Winter Storm Warning 5, NWS Riverton, WY

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE RIVERTON WY
236 AM MST MON MAR 2 2015

.SHORT TERM...TODAY THROUGH WEDNESDAY NIGHT

FORECAST STILL ON TRACK FOR THE UPCOMING STORM SYSTEM TO IMPACT THE
AREA THROUGH TUESDAY EVENING. PRECIPITATION WILL BEGIN ACROSS
SOUTHERN SWEETWATER COUNTY THIS MORNING AND AFTERNOON...BUT
TEMPERATURES WILL BE TOO MILD TO PRODUCE MUCH IN THE WAY OF
HAZARDOUS CONDITIONS.

A CANADIAN COLD FRONT AND ASSOCIATED SNOWFALL WILL IMPACT NORTHERN
WYOMING THIS EVENING WITH PERIODS OF MODERATE SNOWFALL...STRONG
WIND...AND MUCH COLDER TEMPERATURES. THIS SYSTEM WILL QUICKLY MOVE
SOUTH THROUGH THE FORECAST AREA THROUGH THE EVENING HOURS. THE
SYSTEM WILL COMBINE WITH THE ALREADY OCCURRING PRECIPITATION ACROSS
SWEETWATER...SOUTHEASTERN FREMONT...AND NATRONA COUNTIES TO CREATE
WINTER STORM CONDITIONS WITH PERIODS OF HEAVY SNOWFALL AND GUSTY
WIND. WINTER STORM WARNINGS HAVE BEEN ISSUED FOR THESE AREAS FOR
THIS EVENING THROUGH WEDNESDAY AFTERNOON.

GENERAL BELIEF IS THAT THE FLOW IS NOT QUITE IDEAL FOR THE INCLUSION
OF THE LANDER FOOTHILLS IN THE WINTER STORM WARNING. THEIR EXPECTED
SNOWFALL AMOUNTS HAVE LEFT THEM TO BE INCLUDED IN THE WINTER WEATHER
ADVISORY...THOUGH IT IS POSSIBLE SOME AREAS IN THE LANDER FOOTHILLS
MAY VERY WELL SEE HIGHER AMOUNTS OF SNOWFALL. ALSO DECIDED TO
INCLUDE THE WESTERN SLOPES OF THE WIND RIVER MOUNTAINS IN THE
ADVISORY TO COVER THE FULL LENGTH OF HIGHWAY 28 THROUGH SOUTH PASS
WHERE WIND AND SNOWFALL WILL RESULT IN HAZARDOUS TRAVEL CONDITIONS
OVERNIGHT.

SNOWFALL STILL LOOKS TO TAPER OFF QUICKLY TUESDAY NIGHT WITH
BUILDING NORTHERLY FLOW. GENERALLY DRY CONDITIONS ANTICIPATED BY
LATE WEDNESDAY MORNING ACROSS THE FORECAST AREA. THE COLDER
TEMPERATURES ASSOCIATED WITH THIS SYSTEM WILL LINGER THROUGH
WEDNESDAY...WITH SINGLE DIGITS EXPECTED WEDNESDAY NIGHT.

.LONG TERM...THURSDAY THROUGH MONDAY

A RELATIVELY DRY NORTHWEST FLOW...AND A WARMING TREND TO SEASONAL
LEVELS WILL OCCUR LATE THIS WEEK...AND REMAIN IN PLACE THROUGH EARLY
NEXT WEEK. THE MAIN CAVEAT IS THE ECMWF STILL SHOWS A DISTINCT
SHORTWAVE TROUGH...AND ASSOCIATED WEAK COLD FRONT PUSHING SOUTHEAST
ACROSS THE AREA IN THE FRIDAY/SATURDAY TIME FRAME. HOWEVER...THE 00Z
GFS AND GEM ARE KEEPING THIS WAVE LESS AMPLIFIED AND FARTHER
NORTHEAST. WILL HAVE SOME SLIGHT MOUNTAIN POPS FOR THIS SYSTEM
FRIDAY AND SATURDAY...BUT IF MODELS TREND TOWARD THE ECMWF...POPS
WILL NEED TO BE EXPANDED AND INCREASED...MAINLY FRIDAY
NIGHT/SATURDAY.

&&

.AVIATION.../18Z ISSUANCE/

EAST OF THE DIVIDE...KCOD/KCPR/KLND/KRIW/KWRL ROUTES
AN EXPANSIVE AREA OF SNOWFALL WILL PERSIST ACROSS THE EAST HALF OF
SWEETWATER COUNTY THROUGH 00Z TODAY RESULTING IN WIDESPREAD IFR/MVFR
CONDITIONS AND MTN OBSCURATIONS. VFR CONDITIONS...FL SCT-BKN200-250
WILL CONTINUE NORTH AND WEST OF THERE THROUGH 21Z THIS AFTERNOON.
A LOW PRESSURE SYSTEM LIFTING NE ACROSS THE GREAT BASIN WILL PUSH
SCT MVFR -SHRASN NORTH TO A VCNTY KLND-KCPR LINE 21Z TODAY-00Z TUE.
CONDITIONS WILL THEN DETERIORATE RAPIDLY AFTER 00Z TUE AS A COLD
FRONT PUSHES DOWN FROM THE NORTH BRINGING WIDESPREAD MVFR/IFR -SN
AND MTN OBSCURATIONS ACROSS THE AREA BY 4Z TUE ALONG WITH INCREASING
NORTH WIND AND SOME BLOWING SNOW.  THE HEAVIEST SNOWFALL AND AREAS OF
LIFR CONDITIONS WILL BE FOUND VCNTY AND SOUTH OF A KCPR-KLND LINE AS
THE SNOWFALL AND LOW CIGS ALREADY IN PLACE ACROSS THE EAST HALF OF
SWEETWATER COUNTY CONTINUE TO INCREASE AND LOWER RESPECTIVELY. THESE
CONDITIONS WILL PERSIST THROUGH 12Z TUE. THESE CONDITIONS WILL BEGIN
TO IMPROVE FROM NORTHWEST TO SOUTHEAST AFTER 12Z TUESDAY.

WEST OF THE DIVIDE...KBPI/KJAC/KPNA/KRKS ROUTES
THE UPPER LEVEL DISTURBANCE BRINGING AN INITIAL BAND OF MVFR/IFR -SN
NORTH INTO SOUTHERN WYOMING TO VCNTY AND SOUTH OF INTERSTATE 80 WILL
IMPROVEMENT SOMEWHAT BY 19Z THIS AFTERNOON. THEN MORE WIDESPREAD
PERSISTENT IFR SNOW IS EXPECTED TO DEVELOP ACROSS SOUTHERN WYOMING
AROUND 20Z TODAY AND PERSIST INTO THE OVERNIGHT HOURS.  A CANADIAN
COLD FRONT PUSHING DOWN FROM THE NORTH WILL SPREAD SNOW SOUTH ALONG
THE DIVIDE THIS EVENING...FILLING WESTERN WYOMING WITH WIDESPREAD
MVFR/IFR -SN BY 06Z TUES ALONG WITH MTNS BECOMING MOSTLY OBSCURED.
KRKS WILL BE IN THE BATTLE ZONE BETWEEN THE NORTHEAST AND WEST WINDS
FOR MUCH OF TUESDAY WITH WEST WINDS WEST OF THERE AND NORTHEAST
WINDS NORTH AND EAST OF THERE. THE SNOWFALL AND CIGS WILL DECREASE
AND LIFT RESPECTIVELY FROM NORTHWEST TO SOUTHEAST DURING THE DAY
TUESDAY.

&&

.FIRE WEATHER...

A WINTRY STORM SYSTEM IS STILL ON TRACK TO IMPACT THE FORECAST AREA
THIS EVENING AND THROUGH WEDNESDAY MORNING. MUCH OF THE AREA IS
ANTICIPATED TO EXPERIENCE LIGHT TO MODERATE SNOWFALL AMOUNTS...WITH
AREAS OF SOUTHWESTERN WYOMING EXPECTED TO SEE ENHANCED SNOWFALL. IN
ADDITION TO SNOWFALL...THE APPROACHING CANADIAN COLD FRONT WILL
BRING MUCH COLDER TEMPERATURES...AND PERIODS OF VERY STRONG WIND
THROUGH THE OVERNIGHT HOURS.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WARNING FROM 6 PM THIS EVENING TO 6 PM MST TUESDAY
WYZ019-020-022-030.

WINTER WEATHER ADVISORY FROM 6 PM THIS EVENING TO 6 PM MST
TUESDAY WYZ002>011-014>018-028-029.

&&

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

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