FXUS63 KOAX 112100
AFDOAX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
300 PM CST FRI DEC 11 2009

.SHORT TERM...TONIGHT THROUGH MONDAY.

MAIN CONCERNS ARE THE CHANCE FOR PCPN FROM SATURDAY INTO SATURDAY
NIGHT...THEN AGAIN FROM SUNDAY NIGHT INTO MONDAY. NO BIG CHANGES
FROM PREVIOUS THINKING. WATER VAPOR SATELLITE LOOP SHOWED SPLIT
MID LEVEL FLOW PATTERN WITH A BLOCKING RIDGE FROM ABOUT 50N/135W
EXTENDING NORTH/NORTHWEST ACROSS ALASKA. THE NORTHERN BRANCH
CONTINUED TO BRING COLD AIR DOWN INTO THE NORTHERN PLAINS AND THE
GREAT LAKES. A DECENT WAVE WAS NOTED IN THE SOUTHERN BRANCH...
MOVING INTO CENTRAL/SOUTHERN CALIFORNIA. STRONGLY CONFLUENT FLOW
WAS NOTED OVER THE EASTERN UNITED STATES...WITH SOME 300 MB WINDS
IN EXCESS OF 160 KNOTS. AT THE SURFACE...HIGH PRESSURE WAS OVER
THE SOUTHEASTERN UNITED STATES WITH SOUTHERLY FLOW ACROSS THE
PLAINS AHEAD OF LOW PRESSURE OVER SOUTHERN SASKATCHEWAN.

LOW TEMPERATURES TONIGHT WILL BE TRICKY WITH COMBINATION OF LOW
LEVEL WARM ADVECTION...SNOWCOVER AND NOT MUCH CLOUD COVER. CLOUDS
IN PLACE AT AND BELOW 5000 FEET OVER THE SOUTHERN PLAINS WILL BE
ADVECTING NORTH. 

HAVE SOME AREAS OF FREEZING DRIZZLE OR PATCHY FREEZING DRIZZLE AND
FOG DEVELOPING SATURDAY...AS THE LOW LEVEL MOISTURE INCREASES. 
DECIDED THE CHANCE LOOKED HIGH ENOUGH WHERE SOME MEASURABLE PCPN 
POSSIBLE LATE SATURDAY AFTERNOON OVER SOUTHWEST IOWA...SO CHANGED 
THAT WORDING TO SLIGHT CHANCE OF LIGHT FREEZING RAIN. LACK OF ICE
CRYSTAL DEVELOPMENT ALOFT IS REASON PCPN TYPE SHOULD BE FREEZING.
MODELS TRY TO WARM SURFACE TEMPERATURES TO ABOVE FREEZING OVER
PARTS OF SOUTHEAST NEBRASKA AND SOUTHWEST IOWA SATURDAY...BUT AT
THIS POINT THINK IT WILL STAY JUST BELOW FREEZING. LOW LEVEL PROGS
SHOW MOISTURE MOVING EAST OUT OF THE AREA LATE SATURDAY NIGHT.

LEFT SUNDAY DRY FOR NOW. IT DOES LOOK COLD...WITH HIGHS MAINLY IN
THE 20S. 

A STRONGER SYSTEM WILL MOVE THROUGH SUNDAY NIGHT AND MONDAY. WARM
ADVECTION INCREASES SUNDAY NIGHT...ALONG WITH LOW LEVEL MOISTURE. 
IT APPEARS SOME FREEZING DRIZZLE OR LIGHT FREEZING RAIN MAY OCCUR 
AGAIN FROM SUNDAY NIGHT INTO MONDAY MORNING. COLDER AIR IS EXPECTED 
TO PUSH IN ON MONDAY...WITH FALLING TEMPERATURES IN THE AFTERNOON.

.LONG TERM...MONDAY NIGHT THROUGH FRIDAY.  

MODELS ADVERTISING DRY CONDITIONS ON TAP FOR THE CNTRL PLAINS WITH 
TEMPS POSSIBLY AROUND NEAR NORMAL BY FRIDAY. UNTIL THEN...LARGE 
SCALE FLOW GENERALLY CONSISTING OF BROAD TROF OVER THE CNTRL/ERN 
CONUS WITH EVENTUAL AMPLIFYING RIDGE TO THE WEST. COLD SFC HIGH 
PRESSURE ENVELOPS THE NRN/CNTRL PLAINS TUESDAY MORNING WITH CAA 
PUSHING ALL THE WAY DOWN TO THE SOUTHERN GULF STATES BY LATE AFTN. 
BY WED MORNING THE SFC HIGH PRESSURE CENTER DRIFTS EWD TO THE MID MS 
VLY REGION...ALLOWING BACKSIDE WAA TO SET UP OVER THE PLAINS. MODELS 
PROG THIS TO BE THE TREND THRU THE REST OF THE FCST PERIOD AS THE 
WEST COAST RIDGE AMPLIFICATION. GFS/ECM/GEM ALL IN GOOD AGREEMENT 
WITH THIS SCENARIO...AND FURTHER SUPPORTED BY RELATIVELY HIGH REMOP 
CONFIDENCE AND GEM ENS. HOWEVER...AM CONCERNED THAT SNOW MELT WILL 
END UP BEING LESS THAN ANTICIPATED THRU THE WEEK AND AT THIS POINT 
MAY BE TOO OPTIMISTIC PUSHING OUR HIGH TEMPS INTO THE MID 30S ON 
FRIDAY. 

&&

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

18Z TAFS

SOUTHERLY FLOW WILL CONTINUE OVERNIGHT. EXPECT VFR CONDITIONS TO 
CONTINUE UNTIL AFTER 12Z. LOW CLOUDS WILL BE INCREASING SATURDAY BY 
AROUND 15Z AT KLNK AND CLOSER TO 18Z AT KOMA. KOFK MIGHT BUT JUST ON 
THE EDGE OF THE LOW CLOUDS. SOME FREEZING DRIZZLE AND FOG WILL BE 
POSSIBLE FROM THE LOW CLOUDS. TAFS WILL BE MODIFIED TO BETTER 
REFLECT THIS AS WE GET CLOSER AND IF CONFIDENCE CONTINUES. IFR MAY
CONTINUE THROUGH SATURDAY AFTERNOON AND EVENING.

&&

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

$$

SHORT TERM...MILLER
LONG TERM....DEE
AVIATION...MILLER