FXUS63 KOAX 200242
AFDOAX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
842 PM CST SUN DEC 19 2010
.DISCUSSION...
CHALLENGING FORECAST THIS EVENING. DESPITE LACK OF ANY SIGNIFICANT
WAVE IN THE AREA...WAA AT H85/H70 OVER A SATURATED SUB LAYER HAS
PRODUCED SOME PATCHY FREEZING DRIZZLE ACROSS NORTHEAST NEBRASKA
THIS EVENING...NORTHWEST OF A LINE FROM ALBION TO WAYNE. A FEW
CALLS HAVE INDICATED NOT A LOT OF COVERAGE...BUT SPOTTY ENOUGH TO
CAUSE A FEW SLICK SPOTS ON ROADWAYS. THICK FREEZING FOG HAS ALSO
CONTRIBUTED TO THAT AS WELL. MEANWHILE...IN THE SOUTHEASTERN
CWFA...LOW CLOUDS HAVE SCRUBBED OUT WITH ONLY HIGH LEVEL MOISTURE
STREAMING OVERHEAD...THUS HAVE DECIDED TO TRIM PREVIOUS SLIGHT
CHANCE POPS ALONG THE SOUTHERN EDGE OUT OF THE OMAHA METRO AREA AS
WELL. OTHERWISE...RAISED TEMPERATURES IN THE SOUTHEAST WHERE
READINGS ARE STILL IN THE LOWER TO MID 30S...AND ALSO REMOVED THE
LOW CLOUDS FROM THE KLNK/KOMA TAF SITES. OVERNIGHT...THERE COULD
STILL BE A MIXED BAG OF PRECIP ACROSS NORTHEAST NEBRASKA NEAR THE
NE/SD BORDER REGION WITH SOME MINOR SNOW ACCUMULATIONS THERE...SO
NO OTHER CHANGES TO THE FORECAST.
&&
.PREV DISCUSSION... /ISSUED 327 PM CST SUN DEC 19 2010/
SHORT TERM...TONIGHT THROUGH WEDNESDAY
LARGE SCALE FLOW PER WV IMAGERY SHOWING CLOSED UPPER LOW SPINNING OFF
THE PAC NW COAST WITH ASSOCIATED TROF EXTENDING DOWN THE WEST COAST.
MEANWHILE AN UPPER TROF WAS SITUATED OVER THE ERN CONUS WITH A
WEAKLY AMPLIFIED RIDGE OVER THE GREAT BASIN/CNTRL ROCKIES.
DETERMINISTIC MODELS IN PRETTY GOOD AGREEMENT THAT COMBINATION OF
BLOCKING TO THE EAST AND WRN DIGGING TROF WILL FORCE RIDGE OVER THE
CONUS TO AMPLIFY THRU THE FCST PD. AT THE SFC TWO DISTINCT BOUNDARIES
EXISTED...ONE FROM ND TO ERN IA AND THE OTHER FROM THE NEB PANHANDLE
TO NR MO. FCST FOR TONIGHT REVOLVING AROUND UPPER RIDGE EVENTUALLY
LIFTING LLVL BAROCLINIC ZONE INTO THE DAKOTAS AND MN...TAKING THE
ACTIVE WX WITH IT. UNTIL THEN...PINNING DOWN PTYPE IS THE MAIN
PROBLEM. GFS/NAM RUN-TO-RUN CONSISTENCY HAS BEEN QUITE GOOD
ADVERTISING MIX BAG OF FZRA/SLEET/SN PER MODEL DOMINATE
PTYPE/CRITICAL THINKS OVER AREA OF OVERRUNNING. THEREFORE WILL
CONTINUE PCPN MIX LATE TONIGHT INTO MONDAY. OTHERWISE...ALL
SOLUTIONS STILL SHOWING BRUNT OF ACTIVE WX/SN ACCUMULATIONS WILL BE
ACROSS THE DAKOTAS/UPPER MIDWEST. HOWEVER...POTENT VORT ENERGY RIDING
ATOP OF THE RIDGE WILL BRING RUSH OF CAA TO THE CNTRL PLAINS EARLY
TUESDAY MORNING ASSOCIATED WITH SWD BUILDING SFC HIGH. COLDEST PD IN
THE SHORT TERM WILL COME WITH WED MORNING LOWS IN THE SINGLE DIGITS.
LONG TERM...WEDNESDAY NIGHT THROUGH SUNDAY
MAIN CONCERN THIS PERIOD WILL BE THE THURS/FRI SYSTEM AS THIS SYSTEM
HAS THE POTENTIAL TO PRODUCE TRAVEL ISSUES DIRECTLY BEFORE THE
HOLIDAY. LARGE-SCALE MODELS ARE STILL STRUGGLING WITH THIS
SYSTEM...AS THEY HAVE LATELY WITH THE DETAILS IN THIS BLOCKING
PATTERN. THUS CONFIDENCE ON TIMING...PLACEMENT AND INTENSITY ARE
VERY LO TODAY...AND DO EXPECT MORE MODEL SHIFTING THROUGH TIME AS WE
NEAR THE EVENT. THUS HAVE FOLLOWED A BLEND APPROACH USING THE NAEFS
AND THE EC.
GIVEN THE ABOVE APPROACH...IT APPEARS THE SYSTEM WILL BE A LITTLE
SLOWER THAN PREVIOUS FORECASTS HAVE INDICATED AND WE HAVE EXTENDED
POPS THROUGH THE DAY ON FRIDAY. INITIALLY ASCENT...NAMELY IN THE
FORM OF STG ISENTROPIC LIFT...WILL GET GOING BY THURSDAY MORNING AND
WL LIKELY LEAD TO THE DEVELOPMENT OF PRECIP THRU THE DAY OVR THE CWA
/ESPECIALLY THE ERN 2/3RD OF THE FA/. DUE TO THE STG WAA...IT STILL
LOOKS LIKE ENOUGH WARM AIR WILL MOV INTO SE NEB/SW IA ON THURSDAY
FOR A MIX OF FZRA/SN THURS MRNG AND A FZRA/SN/RA MIX THURS AFTN AND
HAVE INCLUDED THIS MIX INTO THE GRIDS. GENERALLY NORTH OF HIGHWAY 92
IN NEB AND HIGHWAY 30 IN IOWA PRECIP LOOKS TO BE ALL SNOW. AS SFC
INVERTED TROF /WHICH SHLD EXTND NWD FM THE LO OVR KS-MO ON THURS/
MOVS EWD ON THURS NIGHT...COLDER AIR WILL FILTER IN AND ANY PRECIP
SHLD BE SNOW. PRECIP WL SLOWLY COME TO AN END FRI MRNG WITH STG CAA
OCCURRING THRU THE DAY. SYSTEM IS STILL 4-5 DAYS OUT AND THUS VERY
EARLY TO TALK ABOUT AMOUNTS OF SNOW...BUT EARLY INDICATIONS ARE IT
LOOKS TO MORE OF AN ADVISORY TYPE EVNT WITH A FEW INCHES POSSIBLE.
CHRISTMAS DAY AND SUN CONT TO LOOK DRY AND COLD.
AVIATION...
TAF SITES KOFK/KOMA/KLNK
18Z TAFS
MVFR TO IFR CIGS HAVE BLANKETED THE TAF SITES...WITH A CLEAR SLOT
NOSING JUST INTO KLNK THIS AFTERNOON THAT WILL FILL BACK IN THIS
EVENING. CIGS WILL LOWER THROUGH THE EVENING AND INTO THE OVERNIGHT
HOURS...WITH IFR TO EVEN LIFR CIGS ALONG WITH RESTRICTED VIS. MAY
SEE LIGHT PRECIP...MAINLY AT KOFK...BUT HAVE KEPT OUT FOR NOW TO
ALLOW NEXT SHIFT TO BETTER DETERMINE PRECIP TYPE AND DURATION.
WINDS WILL CONTINUE OUT OF THE SOUTHEAST...WITH SPEEDS INCREASING TO
10-15KT BETWEEN 12-18Z MONDAY.
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
IA...NONE.
&&
$$
DEWALD