Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 070940
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
240 AM MST SUN FEB 7 2016

.SHORT TERM...TONIGHT THROUGH TUESDAY NIGHT

NOW THAT THE DRY PACIFIC COOL FRONT HAS SWEPT ACROSS THE AREA...THE
STRONG SOUTHWEST WINDS ALONG THE SOUTHERN WIND CORRIDOR HAVE BEEN
REPLACED WITH STRONG WEST AND NORTHWEST WINDS ACROSS SWEETWATER
COUNTY AND THE WIND RIVER BASIN WHERE CROWHEART GUSTED TO 63 MPH
AND KRIW 42 MPH. THE BRUNT OF THE 700MB COLD FRONT TRACKED ACROSS
JOHNSON COUNTY WHERE NW WINDS HAVE ALSO INCREASED BUT NOT TO THE
SAME MAGNITUDE. THE PRESSURE GRADIENT WILL GRADUALLY EASE OFF
THROUGH MONDAY AS A PROMINENT RIDGE BUILDS IN FROM THE WEST. WNW
WINDS WILL DIMINISH THROUGH THE MORNING HOURS BUT WILL INCREASE
ONCE AGAIN TODAY ACROSS THE SOUTHERN WIND CORRIDOR BUT NOT AS
STRONG AS SATURDAY. SINCE THERE IS STILL QUITE A DEEP BLANKET OF
SNOW ACROSS THIS AREA...ESPECIALLY AROUND CPR...THERE WILL STILL
LIKELY BE SOME DRIFTING SNOW BUT THE VISIBILITY SHOULD NOT BE
AFFECTED AS MUCH BY ANY BLOWING SNOW. BYG/JOHNSON COUNTY SHOULD
SEE A RESURGENCE OF NW WIND LATER THIS MORNING BEHIND THE NEXT AND
LAST SHORTWAVE TO MAINLY AFFECT NORTHEAST WY THIS MORNING. BY
MONDAY...WINDS WILL BE MUCH LIGHTER. EXCEPT FOR A FEW ISOLATED
SNOW FLURRIES OR AREAS OF LIGHT SNOW IN THE FAR WEST MTNS THIS
MORNING...THE SHORT TERM FCST WILL BE PRECIP FREE. BY TUESDAY
MORNING...ENOUGH WARM AIR ADVECTION ALOFT WILL TAKE PLACE TO
STEEPEN THE POSITIVE LAPSE RATE FOR PATCHY FOG TO FORM IN THE SNOW
COVERED BASINS AND VALLEYS. TEMPS WILL BE WARMING UP THROUGH MID
WEEK WITH THE TRAPPED BASINS AND VALLEY FOLLOWING BEHIND.

.LONG TERM...WEDNESDAY THROUGH SUNDAY

SYNOPSIS...UPPER RIDGE OF HIGH PRESSURE WILL BRING DRY AND
UNSEASONABLY WARM WEATHER THROUGH FRIDAY EXCEPT FOR SOME WESTERN
VALLEYS WHERE STEEP INVERSIONS SET UP.  NEXT WEEKEND...A PACIFIC
COLD FRONT WILL BRING CHANCES OF SNOW SHOWERS MAINLY THE WEST WITH
WINDY AREAS ACROSS CENTRAL AND SOUTHERN WYOMING.

DISCUSSION...A STRONG RIDGE OF HIGH PRESSURE ALONG THE WEST COAST
WILL GRADUALLY SHIFT EASTWARD AND DEAMPLIFY THROUGH FRIDAY. THE
MAIN FORECAST CHALLENGE CONTINUES TO BE TEMPERATURES...WITH
JACKSON AND STAR VALLEYS THE MOST LIKELY TO REMAIN UNDER STEEP
INVERSIONS...WITH LOWS IN THE SINGLE DIGITS AND HIGHS REMAINING
MOSTLY BELOW FREEZING THROUGH THURSDAY. ON THE OTHER END...SNOW-
FREE AREAS IN THE NORTHERN FOOTHILLS...BUFFALO AND CODY...WILL SEE
HIGHS MAINLY IN THE 50S THROUGH SATURDAY. THE BIGGEST QUESTION
WILL BE THE SNOW COVERED AREAS ACROSS THE SOUTH INTO NATRONA AND
FREMONT COUNTIES. THESE AREAS WILL BE SLOWER TO WARM UP AS THE
SNOWPACK MELTS OFF. FORECAST CONTINUES TO KEEP THESE AREAS A FEW
DEGREES BELOW GUIDANCE NUMBERS. ON THURSDAY...SOME STRENGTHENING
OF MID-LEVEL NW FLOW AND WEAK COLD ADVECTION ON THURSDAY MAY BE
ENOUGH MIX OUT THE LOWER BIGHORN AND WIND RIVER BASINS.

ECMWF AND GFS SHOW SOME SPREAD WITH THE DETAILS OF NEXT PACIFIC
TROUGH THAT WILL SPLIT THROUGH THE RIDGE NEXT WEEKEND...BUT TIMING
IS GOOD ENOUGH SHOW COLD FRONTAL PASSAGE SATURDAY NIGHT WITH
INCREASING CHANCES OF SNOW IN THE WEST...WINDY AREAS ACROSS CENTRAL
WYOMING BEHIND THE FRONT ON SUNDAY TO FORECAST INCREASING CHANCES OF
SNOW INTO THE WEST SATURDAY NIGHT WITH FR CONTINUING INTO
SUNDAY...WITH WINDY AREAS ACROSS CENTRAL WYOMING BEHIND THE COLD
FRONT ON SUNDAY.  TEMPERATURES WILL REMAIN SEASONABLY MILD BEHIND
THE FRONT.

&&

.AVIATION.../12Z ISSUANCE/

ANY MOUNTAIN SNOW SHOWERS SHOULD COME TO AN END BY AROUND 15Z...WITH
VFR CONDITIONS EXPECTED AT ALL TERMINALS. KCPR COULD SEE SOME
CEILINGS BETWEEN 040-080 KFT AGL THIS MORNING...BUT THIS AREA OF
LOW/MID LEVEL CLOUDINESS SHOULD SCATTER OUT BY MIDDAY...WITH ONLY
FEW-SCT HIGH CLOUDS FOR THE REST OF THE DAY. OTHERWISE...BREEZY TO
WINDY WEST TO NORTHWEST WIND WILL BE OBSERVED ACROSS NORTHERN
JOHNSON...UPPER WIND RIVER BASIN...AND SWEETWATER COUNTY...BUT NOT
AS WINDY AS WHAT OCCURRED SATURDAY OR SATURDAY EVENING.
TONIGHT...THE MAIN CONCERN WILL BE WARM AIR ADVECTION LOW CLOUDS
DEVELOPING OVER FAR WESTERN WYOMING...WHICH COULD IMPACT KJAC
TERMINAL. THESE CLOUDS COULD BE MVFR...BUT WILL KEEP THEM IN LOW VFR
RANGE FOR NOW.

&&

.FIRE WEATHER...

PERIODS OF STRONG WIND WILL REMAIN ACROSS PORTIONS OF SWEETWATER
COUNTY...THE WIND RIVER BASIN AND NORTHERN JOHNSON COUNTY THROUGH
THIS MORNING. LIGHT SNOWFALL WILL ALSO REMAIN PRESENT OVER AREAS
OF WESTERN WYOMING...WITH SNOWFALL GENERALLY TAPERING OFF THROUGH
THE EARLY MORNING HOURS. HIGH PRESSURE WILL GAIN DOMINANCE OVER
THE AREA THIS AFTERNOON...THOUGH A RETURN OF GUSTY WIND IS
POSSIBLE. AS HIGH PRESSURE SETTLES FURTHER DURING THE WORK
WEEK...WIND WILL RELAX ACROSS THE AREA. MIXING HEIGHTS ARE
EXPECTED TO REMAIN LOW ACROSS THE LOWER ELEVATIONS...KEEPING SMOKE
DISPERSAL CATEGORIES ON THE LOWER SIDE.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...LIPSON
LONG TERM...AEM
AVIATION...WM
FIRE WEATHER...LIPSON


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