Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 271054
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
354 AM MST THU NOV 27 2014

.SHORT TERM...(TODAY THROUGH SATURDAY)
ISSUED AT 350 AM MST THU NOV 27 2014

MAIN WEATHER STORY OVER THE NEXT FEW DAYS WILL BE THE MILD TEMPS AND
WINDY CONDITIONS ACROSS SOUTHEAST WY. WEST WINDS HAVE FINALLY BEGAN
TO DEVELOP AND INCREASE SINCE MIDNIGHT IN THE SOUTH LARAMIE RANGE
FOOTHILLS AND ALONG INTERSTATE 25 BETWEEN CHEYENNE AND WHEATLAND.
THIS HAS OCCURRED AS THE SFC TROUGH HAS SHIFTED EASTWARD TOWARD
THE WY-NE BORDER. WE SAW A 20 DEGREE WARMUP HERE IN CHEYENNE WITH
THE ONSET OF WESTERLY DOWNSLOPE WINDS. STILL CONFIDENT THAT WINDS
WILL APPROACH HIGH WIND CRITERIA IN BORDEAUX AND OTHER AREAS ALONG
THE SOUTH LARAMIE RANGE. A NAM SOUNDING AT BORDEAUX SHOWS WINDS
JUST OFF THE SFC INCREASING TO 45-50 KT BY SUNRISE. WHILE LOW
LEVEL LAPSE RATES WILL NOT BE GREAT DURING THE DAYTIME TODAY DUE
TO QUITE A BIT OF HIGH CLOUDINESS...THERE WILL STILL BE ENOUGH
MIXING TO CAUSE WINDS TO COME UP. IN ADDITION THE CAG-CPR GRADIENT
REMAINS AT 55-65 METERS THROUGH THE AFTERNOON. THUS...WILL KEEP
THE HIGH WIND WARNING GOING UNTIL 5 PM EVEN THROUGH THIS WILL
LIKELY BE A MARGINAL EVENT FOR THE WIND PRONE AREAS. HIGHS WILL BE
A GOOD 15 DEGREES WARMER THIS AFTN WITH THE WARM ADVECTION AND
WEST WINDS.

SYNOPTIC PATTERN REALLY DOES NOT CHANGE MUCH THROUGH SATURDAY.
UPPER LEVEL JET IS TO THE NORTH OF THE AREA WITH A STRONG LOW
LEVEL GRADIENT PERSISTING ACROSS SOUTHEAST WY. THE CAG-CPR
GRADIENT BOUNCES AROUND 60-65 FROM 00Z FRI THROUGH 00Z SUN. CROSS
SECTIONS ALSO SHOW 50-55 KT IN THE 750-700MB LAYER. THUS...THE
POTENTIAL FOR HIGH WINDS ACROSS THE WIND PRONE AREAS WILL CONTINUE
ALL THE WAY THROUGH SATURDAY. CONTEMPLATED EXTENDING THE HIGH WIND
WARNING INTO FRIDAY...HOWEVER WILL LET THE DAY SHIFT MAKE THAT
CALL AS THEY MONITOR WINDS DURING THE DAYTIME. IT IS STILL LOOKING
LIKE A PROLONGED EVENT FOR PLACES LIKE ARLINGTON AND BORDEAUX WITH
THE WINDS FLUCTUATING AROUND HIGH WIND CRITERIA. THE LOW LEVEL
GRADIENTS AND WINDS ALOFT DO NOT SUPPORT WIDESPREAD GUST POTENTIAL
ABOVE 60-65 MPH. WITH A LACK OF GOOD MIXING THROUGH SATURDAY...DO
NOT SEE HIGH WINDS OUTSIDE OF THE WIND PRONE AREAS BUT IT WILL
DEFINITELY BE WINDY. HAVE TEMPS RISING ANOTHER 5 DEGREES FOR
FRIDAY AND LEVELING OFF ON SATURDAY. A WARM ENDING TO AN OTHERWISE
COLD MONTH OF NOVEMBER.

.LONG TERM...(SATURDAY NIGHT THROUGH WEDNESDAY)
ISSUED AT 350 AM MST THU NOV 27 2014

MINOR DIFFERENCES ARE NOTED WITH THE 00Z/06Z MODEL GUIDANCE FOR
THE LATTER PART OF THE HOLIDAY WEEKEND. NEXT UPPER TROUGH DIGS
SOUTHEAST THROUGH THE NORTHERN ROCKIES AND PLAINS SUNDAY WITH AN
ACCOMPANYING CANADIAN COLD FRONTAL PASSAGE. IT WILL BE QUITE WINDY
FOR THE WIND PRONE AREAS SATURDAY NIGHT AND SUNDAY MORNING...SLOWLY
DECREASING THROUGH THE AFTERNOON. AFTER UNSEASONABLY MILD TEMPERATURES
SATURDAY...SUNDAY/S HIGHS WILL BE 20-25 DEGREES COLDER. THE FRONT
STALLS ALONG THE FRONT RANGE SUNDAY AFTERNOON. PACIFIC MOISTURE
WILL OVERRUN THE SHALLOW COLD DOME ACROSS THE HIGH PLAINS WITH
RAIN AND SNOW DEVELOPING. MOIST UPSLOPE WILL PRODUCE WIDESPREAD
MIXED PRECIPITATION ALONG AND WEST OF THE LARAMIE RANGE. THE
PRECIPITATION TAPERS OFF OVER THE MOUNTAINS SUNDAY NIGHT AS DRIER
AIR INFILTRATES THE FORECAST AREA FROM THE NORTHWEST.

FORECAST CONFIDENCE DECREASES EARLY NEXT WEEK WITH OPPOSING MODEL
SOLUTIONS. THE ECMWF BRINGS MORE SHORTWAVE ENERGY SOUTHEAST ACROSS
THE CWA...AMPLIFYING THE MEAN TROUGH OVER THE NORTH CENTRAL CONUS.
THIS OPENS THE DOOR FOR A REINFORCEMENT OF COLD AIR FROM SOUTHERN
CANADA. CONVERSELY...THE GFS MAINTAINS A MORE ZONAL FLOW ALOFT
WITH A MILDER PACIFIC AIR MASS. THE ECMX MOS HIGH TEMPERATURE
MONDAY AT CHEYENNE IS 23 WHILE THE GFSX MOS HIGH TEMPERATURE IS
45. GIVEN THE WIDE TEMPERATURE DIFFERENCE...CLOSER TO THE GFS FOR
NOW. IF FUTURE RUNS OF THE GFS TREND TOWARD THE COLDER ECMWF
SOLUTION...MONDAY/S HIGHS WILL NEED TO BE LOWERED.

GUSTY DOWNSLOPE WEST WINDS TUESDAY WILL LEAD TO A MODEST WARMUP
FOR THE PLAINS WITH HIGHS IN THE 40S TO AROUND 50. TUESDAY WILL
BE DRY. THE LEADING EDGE OF PACIFIC MOISTURE WILL EXTEND NORTHEAST
ACROSS WESTERN CO INTO SOUTHERN WY TUESDAY NIGHT...AND SOUTHEAST
WY ON WEDNESDAY. WAA AND WEAK QG LIFT WILL RESULT IN LIGHT SNOW
WEST OF THE LARAMIE RANGE TUESDAY NIGHT...WITH RAIN AND/OR SNOW
SPREADING EAST ONTO THE PLAINS WEDNESDAY.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z FRIDAY MORNING)
ISSUED AT 250 AM MST THU NOV 27 2014

SCT TO BKN MID AND HIGH CLOUDS WILL CONTINUE TO SPREAD NORTHWEST
TO SOUTHEAST DURING THE FORECAST PERIOD. MOIST BOUNDARY LAYER FROM
THE EASTERN WY PLAINS INTO WESTERN NE PANHANDLE AND LIGHT WINDS
WILL RESULT IN AREAS OF FOG PRODUCING MVFR VSBYS ALONG WITH OCNL
MVFR CIGS EARLY THIS MORNING. CONDITIONS WILL IMPROVE TO VFR
THEREAFTER WITH GUSTY WEST SURFACE WINDS THROUGH THE AFTERNOON.
STRONGEST WINDS WILL BE CONFINED TO THE MOUNTAINS AND FOOTHILLS
WHERE GUSTS OF 40 TO 50 KT WILL BE POSSIBLE.

&&

.FIRE WEATHER...
ISSUED AT 250 AM MST THU NOV 27 2014

MINIMAL FIRE WEATHER CONCERNS THROUGH THE HOLIDAY WEEKEND. TEMPERATURES
WILL BE QUITE MILD OVER THE NEXT FEW DAYS. MINIMUM AFTERNOON HUMIDITY
VALUES WILL BE LOWEST ON FRIDAY AND SATURDAY WITH A FEW LOCATIONS TO
THE EAST OF THE LARAMIE RANGE IN THE 15-20 PERCENT RANGE. IT WILL BE
WINDY ACROSS SOUTHEAST WYOMING THROUGH SATURDAY WITH GUSTS TO 35-40
MPH COMMON...ESPECIALLY DURING THE AFTERNOONS.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...HIGH WIND WARNING UNTIL 5 PM MST THIS AFTERNOON FOR WYZ106-110-
     116-117.

NE...NONE.
&&

$$

SHORT TERM...ZF
LONG TERM...MJ
AVIATION...MJ
FIRE WEATHER...ZF



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