Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 011732
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
1031 AM MST SUN FEB 1 2015

.SHORT TERM...(TODAY THROUGH MONDAY NIGHT)
ISSUED AT 550 AM MST SUN FEB 1 2015

LIGHT SNOW SHOWERS CONTINUE EARLY THIS MORNING DOWNSTREAM OF THE
MOUNTAINS OF SOUTHEAST WYOMING AND ALONG THE PINE RIDGE IN THE
NORTHERN NEBRASKA PANHANDLE. THE MIDLEVEL SHORTWAVE TROUGH IS
EXITING THE CWA WHILE THE LEFT EXIT REGION OF THE JET IS MOVING
OVERHEAD. BREEZY NORTHWEST WINDS IN THE LOW LEVELS ARE ADDING A
BIT OF OROGRAPHIC INFLUENCE TO THE BROADSCALE LIFT FROM THE
JET...HOWEVER DRIER AIR IS MOVING IN FROM THE NORTH THUS SNOW
RATES REMAIN ON THE LIGHTER SIDE. BIGGEST IMPACT WILL REMAIN NEAR
THE PINE RIDGE...INCLUDING CHADRON AND ALLIANCE...WHERE ROADS WILL
BE SLICK AND SNOW COVERED IN SOME AREAS. EXPECT SHOWERS TO END
SHORTLY AFTER SUNRISE WITH COOL TEMPS AND BREEZY NORTHWEST WINDS
TO CONTINUE THROUGH MUCH OF TODAY.

ATTENTION THEN TURNS TO THE RETURN OF A FAVORABLE WINDY PATTERN FOR
THE WIND PRONE AREAS OF SOUTHEAST WYOMING. 00Z MODELS CONTINUE TO
DEPICT MARGINAL WINDS DEVELOPING TONIGHT IN THE WIND PRONE AREAS AS
A WEAK DISTURBANCE MOVES OVERHEAD AND DEEPENS THE LEESIDE PRESSURE
TROUGH. THE LLVL PRESSURE GRADIENT IS STILL PROGGED TO STRENGTHEN
BUT HOVER AROUND 55 DAM THRU TONIGHT...WHICH IS CONSISTENT WITH
PREVIOUS RUNS. CONCERNED THAT THE RAPID STRENGTHENING OF THE
GRADIENT AFTER SUNSET TONIGHT WILL PRODUCE LOCALLY STRONG WINDS IN
THE ARLINGTON AND BORDEAUX AREAS...BUT NOT CONFIDENT ENOUGH THE
WINDS WILL BE HIGH ENOUGH TO WARRANT ANY HIGH WIND HIGHLIGHTS. STILL
PRESENTED GUSTS OF 50 TO 55 MPH IN THE FORECAST THO...WITH PERHAPS A
FEW LOCALLY HIGHER GUSTS POSSIBLE EARLY MONDAY MORNING. THE MAIN
CONCERN WILL BE MONDAY NIGHTS WIND EVENT WHERE THE GRADIENT WILL
BECOME QUITE STRONG LATE MONDAY NIGHT AND WILL REMAIN SO THROUGH
TUESDAY AS A SLIGHTLY STRONGER SHORTWAVE MOVES OVERHEAD. LOOKING
AT VALUES RANGING FROM 60 TO 70 DAM WHICH IS QUITE FAVORABLE FOR
MORE FREQUENT AND HIGHER GUSTS OF 60 TO 65 MPH IN THE WIND
CORRIDOR FROM ARLINGTON TO BORDEAUX...AND IN THE SOUTHERN LARAMIE
RANGE AND FOOTHILLS...ALTHO WOULDNT BE SURPRISED TO SEE LOCALLY
HIGHER GUSTS NEAR 70 MPH AS WELL. SINCE THIS PATTERN IS
CLIMATOLOGICALLY FAVORABLE FOR HIGH WINDS...AND MODELS HAVE BEEN
MAINTAINING THE IDEA THAT WINDS WILL BE STRONGEST ON MONDAY
NIGHT...WENT AHEAD WITH A HIGH WIND WATCH FOR THIS EVENT WHICH
WILL LAST THRU TUESDAY AFTERNOON.

OTHERWISE...TEMPS WILL BOUNCE BACK INTO THE 40S AND 50S FOR MUCH OF
THE AREA...WHILE OROGRAPHIC SNOW WILL RETURN TO THE MOUNTAINS LATE
TONIGHT THROUGH MIDWEEK AS MIDLEVEL MOISTURE AND SOUTHWESTERLY
UPSLOPE WINDS GENERATE OCCASIONAL SNOW SHOWERS. WITHOUT ANY
SIGNIFICANT UPPER LEVEL FORCING PROGGED THROUGH THIS TIME...THINK
DEEP LEVEL LIFT WILL REMAIN LOW WITH SNOW DEVELOPMENT TIED MAINLY
TOWARD OROGRAPHIC EFFECTS. THEREFORE...LIKELY TO SEE CONSISTENT BUT
LIGHT SNOW SHOWERS LATE TONIGHT THROUGH MONDAY NIGHT WITH IMPACTS
GENERALLY ON THE LOW SIDE FOR THE MOUNTAINS.

.LONG TERM...(TUESDAY THROUGH SATURDAY)
ISSUED AT 550 AM MST SUN FEB 1 2015

THE MODELS CONTINUE TO INDICATE THAT TUES WILL BE QUITE WINDY ACROSS
SOUTHEAST WYOMING.  THIS IS DUE TO THE COMBINATION OF A STRONG LLVL
GRADIENT (CAG-CPR IS 65-70 METERS) AND GOOD MIXING.  CURRENT
THINKING IS HIGH WINDS WILL BE CONFINED TO THE WIND PRONE
AREAS...ALTHOUGH THE GFS SOUNDING FROM CHEYENNE SUGGESTS THAT GUSTS
TO 45-50 KTS WILL BE POSSIBLE.  WITH A LOT OF CLOUD COVER...NOT
CONVINCED WE WILL SEE AS GOOD LLVL LAPSE RATES AS THE GFS INDICATES.
 THE GRADIENT BEGINS TO DECREASE BY LATE TUES AFTN AND WEST WINDS
WILL LIKELY COME DOWN AFTER 00Z WED.  TEMPS ON TUES WILL BE AROUND
10 DEGREES ABOVE NORMAL WITH THE PRONOUNCED DOWNSLOPE IN PLACE.

LARGE SCALE ASCENT IS PROGGED TO INCREASE BY TUES NIGHT AND MORESO
WED MORNING IN ADVANCE OF A SHORTWAVE IN THE FAST NORTHWESTERLY FLOW
ALOFT.  BOTH THE GFS AND ECMWF SHOW WIDESPREAD SNOWFALL DEVELOPING
OVER MUCH OF THE CWA BY WED MORNING AS SFC UPSLOPE BEHIND THE COLD
FRONT COMBINES WITH INCREASING UPPER LEVEL DIFFLUENCE.  QPF AMOUNTS
FROM WED MORNING THROUGH THE AFTN ARE GENERALLY 0.3-0.5 INCHES...SO
THIS COULD BE A GOOD ADVISORY EVENT.  WINDS ARE GENERALLY LESS THAN
15 KTS SO BLOWING SNOW SHOULD NOT BE MUCH OF A CONCERN.  WILL
CONTINUE TO MONITOR THE SYSTEM SINCE IT HAS THE POTENTIAL TO BRING
WIDESPREAD MODERATE SNOW AMOUNTS.  SNOWFALL RATES WILL DEFINITELY
PICK UP IN THE SIERRA MADRE AND SNOWY RANGES BY LATE TUES NIGHT.
PRECIP WILL COME TO AN END BY WED EVENING.

THE REMAINDER OF THE EXTENDED PERIOD WILL FEATURE INCREASING HEIGHTS
AND TEMPS IN A RATHER PROGRESSIVE PATTERN.  THE ECMWF SHOWS 700MB
TEMPS RISING TO 6C BY FRI ALONG WITH INCREASING WEST WINDS...SO
TEMPS WOULD BE WELL ABOVE NORMAL.  WITH A STRONG ZONAL JET STREAMING
INTO WYOMING BY FRI AND INTO NEXT WEEKEND AND LLVL GRADIENTS
RISING...EXPECT A GOOD DEAL OF WIND.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z MONDAY MORNING)
ISSUED AT 1031 AM MST SUN FEB 1 2015

MVFR CIGS WILL OVER THE PLAINS LATE THIS MORNING ALONG WITH A FEW
SNOW SHOWERS EXPECTED TO GRADUALLY BREAK UP EARLY THIS AFTERNOON
WITH MAINLY VFR BY LATE AFTERNOON.  CLOUDS INCRG AGAIN OVERNIGHT
ALONG WITH INCREASING WINDS AROUND THE SE WY MTNS.

&&

.FIRE WEATHER...
ISSUED AT 550 AM MST SUN FEB 1 2015

TODAY WILL REMAIN COOL WITH SNOW COMING TO AN END THIS MORNING.
TEMPERATURES WILL INCREASE BACK INTO THE 40S AND 50S FOR THE START
OF THE WORK WEEK...ALONG WINDY CONDITIONS IN THE WIND PRONE
AREAS OF SOUTHEAST WYOMING. SNOW SHOWERS WILL REDEVELOP IN THE
MOUNTAINS LATE TONIGHT AND WILL CONTINUE OFF AND ON THROUGH MIDWEEK.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...HIGH WIND WATCH FROM MONDAY EVENING THROUGH TUESDAY AFTERNOON
     FOR WYZ106-110-116-117.

NE...NONE.
&&

$$

SHORT TERM...RJM
LONG TERM...ZF
AVIATION...RE
FIRE WEATHER...RJM


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