Area Forecast Discussion
Issued by NWS Cheyenne, WY

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000
FXUS65 KCYS 142147
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
347 PM MDT MON APR 14 2014

.SHORT TERM...(THIS EVENING THROUGH THURSDAY)
ISSUED AT 338 PM MDT MON APR 14 2014

TONIGHT...SNOWEATER DOWNSLOPE WINDS...CHINOOK WIND...DOING A DECENT
JOB OF ERODING OUR SNOWFIELD...SEEN ON VISIBLE SATELLITE
IMAGERY...AS WELL AS WITH THE INTERESTING TEMPERATURE CONTRASTS.  AT
3 PM...LARAMIE AND CHEYENNE ARE ONLY IN THE UPPER 20S TO NEAR 30
WITH MORE SNOWPACK AND WINDS OFF THE SNOWFIELD...WHILE IN
CONTRAST...TORRINGTON AND SCOTTSBLUFF ARE IN THE UPPER 30S TO LOWER
40S WITH NORTHWEST WINDS PARALLEL TO THE NORTH PLATTE RIVER VALLEY
AND NOT OFF THE SNOWFIELD.

TEMPERATURES WILL FALL RATHER ABRUPTLY THIS EVENING...THEN NOT AS
QUICKLY AFTER MIDNIGHT AS SURFACE LEE TROUGHING BECOMES BETTER
ESTABLISHED AND LOW LEVEL WINDS...MIXING STRENGTHEN AFTER MIDNIGHT.

TUESDAY...IF YOU LIKE MILD WEATHER...YOU WILL ENJOY THIS DAY.
PROGRESSIVE LOW AMPLITUDE SHORTWAVE TROUGH ALOFT SCOOTS EASTWARD
ACROSS IDAHO AND WESTERN WYOMING...INDUCING SURFACE LEE TROUGH
DEVELOPMENT OVER THE WESTERN DAKOTAS AND EASTERN MONTANA AND AIDING
IN OUR DOWNSLOPE WARMING. BASED ON PROJECTED 700 MB TEMPERATURES
NEAR 0 CELSIUS...AND 1000-500 MB THICKNESSES NEAR 5550 METERS...AND
DOWNSLOPE WARMING...THE WARMER GFS MET MOS MAXIMUMS LOOKS BEST FOR
TEMPERATURES WITH OUR MERCURY SOARING INTO THE 50S WEST OF
INTERSTATE 25 AND 60S EAST OF I-25.

TUESDAY NIGHT...NEXT COLD FRONT AND ITS ASSOCIATED COLD FRONT SWEEP
QUICKLY SOUTHEAST ACROSS OUR COUNTIES IN THE LATE EVENING AND AFTER
MIDNIGHT. BEST DYNAMICS AND DEEPER MOISTURE WILL COEXIST ACROSS OUR
NORTHERN COUNTIES...WITH A GLANCING OROGRAPHIC PRECIPITATION EVENT
ACROSS OUR SNOWY AND SIERRA MADRE RANGES...THUS OUR TEAM HAS PAINTED
20 TO 50 PERCENT POPS NORTH OF A LARAMIE TO ALLIANCE LINE...WITH 60
TO 100 PERCENT POPS OVER THE MOUNTAINS.

WEDNESDAY...SECONDARY COLDER AIR FILTERS IN DURING THE DAY WITH COLD
NORTH WINDS USHERING IN THE COLDER CANADIAN AIRMASS. UPSLOPE SNOWS
EXPECTED TO DEVELOP ALONG THE SPINE OF THE LARAMIE RANGE AND
INTERSTATE 25 CORRIDOR IN THE AFTERNOON.

WEDNESDAY NIGHT...DECENT SETUP FOR DYNAMIC AND UPSLOPE SNOW MACHINE
TO CRANK UP OVER SOUTHERN ALBANY AND LARAMIE COUNTIES OF WYOMING
INCLUDING LARAMIE...CHEYENNE AND THE INTERSTATE 80 SUMMIT WITH
COMBINATION OF SATURATED LOW AND MID LEVELS OF THE ATMOSPHERE...
UPSLOPE AND DYNAMICS...COMBINED WITH FAVORABLE 500-300 MB AND
700-500 MB QUASIGEOSTROPHIC LIFT...THUS HAVE PAINTED 70 TO 100
PERCENT POPS FROM LARAMIE TO CHEYENNE TO PINE BLUFFS AFTER MIDNIGHT.
WITH SOUPY LOW LEVELS...AREAS THAT DO NOT GET MUCH SNOW WILL HAVE
FOG AND HAVE PAINTED FOG IN AS WELL TO MATCH THE NAM BOUNDARY LAYER
RELATIVE HUMIDITY PROGS.

.LONG TERM...(THURSDAY THROUGH MONDAY)
ISSUED AT 345 PM MDT MON APR 14 2014

LONG RANGE MODELS IN REASONABLE AGREEMENT LATE THIS WEEK AND
THROUGH NEXT WEEKEND...SHOWING ANOTHER COLD DAY ON THURSDAY AS
LIGHT SNOW IN THE MORNING GRADUALLY PUSHES EAST OF THE AREA. WITH
THE POTENTIAL OF LIGHT SNOW ACCUMULATIONS NEAR THE COLORADO
BORDER...TEMPERATURES DURING THE DAY MAY STRUGGLE TO REACH THE MID
TO UPPER 30S ALONG AND EAST OF THE LARAMIE RANGE AS 700MB
TEMPERATURES REMAIN BETWEEN -4C TO -8C. KEPT POP BETWEEN 20 TO 40
PERCENT EARLY THURSDAY...WITH POP GRADUALLY LOWERING THROUGH THE
DAY. OUTSIDE OF A PACIFIC COLD FRONT RAPIDLY MOVING EASTWARD
ACROSS THE FORECAST AREA ON FRIDAY/FRIDAY NIGHT...DRY WEATHER AND
WARM TEMPERATURES ARE EXPECTED. WINDY CONDITIONS ARE POSSIBLE
FRIDAY AS THE FRONT PUSHES THROUGH THE AREA...BUT THE ECMWF SHOWS
THE MIDLEVEL PRESSURE GRADIENT MUCH FURTHER NORTH WITH NOT TOO
MUCH WIND. IN ADDITION...THIS SOLUTION ALSO SHOWS THE SOUTHERN
BRANCH OF THE JET MUCH FURTHER NORTH ON SATURDAY AS AN UPPER LEVEL
DISTURBANCE IN ARIZONA EJECTS NORTHEASTWARD...RESULTING IN SOME
SHOWER AND TSTORM ACTIVITY FURTHER SOUTH NEAR THE COLORADO BORDER.
KEPT A SLIGHT CHANCE OF SHOWERS IN THE MOUNTAINS FOR NOW...WITH
POP BELOW 15 PERCENT ACROSS THE HIGH PLAINS. TEMPERATURES WILL
INCREASE INTO THE 60S TO NEAR 70 FOR FRIDAY AND SATURDAY...WITH
VERY LITTLE PRONOUNCED COOLING EXPECTED FROM THE FRONT. BECAUSE
THE GFS AND ECMWF SHOW A DIFFERENT SOLUTION THIS WEEKEND REGARDING
THE SOUTHERN BRANCH OF THE JET STREAM...SOLUTION DIFFER FOR SUNDAY
AND MONDAY AS WELL WITH THE GFS SHOWING A HIGH AMPLITUDE RIDGE
BUILDING INTO THE CENTRAL AND NORTHERN ROCKY MOUNTAINS. THE ECMWF
SHOWS THE RIDGE FURTHER WEST AND SOUTH. EITHER WAY...EXPECT DRY
CONDITIONS AND WARM TEMPERATURES ON SUNDAY AND MONDAY FOR
NOW...BUT CONFIDENCE IS RATHER LOW IN THIS SOLUTION BECAUSE THE
GFS HAS HAD A TENDENCY THIS YEAR TO SHOW HIGH AMPLITUDE RIDGES ON
DAYS 6 AND 7...BUT THEN SOLUTIONS QUICKLY CHANGE A DAY OR TWO
LATER DUE TO THE MORE POTENT NORTHERN BRANCH OF THE JET. KEPT
TEMPERATURES ABOVE NORMAL...BUT DID NOT GO QUITE AS HIGH AS THE
GFS SUGGESTS.

&&

.AVIATION...FOR THE 18Z TAFS THROUGH TUESDAY MORNING)

VFR CONDITIONS EXPECTED ACROSS THE ENTIRE AREA THIS AFTERNOON AND
THROUGH LATE THIS EVENING. BREEZY CONDITIONS ARE EXPECTED THIS
AFTERNOON WITH GUSTY WEST TO NORTHWEST WINDS GUSTING TO 30 KNOTS AT
TIMES. THERE IS A SLIGHT CHANCE OF FOG DEVELOPING IN THE MORE
SHELTERED VALLEYS TONIGHT DUE SNOW MELT...BUT CONFIDENCE IS RATHER
LOW AT THIS TIME.

&&

.FIRE WEATHER...
ISSUED AT 308 PM MDT MON APR 14 2014

MINIMUM AFTERNOON HUMIDITIES ON TUESDAY WILL RANGE
FROM 20 TO 30 PERCENT...ALONG WITH WEST WINDS OF 25 TO 35 MPH ACROSS
CARBON...ALBANY...WESTERN PLATTE AND WESTERN LARAMIE COUNTIES.
COLDER TEMPERATURES WEDNESDAY AND THURSDAY WILL PRODUCE HIGHER
AFTERNOON HUMIDITIES AND ALLEVIATE CONCERNS. ON FRIDAY...AFTERNOON
HUMIDITIES WILL FALL TO 25 TO 35 PERCENT ALONG WITH SOUTH TO
SOUTHWEST WINDS OF 10 TO 25 MPH.

&&

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

$$

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








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