Area Forecast Discussion
Issued by NWS Riverton, WY

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000
FXUS65 KRIW 280519
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1019 PM MST SAT DEC 27 2014

.SHORT TERM...TONIGHT THROUGH SUNDAY

UPDATE...
LESS CLOUD COVER HAS ALLOWED TEMPERATURES TO PLUMMET IN A FEW
LOW LYING CALM AREAS THIS EVENING. LOWERED OVERNIGHT LOWS
CONSIDERABLY IN PLACES LIKE THP...WRL...BPI AND PNA. CLOUDS SHOULD
INCREASE OVER THE NEXT SEVERAL HOURS CAPPING MORE SIGNIFICANT DROPS.


A PACIFIC LOW PRESSURE TROUGH DIGGING INTO THE PACIFIC NORTHWEST
WILL SPREAD PACIFIC MOISTURE INTO WESTERN WYOMING TONIGHT THROUGH
SUNDAY.  WITH TIME THE LOW WILL TRACK ACROSS WYOMING INTO THE
CENTRAL PLAINS WHEN IT WILL BRING SOUTH AN ARCTIC COLD FRONT IN
THE NORTHERLY FLOW ON THE WEST SIDE OF THE LOW. TEMPERATURES WILL
GO FROM COLD TO BITTER COLD WITH TIME. SNOW DENSITY SHOULD BE VERY
LOW WITH THIS EVENT...WHICH WILL COMPLICATE THE SNOW ACCUMULATION
THAT OCCURS. THIS SHOULD BE THE LOWEST DENSITY SNOW OF THE SEASON.
HAVE ISSUED WINTER WEATHER ADVISORIES FOR THE WESTERN ZONES TONIGHT
THROUGH SUNDAY NIGHT.

.LONG TERM...SUNDAY NIGHT THROUGH SATURDAY

SNOWFALL WILL CONTINUE WEST OF THE DIVIDE SUNDAY NIGHT...WITH
SIGNIFICANT SNOWFALL ACCUMULATIONS POSSIBLE ACROSS THE WESTERN
MOUNTAINS AND VALLEYS THROUGH THE OVERNIGHT HOURS. ADDITIONAL DETAILS
REGARDING THIS SNOWFALL CAN BE SEEN IN THE WINTER STORM
WATCH...WHICH WILL CONTINUE THROUGH SUNDAY NIGHT FOR THE WESTERN
MOUNTAINS AND VALLEYS. SNOWFALL WILL ALSO STEADILY INCREASE EAST OF
THE DIVIDE SUNDAY NIGHT...ESPECIALLY OVER NATRONA COUNTY AND THE
BIGHORN MOUNTAINS.

SNOWFALL WILL CONTINUE THROUGH MONDAY FOR SWEETWATER...NATRONA...
AND FREMONT COUNTIES INCLUDING THE WIND RIVER MOUNTAINS. MUCH COLDER
TEMPERATURES WILL CONSEQUENTLY BE FOUND ACROSS THE AREA AS THIS
SYSTEM USHERS IN AN ARCTIC AIRMASS. SUBZERO TEMPERATURES MAY
CONTINUE THROUGH THE DAY ON TUESDAY IN RESPONSE TO THE COLDER
AIRMASS AND SNOW ON THE GROUND.

DRYING CONDITIONS WILL BE FOUND BEHIND THIS SYSTEM...WITH CLEARING
SKIES EXPECTED. CLEAR SKIES WILL COMBINE WITH THE SNOW COVER TO
CREATE SOME MORNING FOG...ESPECIALLY IN THE FAVORED LOWER LYING
AREAS. FOG WILL REMAIN THROUGHOUT THE DAY FOR SOME LOCATIONS...AND
RETURN WEDNESDAY NIGHT.

ANOTHER SYSTEM APPROACHING FROM THE NORTH WILL BEGIN TO BRING SOME
LIGHT SNOWFALL ACROSS THE NORTHERN THIRD OF THE FORECAST AREA
THURSDAY EVENING...WITH SNOWFALL SPREADING ACROSS THE WESTERN
MOUNTAINS AND VALLEYS THROUGH FRIDAY NIGHT. SNOWFALL COVERAGE LOOKS
FAVORABLE TO AGAIN SPREAD EAST OF THE DIVIDE BY SATURDAY
MORNING...AND MAY IMPACT THE AREA THROUGH MUCH OF THE WEEKEND.

.AVIATION.../06Z ISSUANCE/

EAST OF THE DIVIDE...KCOD/KCPR/KLND/KRIW/KWRL ROUTES

VFR CONDITIONS WILL PREVAIL AT THE AIRPORTS THROUGH 18Z SUNDAY.
OVER THE MOUNTAINS ALONG AND EAST OF THE CONTINENTAL DIVIDE...
MVFR TO IFR CEILINGS AND VISIBILITIES REDUCED IN SNOW AND BLOWING
SNOW WILL BE ON THE INCREASE THROUGH 18Z SUNDAY...SPREADING INTO
THE FAR NORTH BY 15Z SUNDAY.  AREAS OF LOW LEVEL WIND SHEAR WILL
BE ENCOUNTERED ALONG AND NEAR THE EAST SLOPES OF THE MOUNTAINS.
AREAS OF MVFR TO IFR CEILINGS AND VISIBILITIES REDUCED IN SNOW AND FOG
WILL MOVE INTO THE NORTH AND SPREAD SOUTH FROM 18Z TO 00Z MONDAY AS
AN ARCTIC COLD FRONT MOVES INTO THE AREA. THE ARCTIC COLD FRONT WILL
BRING A PERIOD OF SNOW...WIND AND BITTER COLD WITH WIDESPREAD MVFR
TO AT TIMES IFR SUNDAY NIGHT THROUGH MONDAY.

WEST OF THE DIVIDE...KBPI/KJAC/KPNA/KRKS ROUTES

WIDESPREAD IFR TO MVFR CIGS AND VISIBILITIES DUE TO SNOW WILL
CONTINUE ACROSS THE WEST THROUGH 00Z MONDAY. AREAS OF VFR CONDITIONS
WILL PERSIST OVER THE LOWER ELEVATIONS OF THE SOUTHWEST IN SUBLETTE
AND SWEETWATER COUNTIES THROUGH 12Z BEFORE INCREASING SNOW SHOWERS
CREATE MVFR TO AT TIMES IFR CONDS IN SNOW AND BLOWING SNOW SUNDAY
AND SUNDAY NIGHT. AN ARCTIC COLD FRONT WILL MOVE WESTWARD ACROSS THE
AREA ON MONDAY WITH WIND AND MORE SNOW.

.FIRE WEATHER...

COLD WINTER WEATHER WITH WIDESPREAD SNOW COVER WILL CONTINUE ACROSS
WESTERN AND CENTRAL WYOMING THROUGH THE WEEKEND.  LOW MIXING HEIGHTS
WILL COMBINE WITH GENERALLY LIGHT WINDS BELOW INVERSIONS FOR POOR
SMOKE DISPERSAL.  SNOW WILL INCREASE ACROSS THE WEST TONIGHT AND SUNDAY
AND BEGIN SPREADING SOUTH EAST OF THE CONTINENTAL DIVIDE SUNDAY
AFTERNOON AND SUNDAY NIGHT. BITTER COLD ARCTIC AIR WILL SPREAD
ACROSS THE AREA SUNDAY NIGHT AND MONDAY.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY UNTIL 5 AM MST MONDAY
WYZ001-012-013-023-024.

&&

$$

UPDATE...PS
SHORT TERM...C.BAKER
LONG TERM...BRANHAM
AVIATION...PS
FIRE WEATHER...C.BAKER







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