Area Forecast Discussion
Issued by NWS Cheyenne, WY

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000
FXUS65 KCYS 212035
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
235 PM MDT TUE OCT 21 2014

.SHORT TERM...(THIS EVENING THROUGH THURSDAY NIGHT)
ISSUED AT 235 PM MDT TUE OCT 21 2014

VORTMAX NOW OVER EASTERN IDAHO WILL MOVE EAST OVERNIGHT INTO WEDS
MORNING WITH THE BULK OF THE ENERGY LIFTING NORTHEAST ACROSS
MONTANA. RADAR SHOWING SOME LIGHT ACTIVITY OVER THE NRN COLORADO
MTNS AND ALONG THE WY/NEB BORDER GRADUALLY INCREASING IN COVERAGE
BUT FAIRLY LIGHT IN INTENSITY. EXPECT THIS TREND TO CONTINUE INTO
THIS EVENING AS THE CWA GETS CLIPPED WITH SOME OF THE ENERGY FROM
THE UPPER SHORTWAVE. STILL CANNOT RULE OUT A FEW RUMBLES OF
THUNDER WITH ANY STRONGER ACTIVITY INTO THIS EVENING WITH SOME
WEAK INSTABILITY AROUND. SHOWERS WILL THEN MOVE OUT OF THE CWA
LATER TONIGHT WITH THE PASSAGE OF ONE UPPER IMPULSE AND A SFC COOL
FRONT. NOT A LOT OF COOLING BEHIND THIS FRONT FOR WEDS AS THE AIR
MASS IS OF PACIFIC ORIGIN. DRY WEDS THROUGH THURSDAY UNDER A
GENERALLY ZONAL UPPER FLOW. WARMER AGAIN THURSDAY AS UPPER RIDGING
BUILDS A BIT OVER THE REGION.

.LONG TERM...(FRIDAY THROUGH TUESDAY)
ISSUED AT 235 PM MDT TUE OCT 21 2014

AFTER A MILD COOL-DOWN IN THE SHORT TERM...WE EXPECT TO SEE
ANOTHER SIGNIFICANT WARM-UP BY EARLY IN THE WEEKEND AS UPPER
RIDGING ALOFT MOVES ACROSS OUR AREA. TEMPS IN THE LOWER ELEVATIONS
BY SATURDAY WILL AGAIN BE IN THE UPPER 70S IN MANY AREAS...WITH
60S ABOVE 7000 FT MSL AND 50S IN THE HIGHER TERRAIN. GFS AND ECMWF
ARE IN FAIR AGREEMENT BRINGING THE NEXT CHANGE TO THE REGION LATE
IN THE WEEKEND WITH AN AMPLIFYING UPPER TROUGH FORECAST TO SWING
ACROSS THE CENTRAL AND NORTHERN ROCKIES ON MONDAY. MODEL SOUNDINGS
SHOW THIS NEXT SYSTEM TO BRING A CHANCE OF SNOW TO THE HIGHER
ELEVATIONS WITH A MIX OF RAIN/SNOW SHOWERS AT THE LOWER
ELEVATIONS SUNDAY NIGHT INTO EARLY MONDAY.  ON THE 12Z
UPDATES...THE ECMWF STILL APPEARS TO BE A LITTLE STRONGER WITH
THE UPPER SYSTEM MOVING ACROSS...BUT THE GFS HAS TRENDED COLDER IN
THE MIDLEVELS AND IS NOW CLOSER TO THE ECMWF WITH THE 700 MB
TEMPERATURES SUNDAY NIGHT INTO EARLY MONDAY. QPF AMOUNTS IN
LATEST MODEL RUNS SHOW A LITTLE LESS ACCUMULATION WHERE SNOW
PERSISTS AS COMPARED TO THE PREVIOUS CYCLE.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z WEDNESDAY MORNING)
ISSUED AT 1143 AM MDT TUE OCT 21 2014

A WEAK COLD FRONT ASSOCIATED WITH A PASSING UPPER LEVEL TROUGH
WILL MOVE INTO THE RAWLINS AREA AROUND 6 PM THIS EVENING AND
PROGRESS EASTWARD ACROSS SOUTHEASTERN WYOMING AND THE WESTERN
NEBRASKA PANHANDLE DURING THE OVERNIGHT PERIOD. THERE IS JUST
ENOUGH INSTABILITY TO EXPECT ISOLATED THUNDERSTORMS TO POP UP
STARTING MID AFTERNOON IN THE RAWLINS AND LARAMIE AREAS. LATEST
HIGH RESOLUTION RAPID REFRESH MODEL SUGGESTS MOSTLY SHOWERS WITH A
FEW THUNDERSTORMS PROGRESSING EAST OF THE LARAMIE RANGE DURING THE
LATE AFTERNOON AND EARLY EVENING HOURS WITH MODEST UPPER LEVEL
FORCING ASSOCIATED WITH A PASSING WEAK UPPER LEVEL JET MAXIMUM.
NOT ENOUGH COVERAGE OF SHOWERS OR STORMS TO WARRANT A PREVAILING
PERIOD OF LOWERED VISIBILITIES/CEILINGS IN THE FORECAST, SO WE
CARRIED VFR CATEGORY PREVAILING ALL PERIODS WITH A VICINITY
MENTION OF SHOWERS OR THUNDERSTORMS MID AFTERNOON THROUGH MID
EVENING FOR MOST SITES. ANY LINGERING SHOWERS OR THUNDERSTORMS
WILL WEAKEN AS WE GO INTO THE LATE EVENING AS THE UPPER LEVEL
SUPPORT LIFTS OUT TO THE NORTHEAST.

&&

.FIRE WEATHER...
ISSUED AT 235 PM MDT TUE OCT 21 2014

CONCERNS EXPECTED TO REMAIN LOW FOR THE REST OF THE WEEK AS
WEATHER CONDITIONS GENERALLY NON-CRITICAL.  LOWEST AFTERNOON
HUMIDITIES WILL GET TO AROUND 20 PERCENT THURSDAY THROUGH THE WEEKEND
BUT WINDS NOT EXPECTED TO BE MUCH OF A FACTOR THROUGH THE PERIOD.

&&

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

$$

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








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