FXUS64 KOUN 221207
AFDOUN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORMAN OK
607 AM CST TUE DEC 22 2009
.AVIATION...LOW CEILINGS WILL OVERSPREAD THE REGION TODAY. WE USED
THE NAM FOR TIMING THE ONSET OF CEILINGS...FOCUSED ALONG THE AXIS
OF RETURNING GULF MOISTURE INTO CENTRAL OKLAHOMA...AND BACK WEST
ALONG A STATIONARY FRONT INTO WESTERN OKLAHOMA. THE WESTERN EDGE
OF CEILINGS IS FORECAST TO STAY CLEAR OF WICHITA FALLS AND A FEW
WESTERN TAF SITES UNTIL LATE AFTERNOON. IT IS POSSIBLE...HOWEVER...
THAT LIGHT FOG COULD FORM AT THE BEGINNING OF THE PERIOD. IT IS
ALSO DIFFICULT TO GAUGE THE HEIGHT OF THE DEVELOPING CEILINGS.
OBSERVATIONS UPSTREAM IN TEXAS WERE MAINLY MVFR...AND EVENING
RAOBS SAMPLED A RELATIVELY WARM BOUNDARY LAYER. MODEL GUIDANCE AND
MODEL SOUNDINGS...ON THE OTHER HAND...FORECAST THE ONSET OF IFR
CEILINGS THIS MORNING. WE LEANED TOWARD THE OBSERVATIONS...WITH A
MORE CONSERVATIVE FORECAST. WE ARE MORE CERTAIN THAT IFR AND
PERHAPS LIFR CEILINGS WILL DEVELOP TUESDAY NIGHT...WITH SOME
VISIBILITY RESTRICTION AS WELL.
&&
.PREV DISCUSSION... /ISSUED 502 AM CST TUE DEC 22 2009/
DISCUSSION...A CYCLONE DEVELOPING WEDNESDAY THROUGH THURSDAY WILL
PRODUCE A VARIETY OF WEATHER. NUMEROUS MESOSCALE DETAILS WILL
DETERMINE PRECIPITATION TYPE AND TIMING. THE 00Z GFS REPRESENTS OUR
MODEL OF CHOICE FOR THESE DETAILS. TWO PRIMARY WAVE OF PRECIPITATION
ARE EXPECTED. THE FIRST WILL BE RAIN ON WEDNESDAY...AND THE SECOND
WILL TRANSITION FROM RAIN TO SNOW EARLY THURSDAY. THE LATTER WAVE IS
NOT EXPECTED TO BE INTENSE ENOUGH...OR PERSIST LONG ENOUGH TO
WARRANT A WINTER STORM WATCH AT THIS TIME.
GULF MOISTURE RETURNS QUICKLY TODAY...PUTTING A CAP ON
TEMPERATURES...AND INTRODUCING LOW STRATUS TO MOST OF THE REGION.
THE EXCEPTION WILL BE SOUTHWEST OKLAHOMA AND FAR WESTERN NORTH
TEXAS...SITUATED ALONG A TROUGH AXIS EXTENDING SOUTHWARD FROM A
SURFACE LOW. WE REDUCED THE COVERAGE OF LOW POPS IN THE DAYTIME
FORECAST...AS TEMPERATURES ARE WARM ENOUGH AND LOW LEVEL WINDS LIGHT
ENOUGH TO PREVENT ANY SIGNIFICANT DRIZZLE. WE KEPT LOW POPS IN
SOUTHEAST OKLAHOMA...WHERE SEVERAL MODELS SHOW THE WARM MOIST GULF
AIR BECOMING SO PRONOUNCED THAT THERE WILL BE SOME INSTABILITY IN
THE UPPER PART OF THE BOUNDARY LAYER. THIS COULD SUPPORT LIGHT RAIN
SHOWERS.
TONIGHT THE MODELS GIVE US HIGH POPS...BUT ONLY A FEW HUNDREDTHS OF
AN INCH OF RAIN. ALTHOUGH MOISTURE WILL BE IN PLACE...IT IS
DIFFICULT TO FIND MUCH OF A FORCING MECHANISM TO SUPPORT SUCH
WIDESPREAD HIGH POPS. THE MOST LIKELY MECHANISM WILL BE THE LOW
LEVEL JET PRODUCING DRIZZLE ALONG AND EAST OF INTERSTATE 35. LOW
LEVEL FRONTOGENESIS MAY ALSO PRODUCE LIGHT RAIN NEAR THE KANSAS
BORDER BACK INTO NORTHWEST OKLAHOMA. WE UNDERCUT POPS FROM CENTRAL
INTO SOUTHWEST OKLAHOMA...AND WESTERN NORTH TEXAS. A FEW
THUNDERSTORMS MAY BREAK OUT IN SOUTHEAST OKLAHOMA...WHERE MOISTURE
WILL CONTINUE TO DEEPEN. IT IS MORE LIKELY...HOWEVER...THAN THUNDER
WILL OCCUR DURING THE DAY WEDNESDAY...AS THE FIRST PRONOUNCED SHORT
WAVE TROUGH EJECTS FROM THE DEVELOPING UPPER LEVEL CYCLONE. THIS
WAVE WILL STRENGTHEN THE DRY SLOT OVER OKLAHOMA WHEN IT MOVES UP
INTO KANSAS WEDNESDAY AFTERNOON. AT THE SAME TIME...COLD AIR WILL
BEGIN TO ARRIVE INTO NORTHWEST OKLAHOMA...AND WE INTRODUCED A PERIOD
OF FREEZING DRIZZLE THAT COULD AFFECT WESTERN OKLAHOMA OVERNIGHT
INTO THURSDAY MORNING.
THE SECOND...AND PRIMARY SHORT WAVE TROUGH...EJECTS FROM WEST TEXAS
UP TOWARD EASTERN OKLAHOMA WEDNESDAY NIGHT. THIS WILL LEAD TO
ADDITIONAL RAIN AND THUNDERSTORMS...ESPECIALLY ALONG AND EAST OF
INTERSTATE 44. GIVEN THE DYNAMIC LIFTING AND ARRIVAL OF COLD LOW
LEVEL AIR...WE SHOULD SEE A CHANGE TO SNOW WHEN THE SYSTEM MATURES
THURSDAY MORNING OVER CENTRAL AND NORTHERN OKLAHOMA. WE FORECAST THE
CHANGEOVER A LITTLE AHEAD OF THE GFS THERMODYNAMIC PROFILE...
ASSUMING THE MODELS USUALLY DO NOT CAPTURE THE EFFECTS OF
EVAPORATIVE COOLING AND STRONG RIDGING ALONG THE HIGH PLAINS THAT
WILL SUPPORT MORE RAPID COOLING. EVEN WITH AN EARLY
CHANGEOVER...THOUGH...THE PRECIPITATION IS NOT LIKELY TO PERSIST IN
ANY SIGNIFICANT WAY BEFORE COLD ADVECTION AND SUBSIDENCE BEGINS TO
DOMINATE IN THE WAKE OF THE UPPER LEVEL WAVE. ALTHOUGH SNOW WRAPPING
AROUND THE MATURE LOW WILL REDUCE VISIBILITY AND MAY ACCUMULATE IN
NORTH CENTRAL OR CENTRAL OKLAHOMA...THE CURRENT FORECAST IS FOR AN
ADVISORY LEVEL EVENT.
THE LONG DURATION COLD THAT WILL FOLLOW THE STORM...FROM THURSDAY
THROUGH THE WEEKEND...COULD BE THE BIGGER STORY. AND FINALLY...THERE
IS A SECOND STORM BEGINNING TO TAKE SHAPE...AS EARLY NEXT WEEK THE
MODELS FORECAST THE NEXT SOUTHERN STREAM TROUGH TO PROGRESS THROUGH
SPLIT FLOW TO OUR WEST. IF THE TROUGH ARRIVES EARLY ENOUGH...COLD
AIR WILL ALREADY BE IN PLACE...AND THAT SYSTEM COULD BE MORE
FAVORABLE FOR SNOW THAN THE CURRENT SYSTEM.
&&
.PRELIMINARY POINT TEMPS/POPS...
OKLAHOMA CITY OK 55 49 59 34 / 0 40 50 70
HOBART OK 57 45 54 30 / 0 10 20 50
WICHITA FALLS TX 66 51 62 37 / 0 20 30 60
GAGE OK 56 34 41 26 / 10 30 60 60
PONCA CITY OK 53 46 58 32 / 10 40 70 60
DURANT OK 58 56 64 45 / 20 70 80 90
&&
.OUN WATCHES/WARNINGS/ADVISORIES...
OK...NONE.
TX...NONE.
&&
$$
02/22/22
BURKE
