Area Forecast Discussion
Issued by NWS Cheyenne, WY

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000
FXUS65 KCYS 201726
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
1026 AM MST THU NOV 20 2014

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 435 AM MST THU NOV 20 2014

SATELLITE PICS SHOW PERHAPS SOME PATCHY FOG OR STRATUS TRYING TO
DEVELOP OVER THE PINE RIDGE AT THIS HOUR...ALTHO IT HASNT REACHED
ANY GROUND SENSORS YET TO PROVE ONE WAY OR ANOTHER. WILL MAINTAIN
MENTION OF FOG AND LOW CLOUDS THRU MIDMORNING IN THE GRIDS FOR
NOW BASED OFF THESE SATELLITE TRENDS. WEAK RIDGING WILL MOVE
OVERHEAD TODAY WITH A WEAK SHORTWAVE TROUGH FOLLOWING CLOSE BEHIND.
THE APPROACHING UPPER TROUGH WILL DEEPEN THE LEESIDE SFC PRESSURE
TROUGH THROUGH THE DAY TO MAINTAIN H7 WINDS OF 30 TO 35 KTS AND
THUS BREEZY SFC WINDS IN THE WIND PRONE AREAS OF SOUTHEAST
WYOMING. TEMPERATURES WILL BE MILD AS THE RIDGE MOVES OVERHEAD AND
WITH WESTERLY DOWNSLOPE WINDS IN PLACE...WITH MOSTLY DRY AND
BREEZY CONDITIONS PREVAILING TODAY AND FRIDAY. SOME LOW TO
MIDLEVEL MOISTURE LOOKS TO MOVE OVER THE MOUNTAINS WITH THE TROUGH
THIS EVENING...SO COULD SEE A FEW LIGHT SNOW SHOWERS DEVELOP OVER
THE HIGH PEAKS WITH LITTLE TO NO ACCUMULATION ANTICIPATED.

THE LEESIDE TROUGH WILL WEAKEN FRIDAY AFTERNOON AS THE SHORTWAVE
TROUGH MOVES TO THE EAST...BUT WILL STRENGTHEN ONCE AGAIN FRIDAY
NIGHT INTO SATURDAY AS A MUCH STRONGER MIDLEVEL WAVE WITHIN THE LFQ
OF A 150+ KT JET DEEPENS THE LEESIDE TROUGH ONCE AGAIN. CONSENSUS
GUIDANCE SHOWS THE CAG-CPR SFC PRESSURE GRADIENT STRENGTHENING
RAPIDLY SATURDAY MORNING IN ADVANCE OF THE APPROACHING SYSTEM...WITH
H7 WINDS INCREASING TO BETWEEN 50 AND 55 KTS JUST BEFORE SUNRISE.
GFS SHOWS A WEAK SFC INVERSION DEVELOPING FRIDAY NIGHT...AND LIFTING
AFTER 12Z SATURDAY TO MOUNTAIN TOP LEVEL. WITH THE GRADIENT RAPIDLY
STRENGTHENING AND THE WEAK INVERSION RISING TO MOUNTAIN TOP...AGREE
WITH PREVIOUS THINKING THAT A HIGH WIND EVENT LOOKS LIKELY MAINLY
FOR THE ARLINGTON - BORDEAUX CORRIDOR STARTING SATURDAY MORNING AND
CONTINUING THROUGH THE LATE AFTERNOON. THE ASSOCIATED PACIFIC FRONT
WILL MOVE WEST - EAST SATURDAY EVENING...WITH 8-10 MB/6 HR PRESSURE
RISES BEHIND THE FRONT MAINTAINING WINDY CONDITIONS IN THE WIND
PRONE AREAS. COULD POSSIBLY EXPAND THE STRONG WIND AREAS TO THE
SOUTHERN LARAMIE RANGE BEHIND THE FRONT AS WELL.

.LONG TERM...(SATURDAY NIGHT THROUGH WEDNESDAY)
ISSUED AT 435 AM MST THU NOV 20 2014

SATURDAY NIGHT/SUNDAY...POTENT PACIFIC ORIGIN COLD FRONT SWEEPS
ACROSS OUR COUNTIES WITH WIDESPREAD OROGRAPHIC SNOWS OVER THE SNOWY
AND SIERRA MADRE RANGES...AND SUSPECT WE WILL NEED TO BEGIN WINTER
WEATHER ADVISORIES OR MORE LIKELY WINTER STORM WARNINGS FOR THE
SNOWY AND SIERRA MADRE RANGES FOR A RELATIVELY LONG DURATION
SNOWFALL EVENT. MOSTLY DRY...COLDER AND WINDY ELSEWHERE WITH
DOWNSLOPING.

MONDAY...CONTINUED WINDY...BLUSTERY AND COOL WITH BRISK NORTHWEST
FLOW ALOFT AND PROGGED SURFACE THROUGH 700 MB GRADIENTS. AS OUR PAST
TWO DAYS DAY SHIFT LONG TERM FORECASTERS MENTIONED EARLIER...WE MAY
NEED TO BEGIN WIND HIGHLITES AT SOME LOCALES. WIDESPREAD OROGRAPHIC
SNOWS CONTINUE IN MOIST FLOW ALOFT OVER THE SNOWY AND SIERRA MADRE
RANGES.

TUESDAY...WINDIEST DAY OF THE LONG TERM PERIOD...AS OUR FORECAST
LONG TERM TEAM HAS MENTIONED THE PAST FEW AFTERNOONS...BASED ON
PROJECTED SURFACE TO 500 MB GRADIENTS AND PROJECTED WIND
SPEEDS...THUS WIND HIGHLIGHTS WILL LIKELY BE NEEDED FOR AT LEAST THE
WIND PRONE LOCALES. OROGRAPHIC SNOWS IN MOIST FLOW ALOFT CONTINUE
OVER THE SNOWY AND SIERRA MADRE RANGES.

WEDNESDAY...ANOTHER QUITE WINDY DAY WITH LIKELY WIND HIGHLIGHTS
BASED ON PROJECTED SURFACE THROUGH 500 MB GRADIENTS AND DEEP
UNIDIRECTIONAL FLOW AND ALSO THE IMPRESSIVE WIND SPEEDS FORECAST BY
THE GFS AND ECMWF MOS GUIDANCE.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z FRIDAY AFTERNOON)
ISSUED AT 1019 AM MST THU NOV 20 2014

VFR CONDITIONS THROUGH THE TAF PERIOD. WINDS WILL BECOME BREEZY
THIS AFTERNOON AT THE WYOMING TERMINALS WITH GUSTS AROUND 25 MPH
POSSIBLE. SCT-TO-BKN COVERAGE OF MID LEVEL CLOUDS AROUND 10K FEET
AGL WILL GRADUALLY SPREAD ACROSS THE AREA TODAY. NO PCPN IS
EXPECTED OUTSIDE OF THE MOUNTAINS.

&&

.FIRE WEATHER...
ISSUED AT 435 AM MST THU NOV 20 2014

NO CONCERNS ANTICIPATED FOR THE REST OF THE WEEK INTO THE WEEKEND
WITH WEATHER FACTORS EXPECTED TO BE NON-CRITICAL. BY LATE SATURDAY
ONWARD INTO NEXT WEEK STRONG WINDS WILL RETURN TO AREAS ESPECIALLY
AROUND THE MOUNTAINS. COOLER AND MORE UNSETTLED WEATHER WILL TAKE
OVER BEGINNING OF NEXT WEEK.

&&

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

$$

SHORT TERM...RJM
LONG TERM...SAR
AVIATION...CLH
FIRE WEATHER...RJM


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