FXUS65 KCYS 301137 CCA
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
400 AM MST MON NOV 30 2009

.SHORT TERM...TODAY THROUGH TUESDAY NIGHT...
SATELLITE LOOP SHOWS A GOOD DEAL OF HIGH CLOUDS ACCOMPANYING A 
WEAK SHORTWAVE TROUGH OVER MT/WY CURRENTLY.  HOWEVER...THESE
CLOUDS SHOULD BE LONG GONE BY LATE MORNING AS THE SHORTWAVE MOVES
OFF TO THE EAST.  FOG FROM 24 HOURS AGO HAS NOT REDEVELOPED BETWEEN
KLAR AND KRWL APPARENTLY DUE TO THE CLOUDS AND MIXING FROM THE 
SHORTWAVE.  THE DOWNSLOPE WINDS AND WARMING H7 TEMPS WILL MEAN
WARMER MAXS TODAY.  FLOW ALOFT WILL BACK SLIGHTLY FROM NW TODAY
TO WNW TONIGHT AHEAD OF CLIPPER SYSTEM SWEEPING IN TUE.  IT WILL
BE MOSTLY CLEAR THIS EVENING THEN SOME CLOUDS WILL SPREAD INTO
WESTERN AND NORTHERN PARTS OF CWA LATER MONDAY NIGHT.  BIGGER WX 
CHANGES AWAIT FOR TUESDAY AS COLD FRONT PUSHES ACROSS THE CWA 
TUE MORNING AND EARLY AFTERNOON.  NORTHERLY UPSLOPE WINDS BEHIND
THE FRONT WILL COMBINE WITH SOME UPPER DYNAMICS AND LEFT FRONT
QUAD OF UPPER JET TO CAUSE A FAIRLY WIDESPREAD AREA OF LIGHT SNOW
TO SPREAD SOUTH OVER THE CWA MAINLY TUE NIGHT BUT STARTING IN THE NW 
QUARTER OF THE CWA TUE AFTERNOON.  00Z MODEL RUNS ARE MORE AGGRESSIVE
WITH THIS IDEA...SO HAVE BOOSTED POPS WHICH WILL BE HIGHEST ALONG THE
FRONT RANGE IN SE WY AND LOWEST OVER THE NEBRASKA PANHANDLE AND THE
SW EDGE OF OUR CWA.  THIS WILL BE A QUICK HITTER THOUGH AS IMPROVING 
CONDITIONS WILL SPREAD FROM NORTH TO SOUTH LATE TUESDAY NIGHT...
LEAVING MUCH COLDER TEMPS FOR EARLY WEDNESDAY MORNING.

.LONG TERM...WEDNESDAY THROUGH SUNDAY...
MODELS SHOWING TYPICAL DIFFICULTIES IN HANDLING UPCOMING PATTERN 
CHANGE WHICH APPEARS WILL BRING MUCH COOLER WEATHER TO THE REGION 
AFTER A PERIOD OF MILD CONDITIONS.  RATHER COLD AND BREEZY 
CONDITIONS EXPECTED WEDNESDAY AS UPPER TROF MOVES THROUGH THE 
NORTHERN AND CENTRAL PLAINS WITH SOME MTN SNOW SHOWERS POSSIBLE.  
QUITE COOL CONDITIONS WILL PERSIST THROUGH THURSDAY AS AREA REMAINS 
UNDER NORTHERLY UPPER FLOW WITH FETCH INTO CENTRAL CANADA.  BRIEF 
RETURN OF MILDER AIR EXPECTED FRIDAY AS SHORT UPPER RIDGE TRANSLATES 
ACROSS THE AREA AND COLD SFC AIRMASS SLIDES OFF TO THE SOUTHEAST.  
MODELS QUITE DIVERGENT WITH SYSTEMS OVER THE WEEKEND WITH GFS 
BRINGING NEXT COLD UPPER LOW INTO THE NORTHERN HIGH PLAINS WHILE 
ECMWF KEEPS UPPER RIDGING IN PLACE OVER THE ROCKYS.  ECMWF SOMEWHAT 
OF AN OUTLIER AND WILL LEAN TOWARD THE GFS FOR NOW THOUGH NOT BE AS 
COLD.  LACK OF ORGANIZED SFC SYSTEMS AND MOISTURE SHOULD PRECLUDE 
MUCH IN THE WAY OF PCPN THOUGH SOME LIGHT SNOWS POSSIBLE ESPECIALLY 
OVER THE MTNS WITH NEXT PUSH OF COLDER AIR SATURDAY.    

&&

.AVIATION...VFR CONDITIONS TODAY THROUGH TUESDAY MORNING.  MVFR AND
EVEN LOCAL IFR CEILINGS AND VSBYS IN LIGHT SNOW WILL SPREAD FROM 
NORTH TO SOUTH LATE TUESDAY AFTERNOON AND ESPECIALLY TUE EVENING.

&&

.FIRE WEATHER...THERE WILL BE LOCAL WINDY AREAS TODAY MAINLY ALONG
THE EAST SLOPES OF THE MOUNTAINS.  WHILE IT WILL BE WARMER TODAY...
MINIMUM HUMIDITIES WILL ONLY BE FROM 20-30 PERCENT IN MOST AREAS.  
COLDER TEMPS WILL SPREAD OVER THE DISTRICT TUESDAY THROUGH WEDNESDAY.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...NONE.
NE...NONE.

&&

$$

SHORT TERM/AVIATION/FIRE WEATHER...JLH
LONG TERM...RE