FXUS65 KCYS 142027
AFDCYS

AREA FORECAST DISCUSSION...CORRECTED
NATIONAL WEATHER SERVICE CHEYENNE WY
125 PM MST MON DEC 14 2009

.SHORT TERM...TONIGHT THROUGH WEDNESDAY...
STATIONARY FRONT REMAINS FROM KIBM TO KEAN TO KDGW EARLY THIS 
AFTERNOON.  TEMPERATURES WERE SLOWLY MODERATING AS THE INVERSION 
SHALLOWS.  MOST OF THE CLOUDS HAVE DISSIPATED AS OF 19Z IN THE COLD
AIR MASS WITH THE EXPECTION OF AREAS TO THE NORTH OF THE PINE 
RIDGE.  THE BOUNDARY SHOULD WORK ITS WAY EAST TONIGHT AND TUESDAY
AS THE INVERSION BECOMES VERY SHALLOW BEHIND THE FRONT AND EVENTUALLY
IS GONE TUESDAY AFTERNOON.  TEMPERATURES WILL AGAIN BE CHILLY OVER 
THE EAST PART OF THE CWA TONIGHT WITH LOWS BELOW ZERO IN MANY AREAS
BELOW 4500 FEET MSL.  THE TEMPERATURES WILL THEN WARM FOR TUESDAY
OVER THE EAST PART OF THE CWA.  AREAS OF FOG AND POSSIBLE LOW CLOUDS
SHOULD FORM AFTER 06Z AT ELEVATIONS BELOW 4500 FEET AND PERSIST TIL
15Z TUESDAY.  TO THE WEST OF THE STATIONARY FRONT...TEMPERATURES ARE
MUCH WARMER AND WEST WINDS HAVE BEEN GUSTING AS HIGH AS 45 MPH.  
HEIGHTS ALOFT CONTINUE TO RISE OVER THE CWA THROUGH WEDNESDAY WITH A
BROAD RIDGE OVER THE ROCKIES ON WEDNESDAY.  TEMPERATURES WILL BE 
WARMER AND CONDITIONS DRY OVER THE ENTIRE CWA TUESDAY THROUGH 
WEDNESDAY.  SCATTERED LOWER AND MID CLOUDS CAN BE EXPECTED OVER 
CARBON AND ALBANY COUNTIES TUESDAY THROUGH WEDNESDAY.  THE MAIN 
CONCERN FOR THIS PART OF THE FORECAST WILL BE WINDS ALONG AND WEST 
OF THE LARAMIE RANGE.  FLOW ALOFT INCREASES LATE TONIGHT AND 
CONTINUES THROUGH EARLY TUESDAY NIGHT OVER THE CWA.  IN ADDITION...A 
SURFACE LOW PRESSURE TROUGH FORMS OVER FAR EASTERN WYOMING.  MODELS
ALL PLACE THE TIGHTEST SURFACE PRESSURE GRADIENT AND STRONGEST 700
MB WINDS OVER THE CWA TUESDAY AND EARLY TUESDAY NIGHT.  THE LOW
LEVEL HIEIGHT DIFFERENCES ACROSS THE CWA ARE FAVORABLE ON THE SREF 
AND GFS DURING THAT TIME...WITH THE NAM MORE LIKE TUESDAY AFTERNOON
AND TUESDAY NIGHT.  WILL ISSUE A HIGH WIND WATCH FOR THE NORTHWEST
PART OFN THE CWA...INCLUDING THE WIND CORRIDOR AND THE NORTH LARAMIE
RANGE FOR TUESDAY AND EARLY TUESDAY NIGHT.  GRADIENTS RELAX SOME AND
WINDS ALOFT DIMINISH BY WEDNESDAY AND SO WINDS SHOULD NOT BE AS 
STRONG OVER THE CWA.  

.LONG TERM...WEDNESDAY NIGHT THROUGH SUNDAY NIGHT...12Z MODELS 
REMAIN INCONSISTENT WITH HANDLING THE SHORTWAVE TROUGH THAT 
TRAVERSES ACROSS THE US WEDNESDAY NIGHT THROUGH FRIDAY NIGHT. THE 
GFS IS NOT AS DEEP AND MOVES THE MAIN PIECE OF ENERGY ACROSS THE 
CENTRAL PLAINS. THE ECMWF RESOLVES A STRONGER WAVE AND MOVES IT 
ACROSS THE ROCKY MOUNTAINS. THE NAM AND CANADIAN MODELS HAVE A 
SOLUTION SOMEWHERE IN THE MIDDLE. SO BASICALLY TOOK A MIDDLE GROUND 
APPROACH TO THE FORECAST...CLOSEST TO THE CANADIAN SOLUTION. THE 
SHORTWAVE ENERGY WILL MOVE ONSHORE INTO THE PACIFIC NORTHWEST 
WEDNESDAY NIGHT AND WILL INDUCE WIDESPREAD HEIGHT FALLS ACROSS THE 
WESTERN US. WITH SURFACE HIGH PRESSURE PERSISTING OVER THE 
ROCKIES...WILL SEE BREEZY WINDS CONTINUE ACROSS SOUTHEAST WYOMING 
THROUGH THURSDAY MORNING. THE UPPER WAVE WILL BEGIN TO DIG SOUTHEAST 
ACROSS THE ROCKIES ON THURSDAY WITH A COLD FRONT MOVING THROUGH THE 
CWA LATE THURSDAY. A JET STREAK ON THE WESTERN SIDE OF THE TROUGH 
WILL MOVE THROUGH WYOMING AT THIS TIME SO THE COMBINATION OF SFC 
UPSLOPE FLOW AND DIFFLUENCE ALOFT WILL PRODUCE SCATTERED SHOWERS 
THURSDAY AFTERNOON THROUGH FRIDAY MORNING...MOVING NORTHWEST TO 
SOUTHEAST ACROSS THE CWA. MAX TEMPS ON THURSDAY WILL BE IN THE 40S 
ACROSS THE PLAINS WITH 20S AND 30S IN THE MOUNTAINS SO EXPECT RAIN 
SHOWERS IN THE EAST WITH SNOW IN THE WEST...BECOMING ALL SNOW AFTER 
SUNSET. THIS SYSTEM LOOKS TO BE A QUICK MOVER SO ONLY LIGHT 
ACCUMULATIONS...IF ANY AT ALL...ARE EXPECTED. FRIDAY WILL BE DRIER 
AND COOLER IN NW FLOW ALOFT AS HIGH PRESSURE BUILDS INTO THE 
REGION...WITH BREEZY NW WINDS AT THE SURFACE. MODELS THEN DIFFER 
GREATLY WITH THE PATTERN FOR THE WEEKEND. THE ECMWF SHOWS A 
PRESISTENT AND POSITIVELY TILTED RIDGE OVERHEAD. THE CANADIAN KEEPS 
STRONG NW FLOW ALOFT. THE GFS BRINGS ANOTHER SHORTWAVE INTO THE 
PACIFIC NORTHWEST. WITH THESE MAJOR DIFFERENCES...MADE LITTLE TO NO 
CHANGES TO THE CURRENT FORECAST OF COOLER...DRIER AND BREEZY 
CONDITIONS THROUGH THE WEEKEND.

&&

.AVIATION...AFTER 06Z TONIGHT AREAS OF MVFR VISIBILITIES AND SOME
MVFR CEILINGS WILL REDEVELOP OVER AREAS OF THE CWA BELOW 4500 FEET
MSL.  THOSE CONDITIONS WILL PERSIST THROUGH 15Z TUESDAY.  OTHERWISE
VFR CONDITIONS CAN BE EXPECTED OVER THE CWA THROUGH WEDNESDAY WITH 
THE EXPECTION OF AREAS OF MVFR CEILINGS OVER CARBON COUNTY MAINLY
DURING THE DAYTIME HOURS.  WESTERLY SURFACE WINDS WILL BE STRONG 
THROUGH WEDNESDAY ALONG AND WEST OF THE LARAMIE RANGE.  SOME GUSTS
WILL BE OVER 50 KNOTS ESPECIALLY TUESDAY AND EARLY TUESDAY NIGHT.
FLOW ALOFT REMAINS FAVORABLE TO PRODUCE MOUNTAIN WAVES THROUGH 
TUESDAY NIGHT TO THE LEE OF THE SNOWY RANGE AND LARAMIE PEAK.

&&

.FIRE WEATHER...GUSTY WESTERLY WINDS ALONG AND WEST OF THE LARAMIE
RANGE WILL CONTINUE THROUGH WEDNESDAY.  MINIMUM RELATIVE HUMIDITY
VALUES WILL DROP TO BELOW 20 AND 30 PERCENT IN AREAS JUST TO THE 
EAST OF THE LARAMIE RANGE TUESDAY AND WEDNESDAY AFTERNOON AS THE
TEMPERATURES RISE TO ABOVE NORMAL.  RECENT SNOWFALL WILL MINIMIZE
FIRE WEATHER CONCERNS OVER THE CWA THROUGH THE END OF THE WEEK. 

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...HIGH WIND WATCH FROM 5 AM TUESDAY TO 11 PM TUESDAY NIGHT FOR
     WYZ103>106..WYZ110.
NE...NONE.

&&

$$

WEILAND/RJM