FXUS65 KCYS 280348
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
848 PM MST FRI NOV 27 2009

.UPDATE...MINOR ADJUSTMENTS TO TEMPERATURES...DEWPOINTS...WINDS
AND CLOUD COVER FOR THE REST OF THE NIGHT.   RUBIN

&&

.PREV DISCUSSION... /ISSUED 251 PM MST FRI NOV 27 2009/ 

SHORT TERM...TONIGHT THROUGH SUNDAY...UPPER RIDGE AXIS HAS MOVED 
OFF TO THE EAST THIS AFTERNOON WITH VERY WARM...DRY AND WINDY
CONDITIONS WIDESPREAD ACROSS THE CWA. COMBINATION OF GUSTS 30 TO
45 MPH TO THE LEE OF THE LARAMIE RANGE AND ALONG THE CHEYENNE
RIDGE WITH RHS OF 5 TO 15 PERCENT HEIGHTENED THE FIRE THREAT FOR
TODAY...BUT FUELS SEEM TO BE BELOW CRITICAL STATUS SO DID NOT ISSUE
ANY HIGHLIGHTS. WINDS WILL EASE THROUGH THE EVENING HOURS AND RHS
WILL IMPROVE OVERNIGHT DIMINISHING THE THREAT. WATER VAPOR IMAGERY
FROM THIS AFTERNOON SHOWS A SHARP UPPER TROUGH MOVING INTO THE
WESTERN US WITH ABUNDANT MOISTURE STREAMING INTO THE
INTERMOUNTAIN WEST IN STRONG SOUTHWEST FLOW ALOFT. THE MAIN JET
CORE WILL STAY NORTH OF THE CWA BUT WILL BE POSITIONED SUCH THAT
GOOD DIFFLUENCE ALOFT WILL SUPPORT BROAD SCALE LIFT THROUGH THE
DAY TOMORROW. THE MAIN PACIFIC FRONT WITH THIS SYSTEM LOOKS TO
PASS THROUGH THE REGION IN THE EARLY MORNING HOURS WITH GUSTY 
NORTHERLY UPSLOPE WINDS DEVELOPING IN ITS WAKE. THE COMBINATION OF
UPSLOPE WINDS AND UPPER LEVEL LIFT WILL PRODUCE SCATTERED AREAS
OF LIGHT SNOW SPREADING FROM NORTH TO SOUTH ACROSS THE CWA THROUGH
THE AFTERNOON AND EVENING. LITTLE ACCUMULATION IS EXPECTED OVERALL
WITH MAYBE A COUPLE OF INCHES IN THE SOUTHERN MOUNTAINS AND UP TO
A HALF INCH ELSEWHERE. THE SNOW WILL QUICKLY EXIT THE CWA BY
SUNDAY MORNING AND A COOLER AIRMASS WILL SETTLE IN AS SFC HIGH
PRESSURE BUILDS ACROSS THE NORTHERN ROCKIES. WILL SEE MAX TEMPS
FOR TOMORROW AND SUNDAY A GOOD 20 TO 25 DEGREES COOLER THAN THE
PAST COUPLE OF DAYS AS THE UPPER TROUGH TAKES ITS TIME MOVING TO
THE EAST.

LONG TERM...SUNDAY NIGHT THROUGH FRIDAY...WILL CONTINUE TO FAVOR 
THE ECMWF OVER THE GFS AS THE GFS LOOKS TOO PROGRESSIVE AND IS AN 
OUTLIER VS OTHER MODELS/ENSEMBLES.  THIS CONTINUES TO FAVOR MILD AND 
DRY WEATHER OVER THE CWA TO CLOSE OUT THE MONTH AS A RATHER FLAT 
UPPER RIDGE PASSES ACROSS THE REGION.  BY LATE TUESDAY AND TUESDAY 
NIGHT SIGNIFICANT COLD FRONT SHOULD SWEEP ACROSS THE CWA LIKELY 
BRINGING A QUICK SHOT OF MAINLY LIGHT SNOWS TUESDAY NIGHT AND 
WEDNESDAY AS WELL AS MUCH COLDER AIR.  SECOND REINFORCING SURGE OF 
COLD AIR SHOULD REACH THE CWA BY LATE THURSDAY AS UPPER SYSTEM 
ROTATES AROUND LARGE UPPER LOW NEAR THE GREAT LAKES AREA.  RATHER 
DRY AIRMASS SHOULD LIMIT PRECIPITATION POTENTIAL WITH MTNS HAVING 
BEST SHOT AT SOME ADDITIONAL LIGHT SNOWS MAINLY ON THURSDAY.  MAINLY 
DRY AND A LITTLE WARMER FRIDAY AS COLD SFC HIGH SAGS INTO THE SRN 
PLAINS AND SFC FLOW TURNS DOWNSLOPE. 

AVIATION...VFR CONDITIONS EXPECTED TO CONTINUE THROUGH THIS EVENING 
WITH JUST SOME MID AND HIGH CLOUDS MOVING ACROSS THE CWA.
SOUTHWEST WINDS WILL CONTINUE TO BE QUITE BREEZY THROUGH THIS
AFTERNOON BEFORE DIMINISHING THIS EVENING. A COLD FRONT WILL MOVE
SOUTH ACROSS THE REGION EARLY TOMORROW MORNING WITH LIGHT SNOW
SHOWERS EXPECTED TO OCCUR DURING THE AFTERNOON AND EVENING. WINDS
WILL VEER TO THE NORTH BEHIND THE FRONT AND WILL GUST 15 TO 20 KT
IN THE MORNING EAST OF THE LARAMIE RANGE. CIGS AND VSBYS WILL
DECREASE TO MVFR BY THE EARLY AFTERNOON IN SNOW SHOWERS...WITH
SOME LOCAL IFR CONDITIONS POSSIBLE IN THE HEAVIER SHOWERS.

FIRE WEATHER...STRONG DOWNSLOPE WINDS HAVE CONTRIBUTED TO VERY WARM 
AND DRY CONDITIONS MAINLY TO THE LEE OF THE LARAMIE RANGE AND ALONG 
THE CHEYENNE RIDGE THIS AFTERNOON. SOUTHWEST WINDS ARE GUSTING 20 TO 
35 MPH WITH SOME AREAS SUCH AS NEAR BORDEAUX GUSTING TO 45 MPH. 
RELATIVE HUMIDITIES HAVE DROPPED TO 5 TO 15 PERCENT ACROSS THIS AREA 
AS WELL WHICH HAS INCREASED FIRE DANGER POTENTIAL. HOWEVER...EXPECT 
WINDS TO DIMINISH THROUGH THE LATER AFTERNOON AND EVENING WITH
GOOD RELATIVE HUMIDITY RECOVERIES TONIGHT WHICH WILL DIMINISH THE
THREAT. A COLD FRONT MOVING THROUGH THE AREA EARLY TOMORROW
MORNING WILL BRING MUCH COOLER TEMPERATURES AND LIGHT SNOW SHOWERS
FOR TOMORROW AND SUNDAY.

&&

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

&&

$$

SHORT TERM/AVIATION...RJM
LONG TERM...RE