Severe Thunderstorm Warning 722, NWS Norman, OK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORMAN OK
306 PM CDT MON SEP 21 2009

.DISCUSSION...A SEASONABLY STRONG COLD FRONT WILL SIGNAL THE ARRIVAL
OF FALL...WITH COOL NORTHERLY WINDS KICKING IN TONIGHT AND TOMORROW.
THE WIND SHIFT WAS ALREADY THROUGH MUCH OF WESTERN AND NORTHERN
OKLAHOMA THIS AFTERNOON. THE FRONT WILL DRIVE MORE QUICKLY TO THE
SOUTH RATHER THAN EAST...AS ITS ASSOCIATED UPPER LEVEL LOW DIGS
STRONGLY SOUTHWARD THROUGH THE ROCKIES.

THIS SYSTEM WILL MEET A WARM AND MOIST AIR MASS OVER CENTRAL AND
SOUTHERN OKLAHOMA...AND WESTERN NORTH TEXAS. SEVERE STORMS WERE
ONGOING MONDAY AFTERNOON JUST TO OUR NORTHEAST...AND ADDITIONAL
STRONG STORMS WILL BUILD DOWN THE FRONT DURING THE EVENING. UPPER
LEVEL FORCING IS MINIMAL...BUT SUSTAINED LIFT IN THE LOW LEVEL
FRONTAL ZONE SHOULD COMBINE WITH THE WEAKLY CAPPED AND MODERATELY
UNSTABLE AIR MASS TO YIELD WIDESPREAD STORMS TONIGHT. STORM MOTIONS
TO THE EAST AND NORTHEAST SHOULD KEEP INDIVIDUAL CELLS NEARLY
SURFACE BASED...INCREASING THE COVERAGE OF SEVERE WEATHER. WIND
SHEAR AND THERMODYNAMIC PROFILES...HOWEVER...FAVOR MARGINALLY SEVERE
HAIL AND WIND...WITH MORE INTENSE AND ORGANIZED STORMS BEING FEWER
IN NUMBER. ONE CONCERN COULD BE INTENSE RAINFALL...AS BOTH THE NAM
AND GFS HAVE A STRONG QPF SIGNAL IN SOUTHEAST OKLAHOMA. GIVEN THE
SPEED OF MOVEMENT OF THE INDIVIDUAL STORMS AND THE FRONT...THOUGH...
IT WOULD TAKE QUITE A BIT OF TRAINING TO PRODUCE EXCESSIVE RAINFALL.

BACK BEHIND THE FRONT...MODELS INDICATE AN ORGANIZED ZONE OF MID
LEVEL FRONTOGENESIS ROTATING THROUGH OUR REGION FROM WEST TO EAST
BEGINNING THE SECOND HALF OF TONIGHT. THE ACTIVITY WILL BE
LIGHTER...WITH ONLY EMBEDDED THUNDER EXPECTED. GIVEN THE COVERAGE OF
BOTH FORCING AND QPF IN THE MODELS...THOUGH...WE INCREASED POPS
ABOVE MAV GUIDANCE FOR TONIGHT AND TOMORROW...AND LOWERED MAX
TEMPERATURES WHERE CLOUD COVER IS EXPECTED TO PERSIST. IN FACT...THE
COOLER NAM 2-METER TEMPERATURES LOOKED PREFERABLE TO THE MAV MOS FOR
HIGH TEMPS BOTH TUE AND WED.

IN THE EXTENDED...THE GFS AND ITS ENSEMBLE HAVE BEEN CONSISTENT IN
KICKING THE UPPER LOW OUT OF THE ROCKIES FROM THURSDAY INTO FRIDAY.
WE REMAIN SOMEWHAT IN THE MID LEVEL DRY SLOT...BUT WITH THE RECENT
WET WEATHER AND WET GROUND...SOME INSTABILITY IS LIKELY TO
DEVELOP...WITH SCATTERED DIURNAL THUNDERSTORMS. NO CHANGES TO THE
GRIDS BEYOND DAY 3.

&&

.PRELIMINARY POINT TEMPS/POPS...
OKLAHOMA CITY OK  58  69  52  73 /  60  40  10   0
HOBART OK         56  67  52  74 /  60  40  10   0
WICHITA FALLS TX  61  69  54  77 /  60  40  10   0
GAGE OK           48  72  42  72 /  50  10  10  10
PONCA CITY OK     54  69  51  73 /  60  30  20   0
DURANT OK         66  73  59  74 /  90  50  20  10

&&

.OUN WATCHES/WARNINGS/ADVISORIES...
OK...NONE.
TX...NONE.
&&

32/22
BURKE

HAZARDOUS WEATHER OUTLOOK...UPDATED
NATIONAL WEATHER SERVICE NORMAN OK
500 PM CDT MON SEP 21 2009

OKZ004>048-050>052-TXZ083>090-221000-
HARPER-WOODS-ALFALFA-GRANT-KAY-ELLIS-WOODWARD-MAJOR-GARFIELD-NOBLE-
ROGER MILLS-DEWEY-CUSTER-BLAINE-KINGFISHER-LOGAN-PAYNE-BECKHAM-
WASHITA-CADDO-CANADIAN-OKLAHOMA-LINCOLN-GRADY-MCCLAIN-CLEVELAND-
POTTAWATOMIE-SEMINOLE-HUGHES-HARMON-GREER-KIOWA-JACKSON-TILLMAN-
COMANCHE-STEPHENS-GARVIN-MURRAY-PONTOTOC-COAL-COTTON-JEFFERSON-
CARTER-JOHNSTON-ATOKA-LOVE-MARSHALL-BRYAN-HARDEMAN-FOARD-WILBARGER-
WICHITA-KNOX-BAYLOR-ARCHER-CLAY-
500 PM CDT MON SEP 21 2009

THIS HAZARDOUS WEATHER OUTLOOK COVERS NORTHERN...WESTERN...
CENTRAL...AND SOUTHERN OKLAHOMA...AND WESTERN NORTH TEXAS.

.DAY ONE...THIS AFTERNOON AND TONIGHT...

THUNDERSTORM OUTLOOK...
THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THROUGH TONIGHT
ACROSS PORTIONS OF OKLAHOMA AND WESTERN NORTH TEXAS.

LOCATION...
THE SLIGHT RISK AREA COVERS LOCATIONS SOUTH AND EAST OF A LINE
EXTENDING FROM CHANDLER TO NORMAN TO DUNCAN AND WICHITA
FALLS.

TIMING...
THE MOST LIKELY TIME FOR SEVERE THUNDERSTORMS WILL BE LATE
THIS AFTERNOON INTO THE MID TO LATE EVENING HOURS.

IMPACTS...
SOME DAMAGE TO AUTOMOBILES AND TENDER VEGETATION FROM LARGE HAIL TO
THE SIZE OF GOLFBALLS.

DAMAGING WIND GUSTS TO 65 MPH.

ISOLATED TORNADOES.

RECOMMENDED ACTIONS...
STORM SPOTTER GROUPS AND EMERGENCY MANAGEMENT PERSONNEL ACROSS THE
RISK AREA SHOULD PLAN FOR SEVERE WEATHER OPERATIONS FROM THIS
AFTERNOON INTO EARLY TUESDAY MORNING.

DISCUSSION...
AN UPPER-LEVEL STORM SYSTEM MOVING SOUTH THROUGH THE CENTRAL ROCKIES
AND HIGH PLAINS WILL PUSH A COLD FRONT ACROSS SOUTHERN
AND EASTERN OKLAHOMA AND NORTH TEXAS THIS EVENING.  INCREASING
INSTABILITY AHEAD OF THE FRONT... COMBINED WITH MODEST VALUES OF
DEEP-LAYER WIND SHEAR... WILL LEAD TO THE DEVELOPMENT OF STRONG TO
SEVERE THUNDERSTORMS... ESPECIALLY NEAR THE COLD FRONT.

THE PRIMARY SEVERE WEATHER THREATS ARE EXPECTED TO BE STRONG WINDS
AND LARGE HAIL. HOWEVER... IF A SURFACE LOW PRESSURE CENTER FORMS
ALONG THE COLD FRONT... IT COULD LOCALLY INCREASE THE SURFACE WIND
SPEEDS. THESE STRONGER WINDS... COMBINED WITH THE DEVELOPMENT OF A
LOW-LEVEL JET... MAY RESULT IN A SMALL TORNADO THREAT THIS EVENING.

PROBABILITY TABLE...
VALID THROUGH 700 AM CDT TUESDAY SEP 22.
PROBABILITY OF THUNDERSTORMS OCCURRING IN THE
              NWS NORMAN COUNTY WARNING AREA...100 PERCENT.
PROBABILITY OF SEVERE STORMS IF STORMS OCCUR...100 PERCENT.

OTHER HAZARDOUS WEATHER...
THUNDERSTORMS LATE THIS EVENING AND OVERNIGHT MAY ALSO PRODUCE
HEAVY RAIN... LEADING TO LOCALIZED FLOODING PROBLEMS. THIS IS
EXPECTED TO BE MOST PRONOUNCED OVER THE SOUTHEAST PART OF OKLAHOMA.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY...

THUNDERSTORM OUTLOOK...
THUNDERSTORM ACTIVITY MAY LINGER INTO TUESDAY. THE STORM SYSTEM
RESPONSIBLE FOR THE COLD FRONT IS EXPECTED TO REMAIN NEARLY
STATIONARY OVER THE PLAINS FOR THE REMAINDER OF THE WEEK... WITH A
CHANCE OF THUNDERSTORMS POSSIBLY ORGANIZING THURSDAY AND FRIDAY AS
THE UPPER STORM SYSTEM BEGINS TO MOVE EAST THROUGH THE CENTRAL
PLAINS.

OTHER HAZARDOUS WEATHER...
NONE.

THE NEXT SCHEDULED HAZARDOUS WEATHER OUTLOOK WILL BE ISSUED AT 5 AM
TUESDAY.

CJS/SIX

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