Severe Thunderstorm Warning 548, NWS Norman, OK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORMAN OK
304 PM CDT FRI AUG 24 2007

.DISCUSSION...
CONVECTION THAT HAS BEEN ONGOING ALL DAY ACROSS THE NORTHWEST HALF
OF OUR FORECAST AREA HAS HELD TEMPERATURES IN THE 70S AND LOWER
80S... WHILE LOWER 90S COVER MOST OF THE REST OF OUR AREA. THE
RATHER SHARP TEMPERATURE BOUNDARY LIES FROM NEAR ALTUS... TO
OKLAHOMA CITY... AND ON EAST TOWARD MUSKOGEE. THIS BOUNDARY MAY
BECOME THE FOCUS FOR STRONGER CONVECTION LATE THIS AFTERNOON AND
INTO THE EVENING. SUPPORT FROM AN UPPER-LEVEL TROUGH WILL LIKELY
SUSTAIN THE EXISTING CONVECTION AS WELL... AND MAY EVEN SET OFF
NEW STORMS LATER TONIGHT ACROSS OUR NORTHERN COUNTIES. CHANCES FOR
SEVERE STORMS ARE PRESENT... BUT NOT OPTIMAL. THE GREATEST SHEAR
IS OVER THE AREA OF THE LEAST INSTABILITY... AND VICE-VERSA. CAPE
VALUES ARE MODERATE TO HIGH JUST SOUTH OF THE SURFACE THERMAL
BOUNDARY... BUT WIND SHEAR IS WEAK.

THE EXACT OUTCOME OF CONVECTIVE DEVELOPMENT TONIGHT WILL HAVE A
SIGNIFICANT IMPACT ON WHAT HAPPENS ON SATURDAY. MODEL POP GUIDANCE
APPEARS TO BE TOO LOW... GIVEN THE FORECAST INSTABILITY AND THE
PROBABLE EXISTENCE OF SURFACE BOUNDARIES. THE PASSAGE OF THE UPPER
TROUGH... HOWEVER... WILL LIMIT CONVECTIVE DEVELOPMENT... SO WE
HAVE ABOVE-GUIDANCE VALUES... BUT NOT NEARLY AS HIGH AS TONIGHT.

AFTER TOMORROW NIGHT... IT APPEARS THAT WE WILL DRY OUT AGAIN FOR
A FEW DAYS... AS THE UPPER HIGH RESTORES ITS DOMINANCE OVER THE
SOUTHERN PLAINS AND THE SURFACE BOUNDARIES DISSIPATE. TOWARD MID-
WEEK... HOWEVER... ANOTHER FRONT IS FORECAST TO MOVE IN FROM THE
NORTHEAST... BRINGING YET ANOTHER CHANCE OF RAIN... AND SOMEWHAT
COOLER TEMPERATURES.

&&

.PRELIMINARY POINT TEMPS/POPS...
OKLAHOMA CITY OK  70  90  70  93 /  70  30  20  10
HOBART OK         71  93  72  94 /  60  30  10   0
WICHITA FALLS TX  76  96  73  97 /  50  20  10   0
GAGE OK           66  90  67  94 /  50  20  20  10
PONCA CITY OK     71  88  71  94 /  70  20  20  10
DURANT OK         74  93  73  93 /  20  20  10  10

&&

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

30/23

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE NORMAN OK
1150 AM CDT FRI AUG 24 2007

OKZ004>048-050>052-TXZ083>090-251200-
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-
1150 AM CDT FRI AUG 24 2007

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 MUCH OF NORTHERN AND CENTRAL OKLAHOMA.

LOCATION...
THE SLIGHT RISK AREA IS NORTH OF A LINE FROM CHANDLER... TO EL
RENO... TO CORDELL... TO ERICK.

TIMING...
THE MOST LIKELY TIME FOR SEVERE THUNDERSTORMS WILL BE FROM 3 PM
THROUGH 11 PM.

RECOMMENDED ACTIONS...
STORM SPOTTER GROUPS AND EMERGENCY MANAGEMENT PERSONNEL ACROSS THE
RISK AREA SHOULD PLAN FOR SEVERE WEATHER OPERATIONS FROM MID
AFTERNOON THROUGH THIS EVENING.

DISCUSSION...
AT MIDDAY... A STATIONARY FRONT EXTENDED FROM THE NORTHERN TEXAS
PANHANDLE NORTHEASTWARD ACROSS CENTRAL AND NORTHEASTERN KANSAS...
WHILE A BROAD UPPER-LEVEL LOW PRESSURE TROUGH EXTENDED FROM EASTERN
MONTANA SOUTHWARD ALONG THE EASTERN HIGH PLAINS OF COLORADO AND NEW
MEXICO. THIS TROUGH WILL MOVE SLOWLY EAST ACROSS THE PLAINS THIS
AFTERNOON AND TONIGHT. MULTIPLE OUTFLOW BOUNDARIES WILL ALSO BE IN
PLACE ACROSS PORTIONS OF CENTRAL AND WESTERN OKLAHOMA FROM OVERNIGHT
AND MORNING CONVECTION.

THUNDERSTORMS WILL BE ONGOING ACROSS PORTIONS OF CENTRAL AND
NORTHERN OKLAHOMA EARLY THIS AFTERNOON... HOWEVER THE PRECIPITATION
AND ASSOCIATED CLOUD COVER WILL LIMIT INSTABILITY... KEEPING THE
RISK OF SEVERE WEATHER MINIMAL THROUGH MID AFTERNOON.

BY LATER THIS AFTERNOON... IF BREAKS IN THE CLOUD COVER CAN
DEVELOP... SURFACE HEATING MAY ALLOW MODERATE AMOUNTS OF INSTABILITY
TO DEVELOP. WINDS ALOFT ARE EXPECTED TO INCREASE AS THE TROUGH TO
OUR WEST APPROACHES... RESULTING IN MODERATELY STRONG VERTICAL WIND
SHEAR THROUGH A DEEP LAYER. THUNDERSTORMS ARE EXPECTED TO REDEVELOP
THIS AFTERNOON ALONG THE MAIN SURFACE BOUNDARY ACROSS THE OKLAHOMA
PANHANDLE INTO CENTRAL KANSAS AS WELL AS ALONG OTHER OUTFLOW
BOUNDARIES LOCATED ACROSS CENTRAL AND NORTHERN OKLAHOMA. IF ENOUGH
INSTABILITY CAN DEVELOP THIS AFTERNOON TO COMBINE WITH THE EXPECTED
WIND SHEAR... CONDITIONS WILL SUPPORT ORGANIZED STRONG TO SEVERE
THUNDERSTORMS AND POSSIBLY A FEW SUPERCELLS... WITH HAIL UP TO THE
SIZE OF GOLFBALLS AND WINDS TO 70 MPH THE MAIN CONCERNS. STORMS ARE
STILL EXPECTED TO ORGANIZE INTO ONE OR MORE LINES OR CLUSTERS
OVERNIGHT. ALTHOUGH SEVERE WEATHER WILL REMAIN POSSIBLE INTO THE
NIGHT... THE MAIN CONCERN WILL SHIFT MORE TO HEAVY RAINFALL AFTER
DARK.

PROBABILITY TABLE...
VALID THROUGH 700 AM CDT SATURDAY AUG 25.
PROBABILITY OF THUNDERSTORMS OCCURRING IN THE
              NWS NORMAN COUNTY WARNING AREA...100 PERCENT.
PROBABILITY OF SEVERE STORMS IF STORMS OCCUR...50 PERCENT.

OTHER HAZARDOUS WEATHER...
NONE.

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY...

THUNDERSTORM OUTLOOK...
THUNDERSTORM CHANCES WILL CONTINUE ON SATURDAY. A FEW OF THESE MAY
BE SEVERE... BUT THE CHANCES WILL DECREASE AS THE UPPER TROUGH MOVES
OVER AND EAST OF THE AREA. A SOMEWHAT STRONGER COLD FRONT IS
EXPECTED TO ARRIVE IN THE SOUTHERN PLAINS AROUND THE MIDDLE OF NEXT
WEEK... WITH ANOTHER INCREASING CHANCE OF THUNDERSTORMS WEDNESDAY
INTO THURSDAY.

OTHER HAZARDOUS WEATHER...
AFTERNOON HEAT INDEX VALUES MAY REACH THE 100 TO 105 RANGE ACROSS
MUCH OF OKLAHOMA AND NORTHERN TEXAS SUNDAY THROUGH TUESDAY.

THE NEXT SCHEDULED HAZARDOUS WEATHER OUTLOOK WILL BE ISSUED AT 7 AM
SATURDAY MORNING.

30

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