FXUS64 KOUN 240532
AFDOUN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORMAN OK
1132 PM CST WED DEC 23 2009
.AVIATION...
A LARGE AREA OF RA... PL... AND SN ACROSS SW OK AND WESTERN NORTH
TX IS THE INITIAL SURGE OF PRECIPITATION ASSOCIATED WITH THE
APPROACHING WINTER STORM SYSTEM. ADDITIONAL AREAS OF MAINLY SN ARE
EXPECTED TO DEVELOP OVERNIGHT AND THU MORNING. ACCUMULATING SN IS
LIKELY... AND WITH STRONG WINDS... BLSN IS A NEAR CERTAINTY
WHEREVER SNOW DOES ACCUMULATE MORE THAN AN INCH OR SO. THERE IS
STILL SOME SIGNIFICANT UNCERTAINTY REGARDING VSBYS THU IN THE BLSN...
BUT IFR VSBYS ARE PROBABLE AT ALL SITES BUT KGAG AND KWWR. STRONG
DOWNWARD MOTION IS EXPECTED AFTER SUNSET THU... WHICH SHOULD CLEAR
THE SKY QUICKLY FROM WEST TO EAST. DIMINISHING WINDS WILL ALLOW
VSBYS TO IMPROVE SIGNIFICANTLY AFTER SUNSET.
&&
.PREV DISCUSSION... /ISSUED 550 PM CST WED DEC 23 2009/
AVIATION...
A STRONG STORM SYSTEM WILL TRACK NE FROM CENTRAL TX THIS
EVENING... TO CENTRAL AR BY 18Z TOMORROW. PRECIPITATION IS
EXPECTED TO DEVELOP AND SPREAD NE ACROSS TX/OK TONIGHT AND THU...
WHILE COLDER AIR ADVANCES SE. RA AND DZ WILL CHANGE OVER TO SN
OVERNIGHT AT ALL TAF SITES... AND A FEW HOURS OF FZDZ... FZRA...
AND/OR PL WILL BE POSSIBLE DURING THE TRANSITION PERIOD. STRONG
WINDS WILL CAUSE BLSN AT ALL SITES AFTER SN BEGINS TO
ACCUMULATE... AND VISIBILITIES WILL BE DEPENDENT MAINLY ON HOW
MUCH SN FALLS NEAR/UPSTREAM OF EACH TAF SITE.
PREV DISCUSSION... /ISSUED 351 PM CST WED DEC 23 2009/
DISCUSSION...
HAVE UPGRADED THE NORTHERN AND WESTERN AREAS OF OKLAHOMA TO A
WINTER STORM WARNING AND ALREADY HAVE ISSUED THE WSW. 12Z MODELS
CONTINUED THE OVERNIGHT TREND OF A WETTER/SNOWIER FORECAST WITH
THE EXPECTED TRACK OF THE UPPER LOW AND LESS LIKELIHOOD OF THE DRY
SLOT SLOWING DOWN THE SHOW. ON THE POSITIVE SIDE... THE PRIMARY
NUMERIC MODELS ARE ON THE SAME PAGE WITH THE TIMING OF THE
SWITCHOVER FROM RAIN TO SNOW. BOTH THE NAM AND GFS TIME-HEIGHT
SECTIONS DO SHOW BRIEF PERIODS OF SOMEWHAT DRIER AIR IN THE
DENDRITIC GROWTH TEMPERATURES ELEVATIONS... SO THERE COULD BE A
BRIEF PERIOD OF FREEZING RAIN OR FREEZING DRIZZLE. SLEET IS NOT
OUT OF THE QUESTION IN NORTHERN OKLAHOMA BUT HAVE NOT INCLUDED
THIS IN THE PACKAGE SINCE IT WOULD BE A MINOR ISSUE COMPARED TO
THE SNOW/FREEZING PRECIP. AS COLD AIR ADVECTS INTO THE AREA... WE
CAN SEE THE PROFILE SUPPORTING SNOW IN NORTHWEST OKLAHOMA EARLY
THIS EVENING... TO THE ENID TO FORT COBB TO VERNON AREAS BY 06Z...
AND TO STILLWATER TO NORMAN TO WICHITA FALLS BY ABOUT 12Z.
OF COURSE THE MODELS DO HAVE DIFFERING OPINIONS ON SNOW AMOUNTS
AND THE AXIS OF HEAVIEST SNOW. THINK THE 12Z GFS WAS TOO
AGGRESSIVE AND HAVE GENERALLY GONE BETWEEN THE FORECAST AMOUNTS
FROM THE GFS AND NAM... ALTHOUGH SOMEWHAT ON THE LIGHTER SIDE
GIVEN THE OVERALL PATTERN EVOLUTION AND THE TENDENCY FOR THE MODEL
SNOW GRID FIELDS TO BEGIN ACCUMULATING SNOW TOO EARLY WHEN THE
PRECIP IS STILL FALLING AS RAIN INITIALLY. BUT THE FORECAST AMOUNTS
ARE STILL ENOUGH TO JUSTIFY A WINTER STORM WARNING ACROSS NORTHERN
PORTIONS OF THE AREA. THE STRONG WINDS ON THE BACK SIDE OF THE
SURFACE LOW WILL BE STRONG AND GUSTY TONIGHT INTO TOMORROW CAUSING
BLOWING SNOW AND NEAR-BLIZZARD CONDITIONS. AGAIN THINK THE GFS IS
A LITTLE TOO AGGRESSIVE WITH WIND SPEEDS GIVEN IT'S DEEPER SURFACE
LOW FARTHER WEST THAN OTHER MODELS... BUT IT WILL STILL BE QUITE
WINDY. PRECIP WILL DIMINISH ACROSS MUCH OF THE AREA TUESDAY NIGHT
ALTHOUGH LINGERING SNOW WILL STILL BE POSSIBLE IN THE NORTH INTO
FRIDAY NIGHT AS UPPER LOW ONLY SLOWLY MOVES FROM KANSAS TOWARD
IOWA.
&&
.PRELIMINARY POINT TEMPS/POPS...
OKLAHOMA CITY OK 30 32 19 35 / 90 90 30 10
HOBART OK 27 31 20 35 / 90 70 10 0
WICHITA FALLS TX 31 36 24 40 / 90 60 10 10
GAGE OK 22 26 12 30 / 70 50 10 0
PONCA CITY OK 31 31 12 29 / 90 90 50 20
DURANT OK 40 41 23 39 / 90 80 20 10
&&
.OUN WATCHES/WARNINGS/ADVISORIES...
OK...WINTER STORM WARNING UNTIL 6 PM CST THURSDAY FOR OKZ007-008-012-
013-016>048-050>052.
WINTER WEATHER ADVISORY UNTIL 6 PM CST THURSDAY FOR OKZ004>006-
009>011-014-015.
TX...WINTER STORM WARNING UNTIL 6 PM CST THURSDAY FOR TXZ083>090.
&&
$$
24/23/23
