Area Forecast Discussion
Issued by NWS Riverton, WY

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000
FXUS65 KRIW 310654
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1154 PM MST FRI JAN 30 2015

UPDATE...ADDED 06Z AVIATION DISCUSSION.

.SHORT TERM...TONIGHT THROUGH SATURDAY (ISSUED AT 230 PM MST)

A WARM PACIFIC LOW OVER THE FOUR CORNERS AREA THIS
AFTERNOON...CONTINUES TO STREAM HIGH CLOUDS ACROSS THE COWBOY
STATE. LOW CLOUDS HAVE MADE THEIR WAY INTO THE I-80 CORRIDOR NEAR
KRKS...WHILE THE RAIN SHOWERS REMAIN WELL TO THE SOUTH IN NE
UT/NW CO. THESE SHOWERS WILL SLOWLY MAKE THEIR WAY NORTHWARD THIS
EVENING. TEMPERATURES ARE EXPECTED TO BE AT OR BELOW FREEZING BY
THIS TIME...PRODUCING LIGHT SNOW SHOWERS ACROSS SWEETWATER COUNTY.
ACCUMULATIONS ARE EXPECTED TO REMAIN LIGHT THROUGH MID MORNING
SATURDAY.

FOG CONTINUES TO HOLD ON OVER NORTHERN PORTIONS OF THE BIGHORN
BASIN...DESPITE THE CLOUDS ALOFT. FOG WILL BEGIN TO FILL IN
FURTHER SOUTH TOWARD KWRL DURING THE OVERNIGHT HOURS. FOG SHOULD
LIFT OUT BY MID MORNING...AS SKIES BEGIN TO CLEAR ACROSS THE AREA.

A COLD FRONT WILL BEGIN TO IMPACT NORTHERN PORTIONS LATE SATURDAY
AFTERNOON...BRINGING LOW CLOUDS AND GUSTY WINDS TO JOHNSON COUNTY.
LIGHT SNOW SHOWERS WILL BE POSSIBLE IN THE BIGHORNS.

.LONG TERM...SATURDAY NIGHT THROUGH FRIDAY NIGHT

THE SHORTWAVE MOVING THROUGH NORTHEASTERN WYOMING SATURDAY NIGHT
WILL HAVE SOME IMPACT OVER THE EASTERN PORTION OF THE FORECAST AREA
THROUGH SUNDAY MORNING. LIGHT SHOWER ACTIVITY IS EXPECTED.

BUILDING NORTHWEST FLOW THEN EXPECTED SUNDAY AFTERNOON AND EVENING
AS A RIDGE OF HIGH PRESSURE BUILDS OFF THE PACIFIC COAST. THIS
SYSTEM WILL BRING SOME MOISTURE INTO NORTHWESTERN WYOMING EARLY
MONDAY MORNING...MAINLY IMPACTING WESTERN AND NORTHERN WYOMING.

ANOTHER...MORE SIGNIFICANT PUSH OF MOISTURE WILL FOLLOW THAT SYSTEM
QUICKLY...WITH PRECIPITATION SPREADING INTO WESTERN WYOMING MONDAY
EVENING. ACTIVITY FROM THIS SYSTEM WILL LINGER THROUGH WEDNESDAY AS
ANOTHER PUSH COMES DOWN FROM THE NORTH AS WELL. THE ACTIVITY WILL
SPREAD TO INCLUDE MUCH OF THE FORECAST AREA. MODELS HAVE SOME
VARIATIONS ON THIS SYSTEM...WITH THE GFS REMAINING THE MOST
AGGRESSIVE MODEL. HOWEVER...ALL MODELS ARE IN FAIR AGREEMENT THAT
COVERAGE WILL INCREASE THROUGH WEDNESDAY MORNING.

CONDITIONS TO IMPROVE WEDNESDAY AFTERNOON AND EVENING. A BUILDING
RIDGE WILL HELP TO CLEAR OUT ACTIVITY...THOUGH SOME VERY LIGHT
ACTIVITY MAY REMAIN POSSIBLE ACROSS THE NORTHWEST THROUGH THURSDAY
AFTERNOON. DRY CONDITIONS EXPECTED BY FRIDAY MORNING...WHICH MAY NOT
LAST LONG.

&&

.AVIATION.../06Z ISSUANCE

AREAS OF FOG WILL OBSCURE TERRAIN ACROSS THE LOWER BIGHORN BASIN
THROUGH 14Z...VCNTY KGEY-KWRL.  A COLD FRONT WILL PUSH SOUTH ACROSS
NORTHERN WYOMING LATE SATURDAY MORNING...LIKELY SCOURING OUT ANY
LINGERING FOG.  HOWEVER...AREAS OF LOWER MVFR/IFR CIGS AND -SN WILL
FOLLOW THE FRONT INTO NORTHERN WYOMING AFTER 20Z...AND SOUTHWARD TO
NEAR A VCNTY KRIW-KCPR LINE BY 00Z SUNDAY.  AREAS OF LOWER MVFR/IFR
CIGS...LCL LIFR CIGS/FG WILL LIKELY REMAIN AGAINST THE EAST SLOPES
OF THE DIVIDE THROUGH 12Z SUNDAY.

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

AREAS OF IFR/MVFR CIGS AND -SN WILL GRADUALLY DECREASE ACROSS THE
INTERSTATE 80 CORRIDOR THROUGH 14Z...BUT PATCHY FOG MAY LINGER IN
THIS AREA THROUGH THE MORNING.  OTHERWISE...VFR CONDITIONS WILL
PREVAIL ACROSS THE AREA 15Z SAT-03Z SUNDAY.  A COLD FRONT WILL
PLUNGE DOWN THE EAST SLOPES OF THE DIVIDE LATE SATURDAY MORNING
THROUGH SATURDAY AFTERNOON WITH SOME MTN OBSCURATIONS POSSIBLE ALONG
THE DIVIDE.  THIS FRONT MAY PUSH LOWER MVFR/IFR CIGS INTO VCNTY KRKS
AFTER 06Z SUNDAY.  FURTHER OUT FROM THE FRONT....LOWER MVFR/IFR CIGS
FROM EASTERN IDAHO MAY PUSH INTO THE FAR WEST...VCNTY KJAC-KAFO
AFTER 03Z SUNDAY.

&&

.FIRE WEATHER...

FIRE DANGER IS LOW FOR ALL AREAS...AND WILL REMAIN SO THROUGH NEXT
WEEK. MEASURABLE PRECIPITATION WILL NOT FALL ACROSS THE FORECAST
AREA UNTIL LATE SATURDAY INTO SUNDAY MORNING EAST OF THE DIVIDE.
FROM SUNDAY NIGHT THROUGH THE NEXT WORK WEEK...A SERIES OF
DISTURBANCES WILL RIDE THROUGH THE REGION...AFFECTING MAINLY THE
WESTERN AND NORTHERN DISPATCH ZONES. SATURDAY WILL SEE
IMPROVEMENT IN BOTH MIXING ABILITY AND DISPERSION...ESPECIALLY
EAST OF THE DIVIDE AND ACROSS THE SOUTHERN ZONES.

&&

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

$$

SHORT TERM...LAVOIE
LONG TERM...BRANHAM
AVIATION...AEM
FIRE WEATHER...LAVOIE








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