FXUS63 KOAX 182223
AFDOAX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
422 PM CST SAT DEC 18 2010
.SHORT TERM...LIFT OVER THE AREA INDUCING NARROW LINE OF LIGHT SNOW
FROM ABOUT NC NEB TO NERN KS ASSOCIATED WITH 700MB SHORTWAVE TROF
BEST SEEN VIA NETWORK PROFILERS...AS WELL AS MODEST UPPER DIVG AND
LLVL WAA. LINE OF ACTIVITY WAS SLOWLY PROGRESSING EAST. OTHERWISE
LARGE SCALE PATTERN PER WV IMAGERY SHOWING LARGE CLOSED UPPER LOW OFF
THE PAC NW COAST...WEAK RIDGING OVER THE CENTRAL ROCKIES...AND BROAD
TROF PREVAILING OVER THE ERN CONUS. OVERALL DETERMINISTIC MODELS IN
GOOD AGREEMENT WITH PROGRESSIVE LARGE SCALE FLOW WITH AFOREMENTIONED
WRN CONUS SYSTEM DIG SWD AND WEAKLY AMPLIFIED RIDGE SITUATED OVER THE
WRN HIGH PLAINS. THE PROBLEM IS DIFFERING SMALL SCALE FEATURES THAT
WILL RESULT IN ACCUMULATING SNOW TONIGHT THRU LATE MONDAY NIGHT. THE
GOOD NEWS IS THAT BEST FORCING PROVIDING GREATEST SNOW TOTALS WILL BE
NORTH OF THE CWA. HOWEVER...WITH OVERRUNNING BECOMING PREVALENT PCPN
TYPE IN PARTS OF OUR AREA WILL BE A ISSUE IN LATER PDS. FOR
TONIGHT...18Z NAM HAS JUST ARRIVED AND IS GOING MUCH MORE BULLISH
LAYING QPF OVER THE SRN CWA RELATED TO STRONG 285K-290K UPGLIDE AND
STRENGTHENING LLVL THERMAL GRADIENT/MID LYR AGEO FORCING STRETCHING
NW-SE FROM THE BLACK HILLS TO NRN MO. THUS HAVE INCREASED POPS
OVERNIGHT GIVEN SLOW NATURE OF BNDRY. FOCUS FOR ACCUMULATING SN WILL
SHIFT NORTH AS THE LLVL CONVG ZONE LIFTS INTO SD/MN AND POTENT VORT
ENERGY CROSSES THRU THE NRN STATES. SFC REFLECTION OVER THE DAKOTAS
WILL DEEPEN AND DRAW CAA IN ON THE BACK SIDE AS IT PUSHES INTO THE
UPPER MIDWEST. PCPN TYPE WILL THEN BECOME AN ISSUE MAINLY OVER THE
NRN CWA AS THE LOWEST LYRS CHILL DOWN. CRIT THKNS/BUFKIT/SREF ALL
SUGGESTING FZRA/SLEET/SN MIX LIKELY OVER THE NRN CWA PARTICULARLY
MONDAY AND MONDAY EVENING. AS OF NOW...THINKING SN ACCUMULATION
TOTALS 1-2 INCHES BY EVENTS END LATE MONDAY NIGHT.
.LONG TERM.....
STAGNANT WX PATTERN WL CONT THRU THE EXTENDED PERIOD WITH A TROF OFF
THE WEST AND EAST COASTS AND A BROAD LOW-AMPLITUDE RIDGE OVER THE
SRN PLAINS. MODELS ARE IN OVER-ALL GOOD AGREEMENT WITH THE
LARGE-SCALE FEATURES...BUT OF COURSE THERE ARE SOME SIG DIFFERENCES
IN THE DETAILS IN TIMING AND PLACEMENT OF THESE FEATURES. THE
FORECAST WILL FEATURE ONE MAIN SYSTEM OF INTEREST FOR WED NIGHT
THROUGH THUR NIGHT...AND OTHERWISE A GOOD DEAL OF CLDS AND NEAR
SEASONAL TMPS.
SFC RIDGE AXIS SHLD BE ALNG THE MO RIVER ON TUES NIGHT AND WL SLOWLY
MOV EWD ON WED WITH RETURN FLOW KICKING UP. THIS PERIOD WILL
GENERALLY SEE LITTLE IN THE WAY OF SENSIBLE WX WITH JUST A GOOD DEAL
OF CLDS KEEPING OVERNIGHT MINS UP AND AFTER MAXES LOWER...WHICH IS
IN LINE WITH CURRENT FORECAST. MODELS THEN TAKE A STG SHRTWV TROF
OUT OF THE ERN PAC TROF...AND MOV IT INLAND ON WED AND INTO THE HIGH
PLAINS ON WED NIGHT. THIS IS EXPECTED TO SPREAD LARGE-SCALE FORCING
FOR ASCENT INTO THE REGION ON WED NIGHT WHICH MAY LEAD TO SOME -SN
OVR THE NW BY THUR MRNG AHEAD OF THE INVERTED TROF. THE CONFIDENCE
IN THE TRACK AND SPEED OF THE FEATURE MOVG THRU THE FA ON THURS IS
PRETTY LO ATTM DUE TO THE SPREAD IN THE ENSEMBLES IN THE NAEFS.
NEVERTHELESS...SINCE ALL GLOBAL MODELS DO HAVE A SYSTEM WE INCREASED
POPS THRU THE DAY ON THURS INTO THE LOWER TO MID CHC RANGE AND
LINGERED CHCS INTO THURS NIGHT. PRECIP TYPE IS ALSO A
CHALLENGE...BUT LOOKS MAINLY SN OVR THE NRN CWA AND MAYBE A MIX OVR
SE NEB AND INTO FAR SW IA. CURRENT FEELING IS THAT THE EC HAS A
LITTLE BETTER HANDLE ATTM WITH THE GEM TO FAR S...AND THE GFS TO
QUICK...BUT THERE IS STILL A GOOD DEAL OF UNCERTAINTY. HAVE GONE
WARMER ON MEX/HPC TMPS OVERNIGHT AND COOLER DURING THE DAY TO
SHORTEN THE DIURNAL RANGE DUE TO CLDS AND PRECIP DURING THIS PERIOD.
SYSTEM SHLD BE OUT OF OUR AREA BY FRI WITH COLD NRLY FLOW MOVG IN
BEHIND. HAVE GONE COLDER THAN THE MEX/HPC DURING THIS PERIOD AND
INTO CHRISTMAS DAY...BUT AT THE MOMENT...THESE TWO DAYS ARE LOOKING
DRY.
AVIATION...
TAF SITES KOFK/KOMA/KLNK
18Z TAFS
MAIN CONCERN THROUGH THE TAF CYCLE WILL BE DECREASING CEILING
HEIGHTS...WITH SOME LIGHT SNOW ALSO POSSIBLE. CIGS HAVE TRENDED
DOWNWARD AS STRATUS INVADES FROM THE WEST. EXPECT MVFR CIGS TO
REACH ALL SITES THIS AFTN...WITH DOWNWARD TREND INTO IFR CONDITIONS
POSSIBLE OVERNIGHT. MAY SEE SOME FLURRIES OR LIGHT SNOW AT TAF
SITES FROM OVERNIGHT INTO THE MORNING...BUT WITH LOW CONFIDENCE ON
LOCATION AND DURATION...WILL KEEP OUT OF TAFS FOR NOW. WINDS WILL
REMAIN LIGHT...BECOMING EASTERLY TO SOUTHEASTERLY OVERNIGHT.
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
IA...NONE.
&&
$$
DEE/JB/MAYES