FXUS65 KCYS 010955
AFDCYS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
255 AM MST TUE DEC 1 2009
.SHORT TERM...TODAY THROUGH WEDNESDAY NIGHT...
RETURN TO MUCH COLDER WEATHER BEGINS TODAY AS STRONG COLD FRONT
CURRENTLY OVER SOUTHEASTERN MONTANA PLUNGES SOUTHWARD AND ACROSS THE
CWA THIS MORNING INTO EARLY AFTERNOON. HIGH TEMPERATURES TODAY
TRICKY AS MAXS WILL BE REACHED JUST BEFORE FROPA WITH TEMPERATURES
LIKELY FALLING DURING THE AFTERNOON IN GOOD CAA. EXPECT AN GENERAL
AREA OF LIGHT SNOW TO ALSO SHIFT SOUTH ACROSS MUCH OF THE CWA BEHIND
THE FRONT...REACHING THE NORTHERN CWA EARLY THIS AFTERNOON AND
SPREADING ACROSS MUCH OF THE REMAINDER LATER THIS AFTERNOON INTO
TONIGHT. NOT A LOT OF SNOW AS MOISTURE LIMITED BUT A GENERAL INCH
OR TWO EXPECTED OVER MAINLY THE PLAINS OF WY WITH A BIT MORE OVER
THE MTNS. VERY COLD AIR WILL CONTINUE TO POUR OUT OF CENTRAL CANADA
SOUTHWARD INTO THE REGION THROUGH WEDNESDAY NIGHT AS LARGE UPPER
TROF WITH A COUPLE EMBEDDED UPPER LOWS EXTEND FROM SOUTHEAST CANADA
INTO THE NORTHERN PLAINS KEEPING THICKNESSES QUITE LOW OVER THE AREA
UNDER NORTHERLY UPPER FLOW. SNOW SHOULD TAPER OFF SOMEWHAT
WEDNESDAY THEN MAY INCREASE A BIT WEDS NIGHT AS WEAK IMPULSES ROTATE
OVER THE HIGH PLAINS AROUND WESTERN PERIPHERY OF UPPER LOW OVER
MINNESOTA
.LONG TERM...THURSDAY THROUGH MONDAY...
THURSDAY...BITTERLY COLD TEMPERATURES CONTINUE AS SURFACE ARCTIC
HIGH PRESSURE RESIDES ACROSS MONTANA AND WYOMING WITH POLAR VORTEX
ALOFT ACROSS THE NORTHERN PLAINS STATES AND NORTH FLOW ALOFT ACROSS
WYOMING. NEAR RECORD LOW MAXIMUM TEMPERATURES AT RAWLINS...LARAMIE
AND CHEYENNE...WITH THESE RECORDS INCLUDING 18 AT RAWLINS IN 1978...
18 AT LARAMIE IN 1978 AND 16 AT CHEYENNE IN 1873. ISOLATED TO
SCATTERED SNOW SHOWERS ACROSS THE MOUNTAINS AND NEAR THE PINE RIDGE
IN CYCLONIC FLOW ALOFT AND WITH ADEQUATE LOW AND MID LEVEL MOISTURE.
FRIDAY...MODERATING HIGH TEMPERATURES AS FLOW ALOFT BACKS TO
NORTHWEST AND 1000-500 MB THICKNESSES INCREASE TO 5350 METERS IN
ADVANCE OF NEXT APPROACHING SHORTWAVE TROUGH FROM WESTERN CANADA AND
NORTHERN MONTANA. DRY WITH DECREASING LOW AND MID LEVEL MOISTURE AND
OROGRAPHICS.
SATURDAY...FLOW ALOFT BACKS TO WEST AS SEEN ON THE GFS AND ECMWF.
CONTINUED COOL WITH HIGH TEMPERATURES IN THE MID 20S TO MID 30S.
SCATTERED OROGRAPHIC SNOW SHOWERS ACROSS AND NEAR THE MOUNTAINS IN
MOIST WEST FLOW ALOFT.
SUNDAY...BROAD TROUGH ALOFT PERSISTS ACROSS OUR PORTION OF THE
ROCKIES AS SEEN ON THE GFS AND ECMWF. COOLER AGAIN WITH HIGH
TEMPERATURES IN THE UPPER TEENS TO NEAR 30 DEGREES WITH 1000-500 MB
THICKNESSES FALLING TO 5160 METERS. ISOLATED TO SCATTERED SNOW
SHOWERS WITH ENOUGH LOW AND MID LEVEL MOISTURE...UPSLOPE AND COLD
AIR ADVECTION WRINGING OUT THE MOISTURE.
MONDAY...01/00Z GFS AND 01/00Z ECMWF DIFFER WITH 500 MB PATTERN WITH
ECMWF SHOWING A LOW AMPLITUDE RIDGE ACROSS IDAHO AND UTAH WHILE GFS
HAS AN UPPER TROUGH ACROSS THESE STATES. IN ANY EVENT...WILL AT
LEAST SEE ISOLATED TO SCATTERED OROGRAPHIC SNOW SHOWERS IN MOIST
FLOW ALOFT ACROSS AND NEAR OUR MOUNTAINS.
&&
.AVIATION...VFR CONDITIONS AREAWIDE EARLY THIS MORNING WILL
DETERIORATE TO MVFR/IFR CONDITIONS DUE TO LOW CIGS FROM NORTH TO
SOUTH LATE THIS MORNING AND AFTERNOON BEHIND SFC COLD FRONT. MAINLY
MVFR/IFR CONDITIONS TONIGHT ESPECIALLY OVER SE WY WITH LOW CIGS AND
AREA OF LIGHT SNOW. VFR DEVELOPING ON WEDNESDAY WITH LOCALIZED MVFR
IN SNOW SHOWERS ACROSS THE SNOWY RANGE.
&&
.FIRE WEATHER...NO FIRE WEATHER CONCERNS EXPECTED THROUGH WEDNESDAY.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...NONE.
NE...NONE.
&&
$$
SHORT TERM/AVIATION/FIRE WEATHER...RE
LONG TERM...RUBIN
