FXUS63 KOAX 201535
AFDOAX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
935 AM CST MON DEC 20 2010
.UPDATE...
UPDATED FOR WEATHER AND TEMPERATURE TRENDS.
&&
.DISCUSSION...
TEMPERATURES HAVE RISEN ABOVE FREEZING THIS MORNING IN ALL BUT
NORTHERNMOST KNOX AND CEDAR COUNTIES...AND MEASURABLE
PRECIPITATION IS PASSING TO THE NORTH OF THE CWA. HAVE UPDATED
WEATHER GRIDS TO MENTION JUST DRIZZLE...WITH A SMALL AREA OF
FREEZING DRIZZLE IN THE FAR NRN CWA...AND WITH NO MEASURABLE POPS
IN THE CWA. WITH TEMPS ALREADY NEAR GOING HIGHS FOR THE DAY IN
SOME AREAS...HAVE INCRASED MAX TEMPS MAINLY IN THE CENTRAL CWA. ALSO
UPDATED CLOUDS TO CAPTURE CLEARING AREA IN THE SRN CWA...THOUGH DO
EXPECT IT TO FILL IN THROUGH THE DAY.
UPDATED GRIDS/ZFP ALREADY SENT.
&&
.PREV DISCUSSION... /ISSUED 309 AM CST MON DEC 20 2010/
DISCUSSION...
MIXED PRECIPITATION THIS MORNING IN OUR NORTH...THEN DEALING WITH A
POTENTIALLY SIGNIFICANT STORM THURSDAY ARE THE PRIMARY FORECAST
CONCERNS.
STRONG UPPER JET OF 120-160KTS WAS PUNCHING THROUGH NORTHERN
CALIFORNIA INTO NORTHEAST WYOMING THIS MORNING. RESULTANT LOWERING
SURFACE PRESSURE IN THE LEE OF THE ROCKIES WAS DRIVING STRONG
ISENTROPIC UPGLIDE ACROSS NEBRASKA AND INTO SOUTH DAKOTA THIS
MORNING. SATURATION AND PRECIPITATION WAS OCCURRING NEAR AND NORTH
OF THE BORDER...BUT WILL LIFT NORTH AND NORTHEAST THIS MORNING AS
SURFACE LOW TRACKS EAST-NORTHEAST THROUGH SOUTH DAKOTA. RADAR
RETURNS WERE NOTED IN OUR NORTHERN CWA...BUT GROUND REPORTS
INDICATED LITTLE PRECIP REACHING THE GROUND. GIVEN STRONG LIFT AND
NEARLY SATURATED LOW LEVELS...WILL INCLUDE MENTION OF FREEZING
DRIZZLE THIS MORNING IN OUR NORTHERN CWA BUT WIDESPREAD HAZARDS DO
NOT LOOK LIKELY. WILL ALSO CARRY SMALL POPS FOR A MIX OF SLEET AND
SNOW FOR THE MORNING BEFORE WARM ADVECTION WING LIFTS NORTHEAST OF
OUR CWA.
SOUTHWEST TO NORTHWEST WINDS SOUTH OF SURFACE LOW TRACK WILL HELP
PROMOTE MIXING THIS AFTERNOON AND WILL MAKE A RUN AT SCOURING OUT
CLOUD COVER. TEMPERATURES WERE HOLDING IN THE MID 20S TO LOWER 30S
ACROSS THE CWA...SO DO NOT SEE A PROBLEM WITH ABOUT A 10 DEGREE RISE
IN TEMPS FOR THE AFTERNOON.
STRONG COLD ADVECTION WILL COMMENCE LATER TONIGHT AS NORTHWEST WINDS
DRIVE CANADIAN AIR SOUTH. WILL LIKELY HAVE ONLY A SMALL BUMP IN
TEMPERATURES DURING THE DAY TUESDAY AFTER MORNING LOWS IN THE TEENS
AND 20S.
HIGH PRESSURE WILL SETTLE OVER THE AREA TUESDAY NIGHT...THEN SLIDE
EAST ON WEDNESDAY. COLD MORNING LOWS WEDNESDAY IN THE SINGLE DIGITS
AND TEENS WILL SLOWLY WARM INTO THE 20S ON WEDNESDAY WITH INCREASE
IN HIGH CLOUDS AHEAD OF NEXT SYSTEM KEEPING LID ON MAX WARMING.
THIS SETS THE STAGE FOR SYSTEM ROLLING INTO THE PLAINS THURSDAY. GFS
IS FASTER AND FARTHER NORTH WITH SURFACE LOW AS COMPARED TO ECMWF.
GFS HAS BEEN CONSISTENT IN TIMING/TRACK...AND HAS SUPPORT FROM A
GOOD MAJORITY OF ITS ENSEMBLE MEMBERS. THIS IS ALSO THE MOST BULLISH
PRECIPITATION SOLUTION FOR OUR AREA. HAVE FOLLOWED THE GFS SOLUTION
MORE CLOSELY GIVEN CONSISTENCY/SUPPORT...BUT WOULD LIKE TO SEE
MODELS CONVERGE ON A SOLUTION BEFORE GOING ALL IN.
WEDNESDAY EVENING TEMPERATURES WILL ALREADY BE IN THE 20S WHEN
STRONG THETA-E ADVECTION COMMENCES OVER TOP COLD SURFACE
TEMPERATURES. FORECAST SOUNDINGS AND PARTIAL THICKNESS PROGS POINT
TO A MIX OF PRECIPITATION TYPES WITH SNOW IN OUR NORTH...SNOW OR
FREEZING RAIN CENTRAL AND FREEZING RAIN OR RAIN IN THE SOUTH
BEGINNING THURSDAY MORNING. AND IF GFS QPF PROGS ARE RIGHT...A
SIGNIFICANT ICING EVENT IS POSSIBLE BEFORE ATMOSPHERE COOLS ENOUGH
FOR ALL SNOW IN THE AFTERNOON OR EVENING. WILL CONTINUE TO MENTION
THIS POTENTIAL IN OUR HAZARDOUS WEATHER OUTLOOK.
SNOW WILL CONTINUE THURSDAY NIGHT INTO FRIDAY BEFORE SYSTEM PULLS
OFF TO THE EAST. THEN TEMPERATURES FRIDAY AND INTO THE WEEKEND WILL
BE HIGHLY AFFECTED BY POTENTIAL NEW SNOW COVER. WILL LEAVE THOSE
ALONE FOR NOW WITH HIGHS IN THE 20S OR TEENS AS COLD HIGH PRESSURE
SETTLES OVERHEAD. LOWS ARE GENERALLY IN THE SINGLE DIGITS OR LOWER
TEENS BUT COULD BE MUCH COLDER IF SNOW PANS OUT.
DERGAN
AVIATION...
TAF SITES KOFK/KOMA/KLNK
06Z TAFS
MAIN AVIATION CONCERNS WILL BE LIFR CIGS AND VARIABLE VSBYS AT KOFK
ALONG WITH PRECIP AND PRECIP TYPE.
SFC LOW PRES OVR ERN WY INTO ERN CO WILL MOVE INTO SOUTH DAKOTA AND
NEBRASKA TODAY. MEANWHILE A SHORTWAVE TROF DEEPENS OVR MT AND NORTH
DAKOTA...LIFTING A DEVELOPING BAND OF SNOW OVER SOUTH
DAKOTA...GRADUALLY NORTH AND EAST DURING THE DAY. FARTHER
SOUTH...FREEZING DRIZZLE WAS NOTED AROUND KONL AND AT TIMES IN
NORTHEAST NEBRASKA. A SOUTHEAST INFLUX OF WARMER TEMPERATURES AT
KOMA AND KLNK HAS ALLOWED TEMPS TO REMAIN ABOVE FREEZING...HOWEVER
AT KOFK...TEMPS SHOULD REMAIN BELOW FREEZING THROUGH LATE MORNING
AND COULD DIP AT OR BELOW FREEZING AT KOMA/KLNK.
LIFR CONDITIONS WITH VARIABLE VSBYS WILL CONTINUE THRU THE PD AND
COULD SEE SOME PATCHY FREEZING DRIZZLE THIS MORNING AT KOFK. DRIER
AIR IN THE LOW LEVELS HAVE SCOURED OUT THE LOWER CLDS WITH SOME
PATCHY MVFR VSBYS...AND VFR CIGS WITH MID CLDS AT KOMA/KLNK. COULD
SEE SOME SPRINKLES THIS AFTERNOON AT KOMA/KLNK ALONG WITH MVFR CIGS
WITH THE H85 WAA AND MID LEVEL UVV AHEAD OF THE H8 FNT. SFC HIGH
PRES WILL BUILD IN TONIGHT AND SHOULD WORK TO IMPROVE CIGS LATER
TONIGHT.
SOUTHEAST WINDS AT 8 TO 14KTS WILL SHIFT TO THE NORTHWEST AFTER
00Z. STRONGER NORTHWEST 10 TO 15KT WINDS ARE FORECAST AT KOFK
TONIGHT.
ZAPOTOCNY
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
IA...NONE.
&&
$$
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