Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 200409
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
1009 PM MDT SUN APR 19 2015

.UPDATE...
ISSUED AT 1009 PM MDT SUN APR 19 2015

INCREASED POPS AND SNOW AMOUNTS A BIT IN THE LOWER ELEVATIONS OF
CARBON AND ALBANY COUNTIES OVER THE NEXT FEW HOURS AS MORE
NUMEROUS ECHOES ARE EVIDENT ON RADAR THIS EVENING...WITH LIGHT
SNOW NOW OBSERVED AT RAWLINS. STILL EXPECT A FEW INCHES OF
ACCUMULATION IN THE SNOWY AND SIERRA MADRE MOUNTAINS OVERNIGHT
WITH PERHAPS AROUND ONE HALF INCH OF ACCUMULATION IN THE LOWER
ELEVATIONS FROM THESE SHOWERS. SNOW WILL QUICKLY SHIFT SOUTHEAST
THROUGH AREAS ALONG AND WEST OF THE LARAMIE RANGE THE NEXT FEW
HOURS...WITH SHOWERS EXPECTED TO BE CLEAR OF THE AREA BY SUNRISE.

&&

.SHORT TERM...(THIS EVENING THROUGH TUESDAY NIGHT)
ISSUED AT 345 PM MDT SUN APR 19 2015

RADAR CONTINUES TO SHOW RETURNS OVER PORTIONS OF THE FORECAST AREA
AT THIS TIME BUT OBSERVATION STATIONS HAVE NOT REPORTED
PRECIPITATION. A FEW SPRINKLES LIKELY HITTING THE GROUND HERE AND
THERE BUT MAINLY LOOKING AT VIRGA. CHANCE FOR MEASURABLE
PRECIPITATION VERY LOW THROUGH THE AFTERNOON AND MUCH OF THE
EVENING. WEAK SHORTWAVE ENERGY AND SUBTLE UPPER LEVEL JET MAX WILL
MOVE ACROSS WESTERN PORTIONS OF THE FORECAST AREA LATE EVENING
INTO THE OVERNIGHT HOURS. SOME LIGHT PRECIPITATION IS POSSIBLE
MAINLY WEST OF THE LARAMIE RANGE. A FEW INCHES OF SNOW ARE A GOOD
BET INTO THE SNOWY AND SIERRA MADRE RANGES WITH VERY LITTLE
PRECIPITATION OUTSIDE OF THE MOUNTAINS.

TEMPERATURES WILL BEGIN TO MODERATE OVER THE NEXT FEW DAYS AS AN
UPPER LEVEL RIDGE SLOWLY BUILDS ACROSS THE ROCKIES. OF COURSE DEEPER
SNOW PACK ALONG AND WEST OF THE LARAMIE RANGE BUT EAST OF RAWLINS
WILL MAKE FOR COOLER TEMPERATURES IN PLACES LIKE LARAMIE UNTIL THE
SNOW MELTS. KEPT HIGH AND LOW TEMPERATURES COOLER OVER THE SNOW
PACK AREAS THE NEXT FEW DAYS. GIVEN THE SNOW PACK COVERAGE BARELY
BUDGED TODAY AND TEMPERATURES ARE HOLDING IN THE 30S OVER THE SNOW
PACK...THE TEMPERATURE FORECAST MAY BE A BIT OPTIMIST.

.LONG TERM...(WEDNESDAY THROUGH SUNDAY)
ISSUED AT 326 PM MDT SUN APR 19 2015

LONG RANGE MODELS ARE STRUGGLING WITH THE PLACEMENT OF SHORTWAVE
ENERGY NEXT WEEK...RESULTING IN NOTICEABLE TIMING DIFFERENCES.
ALL MODELS ARE SHOWING SPLIT FLOW ACROSS THE AREA...BUT THE ECMWF
AND GEM ARE CONSIDERABLY FURTHER SOUTH WITH THE NORTHERN BRANCH OF
THE POLAR JET...PLACING THE FEATURE AND ASSOCIATED WAVE ACTIVITY
ALONG THE NORTHERN THIRD OF THE UNITED STATES. THE GFS ON THE
OTHER HAND IS FURTHER NORTH AND WEAKER. THIS EVOLUTION ALONG THE
WEST COAST OF THE UNITED STATES WILL BE KEY FOR THE FORECAST LATE
THIS WEEK ACROSS THE FRONT RANGE AND CENTRAL PLAINS. TEMPERATURES
WILL BE SEASONABLY MILD ON WEDNESDAY...WITH HIGHS IN THE MID 50S
TO MID 60S ACROSS THE FORECAST AREA...WARMEST OVER THE LOWER
ELEVATIONS OF FAR EASTERN SE WYOMING AND WESTERN NEBRASKA. MODELS
INDICATE A SURFACE HIGH BUILDING OVER THE GREAT PLAINS LATE
WEDNESDAY AND ON THURSDAY...RESULTING IN WINDS VEERING INTO THE
EAST AND SOUTHEAST. KEPT SHOWERS AND TSTORMS IN THE FORECAST FOR
WEDNESDAY AND THURSDAY...MAINLY WEST OF THE LARAMIE RANGE.

THE MAIN FORECAST CONCERN IS THURSDAY NIGHT THROUGH FRIDAY...AS
A POTENT SHORTWAVE DISTURBANCE LIFTS NORTHEAST OUT OF ARIZONA. AS
STATED EARLIER...THE ECMWF AND GEM ARE MORE PROGRESSIVE WITH THIS
FEATURE DUE TO THE PLACEMENT OF THE NORTHERN BRANCH OF THE POLAR
JET. THE GFS IS CONSIDERABLY SLOWER INITIALLY AND A BIT FURTHER
SOUTH. MODELS STILL HINTING TOWARDS A DECENT RAIN EVENT SOUTH OF
THE PLATTE RIVER VALLEY...WITH SOME SNOW IN THE MOUNTAINS.
SNOWFALL DOES NOT APPEAR TO BE A THREAT WITH THIS SYSTEM...BUT THE
PATTERN APPEARS TO BE UNSETTLED LATE THIS WEEK AND POTENTIALLY
INTO NEXT WEEKEND AS ANOTHER UPPER LEVEL DISTURBANCE PUSHES
EASTWARD ACROSS THE AREA ON SATURDAY. INCREASED POP BETWEEN 30 TO
50 PERCENT ACROSS THE SOUTH...INCLUDING THE I80 CORRIDOR. CAN NOT
RULE OUT A FEW ISOLATED THUNDERSTORMS IN THIS PATTERN AS
WELL...MAINLY ACROSS SOUTHEAST WYOMING INITIALLY...AND THEN
GRADUALLY SPREADING EAST ACROSS WESTERN NEBRASKA BY NEXT WEEKEND.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z MONDAY EVENING)
ISSUED AT 533 PM MDT SUN APR 19 2015

MOSTLY VFR CONDITIONS THROUGH THE TAF PERIOD. MVFR CIGS AND
ISOLATED RAIN/SNOW SHOWERS WILL BE POSSIBLE AT LAR AND RWL BY
LATE THIS EVENING THROUGH 12Z MON. NORTHWEST WINDS WILL
OCCASIONALLY GUST TO 25 KTS ACROSS THE PLAINS THROUGH 02Z AND THEN
DECREASE.


&&

.FIRE WEATHER...
ISSUED AT 326 PM MDT SUN APR 19 2015

DRY CONDITIONS WILL BE FOUND ACROSS THE AREA THROUGH MID WEEK
ALONG WITH WARMER TEMPERATURES. FIRE DANGER WILL NOT BE
A CONCERN THIS WEEK. THE LOWEST MINIMUM HUMIDITY VALUES WILL
BE TUESDAY WITH VALUES DROPPING INTO THE 20S.

&&

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

$$

UPDATE...RJM
SHORT TERM...SML
LONG TERM...TJT
AVIATION...ZF
FIRE WEATHER...SML



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