Flash Flood Warning 24, NWS Norman, OK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORMAN OK
444 AM CDT THU SEP 11 2003

WIDESPREAD TSRA CONTINUES ACROSS ALL BUT SE PARTS OF THE FORECAST
AREA THIS MORNING. MOST INTENSE UPDRAFTS AND FREQUENT LIGHTNING HAVE
BEEN ALONG LEADING EDGES OF CONVECTIVE OUTFLOW BOUNDARIES OVER SOUTH
CENTRAL AND SE KANSAS...WESTERN NORTH TEXAS...AND RECENTLY JUST
SOUTHWEST OF OKLAHOMA CITY. WEST OF THESE AREAS HAS BEEN PERSISTENT
STRATIFORM RAIN WITH MOSTLY LIGHT TO MODERATE RAINFALL RATES AND
SOME EMBEDDED TS. SYNOPTIC COLD FRONT IS STILL WELL WEST AND NORTH
OF THE AREA...BUT SLOW EASTWARD MOVEMENT INTO THE FORECAST AREA IS
STILL EXPECTED AS STRONG WESTERLY UPPER JET OVER THE PACIFIC
NORTHWEST PUSHED FRONT EASTWARD.

OTHER THAN PARTS OF SOUTHWEST OKLAHOMA THAT RECEIVED EXCESSIVE RAIN
EARLIER IN THE NIGHT BUT HAVE SINCE TRANSITIONED TO STRATIFORM
RAIN...THE FORECAST AREA HAS HIGH FLASH FLOOD GUIDANCE AND BELIEVE
MOST AREAS CAN STAND TO RECEIVE 3 TO 4 INCHES OF RAIN BEFORE
FLOODING BECOMES A PROBLEM. THESE AMOUNTS ARE EXPECTED TO BE
PRIMARILY LOCALIZED DUE TO ABUNDANT CLOUD COVER REDUCING INSTABILITY
...AND A WEAKENING LOW LEVEL JET THIS MORNING.

FORECAST BECOMES MORE UNCERTAIN AFTER TODAY AS GFS/ETA SHOW
DIFFERING SOLUTION WITH REGARDS TO EVOLUTION OF MID/UPPER LEVEL FLOW
AND ASSOCIATED SURFACE FEATURES. COMPARISONS OF THE 00 HOUR
INITIALIZATIONS FROM THE GFS/ETA FAVOR THE GFS WITH THE 250 MB SPEED
MAX BETTER RESOLVED AT SPOKANE/BOISE/ELKO IN THE GFS COMPARED TO THE
ETA WHICH MAY HELP TO EXPLAIN WHY THE ETA SHOWS A STRONGER AND
SLOWER CUTOFF LOW DEVELOPING SOUTHWEST OF THE AREA AFTER 48 HRS. THE
GFS REMAINS MORE PROGRESSIVE BUT EVEN ITS SOLUTION HAS CONCERN WITH
CONVECTIVE FEEDBACK APPEARING TO MODIFY THE SYNOPTIC PATTERN.
FORECAST CONFIDENCE REMAINS LOW AT THIS POINT AND FEEL ITS BEST TO
MAKE ONLY A FEW CHANGES TO THE OVERALL PACKAGE.

HAVE DECIDED TO LIMIT POPS TO JUST EASTERN PARTS OF THE AREA
BEGINNING TONIGHT AS EVEN THE ETA SHOWS DIMINISHING LOWER/MID LEVEL
MOISTURE LIFT AND MORE STABLE AIR ENTERING/DEVELOPING IN NORTHWEST
PARTS OF THE AREA. THIS TREND IS EXPECTED TO CONTINUE ACROSS WESTERN
PARTS OF THE AREA FRIDAY AND FRIDAY NIGHT. BY SATURDAY ETA STILL
PREFERS TO ALLOW SURFACE LOW TO BEGIN REDEVELOPING FARTHER WEST WITH
THE FRONT RETROGRADING. GIVEN MODEL DIFFERENCES HAVE MADE VERY FEW
CHANGES...IF ANY...AFTER FRIDAY NIGHT.

OKC  77 63 77 60 / 99 60 30 30
HBR  75 57 78 58 / 99 30 00 10
SPS  77 64 78 60 / 99 50 30 30
GAG  71 51 78 55 / 90 00 00 00
PNC  77 61 77 60 / 99 60 30 40
DUA  81 68 76 62 / 70 99 70 50

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

OKZ004>048-050>052-TXZ083>090-111300-

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE NORMAN OK
1152 AM CDT WED SEP 10 2003

THIS HAZARDOUS WEATHER OUTLOOK PERTAINS TO 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 THIS EVENING AND
OVERNIGHT ACROSS PORTIONS OF NORTHERN AND WESTERN OKLAHOMA...INTO A
SMALL PART OF WESTERN NORTH TEXAS.

LOCATION...
THE SLIGHT RISK AREA COVERS LOCATIONS NORTH AND WEST OF A LINE
EXTENDING FROM SEYMOUR TEXAS...TO HOBART...TO WATONGA...TO ENID AND
MEDFORD.

TIMING...
THE MOST LIKELY TIME FOR SEVERE THUNDERSTORM DEVELOPMENT WILL BE BY
10 PM AND CONTINUE THROUGH THE OVERNIGHT HOURS.

IMPACTS...
THE STRONGEST STORMS WILL BE CAPABLE OF PRODUCING WIND GUSTS TO NEAR
70 MPH...WHICH COULD CAUSE DAMAGE TO TREE LIMBS AND POSSIBLY TO
MOBILE HOMES. LARGE HAIL UP TO GOLFBALL SIZE MAY ALSO CAUSE DAMAGE
TO VEGETATION AND VEHICLES.

RECOMMENDED ACTIONS...
STORM SPOTTER GROUPS AND EMERGENCY MANAGEMENT PERSONNEL ACROSS THE
SLIGHT RISK AREA MAY NEED TO IMPLEMENT SEVERE WEATHER OPERATIONS
THIS EVENING THROUGH TONIGHT.

DISCUSSION...
THUNDERSTORMS ARE EXPECTED TO DEVELOP LATE THIS AFTERNOON AND
EVENING ACROSS WESTERN KANSAS...SOUTHWARD INTO THE OKLAHOMA AND
TEXAS PANHANDLES. THESE STORMS ARE EXPECTED TO ORGANIZE INTO A
LINEAR COMPLEX DURING THE EVENING AND OVERNIGHT HOURS ALONG A
DEVELOPING COLD FRONT. THIS COMPLEX WILL THEN MOVE INTO AND ACROSS
WESTERN PORTIONS OF THE NWS NORMAN COUNTY WARNING AREA. SUFFICIENT
DEEP LAYER WIND SHEAR AND INSTABILITY WILL SUPPORT SEVERE
THUNDERSTORMS...INCLUDING SOME SUPERCELLS.

PROBABILITY TABLE...
VALID THROUGH 700 AM CDT THURSDAY SEPTEMBER 11.
PROBABILITY OF THUNDERSTORMS OCCURRING IN THE
              NWS NORMAN COUNTY WARNING AREA...80 PERCENT.
PROBABILITY OF SEVERE STORMS IF STORMS OCCUR...40 PERCENT.

OTHER HAZARDOUS WEATHER...
GUSTY SOUTH WINDS WILL REQUIRE EXTRA CAUTION BY BOATERS ON AREA
LAKES TODAY.

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

THUNDERSTORM OUTLOOK...
A LARGE AREA OF SHOWERS AND THUNDERSTORMS IS EXPECTED TO BE ONGOING
THURSDAY MORNING. THIS ACTIVITY WILL EXIST ALONG AND JUST BEHIND A
COLD FRONT THAT WILL MOVE THROUGH OKLAHOMA AND WESTERN NORTH TEXAS
THURSDAY AND THURSDAY NIGHT. DUE TO THE ANTICIPATED ORIENTATION OF
THE FRONTAL BOUNDARY AND MID LEVEL WIND FIELDS...TRAINING ECHOES ARE
LIKELY. VERY HEAVY RAIN WILL BE THE PRIMARY CONCERN THURSDAY THROUGH
FRIDAY. DUE TO CONTINUED MOIST SOIL FROM LAST WEEKS HEAVY
RAINFALL...RIVER AND FLASH FLOODING WILL BE POSSIBLE IN SOME AREAS
ACROSS OKLAHOMA AND WESTERN NORTH TEXAS.

EVEN AFTER THE FRONT PASSES THROUGH THE AREA...RESIDUAL MID LEVEL
MOISTURE AND UPPER LEVEL ENERGY TO OUR WEST WILL RESULT IN A CHANCE
OF SHOWERS AND THUNDERSTORMS CONTINUING INTO THE WEEKEND.

OTHER HAZARDOUS WEATHER...
NONE.

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

MAXWELL

LOCAL STORM REPORT
NATIONAL WEATHER SERVICE NORMAN OK
1247 AM CDT THU SEP 11 2003

TIME (CDT) .....CITY LOCATION.....STATE   ...EVENT/REMARKS...
           ....COUNTY LOCATION....

1135 PM    4 SE ERICK                OK   58 MPH WIND GUST
09/10/03   BECKHAM                        MEASURED BY OKLAHOMA
                                          MESONET

OKZ005-006-110800-

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE NORMAN OK
237 AM CDT THU SEP 11 2003

...SIGNIFICANT WEATHER ADVISORY...

THIS SIGNIFICANT WEATHER ADVISORY IS FOR ALFALFA AND WOODS COUNTIES.

A LINE OF STRONG THUNDERSTORMS WAS LOCATED FROM NEAR DRIFTWOOD TO
JUST EAST OF ALVA AT 237 AM CDT...MOVING NORTHEAST AT 15 MPH.

SEVERE WEATHER IS NOT EXPECTED AND NO WARNINGS ARE ANTICIPATED AT
THIS TIME. HOWEVER...THE THUNDERSTORMS WILL BE CAPABLE OF PRODUCING
SMALL HAIL AND 45 MPH WIND GUSTS.

11

LOCAL STORM REPORT
NATIONAL WEATHER SERVICE NORMAN OK
508 AM CDT THU SEP 11 2003

TIME (CDT) .....CITY LOCATION.....STATE   ...EVENT/REMARKS...
           ....COUNTY LOCATION....

0100 AM    ERICK                     OK   FLOODING
09/11/03   BECKHAM                        ELDER MAN EVACUATED FROM
                                          VEHICLE STALLED BY HIGH
                                          STANDING WATER
                                          REPORTED BY SHERIFF OFFICE

0100 AM    1 N  ERICK                OK   FLOODING
09/11/03   BECKHAM                        TWO SEMI TRACTOR TRAILER
                                          VEHICLES HYDROPLANED ONTO
                                          INTERSTATE MEDIAN
                                          REPORTED BY SHERIFF OFFICE

0450 AM    1 N ERICK                 OK   FLOODING
09/11/03   BECKHAM                        TWO SEMI TRACTOR TRAILER
                                          VEHICLES HYDROPLANED ONTO
                                          INTERSTATE MEDIAN
                                          REPORTED BY SHERIFF OFFICE

SBS