FXUS64 KOUN 120126
AFDOUN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORMAN OK
726 PM CST FRI DEC 11 2009
.UPDATE...THE OVERNIGHT FORECAST IS COMPLEX WHEN CONSIDERING THE
EVOLUTION OF SEVERAL DIFFERENT CLOUD GROUPS...THEIR EFFECTS ON
TEMPERATURE...AND THE POSSIBILITY OF SUB FREEZING SURFACES DURING
THE ONSET OF DRIZZLE OR LIGHT RAIN. MODELS HAD NOT PERFORMED WELL
IN ANTICIPATING THE DEVELOPMENT OF A MID LEVEL CLOUD DECK EARLIER
TODAY. OBSERVATIONAL EVIDENCE SUGGESTED THE CLOUDS WERE CONFINED
TO A VERY THIN LAYER AROUND 750 MB...OR ROUGHLY ON THE 290 K
ISENTROPIC SURFACE. SATELLITE TRENDS SHOWED BREAKS DEVELOPING
OVER CENTRAL OKLAHOMA...AND MODEL FORECASTS AT 290 K SUGGEST A
PERIOD OF WEAKENING UPGLIDE BEFORE MORE SUBSTANTIAL UPGLIDE OCCURS
AFTER MIDNIGHT. DURING THE INTERIM...THE MID CLOUDS MAY
DISSIPATE...AND WITH HIGH CLOUDS EXPECTED TO BE THICKEST IN
KANSAS...THERE IS OPPORTUNITY FOR SOME RADIATIONAL COOLING IN
OKLAHOMA AND WESTERN NORTH TEXAS.
GIVEN THE EARLY EVENING TEMPERATURES AND DEWPOINTS...IT IS LIKELY
THAT MUCH OF THE AREA NORTH OF ADA...DUNCAN...AND VERNON...WILL
FALL BELOW FREEZING. THIS WILL BECOME IMPORTANT LATE
TONIGHT...WHEN THE LOW LEVEL JET BRINGS A SUBSTANTIAL INCREASE IN
LOW CLOUDS...DRIZZLE...AND PATCHY LIGHT RAIN. PARTS OF
WESTERN...CENTRAL...AND NORTHERN OKLAHOMA MAY TECHNICALLY
EXPERIENCE FREEZING DRIZZLE LATE TONIGHT AND EARLY SATURDAY
MORNING...AND THIS IS NOW REFLECTED IN THE FORECAST GRIDS.
AT THE SAME TIME AS PRECIPITATION BEGINS...HOWEVER...THE THICKENING
CLOUD COVER AND INCREASING SOUTHERLY WINDS WILL ACT TO RAISE
TEMPERATURES. THEREFORE...IT STILL APPEARS THAT ONLY SHORT
DURATION...TRACE AMOUNTS...OF ICE SHOULD BE EXPECTED...WITH
RELATIVELY LITTLE IMPACT.
FOG MAY BE OF GREATER IMPACT TO THE FORECAST. GIVEN THE PROXIMITY
OF WESTERN OKLAHOMA AND NORTH TEXAS TO A RETREATING WARM
FRONT...AND THE RADIATIONAL COOLING THAT WILL PRECEDE THE ARRIVAL
OF DEEP MOISTURE...FOG COULD FORM TO A SUBSTANTIAL DEPTH EARLY
SATURDAY. CEILINGS WILL ALSO LOWER TOWARD THE GROUND OVER THE REST
OF OKLAHOMA SATURDAY MORNING. GIVEN THE LOW SUN ANGLE AND
SHORTENED DECEMBER DAYS...WE DECREASED HIGH TEMPERATURES FOR
SATURDAY...GOING WITH THE NAM 2 METER TEMPERATURES.
&&
BURKE
&&
.PREV DISCUSSION... /ISSUED 528 PM CST FRI DEC 11 2009/
AVIATION...
CEILINGS WILL BECOME IFR BY 06Z IN CLOUDS AND DRIZZLE OVER THE
EASTERN 3/4 OF OKLAHOMA. CONITIONS ARE EXPECTED TO BE GREATER THAN
IFR BY 18Z.
&&
.PREV DISCUSSION... /ISSUED 528 PM CST FRI DEC 11 2009/
EARLY NEXT WEEK... OPERATIONAL GFS HAS GONE BACK TO A WARMER
SOLUTION DESPITE STILL SHOWING SURFACE RIDGE POKING INTO THE AREA
FROM BIG HIGH IN THE NORTHERN PLAINS/CANADIAN PRAIRIES. BELIEVE
THAT A COLD SOLUTION /AS ADVERTISED BY THE ECMWF AND HPC/ MAKES
MORE SENSE AND WILL KEEP THE CURRENT COLD FORECAST.
&&
.PRELIMINARY POINT TEMPS/POPS...
OKLAHOMA CITY OK 30 49 38 60 / 10 10 10 10
HOBART OK 29 55 35 62 / 10 10 0 0
WICHITA FALLS TX 35 57 40 72 / 10 10 0 10
GAGE OK 27 56 27 59 / 0 0 0 0
PONCA CITY OK 28 45 34 56 / 0 10 10 10
DURANT OK 35 44 43 69 / 30 40 10 10
&&
.OUN WATCHES/WARNINGS/ADVISORIES...
OK...NONE.
TX...NONE.
&&
$$
22/09
