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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS63 KOAX 021738
AFDOAX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
1138 AM CST MON DEC 2 2013

.AVIATION...
-- Changed Discussion --
18Z TAFS FOR KOFK...KOMA AND KLNK

VFR CONDITIONS WILL CONTINUE THROUGH THE TAF CYCLE. MID AND HIGH
CLOUDS ARE EXPECTED TO MOVE IN LATER TODAY IN ADVANCE OF A STRONG
COLD FRONT THAT IS PROGGED TO MOVE INTO KOFK LATE IN THE TAF
CYCLE AROUND 15-18Z. DID INCLUDE A WIND SHIFT TO THE NORTHWEST IN
THE LAST FEW HOURS OF THE TAF CYCLE AT KOFK.

KERN
-- End Changed Discussion --

&&

.PREV DISCUSSION... /ISSUED 309 AM CST MON DEC 2 2013/

DISCUSSION...

TIMING AND STRENGTH OF INITIAL ARCTIC SURGE TUESDAY/TUESDAY NIGHT
MAIN FORECAST CHALLENGE. NOT ONLY IT OBVIOUS IMPACT ON
TEMPERATURES BUT ALSO POSSIBLY PRECIP TYPE/INTENSITY. MODEL
DIFFERENCES REMAIN WITH GFS/NAM PROVIDING A FASTER/COLDER SOLUTION
AND GEM/ECMWF A LITTLE SLOWER AND WARMER. GFS IS STICKING TO ITS
PRIOR SOLUTION IN DRIVING A LEAD WAVE ACROSS NRN PLAINS HELPING TO
PUSH THE COLDER AIR FASTER SE. SINCE CURRENT SLOWER MODELS...I.E.
NAMELY THE ECMWF...HAVE COME AROUND TO A FASTER SOLUTION THAN
EARLIER...HAVE TENDED TO LEAN TOWARD GFS. HOWEVER...HAVE INCLUDED
SOME ECMWF IN FORCING THINKING IN CASE A SLOWER H85-H7 FRONT
CROSSES THE FA PER THAT MODEL...AND ALSO GEM...WHICH COULD PROVIDE
A LAGGING PERIOD OF FRONTOGENETICAL FORCING COMPARED TO QUICK IN
AND OUT PER 00Z GFS.

FOR TODAY/TONIGHT...WARM FRONT FORECAST TO MOVE INTO NERN ZONES
BY MIDDAY BEFORE POSSIBLY STALLING. CROSS SECTIONS FROM GFS/NAM
SUGGEST THE CONSIDERABLE MID/HIGH CLOUDS CURRENTLY IN PLACE PER
EARLY MORNING STLT SHOULD THIN SOME BY NOON. SINCE GUIDANCE HAS
FAIRLY CONSISTENTLY UNDER-FORECAST HIGHS LAST SEVERAL
DAYS...AND AT LEAST PARTIAL SUNSHINE EXPECTED WITH MILD H85
TEMPS...ADJUSTED MOST TEMPERATURES UP TOWARD WARMER GUIDANCE. THE
EXCEPTION WAS MAINLY THE NORTHEAST WHERE FRONT MAY STALL AND/OR
CLOUDS REMAIN THICKER. GENERALLY A MILD NIGHT EXPECTED AS RETURN
FLOW SETS UP AHEAD OF FRONT...ALTHOUGH ANY DECOUPLING WITH LACK OF
CLOUDS WOULD LEAD TO LOCALIZED AREAS WITH COLDER TEMPS THAN GOING
FORECAST WILL INCLUDE.

TUESDAY/TUESDAY NIGHT...AS MENTIONED ABOVE MODEL DIFFERENCES BEGIN
DECIDING WHEN PRECIP WILL DEVELOP. FASTER GFS DEVELOPS A
FRONTOGENETICAL BAND MAINLY DURING THE TUESDAY AFTERNOON PERIOD
WHILE ECMWF/GEM LEANED MORE TOWARD TUESDAY NIGHT. 00Z NAM (AND
EVEN A QUICK GLANCE AT 06Z)...ALTHOUGH FAST LIKE THE GFS...WITH
ALSO A PERIOD OF STRONG H7-H5 FRONTOGENETICAL FORCING...REALLY
DOWNPLAYED PRECIP WITH NONE FORECAST ACROSS THE CWA. BECAUSE OF
THE FASTER GFS INCLUDED SMALL POPS LATE TUE AFTN FAR N ZONES.
BOOSTED THEM TUE NIGHT ACROSS THE NORTH TO ACCOUNT FOR THE
TRAILING ELEVATED FRONT PROVIDING FORCING PER GEM/ECMWF. FORECAST
SOUNDINGS FROM GFS AND EVEN ECMWF GENERALLY SUGGESTED PRECIP WOULD
QUICKLY CHANGE TO SNOW...ALTHOUGH A BRIEF MIX OF ZR/IP POSSIBLE AS
COLD AIR QUICKLY UNDERCUTS SLOWER FRONT ALOFT. BOOSTED MAX TEMPS
A LITTLE NEAR AND SE OF A LINCOLN TO OMAHA TO HARLAN LINE SINCE
SOME INITIAL MIXING WITH FRONT COULD BRIEFLY BOOST TEMPERATURES
MIDDLE AND SERN SECTIONS WITH A AFTN FROPA OCCURRING SE.
OTHERWISE...EXPECT COLD AIR TO QUICKLY SURGE ACROSS THE FA TUE
NIGHT WITH READINGS PROBABLY CLOSER TO COLDER NAM/GFS THAN ECMWF.

LOW PRESSURE OVR MN ASSOCIATED WITH LEAD WAVE COULD PROVIDE AREA
WITH DRYING DOWNSLOPE WINDS ON WED WITH STRONG MIXING LEADING TO
GUSTY WINDS BUT ALSO SOME POSSIBLE REBOUND IN TEMPS. DID INCLUDE
SMALL MORNING POPS NERN ZONES...AGAIN BASED ON A POSSIBLE LAG IN
H85-H7 FRONT PER ECMWF.

AFTER THAT FORECAST TO REMAIN VERY COLD WITH TEMPS MUCH BELOW
NORMAL. SMALL POPS WERE LEFT IN WED NIGHT MOST AREAS AND SOUTH ON
THU AS GFS CONTINUED TO SPREAD LIGHT QPF INTO SRN ZONES AS SWRLY
UPPER FLOW/JET RIDE OVER ARCTIC AIR. OTHER POPS WERE NEXT SUNDAY
AS AN UPPER TROUGH MOVES INTO WRN NEBRASKA CROSSING COLD AIRMASS.
DECENT AGREEMENT WAS NOTED BETWEEN 00Z GFS/ECMWF...ALTHOUGH NO
CHANGE FROM LOW CHANCE POPS THAT FAR OUT.

CHERMOK

&&

.OAX WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
IA...NONE.
&&

$$