FXUS64 KOUN 252054
AFDOUN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORMAN OK
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 FROM MIDNIGHT TONIGHT TO 9 AM CST THURSDAY FOR
OKZ008-013-019-020-025-026-028>031-039-040-044-045.
FROST ADVISORY FROM MIDNIGHT TONIGHT TO 9 AM CST THURSDAY FOR
OKZ032-041>043-046>048-050>052.
TX...FREEZE WARNING FROM MIDNIGHT TONIGHT TO 9 AM CST THURSDAY FOR
TXZ086-089-090.
&&
$$
03/22
BURKE
