Expires:No;;251878 FXUS64 KOUN 260335 AFDOUN AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NORMAN OK 935 PM CST WED NOV 25 2009 .UPDATE... AGAIN IT LOOKS LIKE A CLOSE CALL TONIGHT AS FAR AS A WIDESPREAD FREEZE IN THE FREEZE WARNING AREA. FROST ADVISORY ALSO WILL BE MARGINAL WITH A FEW SITES STILL IN THE 50S IN SCENTRAL/SE OK AS OF 9 PM. WE WILL LET THE HEADLINES RIDE... BUT LIGHT NW WINDS AGAIN MAY STAY UP JUST ENOUGH TO PREVENT MANY PARTS OF THE AREA FROM RADIATING DOWN TO FROST/FREEZE LEVELS. BASICALLY NO SIGNIFICANT CHANGE TO THE FORECAST AT THIS TIME. && .PREV DISCUSSION... /ISSUED 523 PM CST WED NOV 25 2009/ AVIATION... /0Z TAFS/...VFR CONDITIONS WILL PREVAIL THROUGHOUT THE TAF PERIOD WITH WINDS GRADUALLY SHIFTING TO THE SOUTH THURSDAY. MAXWELL PREV DISCUSSION... /ISSUED 254 PM CST WED NOV 25 2009/ DISCUSSION...THE 12Z GFS FITS OUR CONTINUING CONCEPT ON HOW AN UPPER TROUGH WILL EVOLVE LATE THIS WEEKEND. THEREFORE...WE LEFT MUCH OF THE FORECAST UNTOUCHED. THE MOST PRESSING MATTER IN THE SHORT TERM IS TO EVALUATE LOW TEMPERATURES AND ANY NEED FOR FROST/FREEZE PRODUCTS. FROM THE MIDDAY AFD...INCORPORATING LOW TEMPERATURES THAT OCCURRED THIS MORNING...WE HAVE EVALUATED THE NUMBER OF NOVEMBER FREEZES RECORDED AT MOST OBSERVING SITES ACROSS OUR FORECAST AREA. THIS DATA SUGGESTS THAT THE GROWING SEASON HAS ENDED TO THE WEST OF A LINE FROM GRANT COUNTY TO GRADY COUNTY...TO COMANCHE...TILLMAN... WILBARGER...AND BAYLOR...INCLUSIVE OF THOSE COUNTIES. FARTHER EAST...MANY LOCATIONS HAVE EXPERIENCED ONE OR TWO LIGHT FREEZES...WITH TEMPERATURES ABOVE 28 DEGREES...AND THE AVAILABLE SITES IN SOME SOUTHEAST COUNTIES HAVE NOT YET EXPERIENCED A FREEZE. WE WILL CONTINUE TO CONSIDER THESE AREAS FOR FROST AND FREEZE PRODUCTS. TONIGHT A FRONT WILL MOVE WELL SOUTH INTO TEXAS. CLEAR SKIES AND DRY AIR WILL FAVOR RADIATIONAL COOLING. WINDS ARE THE ONLY QUESTION. SPEEDS ARE LIKELY TO DIMINISH MORE UNIFORMLY NEAR THE PRESSURE RIDGE OVER WESTERN OKLAHOMA AND WESTERN NORTH TEXAS. FARTHER EAST...CYCLONIC FLOW JUST ABOVE THE SURFACE WILL MAINTAIN SOME HEALTHY WIND SPEEDS AT 925 TO 850 MB. GIVEN THE LOW DEWPOINTS AND LENGTHY NIGHT /GIVING MORE TIME TO DECOUPLE/ WE ARE INCLINED TO LEAN TOWARD THE MET GUIDANCE...AND UNDERCUT MAV BY 4 TO 7 DEGREES. THE RESULT IS A FREEZE WARNING AND FROST ADVISORY IN EFFECT FOR LATE TONIGHT AND EARLY THURSDAY. IT IS POSSIBLE THAT THE AREA AVAILABLE FOR FREEZE AND FROST PRODUCTS WILL EXPERIENCE ONLY LIGHT FREEZES BOTH TONIGHT AND THURSDAY NIGHT. BY THE TIME THAT THE NEXT COLD WEATHER ARRIVES...IT WILL BE DECEMBER ON THE CALENDAR...AND WELL PAST THE CLIMATOLOGICAL AVERAGE DATE FOR FIRST FREEZE. WE MAY THEN CHOOSE TO HANDLE ANY COLD AIR OUTBREAKS WITH SPECIAL WEATHER STATEMENTS...AND ASSUME THAT THE GROWING SEASON HAS ENDED. FOLLOWING A TRANQUIL THANKSGIVING DAY...FRIDAY WILL SEE THE RETURN OF BREEZY SOUTH WINDS AND MILD TEMPERATURES. A MID LEVEL RIDGE AND PLUME OF WARM AIR WILL TRAVERSE THE PLAINS...YIELDING HIGHS IN THE 60S AND LOW 70S. FIRE POTENTIAL WILL BE ELEVATED...AS HUMIDITY FALLS NEAR 20 PERCENT IN THE WEST. WINDS...HOWEVER...ARE EXPECTED TO REMAIN MARGINAL FOR RED FLAG...WITH SUSTAINED SPEEDS BELOW 20 MPH. FORECAST MODELS ARE COMING INTO BETTER AGREEMENT WITH THE TIMING AND MOVEMENT OF A COLD FRONT THAT IS DUE INTO OKLAHOMA SATURDAY NIGHT. AS ANTICIPATED...THE MODELS ARE CONVERGING TOWARD A SPLIT UPPER LEVEL FLOW PATTERN...WHICH TAKES MOST OF THE SUPPORT FOR THIS FRONT ACROSS THE CENTRAL PLAINS...WHILE ANOTHER VORT MAX FORMS IN THE BASE OF THE TROUGH TO OUR SOUTHWEST. SOME OF THE MORE LIKELY SOLUTIONS EITHER MOVE THE VORT MAX THROUGH TEXAS AS A CLOSED LOW...OR DAMPEN AND STRETCH THE VORT MAX AS IT APPROACHES WITHIN A POSITIVELY TILTED TROUGH. NEITHER SCENARIO PRODUCES SUSTAINED OR INTENSE LIFTING IN OUR FORECAST AREA...AND THE CONSENSUS IS MOVING TOWARD THE WAVE ALONG THE LOW LEVEL FRONT BEING PLACED FARTHER SOUTH AND EAST. THUS...WE WILL CONTINUE WITH CONSERVATIVE ODDS FOR RAIN. WINTRY WEATHER SHOULD NOT PROVE TO BE WIDESPREAD WITH THIS TYPE OF A SYSTEM...AND IT IS NOT INDICATED IN THE CURRENT GRIDS...BUT THERE IS STILL A SLIGHT CHANCE FOR SOME LIGHT FROZEN PRECIPITATION IN FAR NORTHWEST OKLAHOMA SUNDAY EVENING. && .PRELIMINARY POINT TEMPS/POPS... OKLAHOMA CITY OK 29 59 37 70 / 0 0 0 0 HOBART OK 29 65 34 69 / 0 0 0 0 WICHITA FALLS TX 32 65 37 72 / 0 0 0 0 GAGE OK 24 63 30 72 / 0 0 0 0 PONCA CITY OK 28 56 33 69 / 0 0 0 0 DURANT OK 34 60 37 64 / 0 0 0 0 && .OUN WATCHES/WARNINGS/ADVISORIES... OK...FREEZE WARNING UNTIL 9 AM CST THURSDAY FOR OKZ008-013-019-020- 025-026-028>031-039-040-044-045. FROST ADVISORY UNTIL 9 AM CST THURSDAY FOR OKZ032-041>043- 046>048-050>052. TX...FREEZE WARNING UNTIL 9 AM CST THURSDAY FOR TXZ086-089-090. && $$ 24/25