FXUS63 KGID 071145
AFDGID

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HASTINGS NE
545 AM CST MON DEC 7 2009

.AVIATION...06Z TAF. KGRI IN THE CALM BEFORE THE STORM THIS
MORNING AS MAINLY CLEAR SKIES IN THE AREA...LIGHT WINDS AND
VFR CONDITIONS. CLOUDS ALREADY ON THE MOVE FROM THE SOUTHWEST
WILL ENTER THE GRAND ISLAND LATE THIS MORNING PERIOD MVFR CIGS
THIS AFTERNOON. MVFR TO EVENTUALLY IFR CONDITIONS WILL SET UP
THIS EVENING WITH SNOW BEGINNING AND VSBYS DROPPING. THIS WILL
BE THE FIRST PART OF THE 24 TO 30 HOUR EVENT WHICH WILL RESULT
IN WIDESPREAD IFR/LIFR CONDITIONS. 

&&

.PREV DISCUSSION... /ISSUED 316 AM CST MON DEC 7 2009/ 

DISCUSSION...ATTENTION IS ON THE APPROACHING WINTER STORM SYSTEM
BEGINNING THIS EVENING AND LASTING THROUGH TUESDAY NIGHT. WATER
VAPOR IMAGERY DEPICTED A BROAD TROUGH FROM MANITOBA SOUTH AND WEST
TO NORTHERN CALIFORNIA. AN ARCTIC AIRMASS WAS ENTRENCHED ACROSS
THE NORTHERN AND CENTRAL PLAINS AND H85 TEMPS WERE ON THE ORDER OF
-15C EARLY THIS MORNING. THE RECENT SNOWFALL ON SUNDAY COMBINED
WITH THE ARCTIC AIRMASS AND GOOD RADIATIONAL CONDITIONS HAVE
ALLOWED TEMPS TO PLUMMET TO THE SINGLE DIGITS. RESIDUAL CLOUD
COVER IN OUR SOUTHEAST HAS HELD TEMPS IN THE TEENS SO FAR.

THE WESTERN CONUS TROUGH WILL DIG SOUTH AND TRANSLATE EASTWARD
TODAY/TONIGHT AND REACH COLORADO EARLY TUESDAY. AHEAD OF THE
APPROACHING SYSTEM...ISENTROPIC LIFT BEGINS TO INCREASE DURING THE
AFTERNOON TODAY AS INDICATED ON THE 290K SURFACE. MODEL FORECAST
SOUNDINGS SATURATE THE COLUMN BY LATE AFTN/EVENING WITH PCPN TYPE
AS AN ALL SNOW EVENT ACROSS OUR CWA. A PROLONGED PERIOD OF LIFT IS
INDICATED FROM THE ONSET ROUGHLY BETWEEN 00Z AND 06Z TUES UNTIL
GENERALLY BETWEEN 00Z AND 06Z WEDNESDAY...GIVE OR TAKE A FEW
HOURS. WE ARE LOOKING AT AROUND A 24 HOUR PERIOD OF SNOWFALL WHERE
SNOW RATIOS COULD RANGE ANYWHERE FROM 10 TO 24 TO ONE DEPENDING ON
THE HOUR...BUT FOR SIMPLICITY SAKE HAVE WENT WITH AN AVERAGE SNOW
RATIO OF 15 TO ONE. MODELS ARE IN DECENT AGREEMENT WITH THE H7
CLOSING OFF IN CO BY 12Z TUESDAY WITH THE TRACK OF THE H7 LOW
PROGRESSING EASTWARD ACROSS KANSAS DURING THE DAY TUESDAY...THEN
THE SYSTEM DEPARTS INTO THE UPPER MIDWEST TUESDAY NIGHT. THE TRACK
OF THE LOW PLACES OUR KANSAS COUNTIES AND THE SOUTHERN TWO THIRDS
OF OUR NEBRASKA CWA WITH THE GREATEST POTENTIAL FOR SIGNIFICANT
SNOWFALL...HOWEVER REALISTICALLY WIDESPREAD SNOWFALL WITH
SIGNIFICANT AMOUNTS ARE EXPECTED ACROSS OUR ENTIRE CWA. THE HIGH
SNOW RATIOS AND LONG DURATION OF THE EVENT WILL LEAD TO SNOWFALL
AMOUNTS IN THE 6 TO 12 INCH RANGE AND BASED ON CURRENT TRENDS OUR
SOUTHEAST ZONES MAY SEE AMOUNTS IN EXCESS OF 12 INCHES.

WINDS WILL BECOME AN INCREASING CONCERN BEGINNING TUESDAY AFTERNOON 
AS THE SURFACE CYCLONE DEEPENS IN COLORADO AND TRACKS EAST/NORTHEAST 
ALONG THE KS/OK BORDER INTO MO TUESDAY NIGHT. IN THE TIGHT
PRESSURE GRADIENT...WINDS WILL INCREASE FROM THE NORTH TO 20 TO
30 MPH AND GUSTS TO 40 MPH ARE POSSIBLE. THE STRONG WINDS
COMBINED WITH THE SNOW WILL CAUSE BLOWING AND DRIFTING SNOW AND
VERY POOR VISIBILITIES TUESDAY AFTERNOON INTO TUESDAY NIGHT. THE
SNOW TAPERS OFF TUESDAY NIGHT HOWEVER THE WINDS REMAIN FAIRLY
BREEZY WEDNESDAY MORNING UNTIL THE GRADIENT RELAXES. BLOWING AND
DRIFTING SNOW WILL STILL BE A HAZARD ON WEDNESDAY MORNING. WIND
CHILLS WILL BE ANOTHER ITEM IN THE WINTRY CONDITIONS AS THE COLD
TEMPERATURES COMBINE WITH THE WINDS TO PRODUCE WIND CHILL READINGS
OF 10 TO 20 DEGREES BELOW ZERO TUESDAY NIGHT.

WILL GO AHEAD WITH A WINTER STORM WARNING FOR THIS EVENT FOR THE
COMBINED FACTORS OF HEAVY SNOW...BLOWING AND DRIFTING SNOW AND
EXTREMELY COLD WIND CHILLS. TRAVEL IS NOT RECOMMENDED DURING THE
DURATION OF THE WARNING WHICH WILL RUN FROM 00Z TUESDAY UNTIL 12Z
WEDNESDAY.

&&

.GID WATCHES/WARNINGS/ADVISORIES...
NE...WINTER STORM WARNING FROM 6 PM THIS EVENING TO 6 AM CST 
     WEDNESDAY FOR NEZ039>041-046>049-060>064-072>077-082>087.

KS...WINTER STORM WARNING FROM 6 PM THIS EVENING TO 6 AM CST 
     WEDNESDAY FOR KSZ005>007-017>019.

&&

$$