Severe Thunderstorm Warning 111, NWS Norman, OK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORMAN OK
240 PM CST TUE MAR 28 2000

COMPLEX FLOW PATTERN EVOLVING ATTM OVER MUCH OF SWRN US WITH LEAD
SHORT WAVE TROF AXIS MOVING INTO ERN NM WITH A SECONDARY IMPULSE
SLIDING INTO SRN AZ.  DRYLINE SHARPENING FROM NEAR ATLUS SWD TO JUST
EAST OF ABI.  DEEP COLD AIR PUSHED INTO ABOUT THE NRN HALF OF OK
THIS MORNING. HOWEVER..AS SUSPECTED YDAY..THE SHALLOW BOUNDARY IS
MIXING OUT ACROSS THE SRN 3 TIERS OF COUNTIES IN OKLAHOMA.
INITIATION IS EXPECTED VERY LATE THIS AFTERNOON OVR PORTIONS OF SW
OK/WRN N TX WITH CONVECTION EVOLVING INTO AND MCS OVERNITE.  A LOOK
OUT THE WINDOW TO THE SW REVEALS WEAK ELEVATED CONVECTION
TRYING TO GET GOING AND 850 MB LI PROGS FROM BOTH THE ETA/AVN SHOW
STRONG ELEVATED INSTABILITY LINGERING THRU THE MORNING WED. WITH
THIS SET UP..HEAVY RAINFALL WILL BE A POSSIBILITY WITH COPIOUS
ELEVATED CONVECTION NORTH OF THE SFC BOUNDARY. HEAVY RAINFALL
WORDING WILL BE CONTINUED CENTRALA ND SOUTHEAST AND A FLASH FLOOD
WATCH WILL BE ISSUED FOR SE ZONES TONITE.

THE SECONDARY IMPULSE WILL TRAVERSE THE AREA TOMORROW..WITH A
CONTINUED CHANCE OF SHOWERS/STORMS.  HOWEVER..THE PRECIP MAY EVOLVE
INTO MORE OF A STABLE LIFT/RAIN EVENT FROM NW TO SOUTHEAST DURING
THE DAY AS INSTABILITY AXIS IS SHUNTED TO THE EAST.  BOTH THE ETA
AND AVN SUGGEST THAT A RATHER LARGE AREA OF DEFORMATION ZONE TYPE
PRECIP WILL LINGER INTO WED NITE OVER THE NE TWO THIRDS OF THE
FORECAST AREA.  THE MODELS NOW SEEM TO BE CONVERGING TO A SOLUTION
OF A NRLY LOW LEVEL SURGE ON THURSDAY..WHICH SHUD ACT TO DECREASE
PRECIP CHANCES. DUE TO UNCERTAINTY..AND MEAN LONGWAVE TROF AXIS
STILL TO OUR WEST..WE WILL NOT COMPLETELY PULL POPS OUT FOR THURSDAY
WITH THIS PACKAGE.  HOWEVER..IF THE CURRENT MODEL TRENDS CONTINUE
WITH THE NEXT RUN..POPS MAY BE ABLE TO BE REMOVED ON THURS AS PRECIP
AREA CONSOLIDATES TO THE UPSLOPE REGIONS TO THE WEST OF OUR FA.

THE EXTENDED FORECAST ALSO HAS CHANGED A BIT.  BOTH THE MRF AND
CANADIAN MODELS BRING THE TAIL END OF A COLD MID LEVEL TROF ACROSS
THE AREA WITH AN ASSOCIATED REINFORCING SHOT OF COLD LOW LEVEL AIR
ON FRIDAY.  MOISTURE SHUD BE VERY LIMITED WITH MEAN NWRLY FLOW..SO
WILL STILL NOT INTRODUCE POPS FOR NOW.  HOWEVER..WITH SUCH COLD AIR
IN MID LEVELS AND IMPLIED INSTABILITY DIVING SWD..WUD NOT BE SURPRISED TO SEE
SOME PRECIP ON FRIDAY IF CURRENT MODEL TRENDS PERSIST.  WARMING
TREND WITH A RETURN TO LOW LEVEL SRLY FLOW APPEARS TO BE DELAYED
UNTIL SAT/SUN NOW. THANKS FOR COORD WITH FTW/TUL.
 MILLER

PRELIM NUMBERS..SUBJECT TO CHANGE..
OKC   46  55  43  62 /  80  80  40  20
HBR   43  55  40  59 /  60  40  10  10
SPS   48  64  45  61 /  60  40  10  10
GAG   37  49  35  58 /  70  70  40  20
PNC   42  54  38  58 /  60  80  40  30
DUA   53  63  45  65 /  80  50  30  20

.OUN...
OK...FFA SE OK TONITE OKZ032-042-043-047-048-051-052.
TX...NONE.

OKZ004>048-050>052-TXZ083>090-282030-

THUNDERSTORM OUTLOOK
NATIONAL WEATHER SERVICE NORMAN OK
1230 PM CST TUE MAR 28 2000

THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS LATE THIS AFTERNOON
AND TONIGHT ACROSS PORTIONS OF WESTERN NORTH TEXAS... MAINLY SOUTH
OF A LINE FROM BENJAMIN TO WICHITA FALLS. NORTH OF THIS AREA...
THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS LATE THIS AFTERNOON
AND TONIGHT ACROSS SOUTHERN OKLAHOMA AND THE REMAINDER OF WESTERN
NORTH TEXAS. THE SLIGHT RISK AREA IS SOUTH OF A LINE FROM
SAYRE... TO ANADARKO... TO NORMAN... TO HOLDENVILLE.

DISCUSSION...A SLOW MOVING COLD FRONT LOCATED IN FAR SOUTHERN
OKLAHOMA AT MIDDAY WAS EXPECTED TO BECOME STATIONARY ALONG OR JUST
SOUTH OF THE RED RIVER DURING THE AFTERNOON. A DRYLINE EXTENDING
FROM CHILDRESS TO NEAR SAN ANGELO IS EXPECTED TO MOVE INTO PORTIONS
OF WESTERN NORTH TEXAS LATE THIS AFTERNOON AND TONIGHT. INCREASING
LOW LEVEL MOISTURE... ALONG WITH AFTERNOON HEATING... WILL RESULT IN
MODERATE TO HIGH INSTABILITIES SOUTH OF THE STATIONARY FRONT.

MEANWHILE... AN UPPER LEVEL TROUGH IN NEW MEXICO WILL MOVE INTO WEST
TEXAS BY EARLY EVENING. STRONG JET LEVEL WINDS IN EXCESS OF 100 MPH
WILL BE SPREADING INTO SOUTHWEST TEXAS BY LATE AFTERNOON.

THE STATIONARY FRONT AND THE DRY LINE ARE EXPECTED TO BE THE INITIAL
FOCUS FOR THE DEVELOPMENT OF SCATTERED THUNDERSTORMS LATER THIS
AFTERNOON AND EVENING ACROSS PORTIONS OF SOUTHWEST OKLAHOMA AND
WESTERN NORTH TEXAS. THE STORMS WILL SPREAD EAST THROUGH THE NIGHT.

NORTH OF THE STATIONARY FRONT...THE PRIMARY SEVERE WEATHER THREAT
WILL BE FROM LARGE HAIL. A FEW THUNDERSTORMS COULD ALSO PRODUCE
STRONG WIND GUSTS.

ALONG AND SOUTH OF THE FRONT... THE THREAT FOR SUPERCELL
THUNDERSTORMS WILL INCREASE....MAINLY FROM THE RED RIVER VALLEY
SOUTH INTO NORTH TEXAS. VERY LARGE HAIL AND DAMAGING WINDS WILL BE
THE PRIMARY SEVERE WEATHER THREATS WITH THESE STORMS. ALTHOUGH
RATHER WEAK LOW LEVEL WINDS EXISTED AT MIDDAY ACROSS THIS AREA...
THE VERTICAL WIND PROFILE COULD BECOME MORE FAVORABLE FOR ISOLATED
TORNADOES LATE THIS AFTERNOON AND EVENING AS THUNDERSTORM OUTFLOW
AND FRONTAL BOUNDARIES BEGIN TO INTERACT.

SCATTERED THUNDERSTORMS ACROSS NORTHERN OKLAHOMA OVERNIGHT ARE
EXPECTED TO REMAIN BELOW SEVERE LEVELS DUE TO WEAKER INSTABILITIES
OVER THE REGION.

LOCALLY HEAVY RAINFALL WILL ALSO BE A THREAT IN SOUTHEAST OKLAHOMA
TONIGHT ALONG AND A NORTH OF THE STATIONARY FRONT.

SPOTTER GROUPS AND EMERGENCY MANAGERS ACROSS SOUTHERN OKLAHOMA AND
WESTERN NORTH TEXAS...SHOULD BE PREPARED FOR POSSIBLE ACTIVATION
LATE THIS AFTERNOON AND TONIGHT.

CJS