Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 261931
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
1231 PM MST FRI DEC 26 2014

.UPDATE...
ISSUED AT 1212 PM MST FRI DEC 26 2014

MINOR GRIDDED FORECAST UPDATE FOR THIS AFTERNOON TO BOOST SOME
HIGH TEMPERATURES AND TO ADJUST WINDS...DEWPOINTS AND AREAL
COVERAGE OF SNOW BASED ON TRENDS. 500 MB TROUGH AXIS MOVES TO
NORTHEAST COLORADO BY SUPPERTIME WITH THE BULK OF THE UPWARD
VERTICAL MOTION AND DEEPER ATMOSPHERIC MOISTURE OVER OUR
COLORADO NEIGHBORS.

&&

.SHORT TERM...(TODAY THROUGH SUNDAY AFTERNOON)
ISSUED AT 445 AM MST FRI DEC 26 2014

WINTER STORM WARNING AND WINTER WEATHER ADVISORY HAVE BEEN
CANCELLED. SOME LIGHT SNOW WILL CONTINUE OVER PORTIONS OF THE
FORECAST AREA TODAY BUT THIS SNOW WILL HAVE LITTLE IMPACT AS
ADDITIONAL SNOW ACCUMULATIONS WILL GENERALLY BE A DUSTING TO
UPWARDS OF AN INCH. ALSO WINDS WILL BE LIGHT TODAY. COULD SEE
UPWARDS OF 2 INCHES ALONG THE SOUTHERN LARAMIE RANGE AND ALONG
THE WY/CO BORDER...BUT THATS AT THE HIGH END OF ANY ACCUMULATIONS
TODAY.

THE LAST PUSH OF UPPER LEVEL ENERGY AND MOISTURE IS MAKING ITS
WAY INTO SOUTHERN PORTIONS OF THE CWA AT THIS TIME. THE UPPER
LEVEL WAVE WILL STALL OUT LATE THIS MORNING AND THEN SHIFT EAST
INTO THE PLAINS LATER TODAY WITH SNOW ENDING FROM NORTHWEST TO
SOUTHEAST ACROSS THE CWA. SNOW WILL END BY LATE THIS AFTERNOON TO
EARLY EVENING ACROSS THE ENTIRE AREA...WITH THE EXCEPTION OF
LIGHT SNOW POSSIBLE INTO THE SNOWY AND SIERRA MADRE RANGES.

MAIN WEATHER CONCERNS TURN AWAY FROM SNOW TODAY TO HIGH WINDS
SATURDAY INTO SUNDAY. NAM SHOWING THE CRAIG TO CASPER 850MB AND
700MB GRADIENTS INCREASING TO OVER 60 METERS BY SATURDAY EVENING.
THE GFS IS SLIGHTLY TIGHTER WITH THE GRADIENT AND INCREASES THE
GRADIENT EARLIER. ISSUED A HIGH WIND WATCH FOR THE ARLINGTON AREA
FROM 18Z SAT TO 18Z SUN...AND FOR THE SOUTHERN LARAMIE RANGE AND
NEAR BORDEAUX FROM 00Z SUN THROUGH 18Z SUN. WITH FRESH NEW SNOW
COVER ON THE GROUND THERE WILL AT LEAST BE SOME BLOWING SNOW AS
THE WINDS INCREASE. AS THE WINDS DECREASE SUNDAY...CHANGES FOR
SNOW WILL INCREASE AS THE NEXT UPPER LEVEL SYSTEM MOVES INTO THE
AREA.

.LONG TERM...(SUNDAY NIGHT THROUGH THURSDAY)
ISSUED AT 345 AM MST FRI DEC 26 2014

MAIN FORECAST CONCERN FOR THE LONG RANGE IS THE ARCTIC COLD FRONT
FORECAST TO PUSH SOUTH ACROSS THE FORECAST AREA SUNDAY NIGHT...IN
ADDITION TO A PERIOD OF SNOW BEGINNING AS EARLY AS SUNDAY
AFTERNOON. THIS ARCTIC AIRMASS HAS THE POTENTIAL TO BE THE COLDEST
SO FAR THIS SEASON WITH BITTER COLD TEMPERATURES POSSIBLE MONDAY
THROUGH EARLY WEDNESDAY.

THERE IS STILL UNCERTAINTY WITH THE WINTER WEATHER EVENT FOR
SUNDAY NIGHT AND MONDAY AS THE ARCTIC FRONT HEADS SOUTHWARD ACROSS
THE FORECAST AREA. THE GFS CONTINUES TO SHOW MORE SNOWFALL AS A
VIGOROUS SHORTWAVE ALOFT INTERACTS WITH THE ARCTIC FRONT...UPSLOPE
FLOW...AND JET DYNAMICS ALOFT. THE OTHER MODELS INCLUDING THE GEM
AND ECMWF SHOW THIS SHORTWAVE REMAINING WELL TO THE WEST OF
WYOMING...BUT STILL SHOW THE BITTER COLD TEMPERATURES AND SNOWFALL
ASSOCIATED WITH MAINLY THE JET DYNAMICS ON MONDAY. KEPT POP
BETWEEN 40 TO 60 PERCENT AND NEAR 100 PERCENT IN THE MOUNTAINS
THROUGH MONDAY NIGHT. EVEN IF THE ECMWF AND GEM SOLUTIONS
VERIFY...WILL STILL BE LOOKING AT LIGHT SNOW ACCUMULATIONS ACROSS
MOST OF THE FORECAST AREA. HOWEVER...THE GFS SHOWS SNOWFALL RATES
SIMILAR TO THE CHRISTMAS EVENT...SO IT STILL REQUIRES ATTENTION AT
THIS TIME.

THE ARCTIC AIRMASS WILL SETTLE OVER THE REGION MONDAY AND
TUESDAY...BUT NOT QUITE AS COLD AS 24 HOURS AGO. 850 MB TEMPS NOW
BETWEEN -17 TO -22 ACROSS MOST OF THE HIGH PLAINS...WHICH IS
AROUND 3C DEGREES WARMER THAN YESTERDAY. IN REALITY...IT IS THE
DIFFERENCE BETWEEN -10F AND AROUND ZERO DURING THE DAY ON TUESDAY.
EITHER WAY...IT WILL BE FRIGID WITH WIND CHILLS LIKELY BETWEEN 15
BELOW TO 30 BELOW ZERO ACROSS MOST OF THE AREA. DURING EARLY
TUESDAY AND EARLY WEDNESDAY MORNING...LOW TEMPERATURES MAY LOWER
BELOW -20 ACROSS PORTIONS OF THE AREA WITH MOST AREAS IN THE TEENS
BELOW ZERO. A SOLID SNOWPACK ACROSS MOST OF THE AREA COMBINED WITH
LLVL TEMPERATURES INVERSIONS AND CLEARING SKIES (ESPECIALLY
TUESDAY NIGHT) WILL RESULT IN DANGEROUS TEMPERATURES AND WIND
CHILL TEMPERATURES.

THANKFULLY...THE ARCTIC AIRMASS WILL NOT STICK AROUND TOO LONG AS
HIGH TEMPERATURES WILL RETURN TO THE TEENS AND LOW 20S BY
WEDNESDAY AFTERNOON...AND POSSIBLY IN THE 20S TO NEAR 30 BY
THURSDAY AS WESTERLY FLOW STRENGTHENS OVER THE HIGH PLAINS. POP
WILL BE BELOW 10 PERCENT WEDNESDAY AND THURSDAY WITH DRY
CONDITIONS EXPECTED. AGAIN...THIS SLIGHT WARMING TREND MAY BE
SHORT LIVED AS ANOTHER ARCTIC AIRMASS WILL BEGIN PUSHING SOUTHWARD
FROM CANADA NEXT FRIDAY.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SATURDAY AFTERNOON)
ISSUED AT 1212 PM MST FRI DEC 26 2014

MOUNTAINS OBSCURED. CEILINGS AND VISIBILITIES GRADUALLY
IMPROVING TO MVFR AND VFR THIS AFTERNOON...WITH MVFR AND
OCCASIONAL IFR PREVAILING TONIGHT...THEN BECOMING ALL VFR LATE
TONIGHT AND SATURDAY MORNING.

&&

.FIRE WEATHER...
ISSUED AT 237 AM MST FRI DEC 26 2014

SNOW WILL TAPER OFF FROM NORTH TO SOUTH TODAY AS A STORM SYSTEM
SHIFTS FROM THE ROCKIES INTO THE PLAINS. ADDITIONAL SNOW
ACCUMULATIONS WILL BE MINIMAL WITH NEW SNOW AMOUNTS GENERALLY LESS
THAN ONE INCH. COLD AND DRY SATURDAY WITH MOSTLY CLEAR SKIES...AND
WINDY TO VERY WINDY ALONG AND WEST OF THE LARAMIE RANGE. STRONG WINDS
WILL CONTINUE INTO SUNDAY MORNING BEFORE DECREASING. ANOTHER SHOT
OF SNOW POSSIBLE SUNDAY INTO MONDAY. VERY COLD MONDAY AND TUESDAY.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...HIGH WIND WATCH FROM SATURDAY MORNING THROUGH SUNDAY MORNING FOR
     WYZ110.

     HIGH WIND WATCH FROM SATURDAY AFTERNOON THROUGH SUNDAY MORNING
     FOR WYZ106-116-117.

NE...NONE.
&&

$$

UPDATE...RUBIN
SHORT TERM...SML
LONG TERM...TJT
AVIATION...RUBIN
FIRE WEATHER...SML


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