FXUS63 KOAX 182045
AFDOAX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
245 PM CST TUE JAN 18 2011
.SHORT TERM...TONIGHT THROUGH FRIDAY.
MAIN CONCERN IS SNOW EVENT STARTING WED AND CONTINUING WED NGT.
WE ISSUED A WINTER STORM WATCH EARLIER IN THE DAY FOR OUR SEVEN
SRN COUNTIES...SINCE THE POTENTIAL FOR AROUND 6 INCHES OF SNOW
SEEMED NEAR 50 PERCENT. WATCH CAN BE CONVERTED TO EITHER NO
HEADLINES...AN ADVISORY OR A WARNING THIS EVENING OR OVERNIGHT.
SURFACE ANALYSIS EARLY THIS AFTN SHOWED A RIDGE OF COLD HIGH PRES
EXTENDING FROM CANADA SWD THROUGH THE PLAINS. LOW PRES WAS STARTING
TO ORGANIZE IN WY AND CO. A WEAK SHORTWAVE TROUGH WAS MOVING OVER
THE AREA THIS AFTN...AND SHOULD CONTINUE TO PRODUCE SOME LIGHT
SNOW INTO THE EVENING. SNOW AMOUNTS EXPECTED TO RANGE FROM A
TRACE UP TO A FEW TENTHS OF AN INCH THIS EVENING.
THE MAIN SFC LOW WILL TRACK FROM ERN CO DOWN INTO TX WITH THE WED
INTO WED NGT EVENT...AND WINDS ARE EXPECTED TO REMAIN FAIRLY
LIGHT WITH MODEST PRES GRADIENT. THE 12Z NAM WAS WETTER THAN THE
12Z GFS...BUT FOR NOW WENT MORE TOWARD THAT SCENARIO SINCE SNOW
RATIOS COULD BE 15 TO 1 OR HIGHER WITH COLD TEMPS. MID LEVEL
MIXING RATIOS FROM 12Z NAM ARE ABOUT 3.4 G/KG AT THE START OF
EVENT ACROSS SERN NE AND DROP TO AROUND 2.3 G/KG BY 06Z THU. THERE
DOES APPEAR TO BE DECENT VERTICAL MOTION IN THE DENDRITIC LAYER...
AND THERE ARE WEAK HINTS OF POTENTIAL FOR MESOSCALE BANDING. THE
12Z NAM BUFKIT SOUNDINGS SUGGESTED 5 TO 7 INCHES OF SNOW POSSIBLE
NEAR THE KS BORDER. 15Z SREF QPF WAS AROUND 0.35 ALONG THE KS
BORDER...WITH SNOW AMOUNTS SIMILAR TO THE 12Z NAM. THE MAIN TREND
FROM PREVIOUS FCST WAS TO DECREASE POPS AND SNOW AMOUNTS IN THE
NRN ZONES...BUT TO INCREASE THEM SLGTLY FOR THE SRN PART OF THE
FCST AREA. THIS WAS IN LINE WITH THINKING FROM EAX AND TOP.
WE COULD SEE MORE LIGHT SNOW WITH A SHORTWAVE MOVING ACROSS THE DKTS
AND MN FRIDAY. WILL KEEP THE PCPN TYPE ALL SNOW AT THIS POINT. BUT
THERE ARE HINTS THAT THERE COULD BE SOME FREEZING PCPN DUE TO WEDGE
OF WARMER AIR ALOFT IN FORECAST SOUNDINGS (NEAR 850 MB). WE ALSO MAY
LOSE OUR ICE CRYSTALS ALOFT...BUT STILL STAY SATURATED IN THE LOW
LEVELS. SO THIS COULD BECOME A CONCERN IN LATER FCSTS.
LOW TEMPS TNGT WILL BE TRICKY...ESPECIALLY IF CLOUDS DECREASE MORE
THAN CURRENTLY EXPECTED. HAVE LOWS GENERALLY ZERO OR BELOW ZERO IN
THE NORTH AND SINGLE DIGITS ABOVE ZERO SOUTH. HIGHS WED SHOULD ONLY
REACH THE TEENS. COLD WEATHER WILL CONTINUE WED NGT INTO THU...WITH
LOWS THU NGT PROBABLY IN THE EVENING. SOUTH WINDS ARE EXPECTED TO
INCREASE DURING THE NGT AND TEMPS MAY START TO RISE LATE.
SOME MODERATION FRI.
.LONG TERM...FRIDAY NIGHT THROUGH TUESDAY.
ACTIVE NORTHWEST FLOW PATTERN REMAINS IN PLACE DURING THE EXTENDED
PERIOD WITH SERIES OF WAVES ROLLING THROUGH THE REGION. BEST CHANCE
FOR PRECIP LOOKS TO BE OVER THE WEEKEND FROM AROUND SATURDAY NIGHT
INTO SUNDAY AS THE COMBINATION OF SURFACE SYSTEM AND UPPER WAVE
PRODUCE GOOD FOCUS AND FORCING FOR SOME LIGHT SNOW. TEMPERATURES
WILL REMAIN PROBLEMATIC DEPENDING ON SKY CONDITIONS BUT GENERALLY
STILL ON THE COLD SIDE FOR THE PERIOD.
&&
.AVIATION...
TAF SITES KOFK/KOMA/KLNK
18Z TAFS
CIGS WERE VARIABLE ACRS THE TAF SITES THIS AFTERNOON AS SFC HIGH
PRES STRETCHED FM THE DAKOTAS SOUTHWARD INTO THE MISSOURI RIVER
VALLEY. CLDS HAD SCATTERED OUT AT KOMA...WITH VFR CIGS AT KLNK AND
MVFR CIGS AT KOFK. THIS SFC RIDGE OF HIGH PRES WILL REMAIN IN PLACE
OVERNIGHT...HOWEVER A MID LEVEL SHORTWAVE TROF WILL PASS THRU THIS
AFTERNOON AND THIS EVENING. A LOOK AT THE IR STLT IMAGERY/WSR-88D
RADAR/METARS SHOWS AN AREA OF LIGHT SNOW AND FLURRIES ASSOCIATED
WITH THIS MID LEVEL WAVE/LOWER LEVEL ISENTROPIC LIFT...WITH SEVERAL
AREAS OF 1-3SM VSBYS IN LIGHT SNOW OVER CNTRL NEB. AS THIS FEATURE
MOVES EAST...EXPECT MORE WDSPRD MVFR CIGS TO FILL IN FM WEST TO EAST
AT THE TAF SITES. BROUGHT THE VSBYS DOWN TO MVFR AT KOFK WITH SOME
LIGHT SNOW AND COULD SEE SOME PATCHY IFR VSBSYS THERE WITH FLURRIES
FARTHER SOUTH AND EAST. OVERNIGHT AFTER THE WAVE MOVES OUT IT WILL
BE A TOUGH CALL AS TO HOW WIDSPREAD THE MVFR CIGS WILL BE. FOR NOW
LEFT THE MVFR CIGS IN WITH LIGHT NORTH WINDS...ALTHOUGH MAY LOSE
THAT LOW DECK FOR A PERIOD OF TIME. WEDNESDAY THE NEXT STORM SYSTEM
WILL BRING THICKENING CLOUDS WITH SNOW...AND DETERIORATING
CONDITIONS ESPECIALLY AFTER 16Z.
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...WINTER STORM WATCH FROM WEDNESDAY MORNING THROUGH LATE WEDNESDAY
NIGHT FOR NEZ078-088>093.
IA...NONE.
&&
$$
SHORT TERM...MILLER
LONG TERM....FOBERT
AVIATION...ZAPOTOCNY