FXUS65 KCYS 112127
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
325 PM MDT SUN MAY 11 2008

.SHORT TERM...TONIGHT THROUGH TUE...
A LOW AMPLITUDE UPPER RIDGE CURRENTLY OVER THE REGION WILL MOVE EAST
TONIGHT WITH THE FLOW ALOFT BACKING TO SOUTHWESTERLY. A NEGATIVELY
TILTED UPPER TROUGH WILL APPROACH FROM THE WEST MON WITH THE TROUGH
AXIS OVER NORTHWEST WY BY LATE MON AFTERNOON. THE TROUGH AXIS WILL
MOVE OVER THE FORECAST AREA LATE MON NIGHT AND SHOULD BE JUST EAST
OF THE AREA BY LATE TUE AS THE TROUGH SPLITS. TONIGHT WILL BE DRY
AND RELATIVELY MILD ALTHOUGH MID LEVEL MOISTURE WILL INCREASE FROM
THE SOUTHWEST. A COLD FRONT WILL PUSH THROUGH THE FORECAST AREA MON
MORNING AND EARLY MON AFTERNOON. POSTFRONTAL WINDS WILL STRENGTHEN
AND MOISTEN. THE INCREASING MID AND LOW LEVEL MOISTURE WILL INTERACT
WITH POSITIVE VORTICITY ADVECTION TO TRIGGER SHOWERS ACROSS THE
FORECAST AREA MON AFTERNOON AND EVENING. RAIN WILL BECOME SNOW MON
NIGHT AND EARLY TUE MORNING OVER MOST OF THE AREA. TUE WILL BE
COOLER WITH A CONTINUED CHANCE OF SHOWERS...ALTHOUGH MOISTURE WILL
DECREASE FROM THE NORTH LATE TUE.

.LONG TERM...TUESDAY NIGHT THROUGH SUNDAY...CLEARING TUE EVENING
WILL BE SHORT-LIVED AS CLOUDS WILL INCREASE FROM THE NW EARLY WED
AHEAD OF NEXT SYSTEM MOVING DOWN ON NW FLOW ALOFT.  GFS IS ABOUT
4-6 HOURS FASTER THAN OTHER MODELS ON THIS SHORTWAVE TROUGH WHICH
MOVES OUT OF SW CANADA TUE NIGHT AND INTO NORTHERN ROCKIES WED.
SLIGHTLY SLOWER SPEED IN PREFERRED.  STILL...SOME RAIN SHOWERS WILL
SPREAD OVER NORTHERN AND WESTERN PARTS OF THE CWA BY NOON WED ALONG
AND BEHIND NEXT COLD FRONT...WITH SCATTERED SHOWERS AND A FEW TSTMS
WED AFTERNOON OVER ENTIRE CWA.  FLOW ALOFT WILL VEER TO NORTHERLY
WED NIGHT AND THURSDAY CAUSING SHORTWAVE TO STRETCH WITH VORTICITY
BECOMING MORE CHANNELED.  COOL AND UNSETTLED CONDITIONS CAN BE
EXPECTED TO LINGER WED NIGHT INTO THU NIGHT WITH AT LEAST SCATTERED
RAIN/SNOW SHOWERS.  DECREASING CLOUDS FRIDAY THOUGH A FEW RAIN/SNOW
SHOWERS COULD LINGER NEAR MOUNTAINS IN THE MORNING.  RISING UPPER
HEIGHTS ON FRIDAY WILL BRING WARMER TEMPS...AND THIS TREND WILL
CONTINUE OVER NEXT WEEKEND AS UPPER RIDGE BUILDS IN FROM THE WEST.

&&

.AVIATION...VFR CONDITIONS TONIGHT. AREAS OF MVFR CEILINGS AND
VISIBILITIES WILL DEVELOP WEST OF THE LARAMIE RANGE MON MORNING AND
WILL SPREAD EAST MON AFTERNOON AS SHOWERS DEVELOP ALONG AND BEHIND
A COLD FRONT.

&&

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

&&

$$

JR/JLH