Severe Thunderstorm Warning 461, NWS Norman, OK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORMAN OK
400 AM CDT WED JUN 27 2001

THE BIG PICTURE CONTINUES TO EVOLVE ABOUT AS EXPECTED WITH UPPER LOW
DRIFTING WEST NEXT 72 HOURS...THEN MORE SOUTHWEST INTO TEXAS OVER
THE WEEKEND.  ALL SHORT AND MEDIUM RANGE MODELS ARE IN PRETTY CLOSE
AGREEMENT ON THE EVOLUTION OF THE SYSTEM.  THIS MAKES SENSE GIVEN
THE MODERATELY STRONG 250 MB JET ON THE NW SIDE OF THE SYSTEM
HELPING TO DRIVE IT WESTWARD. AS A RESULT...ATMOSPHERE WILL SLOWLY
COOL IN MID LEVELS FROM EAST TO WEST RESULTING IN STEEP LOW LEVEL
LAPSE RATES DURING THE AFTERNOON HOURS.

AT THIS TIME IT APPEARS THE BEST CHANCES FOR THUNDERSTORM ACTIVITY
DURING THE NEXT FIVE DAYS WILL BE FRI-SAT WITH THE UPPER LOW
DRIFTING ACROSS THE EASTERN HALF OF OKLAHOMA AT THAT TIME.
BUT...ISOLATED TO WIDELY SCATTERED CONVECTION WILL BE POSSIBLE
STARTING TODAY IN THE CENTRAL AND EAST PARTS OF THE CWA. MAIN
PROBLEM TODAY IS LACK OF SFC BOUNDARIES IN WHICH TO FOCUS
DEVELOPMENT...BUT THIS SITUATION MAY CHANGE THU INTO FRI DEPENDING
ON THE AMOUNT OF CONVECTION WHICH ENSUES DURING THE NEXT FEW DAYS
WHICH WOULD THEN LEAVE SOME BOUNDARIES AROUND.  FORECAST SOUNDINGS
TODAY SHOW AN INVERTED-V LOOK BY THIS AFTERNOON...INCREASING THE
POTENTIAL FOR WIND GUSTS WITH ANY STORMS WHICH DEVELOP.

AS THE UPPER LOW MOVES CLOSER DURING THE WEEK...NORTHERLY WINDS ALOFT
WILL GRADUALLY STRENGTHEN OVER THE AREA TO ABOUT 25-30 KNOTS AT 500
MB.  WITH CONTINUED SOUTHERLY FLOW AT LOW LEVELS...THIS WOULD
IMPROVE SHEAR PROFILES THU-FRI SUCH THAT STORMS WOULD BE MORE
ORGANIZED RATHER THAN SIMPLY DIURNAL PULSE TYPE ACTIVITY AS WOULD BE
IMPLIED BY JUST A COLD POOL ALOFT AND AFTERNOON HEATING.

WILL NOT MAKE MUCH CHANGE OVERALL TO THE GOING FORECAST.  UPPER LOW
AND CONVECTION CHANCES WILL KEEP AFTERNOON HEATING IN CHECK WITH
HIGHS DROPPING DOWN 3-5 DEGREES AS THE LOW APPROACHES...THEN SLOWLY
WARMING BACK INTO THE LOWER AND MIDDLE 90S EARLY NEXT WEEK AS TEMPS
IN MID LEVELS WARM AND CLOUD COVER IS SUPPRESSED A BIT MORE.

FCSTID = 33/DLF
OKC   90  68  88  70 /  30  30  40  30
HBR   94  68  91  70 /  10  10  20  20
SPS   93  68  90  70 /  30  30  40  30
GAG   94  68  90  68 /  10  10  20  20
PNC   90  68  88  70 /  30  30  40  30
DUA   89  69  88  70 /  30  30  40  30

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

OKZ004>048-050>052-TXZ083>090-271430-

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE NORMAN OK
700 AM CDT WED JUN 27 2001

NO ORGANIZED HAZARDOUS WEATHER IS EXPECTED TODAY OR TONIGHT ACROSS
WESTERN...CENTRAL OR SOUTHEAST OKLAHOMA...OR WESTERN NORTH TEXAS.

SCATTERED THUNDERSTORM ACTIVITY WILL BE POSSIBLE ACROSS ALL BUT
EXTREME WESTERN PORTIONS OF OKLAHOMA AND NORTH TEXAS TODAY AND
TONIGHT...AS AN UPPER LEVEL STORM SYSTEM SLOWLY MOVES TOWARD THE
REGION FROM THE MID MISSISSIPPI RIVER VALLEY. WITH ONLY MARGINAL
INSTABILITY AND WEAK VERTICAL WIND SHEAR...NO ORGANIZED SEVERE
THUNDERSTORM ACTIVITY IS EXPECTED THROUGH TONIGHT...ALTHOUGH SOME OF
THE STRONGER STORMS COULD PRODUCE SMALL HAIL AND STRONG WIND GUSTS.

ON THURSDAY...THUNDERSTORM CHANCES WILL INCREASE...ESPECIALLY DURING
THE AFTERNOON AND EVENING HOURS. AS THE UPPER LEVEL STORM SYSTEM
MOVES CLOSER...COOLING OF THE MID AND UPPER LEVELS OF THE ATMOSPHERE
AND SLIGHTLY HIGHER WIND SHEAR VALUES WILL RESULT IN AN INCREASED
THREAT FOR SEVERE THUNDERSTORMS. THE LATEST NUMERICAL MODEL DATA
SUGGESTS THAT ISOLATED SUPERCELLS WILL BE POSSIBLE THURSDAY AS WIND
SPEEDS INCREASE AND THE VERTICAL WIND PROFILE REMAINS STRONGLY
VEERED. IF THIS SCENARIO HOLDS TRUE...LARGE HAIL AND DAMAGING WIND
GUSTS WOULD BE THE PRIMARY THREATS.

ALTHOUGH NO SPOTTER ACTIVATION IS EXPECTED THROUGH TONIGHT...IT MAY
BE NECESSARY ON THURSDAY AS THE SEVERE WEATHER THREAT IS EXPECTED TO
INCREASE. STAY TUNED TO NOAA WEATHER RADIO...AMATEUR RADIO NETS...OR
YOUR FAVORITE TV AND RADIO STATIONS FOR THE LATEST STATEMENTS AND
FORECASTS.

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