FXUS63 KOAX 290844
AFDOAX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
244 AM CST SUN NOV 29 2009

.DISCUSSION...
TEMPERATURES CONTINUE TO BE THE MAIN FORECAST CONCERN THROUGH THE 
WEEK. 

LITTLE HAS CHANGED FROM YESTERDAY CONCERNING EVOLUTION OF UPPER AIR 
PATTERN AND ASSOCIATED SURFACE FEATURES THROUGH MID TO LATE WEEK. 
NORTHERN STREAM TROUGH WAS DIVING INTO THE PLAINS THIS MORNING WITH 
UPPER LOW CENTERED OVER THE NORTHERN BAJA. NORTHERN TROUGH WILL MOVE 
THROUGH THE GREAT LAKES MONDAY AND OFF THE EAST COAST TUESDAY. THIS 
WILL RESULT IN A PERIOD OF ZONAL FLOW ACROSS OUR CWA...ALLOWING 
TEMPS TO WARM. HOWEVER A SECOND TROUGH WILL DIVE INTO THE REGION 
TUESDAY NIGHT/WEDNESDAY...THEN MERGE WITH SOUTHERN STREAM LOW MOVING 
INTO THE OHIO VALLEY. MUCH COLDER AIR WILL THEN SETTLE INTO THE 
REGION...BRINGING NEAR OR BELOW NORMAL TEMPS FOR LATE WEEK INTO THE 
WEEKEND. 

CURRENTLY A COLD FRONT HAS PUSHED SOUTH OF NEBRASKA AND SOUTHWEST 
IOWA THIS MORNING WITH NORTHWEST LOW LEVEL FLOW ACROSS OUR CWA. 
WINDS OF 10 TO 20 MPH AND ABUNDANT MID/HIGH LEVEL CLOUDS HAVE HELD 
TEMPERATURES IN THE 30S SO FAR IN OUR COLDEST SPOTS...BUT CLEARING 
FROM THE NORTH SHOULD ALLOW TEMPS TO DROP BEFORE DAYBREAK. LOOKING 
UPSTREAM BEHIND THE COLD FRONT YESTERDAY...AN AVERAGE OF AN 8 TO 12 
DEGREE WARMUP OCCURRED ON SATURDAY...SO AM EXPECTING THE SAME HERE 
TODAY. HOWEVER SOUTHERN AREAS SHOULD HAVE A SMALLER DIURNAL RANGE 
DUE TO LONGER DURATION OF CLOUD COVER.

CLEARING SKIES TONIGHT AND DIMINISHING WINDS SHOULD ALLOW TEMPS TO 
DROP INTO THE 20S ALL AREAS. A BAND OF MID LEVEL WARM ADVECTION MAY 
BRING CLOUDS BACK TO THE NORTH BEFORE MORNING...HALTING TEMP FALL. 
THEN WESTERLY LOW LEVEL FLOW ON MONDAY ALONG WITH LOTS OF SUNSHINE 
WILL PUSH TEMPS BACK TOWARD 50.

COLD FRONT ASSOCIATED WITH SECOND NORTHERN STREAM TROUGH IS PROGGED 
INTO THE CWA ON TUESDAY. TIMING OF THIS FRONT WILL BE AN ISSUE FOR 
TEMPERATURES THEN. LATEST 00Z NAM AND ECMWF SUGGEST A SOMEWHAT 
SLOWER COLD FRONT THAN THE GFS...KEEPING WIND SHIFT OUT OF THE  
SOUTHERN HALF OF THE CWA THROUGH MAX WARMING TUESDAY. THIS WOULD PUT 
TEMPS WELL INTO THE 50S IN OUR SOUTHERN CWA WITH 40S NORTH. HAVE 
FOLLOWED THIS TIMING BASED ON RUN-TO-RUN CONSISTENCY FROM THE ECMWF. 

AIR BEHIND THIS COLD FRONT IS MUCH COLDER THAN CURRENT FRONTAL 
SYSTEM...WITH THE ECMWF DROPPING 850 TEMPS FROM 8-10C TUESDAY 
AFTERNOON TO MINUS 6-8C BY WEDNESDAY AFTERNOON. AND IT ONLY GETS 
COLDER FROM THERE AS THURSDAY AND FRIDAY AFTERNOON 850 TEMPS ARE 
PROGGED IN THE MINUS TEENS. OUR CURRENT FORECAST OF LOWS IN THE 
TEENS AND HIGHS IN THE 30S LOOK OKAY FOR NOW. 

THE MODELS DIVERGE FOR THE WEEKEND WITH THE ECMWF KEEPING BROAD 
TROUGH OVER THE EASTERN TWO-THIRDS OF THE COUNTRY...WHILE THE GFS 
SUGGESTS A SIGNIFICANT TROUGH/LOW WILL DROP OUT OF WESTERN 
CANADA...BRINGING WARMING/ZONAL FLOW TO THE PLAINS FRIDAY AND 
SATURDAY. WILL HAVE TO WAIT AND SEE ON THIS ONE...AND OUR CURRENT 
HIGHS NEAR 40 LOOK LIKE A DECENT COMPROMISE FOR NOW.

DERGAN

&&

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

29/06Z TAFS

SURFACE HIGH PRESSURE CENTERED OVER THE ROCKIES AND COVERING THE 
NORTHERN AND CENTRAL PLAINS WILL MOVE LITTLE THROUGHOUT THE FORECAST 
PERIOD.  LOW CLOUDS OVER IOWA HAVE BACKED INTO THE KOMA AREA AND IS 
EXPECTED TO REMAIN BKN012-014 THROUGH 15Z.  WINDS WILL BE 350 TO 340 
DEGREES AT 15 KNOTS WITH SOME GUSTS AS HIGH AS 22 KNOTS AT KLNK. 

SMITH

&&

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

$$