>090-232100-

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE NORMAN OK
100 PM CDT THU AUG 23 2001

THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS LATE THIS AFTERNOON
AND EARLY TONIGHT OVER PARTS OF WESTERN AND NORTHERN OKLAHOMA...NORTH
OF A LINE FROM HOLLIS...TO KINGFISHER...TO STILLWATER. DAMAGING
WINDS AND LARGE HAIL WILL BE THE MAIN THREATS. HEAVY RAIN ALSO WILL
BE POSSIBLE.

AT MIDDAY A SURFACE BOUNDARY EXTENDED FROM THE TEXAS PANHANDLE...
NORTHEAST AND EAST ACROSS SOUTHERN KANSAS. A FAIRLY STRONG UPPER
LEVEL STORM SYSTEM WAS CENTERED OVER EASTERN COLORADO...AND WAS
MOVING SLOWLY EAST. SUNNY SKIES OVER MUCH OF WESTERN AND NORTHERN
OKLAHOMA WERE ALLOWING THE AIR TO DESTABILIZE ALONG AND SOUTH OF THE
BOUNDARY ACROSS SOUTHERN KANSAS.

THE BOUNDARY MAY DRIFT SOUTH INTO FAR NORTHERN OKLAHOMA LATER THIS
AFTERNOON. AS AFTERNOON HEATING CONTINUES AND THE AIR DESTABILIZES
FURTHER...AND AS THE UPPER SYSTEM MOVES EAST...THUNDERSTORMS ARE
EXPECTED TO DEVELOP AND INCREASE NEAR THE BOUNDARY LATE THIS
AFTERNOON. MODERATE INSTABILITY AND INCREASING WINDS ALOFT INDICATE
THAT A FEW THUNDERSTORMS MAY BECOME SEVERE...WITH LARGE HAIL AND
DAMAGING WINDS THE MAIN THREATS THROUGH EARLY EVENING.

THUNDERSTORMS ARE EXPECTED TO BECOME MORE ORGANIZED THIS EVENING
AND PUSH SOUTH OR SOUTHEAST INTO OR THROUGH MUCH OF NORTHERN AND
WESTERN OKLAHOMA TONIGHT. DAMAGING WINDS WILL BE THE MAIN
THREAT LATER THIS EVENING...ALTHOUGH LARGE HAIL WILL STILL BE
POSSIBLE AS TEMPERATURES ALOFT COOL WITH THE APPROACH OF THE UPPER
LEVEL SYSTEM. THUNDERSTORMS ALSO MAY PRODUCE LOCALLY HEAVY RAIN THIS
EVENING...WHICH COULD CAUSE LOCALIZED FLOODING IN SOME AREAS.

EMERGENCY MANAGERS AND SPOTTER GROUPS IN THE SLIGHT RISK AREA SHOULD
BE PREPARED FOR POSSIBLE ACTIVATION BEGINNING LATE THIS AFTERNOON...
AND CONTINUING AT LEAST THROUGH LATE EVENING.

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