FXUS63 KGID 030004 AAA
AFDGID

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE HASTINGS NE
604 PM CST WED DEC 2 2009

.AVIATION...FOR THE 00Z KGRI TAF. RELATIVELY QUIET AVIATION
WEATHER PERIOD ANTICIPATED FOR GRAND ISLAND OVER THE NEXT 24 HOURS
AS A VFR CLOUD CEILING AND POSSIBLY SOME SNOW FLURRIES ON THURSDAY
WILL BE THE MAIN ISSUES. INITIALLY FOR THIS EVENING TO
OVERNIGHT...AN UNLIMITED CEILING WILL SLOWLY GIVE WAY TO A BROKEN
VFR CEILING AROUND 4 TO 5 KFT AFTER MIDNIGHT WHILE WINDS REMAIN
OUT OF THE NORTHWEST AT AROUND 10 TO 12 KNOTS. ATTENTION THEN
SHIFTS TOWARD THE AFTERNOON HOURS ON THURSDAY AS SOME LIGHT SNOW
MAY BE POSSIBLE ALTHOUGH COVERAGE LOOKS LOW ENOUGH TO LEAVE OUT OF THE
FORECAST FOR NOW BUT THIS WILL NEED TO BE EVALUATED FURTHER IN
SUBSEQUENT FORECASTS.

&&

.PREV DISCUSSION... /ISSUED 245 PM CST WED DEC 2 2009/ 

SHORT TERM...TONIGHT THROUGH THURSDAY NIGHT. THE FOCUS IS ON COLD
TEMPS. THE PATTERN ALOFT FEATURED AN UPPER RIDGE AXIS IN THE
PACIFIC/ALONG THE WESTERN CONUS...WITH A LARGE SCALE TROUGH
ORIENTED FROM ONTARIO SOUTH AND WEST INTO THE CENTRAL ROCKIES INTO
THE CENTRAL PLAINS. MUCH COLDER AIR HAS SETTLED INTO OUR REGION AS
THE POLAR VORTEX CLOSES AND DUMBBELLS AROUND ACROSS THE UPPER
MIDWEST WITH THE SECOND CIRCULATION IN THE HUDSON BAY. THE
SOUTHERN LOBE OF ENERGY WILL DIG SOUTHEAST ONTO THE PLAINS TONIGHT
WHILE THE MAIN TROUGH EXPANDS TO THE SOUTH AND WEST ACROSS THE
INTERIOR CONUS. THIS WILL BRING A REINFORCING SHOT OF THE COLD
ARCTIC AIR INTO OUR REGION. MOISTURE IS LIMITED BUT WITH THE
PRESENCE OF FRONTOGENETIC FORCING AND INTERMITTENT LIFT IN THE
DENDRITIC LAYER SOME FLURRIES ARE POSSIBLE LATE TONIGHT INTO THE
DAY ON THURSDAY.

TEMPERATURES WILL BE DOWNRIGHT COLD IN COMPARISON TO READINGS 
EXPERIENCED IN THE LAST SEVERAL DAYS/WEEKS.  SURFACE DPS ARE 
CURRENTLY IN THE SINGLE DIGITS TO TEENS AND TEMPS TONIGHT SHOULD 
EASILY DROP BELOW 20 DEGREES WITH MAINLY TEENS EXPECTED FOR LOWS.  

TEMPERATURES WILL STRUGGLE IN THE COLD AIRMASS ON THURSDAY AND 
FORECAST SOUNDINGS INDICATE CONVECTIVE TEMPS IN THE MID/UPPER 20S.  
SKIES SHOULD BE MOSTLY CLOUDY AND DAYTIME TEMPERATURES ARE ONLY 
EXPECTED TO REACH THE UPPER 20S TO LOWER 30S.  ANOTHER LOBE OF 
ENERGY SWINGS THROUGH THURSDAY NIGHT AND THERE MAY BE SOME FLURRIES 
AGAIN BUT WILL WAIT AND SEE HOW MODELS ARE DOING WITH THIS TONIGHT 
AND DURING THE DAY THURSDAY FIRST BEFORE INSERTING JUST YET.  
TEMPERATURES WILL REMAIN QUITE COLD WITH LOWS FORECAST TO RANGE FROM 
10 TO 15 DEGREES.

LONG TERM...12Z FRIDAY THROUGH WEDNESDAY.  THE MAIN ISSUES IN THE 
EXTENDED WILL BE TEMPERATURES AND THEN THE CHANCE OF PRECIPITATION 
SUNDAY THROUGH TUESDAY.  A COLD START TO THE EXTENDED PERIOD IS 
EXPECTED WITH NORTHERLY FLOW IN PLACE ALOFT AND H85 TEMPERATURES 
AROUND -12C FOR FRIDAY. TEMPERATURES SHOULD WARM A BIT ON SATURDAY 
AS A RIDGE ACROSS THE WESTERN UNITED STATES MOVES EAST.  THIS ALLOW 
H85 WARM AIR ADVECTION TO TAKE HOLD...AND H85 TEMPERATURES RESPOND 
BY RISING TO NEAR -3C FOR SATURDAY.  THE COLDER AIR DOES NOT TAKE 
LONG TO COME BACK AS AN UPPER WAVE OVER THE NORTHERN ROCKIES SLIDES 
SOUTHEAST BY SATURDAY NIGHT.  THIS IN TURN DROPS ANOTHER COLD FRONT 
INTO THE CENTRAL PLAINS WITH H85 TEMPERATURES AGAIN FALLING TO NEAR 
-10C FOR SUNDAY.  THERE COULD ALSO BE A LITTLE LIGHT SNOW OR 
FLURRIES WITH THE ARRIVAL OF THE COLD AIR ON SUNDAY...AND THE 
CURRENT FORECAST HAS THIS WELL COVERED WITH SMALL POPS.   

ANOTHER DRY PERIOD IS EXPECTED ON MONDAY WITH A FAIRLY FLAT/ZONAL 
FLOW ACROSS THE CENTRAL UNITED STATES.  THIS AGAIN DOES NOT LAST 
VERY LONG WITH ANOTHER UPPER WAVE ARRIVING MONDAY NIGHT INTO 
TUESDAY.  AHEAD OF THE THE WAVE THERE COULD BE SOME ISENTROPIC LIFT 
(280-285K SFCS) WHICH MAY ALSO HELP BRING A CHANCE OF SNOW TO MONDAY 
NIGHT.  THE SNOW CHANCE THEN CONTINUES INTO TUESDAY BEFORE EXITING 
FROM WEST TO EAST TUESDAY NIGHT.  THOUGH THE GFS LAST FEW 
DETERMINISTIC GFS RUNS AND THE 06Z NCEP/GFS ENSEMBLES TEND TO FOCUS 
THE BEST SNOW CHANCES ON MONDAY NIGHT...THE DETERMINISTIC ECMWF HAS 
NOT BEEN VERY CONSISTENT FROM RUN TO RUN.  IN FACT...THE 12Z ECMWF 
IS NEARLY DRY FOR MONDAY NIGHT AND GENERALLY SHOWS A BETTER CHANCE 
OF SNOW FOR TUESDAY.  FOR NOW...HAVE GENERALLY LEANED ON THE 
GFS...BUT THE DIFFERENCES BETWEEN THE ECMWF AND THE GFS HAS TENDED 
TO REDUCE CONFIDENCE A BIT IN THE OUTER PERIODS.      

&&

.GID WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
KS...NONE.
&&

$$