Hail and Damaging Wind in Oklahoma, July 1, 2009

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORMAN OK
313 PM CDT WED JUL 1 2009

.DISCUSSION...SURFACE ANALYSIS TRACES A COLD FRONT RUNNING
PARALLEL TO THE NORTHWESTERLY UPPER FLOW...FROM EASTERN KANSAS INTO
EASTERN ARKANSAS. A TROUGH EXTENDS WEST ACROSS SOUTHERN OKLAHOMA AND
BENDS BACK THROUGH WESTERN OKLAHOMA. THIS IS THE BOUNDARY THAT
FOCUSED STORMS YESTERDAY...AND IT MAY DO SO AGAIN TODAY. A SUBTLE
UPPER TROUGH WILL OVERTAKE THE SURFACE TROUGH IN THE ARDMORE TO
DURANT AREA...AND A CONVECTIVE REMNANT...OR MESOSCALE CONVECTIVE
VORTEX...WILL OVERTAKE THE SURFACE TROUGH NEAR THE QUARTZ AND
WICHITA MOUNTAINS AROUND PEAK HEATING. IF STORMS DO FORM...LARGE
TEMP/DEWPOINT SPREADS WILL ALLOW FOR SOME MICROBURSTS WITH STRONG
WINDS. MID LEVEL LAPSE RATES AND INSTABILITY DECREASE TO THE WEST...
AND LESS COVERAGE IS EXPECTED COMPARED TO YESTERDAY. STILL...WE
WILL CARRY LOW POPS INTO THE EVENING PERIOD.

EARLY THURSDAY MORNING...THUNDERSTORMS CAUGHT IN NORTHWEST FLOW WILL
LIKELY APPROACH NORTHEAST OKLAHOMA...AND COULD PLACE AN OUTFLOW
BOUNDARY INTO NORTH CENTRAL OKLAHOMA. ALTHOUGH THE FLOW PATTERN
FAVORS THIS...A LIMITING FACTOR WILL BE LOW INSTABILITY. PERHAPS A
BETTER CHANCE FOR THUNDERSTORMS ON THURSDAY WILL BE ALONG THE
RETREATING SURFACE TROUGH. THE NAM BREAKS OUT A FEW STORMS IN
NORTHWEST OKLAHOMA...AND WE INCLUDED LOW POPS...GIVEN THAT THE
STRONG SUN ANGLE AND WEAK CONVERGENCE HAVE PROVEN VERY EFFECTIVE AT
YIELDING ISOLATED STORMS THE PAST COUPLE OF WEEKS.

THE MAV MOS HAS PERFORMED FAIRLY WELL ON HIGH TEMPERATURES...AND THE
LATEST GUIDANCE REFLECTS INCREASING HEAT TO THE WEST OF THE SURFACE
TROUGH...WITH A GRADIENT TOWARD SLIGHTLY LOWER TEMPERATURES OVER
CENTRAL AND NORTH CENTRAL OKLAHOMA THURSDAY. FRIDAY IS A TRANSITION
DAY...WITH INCREASED RIDGING ALOFT IN ADVANCE OF THE NEXT FRONT.
FRIDAY WILL LIKELY BE THE DRIEST AND HOTTEST DAY. TEMPERATURES WILL
THEN START TO COOL FROM NORTH TO SOUTH AS THE FRONT ARRIVES THIS
WEEKEND...BUT IT MAY BE MONDAY BEFORE IT IS SIGNIFICANTLY COOLER IN
THE RED RIVER VALLEY AND NORTH TEXAS.

DESPITE THE HOT WEATHER...IT APPEARS UNLIKELY THAT RELATIVE HUMIDITY
WILL SUPPORT THE NEED FOR A HEAT ADVISORY. DEEP GULF MOISTURE
REMAINS ALONG THE COAST...SOUTH OF A LINGERING WEAK FRONTAL
BOUNDARY. EVEN AS SOUTHERLY FLOW INCREASES INTO THE PLAINS...
SUBSIDENCE AND DEEP MIXING BENEATH THE UPPER RIDGE IN TEXAS WILL
INHIBIT THE TRANSPORT OF MOISTURE. THE MOS DEWPOINTS APPEARED
UNREASONABLY HIGH IN THE MID AFTERNOON EACH DAY THROUGH THE
WEEKEND...SO WE STRUCTURED OUR DEWPOINT FORECAST AROUND THE SREF
MEAN...AND PERSISTENCE OF RECENT TRENDS. THE RESULT IS HEAT INDICES
AROUND 100 TO 102 DEGREES...WELL BELOW ADVISORY CRITERIA.

THE MOS POPS ALSO FAILED TO REPRESENT THE CONSISTENT SIGNAL IN THE
GFS AND ECMWF...WHICH FAVORS A GOOD CHANCE OF THUNDERSTORMS IN THE
FRONTAL ZONE...BEGINNING OVER NORTHERN OKLAHOMA SATURDAY
AFTERNOON...AND PROGRESSING SOUTHWARD THROUGH SUNDAY NIGHT. WE CHOSE
TO INCREASE POPS AND LOWER MAX TEMPS USING THE MODEL QPF AND RAW
TEMPERATURE FIELDS AS A GUIDE.

&&

.PRELIMINARY POINT TEMPS/POPS...
OKLAHOMA CITY OK  68  96  72 100 /  10  10  10   0
HOBART OK         72 101  74 102 /  10  10  10   0
WICHITA FALLS TX  73  99  75 101 /  20  10   0   0
GAGE OK           66  98  72 100 /   0  10  10  10
PONCA CITY OK     65  93  72  99 /  10  20  20  10
DURANT OK         72  98  72  99 /  10  10  10  10

&&

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

11/22
BURKE

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE NORMAN OK
1200 PM CDT WED JUL 1 2009

OKZ004>048-050>052-TXZ083>090-021000-
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-
1200 PM CDT WED JUL 1 2009

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

.DAY ONE...TODAY AND TONIGHT...

THUNDERSTORM OUTLOOK...
ISOLATED SEVERE THUNDERSTORMS WILL BE POSSIBLE ACROSS FAR WESTERN
AND SOUTHERN OKLAHOMA...AND WESTERN NORTH TEXAS LATE THIS AFTERNOON
AND EARLY EVENING.

DISCUSSION...
A WEAKENING TROUGH OF LOW PRESSURE WILL BECOME STATIONARY OVER FAR
WESTERN AND SOUTHERN OKLAHOMA...AND WESTERN NORTH TEXAS. LATE THIS
AFTERNOON THIS BOUNDARY IS EXPECTED TO EXTEND FROM AROUND ERICK AND
SAYRE...SOUTH AND SOUTHEAST TOWARD FREDERICK AND WICHITA FALLS...
OVER TOWARD MADILL AND DURANT. DRIER AIR WELL NORTH OF THIS
BOUNDARY...ACROSS MOST OF NORTHERN AND CENTRAL OKLAHOMA...SHOULD
PREVENT STORMS FROM DEVELOPING. HOWEVER...NEAR THE BOUNDARY...
LOWER-LEVEL MOISTURE WILL BECOME CONCENTRATED AND LEAD TO AT LEAST
SOME INSTABILITY. AS A MID-LEVEL DISTURBANCE MOVES SOUTH OVER THE
MENTIONED BOUNDARY...WEAK RISING MOTION ASSOCIATED WITH THE
DISTURBANCE AND WEAK SURFACE CONVERGENCE...MAY YIELD ISOLATED OR
SCATTERED THUNDERSTORMS LATE THIS AFTERNOON. THE MAIN IMPACTS WILL
BE HEAVY RAIN AND STRONG WIND GUSTS WITH MOST STORMS...BUT ISOLATED
DAMAGING WIND GUSTS AND MARGINALLY SEVERE-SIZE HAIL CANNOT BE RULED
OUT.

A COMPLEX OF THUNDERSTORMS MAY FORM WELL NORTH OF OKLAHOMA LATE
TODAY AND TRY TO MOVE TOWARD NORTHERN PARTS OF THE STATE. IF THIS
THUNDERSTORM COMPLEX DOES INDEED FORM...AND MAINTAINS ITSELF THROUGH
THE OVERNIGHT HOURS...SOME STORMS MAY AFFECT FAR NORTH-CENTRAL
OKLAHOMA LATE TONIGHT. ALTHOUGH SEVERE WEATHER IS NOT EXPECTED...
STRONG WIND GUSTS AND HEAVY RAIN WILL BE POSSIBLE.

PROBABILITY TABLE...
VALID THROUGH 500 AM CDT THURSDAY JUL 2.
PROBABILITY OF THUNDERSTORMS OCCURRING IN THE
              NWS NORMAN COUNTY WARNING AREA...40 PERCENT.
PROBABILITY OF SEVERE STORMS IF STORMS OCCUR...30 PERCENT.

OTHER HAZARDOUS WEATHER...
NONE.

.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY...

THUNDERSTORM OUTLOOK...
THERE WILL BE A CHANCE OF THUNDERSTORMS ACROSS NORTH-CENTRAL
OKLAHOMA EARLY THURSDAY MORNING...AND AGAIN THURSDAY NIGHT INTO
SATURDAY. THUNDERSTORM CHANCES WILL INCREASE REGION-WIDE SATURDAY
NIGHT INTO EARLY NEXT WEEK...WITH THE GREATEST CHANCES REMAINING
OVER NORTHERN OKLAHOMA.

OTHER HAZARDOUS WEATHER...
AFTERNOON HEAT INDEX VALUES MAY APPROACH 105 DEGREES IN PARTS OF
WESTERN NORTH TEXAS AND SOUTHERN AND CENTRAL OKLAHOMA FRIDAY AND
SATURDAY. PEOPLE SPENDING TIME OUTDOORS SHOULD USE CAUTION TO
PREVENT HEAT RELATED ILLNESSES.

THE NEXT SCHEDULED HAZARDOUS WEATHER OUTLOOK WILL BE ISSUED BY 5 AM
THURSDAY.

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE NORMAN OK
409 PM CDT WED JUL 1 2009

OKZ041-046-047-012130-
MURRAY OK-JOHNSTON OK-CARTER OK-
409 PM CDT WED JUL 1 2009

...SIGNIFICANT WEATHER ADVISORY...

THIS SIGNIFICANT WEATHER ADVISORY IS FOR CARTER...JOHNSTON AND MURRAY
COUNTIES.

A LINE OF STRONG THUNDERSTORMS WAS LOCATED FROM 9 MILES EAST OF GENE
AUTRY TO 11 MILES NORTHWEST OF SPRINGER AT 408 PM CDT...MOVING
SOUTHEAST AT 15 MPH.

SMALL HAIL AND WINDS AROUND 50 MPH ARE POSSIBLE... ALONG WITH VERY
HEAVY RAIN THAT WILL LIMIT VISIBILITY AND LIGHTNING.

PEOPLE IN CARTER...JOHNSTON AND MURRAY COUNTIES SHOULD MONITOR THE
WEATHER SITUATION CLOSELY. LISTEN FOR WARNINGS AND REMAIN ALERT FOR
THREATENING WEATHER CONDITIONS.

30

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE NORMAN OK
431 PM CDT WED JUL 1 2009

OKZ046-047-012205-
JOHNSTON OK-CARTER OK-
431 PM CDT WED JUL 1 2009

...SIGNIFICANT WEATHER ADVISORY...

THIS SIGNIFICANT WEATHER ADVISORY IS FOR CARTER AND JOHNSTON
COUNTIES.

A LINE OF STRONG THUNDERSTORMS WAS LOCATED FROM MILO TO 3 MILES EAST
OF GENE AUTRY AT 429 PM CDT...MOVING SOUTH AT 5 MPH.

SMALL HAIL...HEAVY RAIN...AND WINDS AROUND 50 MPH ARE LIKELY. THESE
STORMS WILL AFFECT ARDMORE...LONE GROVE...AND TRAVELERS ALONG
INTERSTATE 35 FROM ARDMORE NORTH TO SPRINGER.

BURKE