Area Forecast Discussion
Issued by NWS Cheyenne, WY

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000
FXUS65 KCYS 250952
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
352 AM MDT MON APR 25 2016

.SHORT TERM...(TODAY THROUGH WEDNESDAY)
ISSUED AT 345 AM MDT MON APR 25 2016

QUIET AND TRANQUIL WEATHER THIS MORNING WILL QUICKLY CHANGE LATER
TODAY AS THE NEXT PACIFIC STORM SYSTEM MOVES TOWARDS THE AREA. IR
SATELLITE LOOP SHOWS THIS STORM JUST GETTING ORGANIZED EARLY THIS
MORNING ACROSS THE GREAT BASIN REGION IN CENTRAL NEVADA. ALL
MODELS SHOW THIS STORM PROGRESSING SLOWLY EASTWARD TODAY INTO
UTAH...AND THEN SLOWLY NORTHEAST INTO WESTERN COLORADO TONIGHT.
PLENTY OF WARM AIR AHEAD OF THIS SYSTEM...SO PRECIP TYPE WILL BE
RAIN BELOW 10000 FEET UNTIL LATE TONIGHT. IN FACT...THINK THE
MOUNTAINS MAY BE ALL RAIN INITIALLY AS WELL. SURFACE WINDS WILL
GRADUALLY SHIFT INTO THE SOUTH AND THEN SOUTHEAST LATER TODAY
WHICH WILL ALLOW SOME LLVL MOISTURE ADVECTION TO OCCUR. COMBINED
WITH COLD AIR ADVECTION ALOFT...THIS PROFILE WILL FAVOR ISOLATED
TO SCATTERED THUNDERSTORMS DEVELOPING OVER SOUTHEAST WYOMING THIS
AFTERNOON AND GRADUALLY MOVING NORTHEAST INTO WESTERN NEBRASKA.
WITH CAPE VALUES APPROACHING 1000 J/KG...CAN NOT RULE OUT SOME
STRONG THUNDERSTORMS ALONG AND EAST OF I25. MAIN THREAT SHOULD BE
FREQUENT LIGHTNING...HEAVY RAIN...AND HAIL. STRONG UPPER LEVEL
DIFFLUENCE AND DECENT LLVL CONVERGENCE MAINLY DUE TO UPSLOPE FLOW
AND FRONTOGENESIS WILL KEEP THIS SHOWER ACTIVITY GOING THROUGH THE
NIGHT AS A COLD FRONT MOVES ACROSS WYOMING. ISOLATED TSTORMS MAY
CONTINUE OVER THE HIGH PLAINS THROUGH THE NIGHT AS WELL. THESE
SHOWERS AND TSTORMS MAY TRAIN OVER THE SAME AREAS PRODUCING
MODERATE TO HEAVY RAINFALL. FURTHER WEST...COLD AIR WILL SPREAD
WEST OF I25 RESULTING IN RAIN CHANGING TO SNOW AFTER MIDNIGHT DOWN
TO 6000 FEET BY EARLY TUESDAY MORNING.

SNOWFALL AND SNOWLEVEL WILL BE THE PRIMARY FORECAST CONCERNS GOING
INTO TUESDAY...WITH CONSIDERABLE UNCERTAINTY REMAINING WITH
TUESDAYS FORECAST. THE 00Z GFS REMAINS THE WARMEST WITH THE LEAST
AMOUNTS OF QPF ACROSS THE AREA WITH THE EXCEPTION OF EAST CENTRAL
WYOMING. UPPER LEVEL LOW WILL TRACK EASTWARD JUST SOUTH OF THE
WYOMING/COLORADO BORDER AND THEN STALL OVER WESTERN NEBRASKA
TUESDAY NIGHT. THE OTHER MODELS SHOW A SIMILAR TRACK THROUGH
TUESDAY BUT ARE MUCH WETTER. THE ECMWF IS THE OUTLIER PAST
TUESDAY...SHOWING THE UPPER LEVEL LOW DRIFTING NORTH INTO SOUTHERN
WYOMING. AS OF RIGHT NOW...MOST CONFIDENT THAT THE MOUNTAINS AND
HIGHER ELEVATION ZONES NORTH OF I80 HAVE THE BEST POTENTIAL TO SEE
SIGNIFICANT SNOW ACCUMULATIONS. EXTENDED THE WINTER STORM WATCH
INTO NORTHERN CARBON AND NORTHERN ALBANY COUNTIES. ALSO INCLUDED
THE I80 SUMMIT IN THE WATCH. WILL LIKELY NEED TO ADJUST THE TIMING
SINCE MODELS ARE TRENDING WARMER INTO EARLY TONIGHT. STILL A BIT
TOO WARM TO INCLUDE THE LOWER ELEVATIONS OF
CONVERSE...PLATTE...AND NIOBRARA COUNTIES IN THE WATCH WITH
SNOWLEVELS HOVERING AROUND 5000 TO 5500 FEET ON TUESDAY. DURING
THE DAYTIME HOURS...HEAVY SNOW WILL STRUGGLE TO STICK ON AREA
ROADWAYS THIS TIME OF THE YEAR ANYWAYS. SO LOCATIONS LIKE
DOUGLAS...LUSK...AND WHEATLAND MAY SEE HEAVY SNOW AT TIMES
TUESDAY...BUT ACCUMULATIONS MAY BE CONFINED TO ELEVATED AND GRASSY
SURFACES. THE MOUNTAINS WILL DO WELL WITH THIS STORM WITH 10 TO 20
INCHES POSSIBLE OVER THE SNOWY RANGE AND NORTHERN LARAMIE RANGE.
FURTHER SOUTH AND EAST...SNOW IS POSSIBLE DOWN TO 5000 FEET
INCLUDING CHEYENNE...PINE BLUFFS...AND KIMBALL TUESDAY EVENING
THROUGH TUESDAY NIGHT...BUT MOST OF THE HEAVIER PRECIP WILL BE
OVER BY THEN WITH ONLY A LIGHT ACCUMULATION POSSIBLE ON ELEVATED
AND GRASSY SURFACES. HOWEVER IF MODELS TREND FURTHER SOUTH WITH
THE STORM AND COLDER...ALONG THE LINES OF THE CURRENT 00Z
GEM...THEN THE WINTER STORM WATCH MAY NEED TO BE EXTENDED FURTHER
SOUTH AND EAST. THIS WILL PRIMARILY BE A RAIN EVENT FOR THE REST
OF WESTERN NEBRASKA. HIGHS WILL STRUGGLE TO REACH 40 ALONG AND
WEST OF I25 ON TUESDAY WITH LOW TO MID 50S EXPECTED ACROSS WESTERN
NEBRASKA.

BY WEDNESDAY...THE UPPER LEVEL LOW WILL GRADUALLY WOBBLE NORTH AND
THEN EASTWARD. PRECIPITATION WILL BECOME MORE SCATTERED IN NATURE
WITH SNOW STILL POSSIBLE ABOVE 5000 FEET AS 700MB TEMPERATURES
WILL REMAIN BETWEEN -4C TO -6C. TEMPERATURES WILL BE 10 TO 20
DEGREES BELOW NORMAL WITH HIGHS IN THE UPPER 30S TO AROUND 40
ACROSS MOST OF SOUTHEAST WYOMING TO THE MID 40S TO NEAR 50 ACROSS
WESTERN NEBRASKA.

.LONG TERM...(WEDNESDAY NIGHT THROUGH SUNDAY)
ISSUED AT 300 AM MDT MON APR 25 2016

A GENERALLY COOL AND UNSETTLED WEATHER PATTERN EXPECTED TO AFFECT
THE CWA THROUGH THE PERIOD AS A COUPLE OF UPPER LOW DUMBBELL
AROUND EACH OTHER OVER THE PLAINS INTO THE NORTHWESTERN CONUS.
THIS WILL RESULT IN DAILY CHANCES FOR RAIN AND SNOW SHOWERS FOR
MUCH OF THE CWA ALONG WITH BELOW AVERAGE TEMPS. PRECIPITATION
SHOULD BE MAINLY IN THE FORM OF RAIN ACROSS LOWER ELEVATIONS WITH
SNOW OVER THE MTNS. RAIN/SNOW LINE MAY DRIFT INTO THE ADJACENT
HIGH PLAINS SOME NIGHTS BUT NOT MUCH IN THE WAY OF ACCUMULATION
SEEN OUTSIDE OF THE MTNS AT THIS TIME. HEAVIEST AND MOST
WIDESPREAD PCPN SHOULD BE ON FRIDAY IN ASSOCIATION WITH THE
STRONGER UPPER SYSTEM THAT WILL MOVE ACROSS THE SOUTHERN ROCKIES
INTO THE CENTRAL PLAINS FRIDAY THROUGH SATURDAY.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z TUESDAY MORNING)
ISSUED AT 300 AM MDT MON APR 25 2016

VFR CONDITIONS EXPECTED FOR ALL TERMINALS TODAY INTO THIS
EVENING. SOME SHOWERS WILL DEVELOP OVER SE WY THIS AFTERNOON.
CONDITIONS WILL LOWER TO WIDESPREAD MVFR/IFR TONIGHT...MAINLY AFT
06Z...AS RAIN AND MTN SNOW SPREAD ACROSS THE REGION.

&&

.FIRE WEATHER...
ISSUED AT 300 AM MDT MON APR 25 2016

NO FIRE WEATHER CONCERNS THROUGH THE WEEK AND INTO
NEXT WEEKEND. BELOW NORMAL TEMPERATURES...WIDESPREAD WETTING
RAINS...AND PERIODS OF SNOW ARE EXPECTED THROUGH THE WEEK.
AFTERNOON THUNDERSTORMS ARE ALSO POSSIBLE TODAY AND TUESDAY.
MINIMUM DAYTIME HUMIDITIES WILL LIKELY NOT DROP BELOW 50 PERCENT
AFTER TODAY UNTIL LATE NEXT WEEKEND. HEAVY SNOW IS POSSIBLE ABOVE
ELEVATIONS OF 5500 FEET.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...

WY...WINTER STORM WATCH FROM THIS EVENING THROUGH TUESDAY AFTERNOON
     FOR WYZ103>105-112-114-116.

NE...NONE.
&&

$$

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



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