Area Forecast Discussion
Issued by NWS Cheyenne, WY

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000
FXUS65 KCYS 281108
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
408 AM MST FRI NOV 28 2014

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 355 AM MST FRI NOV 28 2014

PREDAWN WATER VAPOR LOOP SHOWED A BROAD UPPER RIDGE CENTERED OVER
THE INTERMOUNTAIN WEST WITH A FAIRLY STRONG WEST-NORTHWEST FLOW
ALOFT. A UPPER TROUGH WAS DIGGING SOUTHEAST ACROSS BRITISH COLUMBIA
TOWARD THE PACIFIC NORTHWEST. A TIGHT 700-850MB GRADIENT WITH 40-55
KT WINDS WAS GENERATING STRONG WEST-SOUTHWEST SURFACE WINDS BETWEEN
CHEYENNE AND THE I-80 SUMMIT AND NORTH AND SOUTH OF CHEYENNE ALONG
I-25. THESE STRONG WINDS WILL PERSIST THROUGH THE EARLY MORNING.
DOWNSLOPE FLOW KEPT TEMPERATURES QUITE MILD FOR THIS TIME OF NIGHT
WITH 40S AND 50S.

MAIN FORECAST CHALLENGES DURING THE SHORT TERM WILL FOCUS ON HIGH
WINDS AND TIMING/IMPACTS FROM ARCTIC COLD FRONTAL PASSAGE SUNDAY.
THE LATEST NUMERICAL MODEL GUIDANCE HAS A GOOD HANDLE ON THE LARGE
SCALE PATTERN...WITH THE FLATTENING OF THE WESTERN CONUS UPPER
RIDGE AS THE UPPER TROUGH TO THE NORTHWEST PROGRESSES SOUTHEAST
INTO THE NORTH CENTRAL CONUS SUNDAY. UNTIL THEN...DOWNSLOPE FLOW
AND 700MB TEMPERATURES AS WARM AS 6C EAST OF THE LARAMIE RANGE WILL
MAINTAIN UNSEASONABLY MILD AND DRY PATTERN TODAY AND SATURDAY.
AFTERNOON HIGH TEMPERATURES TODAY AND SATURDAY WILL RANGE FROM 60
TO 65 DEGREES FOR THE PLAINS...WITH 40S AND 50S ALONG AND WEST OF
THE LARAMIE RANGE. BOTH THE GFS AND NAM PROG 700MB WINDS IN THE
45-55 KT RANGE TODAY...INCREASING TO 55-65 KT TONIGHT AND
MAINTAINING THAT INTENSITY THROUGH SATURDAY. THE 00Z MESOETA
CRAIG-CASPER 700-850MB HEIGHT GRADIENTS LIKEWISE INCREASE FROM
55-60M TODAY TO 60-70M TONIGHT AND SATURDAY. MITIGATING FACTORS
FOR THE DEVELOPMENT OF HIGH WINDS HAS BEEN CLOUD COVER...STOUT LOW
LEVEL INVERSION AND WEAK LAPSE RATES. TODAY AND SATURDAY WILL SEE
LESS CLOUD COVER. INVERSION WAS PRESENT EARLY THIS MORNING...AND
PER BUFKIT FORECAST SOUNDINGS...WILL WEAKEN ENOUGH THIS AFTERNOON
TO ALLOW STRONGER WINDS ALOFT TO MIX DOWN TO THE SURFACE. HIGH
WINDS LOOK MORE FAVORABLE LATER TONIGHT AS CROSS MOUNTAIN FLOW
APPROACHES 60 KT...AND DURING DAYLIGHT HOURS SATURDAY WITH
FORECAST STEEPER LOW-MID LEVEL LAPSE RATES. THAT SAID...HAVE
ISSUED A HIGH WIND WATCH FOR WIND PRONE AREAS INCLUDING
FERRIS/SEMINOE/SHIRLEY MOUNTAIN RANGE BEGINNING LATE THIS
AFTERNOON AND CONTINUING THROUGH SATURDAY AFTERNOON.

WINDS DECREASE SATURDAY NIGHT AS THE ARCTIC COLD FRONT PUSHES
THROUGH SOUTHEAST WY AND WESTERN NE. THE SHALLOW COLD AIR MASS
WILL SPREAD SOUTH AND WEST TOWARD THE FRONT RANGE WITH BRISK
NORTHERLY SURFACE WINDS. ALONG AND BEHIND THE FRONT...LIGHT RAIN
WILL QUICKLY CHANGE TO SNOW WITH THE ARRIVAL OF THE COLD AIR MASS.
MODELS PROG MOST OF THE SNOWFALL TO BE LIGHT...EXCEPT OVER THE
HIGHER TERRAIN WHERE IT WILL BE MODERATE AT TIMES. ACCUMULATIONS
SATURDAY NIGHT AND SUNDAY WILL VARY FROM 1/2 INCH FOR THE EASTERN
WY PLAINS AND NORTHERN NE PANHANDLE TO 1 TO 3 INCHES FOR THE NORTH
LARAMIE RANGE. PRECIPITATION WILL MIX WITH OR CHANGE BRIEFLY TO
RAIN FOR THE LOWER VALLEYS WEST OF THE LARAMIE RANGE WHERE
TEMPERATURES WILL HOVER BETWEEN 35 AND 40 DEGREES. HIGH TEMPERATURES
SUNDAY WILL BE AS MUCH AS 35 DEGREES COLDER FOR THE PLAINS. BRISK
NORTH WINDS WILL MAKE IT FEEL LIKE SINGLE DIGITS AND TEENS.

.LONG TERM...(SUNDAY NIGHT THROUGH THURSDAY)
ISSUED AT 330 AM MST FRI NOV 28 2014

COLD AIR MASS WILL BE IN PLACE ON SUNDAY NIGHT IN THE WAKE OF THE
FRONTAL PASSAGE. KEPT CHANCE POPS IN PLACE FOR AREAS NEAR THE
COLORADO BORDER EARLY IN THE NIGHT WITH LOW LEVEL UPSLOPE IN
PLACE. SINCE DEEP LAYER FORCING FOR ASCENT IS LARGELY
ABSENT...SNOW ACCUMULATIONS WILL LARGELY BE LESS THAN 1-2 INCHES.
MONDAY WILL BE ON THE COOL SIDE WITH WINDS TURNING TO THE SOUTH AS
THE SFC HIGH SLIDES EASTWARD TOWARD IOWA. FOCUS THEN TURNS TO THE
PROGRESSIVE SHORTWAVE THAT IS PROGGED TO MOVE QUICKLY EASTWARD
ALONG THE CANADIAN BORDER ON MONDAY NIGHT. THE LOW LEVEL GRADIENT
WILL INCREASE ACROSS SOUTHEAST WY WITH THE 850MB CAG-CPR GRADIENT
AROUND 60 METERS BY 12Z TUESDAY. COULD SEE HIGH WINDS COMING BACK
TO PLACES LIKE ARLINGTON AND BORDEAUX...HOWEVER IT WOULD BE A
QUICK EVENT WITH WINDS BEGINNING TO SUBSIDE BY THE AFTN. TEMPS
WILL WARM TO ABOVE AVERAGE ON TUESDAY WITH THE WARM ADVECTION AND
DOWNSLOPE IN PLACE. CUTOFF LOW OFF THE CALIFORNIA COAST ON TUESDAY
WILL WEAKEN AND SHIFT EASTWARD INTO THE GREAT BASIN BY WED. WITH
INCREASING PACIFIC MOISTURE AND MOIST WESTERLY FLOW AIDING
OROGRAPHICS...HAVE A CHANCE OF SNOW IN THE SIERRA MADRE AND SNOWY
RANGES FOR WED AND WED NIGHT. OVERALL THE TEMPS ON WED AND THURS
WILL BE SEASONAL AND WINDS NOT TOO STRONG.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z FRIDAY NIGHT)
ISSUED AT 1006 PM MST THU NOV 27 2014

VFR THROUGH NEXT 24 HOURS...BUT HAVE STRONG WINDS TO DEAL WITH FOR
OUR SOUTHEAST WYOMING AIRPORTS. MODERATE OR GREATER TURBULENCE ON
LANDINGS AND TAKEOFFS AS WIND SPEEDS OFF THE SURFACE CLOSE TO 60 KT
FRIDAY. SHOULD SEE LOTS OF MOUNTAIN WAVE TURBULENCE OFF THE LARAMIE
RANGE...ESPECIALLY DURING THE DAYLIGHT HOURS.

&&

.FIRE WEATHER...
ISSUED AT 300 AM MST FRI NOV 28 2014

MINIMAL FIRE WEATHER ISSUES ANTICIPATED THIS HOLIDAY WEEKEND.
UNSEASONABLY MILD TEMPERATURES WILL CONTINUE TODAY AND SATURDAY.
LOWEST RELATIVE HUMIDITIES WILL RANGE FROM 15 TO 20 PERCENT
IMMEDIATELY EAST OF THE LARAMIE RANGE. STRONG AND GUSTY WEST TO
SOUTHWEST WINDS WILL PREVAIL ACROSS MUCH OF SOUTHEAST WYOMING...
MAINLY DURING THE DAYLIGHT HOURS TODAY AND SATURDAY. A ARCTIC
COLD FRONT WILL PUSH SOUTH ACROSS THE PLAINS AND STALL NEAR THE
FRONT RANGE SUNDAY...BRINGING MUCH COLDER TEMPERATURES AND CHANCES
FOR LIGHT RAIN AND SNOW.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...HIGH WIND WATCH FROM LATE THIS AFTERNOON THROUGH SATURDAY
     AFTERNOON FOR WYZ104-106-110-116-117.

NE...NONE.
&&

$$

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



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