FXUS63 KOAX 170953
AFDOAX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
353 AM CST MON JAN 17 2011
.DISCUSSION...
FORECAST CONCERNS INCLUDE PCPN CHCS/TYPE TODAY...HOW MUCH COLD AIR
WILL SPILL SOUTH BEHIND FRONT/HOW QUICKLY LATER TODAY AND THEN
HOW MUCH SNOW CAN BE EXPECTED ON WEDNESDAY.
EARLY MORNING STLT SHOWED APPARENT VORT MAX VCNTY NW IA/SW MN WITH
MOST OF THE PCPN AT 09Z CONFINED TO SWRN IA/FAR SE OAX CWA. CIGS
HAVE GENERALLY IMPROVED TO MID DECK POST PCPN AND THUS WOULD
EXPECT ANY PSBL DZ/FZDZ TO HOLD OFF TILL LATER THIS AFTN AHEAD OF
AND BHND FRONT. TEMPS WERE CONTINUING TO RISE WITH 32+F SFC TEMPS
JUST A FEW COUNTIES WEST AND SOUTH OF THE SWRN CWA. OTHER PCPN WAS
UPSTREAM FM SWRN SD INTO NCNTRL NEBR...MOSTLY ON WARM SIDE OF WRM
FRONT. PCPN WAS AIDED BY LOW/MID LVL FRONTOGENESIS ON EDGE OF
STEEPER H7-H5 LAPSE RATES...WHICH SHIFTS A BIT TODAY.
HOWEVER...AFT 18Z QVECTORS FCST TO BECOME MODESTLY DIVERGENT
SUGGESTING PCPN MAY MOVE SE AND WEAKEN THIS MORNING AND THEN
MOSTLY FALL APART OR BE SE OF MUCH OF THE CWA THIS AFTN. THUS
TRIMMED BACK POPS A BIT WITH HIGHEST NW THIS AM AND OVR FAR ERN
CWA. STILL SOME RISK OF FREEZING PCPN WITH ANYTHING THAT MAKES IT
BACK INTO THE CWA THIS MORNING AND EARLY AFTN E/NE...BUT NO
ADVSRY ATTM AS AMOUNTS THIS AFTN SHOULD BE MOSTLY LIGHT OR TEMPS
COULD BOUNCE TO/ABOVE FREEZING SHORTLY AFT PCPN WOULD BEGIN W/SW
THIS AM. THAT SAID...SLICK ROADS WL BE MENTIONED FOR SW IA IN HWO
WHERE A BIT MORE FZRA OCCURRED AROUND AND A LITTLE AFT MIDNIGHT.
COLD FRONT EXPECTED TO REACH NR A LCG-OLU LINE BY 21Z AND THEN
QUICKLY SURGE SE OF OMA/LNK BY 00Z. ADJUSTED HRLY TEMPS TO REFLECT
A SLOW RISE THRU FRONTAL PASSAGE WITH PERHAPS STEADY OR A DEG RISE
IN TEMPS DUE TO MIXING AS WINDS INITIALLY SHIFT TO NW BEFORE THEY
FALL. COLD AIR COULD CHANGE ANY PCPN BACK TO FZRA/FZDZ BRIEFLY
BUT FORECAST SOUNDING BLEND BETWEEN GFS/NAM WERE MARGINAL FOR FZDZ
SUPPORT. DID MENTION BLOWING SNOW NERN NEBR WITH SURGE LATE THIS
AFTN INTO EARLY TNGT SINCE NEBR DOR HAD BEEN REPORTING SOME
BLOWING SNOW IN WARM ADVCTN SWRLY WINDS EARLIER TONIGHT. MODELS
STILL SUGGEST BULK OF COLD AIR WILL REMAIN TO OUR N LATE
TNGT/TUE...BUT WITH SFC TEMPS NEAR ZERO ENTERING NERN MT/NWRN
ND...TEMPS COULD BE CLOSE TO PREV FCST AND LTL/NO CHANGES
MADE...GENERALLY IN BETWEEN COOL MAV AND WARMER MET.
ONLY MODEST WARMUP EXPECTED ON TUE AND INCREASING CLOUDS SHOULD
LIMIT TEMP DROP WRN CWA TUE NGT. SOME RISK THAT NERN ZONES WL DROP
BELOW ZERO AND LEFT THOSE NUMBERS ALONE. A DECENT PERIOD OF
ISENTROPIC LIFT FORECAST FOR CWA WED WITH MODELS INDICATING 0.25+
PCPN BULLSEYE CROSSING CWA SOMEWHERE...WITH 00Z NAM KEYING AREAS
FARTHEST N. WOULD EXPECT HIGH SNOW TO LIQUID RATIOS WITH SYSTEM
AND MIXING RATIOS FCST WOULD SUGGEST AN AREA OF 4-6 INCHES SETTING
UP SOMEWHERE IN THE CWA WITH AT LEAST 12 HRS LIFT. EXPANDED LIKELY
POP AREA TO MOST OF CWA AND WL CONT MENTION IN HWO...ALTHOUGH CANNOT
PIN DOWN WHERE HEAVIEST WILL FALL ATTM.
IF SKIES CLEAR QUICKLY ENOUGH BY THU AM TEMPS COULD DROP
SIGNIFICANTLY BLO FCST BUT LTL CHANGES WITH THIS FCST. LTL/NO
CHANGES ALSO MADE TO REST OF EXTENDED.
&&
.AVIATION...
TAF SITES KOFK/KOMA/KLNK
06Z TAFS
VFR CONDITIONS WILL CONTINUE THRU MUCH OF THE MORNING AS UPPER WAVE
MOVES EAST OF THE REGION AND MIXED WINTRY PCPN MOVES EAST INTO IOWA.
AIR COLUMN DRIES FOR A COUPLE OF HOURS THEN FOCUS TURNS TO THE NEXT
WAVE MOVING SOUTHEAST OUT OF WRN SD WHICH SHOULD BRING AN INCREASE
IN LOW AND MID LEVEL MOISTURE TO THE TAF SITES THIS AFTERNOON. COLD
FRONT PUSHES THRU CLOSE TO 00Z TONIGHT WITH MVFR TO IFR CIGS LIKELY
BEHIND THIS WITH SOME PATCHY FREEZING DRIZZLE POSSIBLE.
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
IA...NONE.
&&
$$
CHERMOK/KERN