FXUS64 KOUN 292326
AFDOUN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORMAN OK
526 PM CST SUN NOV 29 2009
.AVIATION...
AREAS OF LIGHT PRECIP OVER PANHANDLES AND W OK ARE MOSTLY ALOFT
BUT WILL INCLUDE VCSH FOR A COUPLE HRS THIS EVENING. OTHERWISE
MID-LEVEL CLOUDS WILL LIFT AND MOVE OUT LATER THIS EVENING LEAVING
CLEAR OR MOSTLY CLEAR SKIES BY MONDAY MORNING.
&&
.PREV DISCUSSION... /ISSUED 234 PM CST SUN NOV 29 2009/
DISCUSSION...
THE PRECIPITATION SHOULD GRADUALLY END FROM THE WEST THIS EVENING ALONG
WITH SOME GRADUAL THINNING OF THE EXISTING EXTENSIVE CLOUD COVER.
THIS TREND IS EXPECTED TO OCCUR IN RESPONSE TO THE ZONE OF MID-
LEVEL WARM ADVECTION SHIFTING SOUTHEAST AND BEING REPLACED WITH
COLD ADVECTION AS A SHORTWAVE DROPS SOUTHEAST THROUGH EASTERN
KANSAS. DRIER AIR AT ALL LEVELS IS ALSO FORECAST TO BE MOVING
INTO THE REGION. HOWEVER... THIS TREND COULD BE DELAYED BY A FEW
MORE HOURS BY AN UPPER WAVE... AND ASSOCIATED PRECIP AREA... MOVING
THROUGH THE SOUTH TEXAS PLAINS... PROVIDING IT HOLDS TOGETHER.
THE GUSTY NORTH WINDS WILL ALSO SLOWLY DIMINISH TONIGHT. SHOULD
THE RATE OF CLEARING AND DECREASING WINDS OCCUR FASTER THAN
CURRENTLY EXPECTED... THE OVERNIGHT LOWS MAY NEED TO BE ADJUSTED
DOWNWARD A BIT MORE.
MONDAY WILL BE PARTLY TO MOSTLY SUNNY AS THE CWA IS TEMPORARILY IN-
BETWEEN WEATHER SYSTEMS WITH DRIER AIR DOMINATING THE REGION.
HOWEVER... THE CLOUD COVER WILL BEGIN SPREADING BACK IN FROM THE
WEST ON TUESDAY IN RESPONSE TO THE COLD NORTHERN MEXICO LOW MOVING
INTO SOUTHWEST TEXAS. THIS WILL LEAD TO A RETURN OF RAIN CHANCES
BEGINNING IN THE WEST TUESDAY AFTERNOON AND INCREASING OVER MUCH
OF THE AREA TUESDAY NIGHT. CURRENTLY THE BEST PRECIPITATION
CHANCES APPEAR TO BE ACROSS SOUTHERN OKLAHOMA AND NORTHERN TEXAS
AS SOMEWHAT DRIER AIR WILL REMAIN OVER NORTHERN OKLAHOMA.
CONCERNING THE NORTHERN MEXICO LOW... THE 12Z NAM IS A LITTLE
FARTHER NORTH AND SLOWER THAN THE 12Z GFS AND AS A RESULT SPREADS
MORE PRECIPITATION FARTHER TO THE NORTH WHILE ALSO KEEPING IT IN THE
AREA FOR LONGER. THE ECM TENDS TO BE IN-BETWEEN. FOR NOW WE WILL
TREND WITH A BLEND OF THE SOMEWHAT MORE NORTHERN POSITION AND A
BIT SLOWER TIMING OF NAM AND ECM.
THE NAM'S THICKNESS PARAMETERS SUGGEST A MIX OF RAIN AND SNOW
COULD OCCUR OVER PARTS OF SOUTHWEST OKLAHOMA AND WESTERN NORTH
TEXAS FOR A SHORT TIME WEDNESDAY MORNING AS COLDER TEMPERATURES
ALOFT... ASSOCIATED WITH THE UPPER LOW... MOVE ACROSS. THE NAM'S BOUNDARY
LAYER TEMPERATURES ARE FORECAST TO BE ONLY SLIGHTLY ABOVE
FREEZING AT THAT TIME. MEANWHILE... THE GFS 850 TO 700 MB
THICKNESSES ARE ALSO COLD ENOUGH TO SUPPORT SNOW... HOWEVER THE
LOWER LEVELS ARE WARMER THAN THE NAM FOR WEDNESDAY MORNING. GIVEN
THE UNCERTAINTY WITH THE TIMING OF THE UPPER LOW AND ITS JUXTAPOSITION
WITH THE VARIOUS THICKNESS/LOW LEVEL TEMPERATURE PARAMETERS AND QPF...
WE WILL NOT GET AGGRESSIVE WITH THIS EVENT ATTM... BUT WILL
INTRODUCE A MIX OF RAIN AND WET SNOW FOR A SHORT WHILE WEDNESDAY
MORNING. GIVEN THE MARGINALLY COLD LOW LEVEL TEMPERATURES AND
RELATIVELY MILD GROUND TEMPERATURES... DOUBT THAT ANY SNOW THAT
MIGHT OCCUR WILL STAY AROUND VERY LONG. HAVING SAID THAT... WE
WILL NEED TO MONITOR A COLD FRONT THAT IS FORECAST TO DROP INTO
KANSAS LATE IN THE DAY TUESDAY AND MOVE INTO THE CWA TUESDAY NIGHT
AND EARLY WEDNESDAY. IF THIS AIR ARRIVES COLDER THAN EXPECTED...
IT COULD RESULT IN SOME EXPANSION OF THE MIXED PRECIPITATION AREA.
LATER IN THE FORECAST PERIOD... CONSIDERABLE UNCERTAINTY EXISTS
FOR NEXT WEEKEND AND INTO EARLY THE FOLLOWING WEEK AS THE GFS AND
ECMWF SHOWING SIGNIFICANTLY DIFFERENT SOLUTIONS WITH THE UPPER
AIR PATTERN. THE GFS ENSEMBLE MEMBERS ALSO EXHIBIT QUITE A BIT OF
VARIABILITY. THEREFORE... WILL MAKE LITTLE CHANGES TO THOSE
PERIODS ATTM.
&&
.PRELIMINARY POINT TEMPS/POPS...
OKLAHOMA CITY OK 32 58 33 54 / 20 0 0 10
HOBART OK 29 57 33 52 / 20 0 0 20
WICHITA FALLS TX 36 59 35 50 / 30 0 0 40
GAGE OK 22 58 29 55 / 0 0 0 10
PONCA CITY OK 29 59 34 55 / 0 0 0 10
DURANT OK 40 57 37 54 / 50 0 0 20
&&
.OUN WATCHES/WARNINGS/ADVISORIES...
OK...NONE.
TX...NONE.
&&
$$
25/24/24
