FXUS63 KGID 061127
AFDGID
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HASTINGS NE
527 AM CST SUN DEC 6 2009
.AVIATION...12Z TAF. RADAR AND SURFACE OBSERVATIONS INDICATE THAT
SNOW IS ALREADY APPROACHING FROM THE WEST. EXPECT THAT THE SNOW
WILL START OFF LATE IN THE MORNING. THE SNOW WILL INCREASE DURING
THE AFTERNOON BEFORE ENDING OVERNIGHT. IFR CONDITIONS ARE EXPECTED
FOR A TIME. THE BEST CHANCE FOR THE LOWEST CEILING AND
VISIBILITIES WILL BE LATE IN THE AFTERNOON. HAVE TRIED TO NARROW
DOWN THE TIME...BUT WILL HAVE TO WATCH IT COULD BE A BIT EARLIER.
THE SNOW WILL COME TO AN END LATE TONIGHT BUT CEILINGS WILL
REMAIN MVFR.
&&
.PREV DISCUSSION... /ISSUED 430 AM CST SUN DEC 6 2009/
DISCUSSION...VERY CHALLENGING FORECAST WITH TWO WINTER SYSTEMS...
THE 2ND OF WHICH IS LOOKING MORE AND MORE LIKE A MAJOR WINTER
STORM.
WINTER WEATHER ADVISORY WAS HOISTED FOR TODAY...MAINLY FOR THE
FACT AVERAGE SNOW AMOUNTS COULD APPROACH 3 INCHES. THE MODELS
HAVE BEEN VERY DILIGENT IN THEIR MOVEMENT OF A SHORTWAVE ACROSS
THE CENTRAL PLAINS TODAY. AIR IS QUITE DRY IN THE LOW LEVELS...
ALTHOUGH WE HAVE SEEN A GRADUAL MOISTENING OVERNIGHT. DENVER
RADAR IS FINALLY SHOWING SNOW BECOMING MORE WIDESPREAD...AND
ANTICIPATE THIS TO MOVE INTO THE THE CWFA BY LATE MORNING AND
CONTINUE THROUGH THIS EVENING. SNOW RATIOS AVERAGING AROUND 18
TO 1 WILL BE THE KEY FACTOR...AS QPF FORECASTS CONTINUE IN THE
0.10 TO 0.20 RANGE. THAT SPELLS 3 INCHES ON AVERAGE...WITH LESSER
AMOUNTS ON THE SOUTH SIDE. REALLY WOULDN/T BE SURPRISE IF THE
MAIN BAND AVERAGED OUT TO 3 INCHES...WITH A FEW REPORTS OF 4 OR 5
INCHES. HAVE INCLUDED SOUTH CENTRAL NEBRASKA IN A WINTER WEATHER
ADVISORY FOR THE SNOW. NORTH CENTRAL KANSAS LOOKED LIKE LESSER
AMOUNTS. THERE IS SOME CONCERN OF FREEZING DRIZZLE THE FURTHER
SOUTH ONE GOES...AND CENTRAL KANSAS HAS AN ADVISORY FOR SUCH
CONDITIONS. IT MAY TURN OUT...OUR ADVISORY WILL NEED TO BE
EXPANDED TO FILL THE GAP...BUT BELIEVE THAT COULD BE DONE WHEN
MORE PRECISE SNOW BAND SETS UP...OR BETTER HANDLE ON POTENTIAL
FREEZING DRIZZLE IMPACTS IS MADE AWARE.
THE 2ND SYSTEM IS REALLY LOOKING LIKE A MAJOR WINTER STORM.
THE MODELS REMAIN IN FIRM AGREEMENT...A SHARP...SLIGHTLY
NEGATIVE TILT WAVE WILL MOVE ACROSS THE AREA TUESDAY. AHEAD
OF THE MAIN WAVE...WIDESPREAD ISENTROPIC LIFT WILL START
BY LATE MONDAY EVENING. BOTH THESE SCENARIO WILL ADD UP
TO A SIGNIFICANT SNOWFALL. SIMILARITIES IN THE MODELS ARE
STRONG...AND THE TRACK OF A H85-700 LOW WILL BE FAVORABLE
FOR A FRONTOGENETIC BAND IN OUR CWFA. MOISTURE IS PRETTY
IMPRESSIVE...AND MODEL QPFS CONTINUE TO BEAR THAT OUT WITH
AMOUNTS IN EXCESS OF 0.75" ACROSS A GOOD CHUNK OF THE CWFA.
LATEST RUNS OF SUGGEST A LITTLE MORE WARM AIR WILL GET SHOVED
FURTHER NORTH TUESDAY...AND THAT MAY PUSH SNOW RATIOS DOWN A
TOUCH (13 OR 14 TO 1 FOR A TIME)...BUT SNOW RATES COULD BE
1 TO 2 INCHES AN HOUR FOR 3 OR 4 HOURS TUESDAY AFTERNOON
AND EARLY TUESDAY EVENING. FINALLY...STOUT NORTH WINDS
WILL CAUSE BIG TIME BLOWING/DRIFTING SNOW ISSUES...ESPECIALLY
TUESDAY NIGHT...SOME OF WHICH COULD CARRY OVER INTO EARLY
WEDNESDAY. IF THERE IS ONE THING WHICH MAY BE A LIMITING
FACTOR...THAT COULD BE THE QUICK MOVEMENT OF THE STORM AND
LACK OF A CLOSED MID LEVEL LOW. DON/T THINK EITHER OF THOSE
ARE ENOUGH TO PRECLUDE THE NEED FOR A WINTER STORM WATCH
BEGINNING MONDAY NIGHT...AND CONTINUING THROUGH TUESDAY NIGHT.
THIS STORM HAS THE POTENTIAL FOR WIDESPREAD SNOWS OF 6 TO 10
INCHES (LOCALLY MORE) AND WHEN COMBINED WITH STRONG WINDS BY
TUESDAY EVENING...FLAT DANGEROUS WINTER STORM CONDITIONS.
FINALLY...AS THIS STORM IS LONG GONE BY WEDNESDAY AFTERNOON...
WE ARE LEFT WITH FRIGID COLD TEMPERATURES...LIKELY AROUND OR
EVEN BELOW ZERO WEDNESDAY NIGHT.
&&
.GID WATCHES/WARNINGS/ADVISORIES...
NE...WINTER WEATHER ADVISORY FROM 9 AM THIS MORNING TO 9 PM CST THIS
EVENING FOR NEZ039>041-046>049-060>064-072>077-082>087.
WINTER STORM WATCH FROM LATE MONDAY NIGHT THROUGH LATE TUESDAY
NIGHT FOR NEZ039>041-046>049-060>064-072>077-082>087.
KS...WINTER STORM WATCH FROM LATE MONDAY NIGHT THROUGH LATE TUESDAY
NIGHT FOR KSZ005>007-017>019.
&&
$$
