FXUS63 KOAX 252115
AFDOAX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
315 PM CST FRI DEC 25 2009

...SEVERE WINTER WEATHER CONDITIONS CONTINUE...

.SHORT TERM...TONIGHT THROUGH MONDAY
UBER-LOW IS SPINNING IN THE CENTRAL US TODAY.  WATER VAPOR IMAGERY 
AND 1.5PVU PRESSURE ANALYSIS AT 20Z INDICATES TWO LOW CENTERS 
ROTATING AROUND EACH OTHER...WITH ONE MOVING NWWD INTO NERN IA/SERN 
MN AND THE SECOND DIVING SEWD AND THEN EWD THROUGH KS INTO MO.  
LARGE AND DEEP UPPER LOW DOMINATED THE CONUS...WITH MUCH OF THE 
CONUS ENCOMPASSED IN THE CIRCULATION.  WARM AIR WAS WRAPPING AROUND 
THE NORTH SIDE OF THE LOW AT MID-LEVEL AND THE SURFACE...WITH MID 
30S TEMPS IN SRN MN/NRN IA.  987MB SURFACE LOW AT 20Z WAS CENTERED 
IN N CNTRL IA...WITH PRESSURE RISES CENTERED OVER KIOW AND FALLS 
CENTERED IN NERN NEB INDICATING RETROGRADING MOTION.

MAIN FORECAST CONCERN IS ADDITIONAL SNOW ASSOCIATED WITH DEEP 
LOW...AS WELL AS CONTINUED WINDS.  BLIZZARD CONDITIONS CONTINUE 
ROUGHLY WEST OF A LINE FROM KLCG AND KTQE TOWARD KBIE...WITH GUSTS 
STILL 40-50MPH+ AND VISIBILITIES 1/4MI OR LESS PER ASOS/AWOS OBS AND 
REPORTS...AND WILL KEEP BLIZZARD WARNING WEST OF THAT LINE THROUGH 
12Z...WITH A WINTER WEATHER ADVISORY AFTER THAT THROUGH 00Z SUN FOR 
CONTINUED SNOW AND BLOWING SNOW.  EAST OF THERE...WILL DOWNGRADE 
BLIZZARD WARNING TO A WINTER WEATHER ADVISORY FOR SNOW AND BLOWING 
SNOW...AND EXTEND THE END TIME TO 00Z SUN.  WINDS WILL DIMINISH 
SOMEWHAT OVERNIGHT AS SFC LOW CONTINUES TO RETROGRADE...RESULTING IN 
A SLACKENED PRESSURE GRADIENT IN ERN NEB.  BY DAYBREAK...WINDS 
EVERYWHERE SHOULD RANGE AROUND 15-25MPH WITH A FEW HIGHER 
GUSTS...AND WITH EVEN WEAKER WINDS IN WRN IA CLOSER TO THE SFC LOW 
CENTER.  SIGNIFICANT TROWAL WILL AID SNOW POTENTIAL THIS EVNG 
THROUGH TOMORROW...SLIDING THROUGH NERN NEB INTO W CNTRL IA.  GARCIA 
METHOD INDICATES 2-3 G/KG MOISTURE AVAILABLE UPSTREAM...BUT WITH 
WIND PULVERIZING SNOWFLAKES AND WITH INTERMITTENT BREAKS IN 
SNOW...WILL KEEP SNOW ACCUMS TO AROUND 2-4 INCHES NORTH AND 1-3 
INCHES SOUTH.  MUCH OF THE ADDITIONAL ACCUMULATION IN THE SRN CWA 
WILL OCCUR THIS EVNG AS PERSISTENT BAND SLIDES THROUGH...ALIGNED 
WELL WITH 700-800MB FRONTOGENETIC BAND.  BELIEVE SNOW WILL CONTINUE 
THROUGH AROUND 12Z SUN...ENDING FROM SW TO NE AS UPPER LOW FINALLY 
BEGINS TO PULL AWAY.  

TEMPS TONIGHT SHOULD BE STEADY OR RISING AS SFC WARM INTRUSION WORKS 
WWD...ESPECIALLY IN THE NRN/NERN CWA.  KEPT DIURNAL RANGE LOW 
THROUGH SUNDAY AS CLOUDS/PRECIP LINGER.  AS LOW MOVES TO THE 
NORTHEAST...SFC HIGH AND MID/UPPER-LEVEL RIDGING WILL PUSH INTO THE 
AREA...WHICH SHOULD KEEP SUN NT/MON/MON NT COLD...WITH TEMPS WELL 
BELOW GUIDANCE.

.LONG TERM...MONDAY NIGHT THROUGH FRIDAY
UPPER SHORTWAVE RIDGING WILL BEGIN EXTENDED PERIOD ACCORDING TO 12Z 
GFS/00Z ECMWF...WHICH HAVE DECENT AGREEMENT...AND NOT TOO DIFFERENT 
FM 00Z GFS ENSEMBLE MEAN.  THIS SHOULD ALLOW A SURFACE RIDGE OVER 
THE CWA TO SHIFT E OF REGION BY 12Z TUE AS MODEST WARM ADVECTION 
BEGINS.  KEPT READINGS BELOW GUIDANCE TUE AM AS TEMPS COULD FALL OFF 
FAIRLY QUICKLY MON EVENING BEFORE RETURN FLOW/CLOUDS DVLP.  TEMPS 
SHOULD MODERATE THEN IN TUE/WED PD BUT HELD BACK BY CURRENT STORMS 
SNOWFALL BOTH DAYS AND POSSIBLE CLOUDS...SPCLY WED.  LEFT IN SLGT 
CHC OF SNOW TUE NGT/WED AS ABOVE MENTIONED RUNS OF GFS/ECMWF 
FORECAST A TROUGH TO CROSS CWA WITH POSSIBLY A LTL MORE ENERGY IN 
SRN STREAM PER 00Z ECMWF LINGERING PCPN CHCS INTO WED PD.  ANOTHER 
TROUGH DIGGING DOWN IN NRN STREAM ON THU WL LIKELY BRING COLDER 
TEMPS IN LATTER PART OF THE EXTENDED...SPCLY IF ECMWF WOULD VERIFY.  
ATTM LOWERED TEMPS THU TOWARD GFS GUIDANCE AND ALLOWED FOR ONLY A 
MODERATE RECOVERY OVER THOSE READINGS THEN FOR FRI.  COULD VERY WELL 
BE LGT SNOW OR FLURRIES WITH COLDER AIR THU BUT WILL LEAVE DRY ATTM 
AND WAIT FOR ANOTHER RUN OR TWO TO INCLUDE IF IT CONTINUES TO BE 
ADVERTISED.   

&&

.AVIATION...
TAF SITES KOFK/KOMA/KLNK 

18Z TAFS

IFR TO LIFR CONDITIONS ARE EXPECTED THRU THE TAF PD WITH SN AND BLSN 
CREATING VISIBILITY RESTRICTIONS. GUSTY NW WINDS OF 20 TO 30 MPH WL 
CONTINUE AS SFC LOW PRESSURE MOVES OVER WRN PORTIONS OF IOWA.

&&

.OAX WATCHES/WARNINGS/ADVISORIES...
NE...WINTER WEATHER ADVISORY UNTIL 6 PM CST SATURDAY FOR NEZ045-052-
     053-067-068-090>093.

     WINTER WEATHER ADVISORY FROM 6 AM TO 6 PM CST SATURDAY FOR 
     NEZ011-012-015>018-030>034-042>044-050-051-065-066-078-088-
     089.

     BLIZZARD WARNING UNTIL 6 AM CST SATURDAY FOR NEZ011-012-015>018-
     030>034-042>044-050-051-065-066-078-088-089.

IA...WINTER WEATHER ADVISORY UNTIL 6 PM CST SATURDAY FOR IAZ043-055-
     056-069-079-080-090-091.

&&

$$

SHORT TERM...MAYES 
LONG TERM...CHERMOK 
AVIATION...KERN