FXUS63 KOAX 052027
AFDOAX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
227 PM CST SAT DEC 5 2009

.SHORT TERM...TONIGHT THROUGH TUESDAY.

DID NOT MAKE MANY CHANGES FROM PREVIOUS FORECAST. 12Z MODELS WERE 
STILL IN GOOD AGREEMENT SHOWING PCPN DEVELOPING ACROSS THE AREA 
SUNDAY MORNING AND THEN CONTINUING INTO SUNDAY EVENING BEFORE ENDING 
BY 09Z MONDAY. GENERALLY WENT WITH THE 12Z GFS MODEL OUTPUT...WHICH
WAS SOMEWHAT OF A COMPROMISE FOR SNOW AMOUNTS SUNDAY COMPARED TO THE 
DRIER NAM AND A GEM/ECMWF BLEND (WHICH WERE WETTER SUNDAY). BUT THE
12Z NAM WAS THE WETTEST MODEL SUNDAY EVENING. THINK THAT AMOUNTS 
WILL MAINLY BE IN THE 2 TO 4 INCH RANGE...BASED ON MID LEVEL MIXING
RATIOS...SO BORDERLINE FOR AN ADVISORY AT THIS POINT. WILL LET NEXT 
COUPLE OF SHIFTS EVALUATE AND DECIDE ON POSSIBLE ADVISORY LATER. 
NEXT SYSTEM SHOULD START SPREADING SNOW BY LATE MONDAY NIGHT AND WE 
COULD SEE SNOW WELL INTO TUESDAY NIGHT.

WATER VAPOR SATELLITE LOOP EARLY THIS AFTN SHOWED A GOOD SYSTEM OVER
THE ROCKIES. THIS HAD 12 HOUR HEIGHT FALLS OF 190 METERS AT 500 MB
AND 250 METERS AT 300 MB AT KBOI. CLOUDINESS WILL THICKEN ACROSS THE
AREA TONIGHT AND SUNDAY MORNING WITH SNOW DEVELOPING AS ATMOSPHERE
SATURATES FROM THE MID LEVELS DOWNWARD. MODELS SUGGEST A WEAKLY 
COUPLE JET STRUCTURE WITH RIGHT ENTRANCE REGION OF 300 MB JETSTREAK 
OVER THE GREAT LAKES AND THE LEFT EXIT REGION OF THE JET STREAK FROM 
NEVADA INTO COLORADO. PCPN WITH SYSTEM SHOULD PULL EAST SUNDAY NIGHT 
AND HIGH PRESSURE AT THE SURFACE WILL BUILD INTO THE DAKOTAS AND 
MINNESOTA MONDAY...GIVING US A BREAK IN THE ACTION.

FOR THE SYSTEM MONDAY NIGHT THROUGH TUESDAY...AGAIN STAYED FAIRLY 
CLOSE TO THE 12Z GFS. 12Z GEM AND ECMWF WERE A LITTLE QUICKER WITH
PCPN DEVELOPMENT. 700-750 MB MIXING RATIOS ARE A BIT HIGHER...AND
EVENT DURATION IS A LITTLE LONGER. THIS SUGGESTS POTENTIAL FOR 4 
TO 8 INCHES OF SNOW SOMEWHERE IN THE REGION. NOT COMPLETELY SOLD ON
EXACTLY WHERE THIS MAY SETUP YET...BUT BEARS WATCHING. 12Z ECMWF
HAS HEAVIEST ALONG NE/KS BORDER TUESDAY (WHICH IS NORTH OF WHERE IT 
WAS YESTERDAY)...GEM HAS HEAVIEST OVER ERN KS INTO WRN MO...AND THE
12Z GFS HIGHLIGHTED SERN NE/SWRN IA/NERN KS/NWRN MO. WILL HIT SYSTEM
RELATIVELY HARD IN HAZARDOUS WEATHER OUTLOOK...BUT NO HEADLINES WITH 
THIS FOR NOW EITHER. NAM WOULD ALSO SUGGEST SOME MIXED PCPN ACROSS
SERN NE TUESDAY...BUT 12Z GFS INDICATES MAINLY SNOW OR ALL SNOW. 

.LONG TERM...TUESDAY NIGHT THROUGH SATURDAY.  

THERE IS ENOUGH MODEL AGREEMENT TO SUGGEST THAT THE BEGINNING OF THE 
TUESDAY NIGHT PERIOD...00Z-06Z WEDNESDAY...WILL BE CLOSE TO THE TIME 
THE WINTER STORM IS REACHING A PEAK INTENSITY IN THE FORECAST AREA.  
MOST OF THE GFS ENSEMBLE MEMBERS CLUSTER THE SURFACE LOW IN THE 
TEXAS OR OKLAHOMA PANHANDLES...AS WELL AS THE 12Z ECMWF...AT 00Z 
WED....THEN RAPIDLY MOVE THE LOW INTO THE REGION OF ST LOUIS-WESTERN 
INDIANA BY 12Z WED.  ECMWF IS THE FARTHEST NORTH WITH THE LOW 
TRACK...AND HAPPENS TO BE THE DEEPEST.  WINDS CERTAINLY WILL BE A 
SIGNIFICANT FACTOR WITH THIS SYSTEM...AND IF SURFACE LOW IS AS DEEP 
AS ECMWF SUGGESTS...GUSTS TO 40 MPH MAY BE POSSIBLE LATE TUESDAY 
NIGHT.  

THIS SYSTEM IS PROGGED TO MOVE FAST...WITH ACCUMULATING SNOW 
EXPECTED TO END BY EARLY MORNING WEDNESDAY.  BLOWING SNOW MAY 
CONTINUE INTO WEDNESDAY MORNING HOWEVER IF THE WINDS REMAIN STRONG.

WITH AN ARCTIC AIRMASS IN PLACE AND SNOWCOVER ON THE GROUND...
TEMPERATURES WILL BE QUITE COLD. LEANED TOWARDS THE COOLEST
SOLUTIONS OF THE ENSEMBLE MOS HIGHS AND LOWS FOR WEDNESDAY THROUGH
SATURDAY. BEST CHANCE FOR WARMING WILL BE SATURDAY WHEN SOUTH FLOW
RETURNS TO THE REGION AND FAIRLY WARM MID LEVEL TEMPERATURES.
STILL EXPECT SNOW COVER BY THEN...SO ANY WARMUP WILL BE LIMITED.

&&

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

18Z TAFS

A SFC TROF IS MOVING THROUGH THE TAF SITES THIS AFTERNOON WITH WINDS 
GRADUALLY TURNING TO THE NORTH AND NORTHEAST...FIRST AT KOFK...THEN 
AT KOMA AND KLNK AFTER 00Z.  SCT-BKN HIGH CLOUDS WILL DOMINATE.  
OVERNIGHT...NORTH AND NORTHEAST FLOW WILL BRING IN INCREASING LOW 
LEVEL RH AND POTENTIAL IFR/MVFR CIGS SUNDAY MORNING. SOME LIFT WITH 
THE APPROACHING STORM SYSTEM MOVES THROUGH IN THE MORNING AND THIS 
WORK TO LOWER CIGS AND BEGIN TO GENERATE LIGHT SNOW. LIFT AND RRQ OF 
THE UPR JET SHOULD WORK TO GENERATE SNOW...AND HAVE INCLUDED A CHC 
AT KOFK AT 15Z....ALTHOUGH MAY NEED TO ADD EARLIER AT KOMA AND KLNK.

&&

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

$$

SHORT TERM...MILLER
LONG TERM...NIETFELD
AVIATION...ZAPOTOCNY