FXUS64 KOUN 231727
AFDOUN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORMAN OK
1127 AM CST WED DEC 23 2009
.AVIATION...
/18Z TAFS/... WINTER STORM WILL AFFECT AREA THIS TAF PERIOD.
PATCHY FZ DZ WILL BE POSSIBLE EVERYWHERE TONIGHT. PRECIP MAY ALSO START
AS A LIQUID /FZRA OR RA/ THEN TRANSITION TO SNOW TONIGHT INTO THU
MORNING. WHILE THE PRECIP TRANSITIONS THERE MAY ALSO BE A BRIEF
PERIOD OF SLEET. THERE CONTINUE TO BE SOME UNCERTAINTIES AS TO INTENSITY/HOW
MUCH WINTRY PRECIP WILL OCCUR THROUGH THE TAF PERIOD. WINDS WILL
ALSO BECOME QUITE STRONG LATE TONIGHT AND CONTINUE THROUGHOUT THE
DAY THURSDAY.
&&
.PREV DISCUSSION... /ISSUED 607 AM CST WED DEC 23 2009/
AVIATION...ALL TAF SITES WERE NEAR OR TO THE WEST OF A STATIONARY
FRONT. THIS PLACED MOST OF THE REGION IN COOL AIR THAT WILL REMAIN
SATURATED...SUPPORTING A FEW LIFR CEILINGS THIS MORNING. SOME
IMPROVEMENT TO IFR IS EXPECTED BY MIDDAY. PRECIPITATION WILL BE
LIGHT AND SCATTERED FOR MOST OF THE DAY...AND THE MAJORITY WILL BE
LIQUID...ALTHOUGH NORTHWEST OKLAHOMA MAY SEE FREEZING DRIZZLE OR
SNOW FROM 12-16 UTC. HEAVIER RAIN IS EXPECTED TO BREAK OUT IN
CENTRAL OKLAHOMA THIS AFTERNOON WHEN AN UPPER LEVEL JET
APPROACHES. ALTHOUGH NOT INCLUDED IN THE CURRENT TAFS...THUNDER
COULD FORM AS FAR NORTH AS OKC. THERE WILL BE A TRANSITION FROM
RAIN TO SNOW OVERNIGHT...ALONG WITH INCREASINGLY GUSTY WINDS.
PREV DISCUSSION... /ISSUED 454 AM CST WED DEC 23 2009/
DISCUSSION...ALTHOUGH THE TRACK OF OUR UPPER LEVEL STORM HAS NOT
WAVERED TOO MUCH...THERE ARE SOME SUBTLE CHANGES SHOWING UP IN THE
OBSERVATIONS AND RECENT MODEL TRENDS. THESE SUBTLE CHANGES COMBINED
TO YIELD A MORE SIGNIFICANT SHIFT IN OUR THINKING...AND LED US TO
ISSUE A WINTER STORM WATCH FOR CENTRAL AND NORTH CENTRAL OKLAHOMA.
THIS MORNING...A QUASISTATIONARY SURFACE BOUNDARY HAD SLIPPED TO
NEAR INTERSTATE 44...ABOUT 6 TO 12 HOURS AHEAD OF SCHEDULE. THE
FRONT WILL NOT COME CHARGING THROUGH TODAY...AS IT WILL WAIT FOR
UPSTREAM HEIGHT FALLS ASSOCIATED WITH THE APPROACHING UPPER LEVEL
LOW. BUT COLD AIR HAS OVERSPREAD PART OF OUR FORECAST AREA THIS
MORNING...AND THE FRONT WILL CONTINUE TO STRENGTHEN...AIDED BY
DIFFERENTIAL HEATING...ADVECTIONS...AND FRONTOGENESIS. AS A
RESULT...WE EXPECT SUB FREEZING TEMPERATURES TO OVERTAKE THE REGION
A LITTLE BIT FASTER WHEN THE FRONT MOVES EAST WITH THE UPPER LOW
LATER TONIGHT. ADDITIONALLY...THE MODEL SOLUTIONS HAVE TRENDED
TOWARD PRODUCING GREATER MID AND UPPER LEVEL ASCENT FROM TONIGHT
INTO MUCH OF THE DAY THURSDAY...WHILE THE LOW TAKES A TRACK
THROUGH NORTH CENTRAL TEXAS AND SOUTHEAST OKLAHOMA...WHICH IS
CLIMATOLOGICALLY FAVORABLE FOR SNOWFALL IN AREAS NORTH OF THE
TRACK. WHILE WE SHOULD NOT PLACE TOO MUCH WEIGHT ON THE SNOW
ACCUMULATION ALGORITHMS FROM ANY PARTICULAR MODEL RUN...THERE HAVE
BEEN A NUMBER OF RUNS OF THE NAM AND GFS OVER THE PAST DAY...THAT
HAVE PRODUCED ACCUMULATING SNOWFALL IN THE AREA OF CONCERN.
THE STORM SYSTEM WILL BE PROGRESSIVE...AND SUBSTANTIAL SNOW MAY LAST
FOR ONLY 4 TO 5 HOURS AT ANY GIVEN LOCATION...BUT WE ARE CONCERNED
ABOUT THE POTENTIAL FOR SOME HEAVY SNOWFALL RATES. THE 00Z NAM
SOUNDINGS...IN PARTICULAR...SHOW STRONG LIFT THROUGH THE DENDRITIC
CRYSTAL ZONE ATOP A DEEP LAYER OF SATURATED AIR THAT IS JUST BELOW
FREEZING. SO WHILE THE GROUND WILL INITIALLY BE WARM...THE INTENSITY
OF THE SNOW COULD COMPENSATE...TO RESULT IN ACCUMULATION. ALSO
DURING THIS TIME...WINDS WILL BECOME BLUSTERY. AN ARCTIC COLD FRONT
EXITING MONTANA EARLY WEDNESDAY MORNING...WILL REACH NORTHWEST
OKLAHOMA BY SUNRISE THURSDAY...AND BLAST THROUGH THE REST OF
OKLAHOMA AND WESTERN NORTH TEXAS BY AFTERNOON.
IT IS IMPORTANT TO POINT OUT THAT THERE IS STILL AN UNUSUAL AMOUNT
OF CHANGE FROM ONE MODEL RUN TO THE NEXT...BUT THAT THE OVERALL
TREND SUGGESTS THERE IS THE THREAT OF WINTER STORM CONDITIONS.
WE HAVE ALSO POSTED WINTER WEATHER ADVISORIES TO THE WEST FOR
LIGHTER SNOW AMOUNTS...BUT COLDER WIND CHILL TEMPERATURES...AND
SOME FREEZING DRIZZLE.
NOT TO BE OUTDONE...IS THE SEVERE THUNDERSTORM POTENTIAL. THE SPC
SLIGHT RISK AREA LOOKS WELL WARRANTED FOR SOUTHERN AND EASTERN
OKLAHOMA. WITH A LEAD TROUGH EJECTING THIS MORNING...MOISTURE MAY
THIN ENOUGH TO ALLOW SOME HEATING ALONG AND NEAR THE INTERSTATE 35
CORRIDOR. STRONG FORCING WILL BEGIN TO ARRIVE FROM THE WEST THIS
AFTERNOON...AND THERE MAY BE A PERIOD IN WHICH WE SEE NEAR SURFACE
BASED STORMS...WITH PLENTY OF SHEAR...AND SUFFICIENT INSTABILITY.
ONCE THE SYSTEM EXITS THURSDAY NIGHT...ARCTIC COLD WILL SETTLE IN
FOR SEVERAL DAYS. THE NEXT UPPER LEVEL DISTURBANCE WILL APPROACH
EARLY NEXT WEEK...AND A CURSORY LOOK AT THE MODELS WOULD STILL
SUPPORT A CHANCE OF RAIN OR SNOW. WE LET THE GFS HANDLE MOST OF THE
EXTENDED FORECAST GRIDS...BUT DID PREFER THE FASTER TIMING OF THE
ECMWF WITH THIS LOWER AMPLITUDE WAVE ARRIVING EARLIER NEXT WEEK.
&&
.PRELIMINARY POINT TEMPS/POPS...
OKLAHOMA CITY OK 45 31 32 18 / 50 90 90 10
HOBART OK 42 29 36 21 / 30 70 50 0
WICHITA FALLS TX 55 34 41 25 / 30 90 40 0
GAGE OK 36 21 32 12 / 70 60 30 0
PONCA CITY OK 46 30 31 12 / 70 70 90 40
DURANT OK 65 40 43 23 / 70 90 70 10
&&
.OUN WATCHES/WARNINGS/ADVISORIES...
OK...WINTER STORM WATCH FROM LATE TONIGHT THROUGH THURSDAY AFTERNOON
FOR OKZ007-008-012-013-018>020-024>030.
WINTER WEATHER ADVISORY FROM 6 PM THIS EVENING TO 6 PM CST
THURSDAY FOR OKZ004>006-009>011-014>016-021.
WINTER WEATHER ADVISORY FROM MIDNIGHT TONIGHT TO 6 PM CST
THURSDAY FOR OKZ017-022-023-033>038.
TX...NONE.
&&
$$
30/26/25
