FXUS63 KOAX 172133
AFDOAX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
333 PM CST FRI DEC 17 2010
.SHORT TERM...TONIGHT THROUGH MONDAY
DIFFICULT FORECAST OVR THE SHRT TERM WITH MULTIPLE CHANCES FOR
LIGHT PRECIP IN THE AREA. FOR TONIGHT CLDS ARE ONCE AGAIN THE MAIN
CONCERN. STRATUS DECK HAS ONCE AGAIN BEEN BREAKING UP IN
PLACES...AND FEEL WE WILL CONT TO SEE BREAKS THRU THE NIGHT. DID
INCREASE OVERNIGHT LOWS THOUGH IN ANTICIPATION OF SOME CLDS IN
THE AREA. THE FIRST SHRTWV OF INTEREST FOR THE FA WAS OBSERVED IN
LATE AFTN WV IMAGERY OVR ID. THIS WL TRACK SEWD THRU SRN NEB AND
INTO NRN MO ON SAT. ISENTROPIC LIFT INCREASES AHEAD OF THIS
FEATURE AND MAY STILL BE ENOUGH TO GENERATE SOME VERY LIGHT PRECIP
ON SAT OVR THE CNTRL AND SRN FA. STILL LOOKS LIKE IT WLD BE A
TRACE EVNT THOUGH AND SO WL KEEP POPS OUT OF THE FORECAST. WOULD
BE FLURRIES ALNG THE I-80 AND MAYBE A MIX OF FLURRIES AND
SPRINKLES IN THE S.
THE PASSAGE OF THE WAVE WILL NOT DOWN THE BROAD LOW-AMPLITUDE
SWRN US RIDGE A TOUCH. AS THIS RIDGE AMPLIFIES ON SAT NIGHT INTO
SUNDAY ACRS THE PLAINS...AHEAD OF A STRONGER SHRTWV TROF PROGGED
FOR SUN NIGHT AND MON...BETTER ORGANIZED AND STRONGER ISENTROPIC
LIFT WL DVLP. SATURATION SHLD OCCUR LATE SAT NIGHT OVR THE NW
FORECAST AREA INITIALLY...WITH A BAND THEN EXTENDING SEWD THRU A
GOOD DEAL OF CWA BY SUN MRNG. WL INCREASE POPS INTO THE LIKELY CAT
FOR THE MRNG AND INTO THE AFTN HOURS. DOESN'T LOOK LIKE A HIGH QPF
EVNT BUT A HIGH CONFIDENCE THAT SOME PRECIP WL OCCUR. MOST OF IT
LOOKS TO BE SN...AND WE WILL RUN WITH THIS AS THE PRECIP TYPE
ATTM. MAY SEE A LITTLE MORE THAN AN INCH IN THE N AND UP TO AN
INCH ALNG I-80 AND A DUSTING IN THE S. WL LIKELY SEE A BREAK IN
PRECIP LATE SUN INTO SUN EVNG BEFORE THE EFFECTS OF THE NEXT
STRONGER SHRTWV TROF STARTS TO SPREAD LARGE-SCALE ASCENT INTO NEB
SUN NIGHT. WE HAVE SIGNIFICANTLY INCREASED LOWS FOR SUN NIGHT WITH
THE THOUGHT OF SERLY LO LVL FLOW CONTINUING AND CLDS AROUND. WE
ARE A GOOD 8 TO 10 ABOVE MET/MAV FOR LOWS DURING THIS TIME.
MODELS HAVE VARYING SOLUTIONS AS TO THE TRACK AND INTENSITY OF THE
SYSTEM MOVING THRU ON MON WITH A GOOD DEAL OF SPREAD INDICATED IN
THE ENSEMBLES. 12Z GFS SEEMS TO FAR SOUTH GIVEN THE INDIVIDUAL
MEMBERS OF THE NAEFS AND THE EC BEING FARTHER N. THUS OUR CURRENT
FEELING IS THAT MUCH OF THE MORE SIG SNOWFALL WL OCCUR IN THE
DAKOTAS INTO MN/IA AND OUT OF OUR FA. NEVERTHELESS...THE GFS IS
WITHIN THE REALM OF POSSIBILITIES AND THUS WE WL NEED TO MONITOR
THE TRACK CLOSELY. WE STILL FEEL THAT A FEW INCHES OF SNOW CLD
OCCUR ALNG HIGHWAY 20 AND N...AND THUS WE INCREASED POPS INTO THE
LIKELY CAT ON MON FOR SN. FARTHER S FM SUN NIGHT INTO MON THE
THERMAL PROFILE SUPPORT A MIX AND MAYBE EVEN JUST SOME LIGHT RAIN
IN THE FAR S. HAVE INCREASED HIGHS ON MON GIVEN THE WARM START
AND CONTD SRLY FLOW IN THE S.
BOUSTEAD
.LONG TERM...MONDAY NIGHT THROUGH FRIDAY
SUTBLE CHANCES FOR PRECIP/PRECIP TYPE AND TEMPS WILL BE THE MAIN
FORECAST CONCERNS THROUGH THE EXTENDED.
TO START...MONDAY NIGHT...A WEST TO EAST UPPER LEVEL JET WILL
STRETCH ACRS THE U.S. WITH A BAND OF SNOW FROM MT AND THE DAKOTAS
INTO MN/IA/WI/IL...WITH LINGERING PRECIP IN NORTHEAST NEBRASKA INTO
WRN IOWA. AT THIS TIME WILL MENTION A MIX DUE TO THE LOSS OF ICE
CRYSTALS MONDAY NIGHT. ONCE THIS WAVE IS THROUGH THERE IS A BREAK
WITH THE NEXT RIPPLE IN THE FLOW TUESDAY NIGHT-WED NIGHT. H85 FLOW
INCREASES ACROSS THE WRN HIGH PLAINS. MIXED PRECIP WILL AGAIN BE
POSSIBLE...HOWEVER THE MORE ORGANIZED PRECIPITATION AREA APPEARS TO
BE OVER THE DAKOTAS. THE MODELS DIVERGE FOR THU AS THE GFS BRINGS A
COLD FRONT THROUGH WITH A DEEPENING MID LEVEL TROF...AND THE ECMWF
BRING BACK DOOR COOLING IN...BUT BEGINS TO BUILD THE RIDGE OVER THE
WRN PLAINS. THESE DIFFERENCES CONTINUE INTO FRI WHERE THE MODELS
ARE 180 DEG DIFFERENT ON THEIR SFC WINDS. FORECAST-WISE HPC HAS
GONE WITH A BLEND OF THE ECE/GFS/GEM. PRECIP CHCS STILL SEEM ON THE
LIGHT SIDE AND DO MENTION MIXED PRECIP THUR/THUR NIGHT...WITH QUITE
A FEW CLDS AROUND. HAVE EXTENDED HIGH TEMPS IN THE 20S NORTH AND IN
THE 30S SOUTH AND IF FLOW IS AMPLIFIED MORE THAN CURRENTLY
EXPECTED...TEMPS COULD MAKE IT IN THE 40S SOUTH THUR. KEPT LOWS
MOSTLY AT OR ABOVE NORMAL.
ZAPOTOCNY
&&
.AVIATION...
TAF SITES KOFK/KOMA/KLNK
18Z TAFS
LARGE STRATOCUMULUS DECK STRETCHED FROM CENTRAL SOUTH DAKOTA INTO
SOUTHEAST KANSAS...AND FROM THE MISSOURI RIVER TO NEAR NORTH
PLATTE. CLOUD LAYER APPEARS TO BE AROUND 2000 FEET THICK...WITH
MVFR CIG BASES. SOME ISOLATED FLURRIES REPORTED BUT THESE SEEM TO
BE ON THE DECREASE. NORTHERN EDGE OF THE DECK IS MOVING SOUTH
AROUND 15-20 KNOTS.
TAF FORECAST IS A FUNCTION OF THE EVOLUTION OF THIS CLOUD DECK.
SOME TURBULENT MIXING IS OCCURRING WITHIN THE LAYER PER THE NELIGH
PROFILER AND 850 MB RUC WIND ANALYSIS...ALONG WITH RADIATIONAL
MIXING. THIS IS WORKING TO ERODE SOME OF THE DECK THIS AFTERNOON
MAINLY FROM AROUND NORFOLK TO ORD NEBRASKA. EXPECT THIS TO CONTINUE
DURING THE DAYLIGHT HOURS...BUT NIGHT TIME INVERSION SHOULD REDUCE
THE MIXING TO ALLOW THE SCT AREAS TO FILL BACK IN TO OVC. KOMA IS
ON THE EASTERN EDGE OF THE JAGGED CLOUD DECK SO THERE MAY BE PERIODS
WHEN ONLY SCT CLOUDS ARE OVER KOMA. GENERALLY LEANED TOWARDS A MORE
PESSIMISTIC CLOUD FORECAST DESPITE MODELS SHOWING A CLEARING TREND.
THESE PATTERNS OFTEN HAVE A TENDENCY TO SUPPORT CLOUDS FOR A LONGER
PERIOD THAN MODELS ARE ABLE TO DETERMINE. FURTHERMORE...WARM AIR
ADVECTION JUST ABOVE THE CLOUD LAYER OVERNIGHT MAY AID IN
REINFORCING OR EXPANDING THE EXISTING CLOUDS.
SOME LIGHT FOG OR HAZE MAY BRING VISIBILITIES DOWN TO 5SM AT
TIMES...BUT DO NOT EXPECT WIDESPREAD FOG DEVELOPMENT.
NIETFELD
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
IA...NONE.
&&
$$