Area Forecast Discussion
Issued by NWS Riverton, WY

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000
FXUS65 KRIW 140626
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1126 PM MST SAT FEB 13 2016

.UPDATE...06Z AVIATION DISCUSSION ADDED.

&&

.AVIATION.../06Z ISSUANCE/

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

A LARGE FETCH OF PACIFIC MOISTURE WILL SPREAD WIDESPREAD MVFR/IFR
SN/-SN INTO THE FAR WEST VALLEYS AND WESTERN MOUNTAINS BETWEEN 08Z-
12Z.  THESE MVFR/IFR CONDITIONS AND WIDESPREAD MTN OBSCURATIONS WILL
PREVAIL VCNTY KPNA-KAFO LINE AND NORTH THROUGH THE REST OF THE
PERIOD WITH POSSIBLY A WINDOW OF IMPROVEMENT LATE SUNDAY AFTERNOON
INTO SUNDAY EVENING.  FURTHER SOUTH...RAIN AND SNOW SHOWER ACTIVITY
WILL BE MORE ISOLD ALONG KBPI-KRKS ROUTES BUT SURROUNDING MTNS WILL
BE FQTLY OBSCURED.  SFC WEST WINDS AT 20-30KTS WITH GUSTS TO 40KTS
WILL PREVAIL ALONG THE INTERSTATE 80 CORRIDOR LATE SUNDAY AFTERNOON
THROUGH MONDAY NIGHT.


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

VFR CONDITIONS WILL PREVAIL THROUGH 18Z SUNDAY.  AREAS OF LLWS WILL
BE ENCOUNTERED VCNTY AND WEST OF KLND-KCOD THROUGH THE MORNING WITH
RIDGE TOP WINDS FROM 290 AT 35KT.   A WEAK UPPER DISTURBANCE MAY
BRING WDLY SCT -SHRASN SE ALONG A VCNTY KCOD-KWRL-KCPR LINE SUNDAY
AFTN/EVE ALONG WITH POSSIBLY BRIEF MVFR CONDITIONS IN THE VCNTY OF
THESE TERMINALS.  OTHERWISE...MAINLY MTNS ABOVE 9KFT WILL REMAIN
FQTLY OBSCD IN SHSN ACROSS CENTRAL WYOMING SUNDAY AFTERNOON AND
NIGHT.

&&

.PREV DISCUSSION... /ISSUED 602 PM MST SAT FEB 13 2016/


UPDATE...
HIGH WIND WARNINGS HAVE BEEN ALLOWED TO EXPIRE ACROSS CENTRAL
WYOMING WITH WINDS EXPECTED TO CONTINUE TO DIMINISH EARLY THIS
EVENING.

PREV DISCUSSION... /ISSUED 215 PM MST SAT FEB 13 2016/

SHORT TERM...TONIGHT THROUGH SUNDAY

MOIST WEST FLOW FROM THE PACIFIC WILL BRING A PROLONGED PERIOD OF
SNOW SUNDAY THROUGH MONDAY TO WESTERN WYOMING. SNOWFALL UP TO 20
INCHES IS EXPECTED IN THE TETON MOUNTAINS WITH UP TO A FOOT IN
THE REST OF THE WESTERN MOUNTAINS. THE VALLEYS ARE EXPECTED TO
RECEIVE 6INCHES AND MAY HAVE SOME RAIN MIXED WITH SNOW MONDAY
AFTERNOON.STRONG WEST WINDS OVER THE PASSES AND HIGH RIDGES WILL
CAUSE SOME BLOWING AND DRIFTING SNOW OVER TETON...TOGWOTEE AND
SALT RIVER PASSES. EAST OF THE CONTINENTAL DIVIDE STRONG WINDS
ARE EXPECTED TO CONTINUE. SNOW WILL SPREAD INTO THE BIGHORN
MOUNTAINS. MOST AREAS WILL HAVE STRONG WEST TO NORTHWEST WINDS.
THE WINDS SHOULD KEEP TEMPERATURES MORE ON THE MILD SIDE WITH
STRONG MIXING INHIBITING THE FORMATION OF INVERSIONS.

LONG TERM...SUNDAY NIGHT THROUGH SATURDAY

MOISTURE WILL CONTINUE TO MOVE ALONG THE NORTHWEST FLOW SUNDAY NIGHT
AND INTO MONDAY WITH OCCASIONALLY HEAVY SNOW EXPECTED ACROSS THE
WEST OVERNIGHT INTO THE MORNING HOURS. A PUSH OF MORE MILD AIR
ARRIVES ON MONDAY AFTERNOON WITH A CHANGE OVER TO RAIN POSSIBLE IN
THE VALLEYS WITH RAIN ON TOP OF SNOW EXPECTED TO CAUSE HAZARDOUS
TRAVEL EVEN BEYOND THE ADVISORY PERIOD AS REFREEZING OCCURS MONDAY
NIGHT. WIND WILL ALSO CONTINUE TO BE AN ISSUE WITH A TIGHT GRADIENT
REMAINING AT THE SURFACE...50KT WIND BARBS AT H7 AND STRONG FORCING
FOR DESCENT BEHIND THE UPPER TROUGH MONDAY AFTERNOON AND EVENING.
EXPECT SIGNIFICANT BLOWING SNOW AT PASS LEVEL. THE DOWNWARD FORCING
WILL ALSO FLOOD THE FOOTHILLS AND LOWER ELEVATIONS WITH GUSTY
WINDS...ESPECIALLY FOR THOSE WHO ARE PRONE TO WEST NORTHWEST FLOW
LIKE THE CODY FOOTHILLS...UPPER WIND RIVER BASIN INTO THE MISSOURI
VALLEY AREA AND PORTIONS OF THE UPPER GREEN RIVER BASIN...WIND GUSTS
OVER 45 MPH WILL BE COMMON IN THESE AREAS MONDAY EVENING.

RIDGING BUILDS IN FROM THE WEST TUESDAY INTO WEDNESDAY WITH MILDER
TEMPERATURES AND WEATHER EXPECTED FOR MID WEEK. A SYSTEM BEGINS TO
MOVE INTO THE WEST AS EARLY AS THURSDAY MORNING AND THEN MOVING EAST
ACROSS THE REST OF THE AREA LATER THURSDAY INTO THURSDAY NIGHT.
PERIODS OF STRONG WIND WILL BE POSSIBLE WITH THE FRONT ALONG WITH
ANOTHER ROUND OF SNOW AND RAIN ACROSS THE WEST AND SOUTH...
EVENTUALLY TURNING TO ALL SNOW BEHIND A COLD FRONT. PRECIPITATION
WILL BE SPOTTY EAST OF THE DIVIDE...IF THERE IS ANY...BUT THIS
SYSTEM LOOKS LIKE IT WILL PRODUCE MAINLY WIND EAST OF THE DIVIDE AT
THIS POINT THURSDAY AND THURSDAY NIGHT.

A FLAT RIDGE BUILDS IN BEHIND THE THURSDAY SYSTEM WITH A CHANCE AT
ANOTHER...MUCH WEAKER DISTURBANCE...GRAZING THE NORTH NEXT WEEKEND.
THERE IS STILL DISAGREEMENT ON THE TIMING OF THIS SYSTEM BUT NONE OF
THE MODELS REALLY HAVE MUCH OF AN IMPACT FOR US AT THIS TIME...BUT
THE DIFFERENCE IN HEIGHTS MAY HAVE AN EFFECT ON TEMPERATURE. DID NOT
SEE A REASON TO CHANGE ANYTHING THAT THE PREVIOUS SHIFT PUT IN THE
FORECAST AT THIS TIME GIVEN THE MODEL DISAGREEMENT.

AVIATION.../00Z ISSUANCE/

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

A COLD FRONT WILL PUSH ACROSS THE AREA 00Z-06Z BRINGING WIDESPREAD
MVFR TO IFR CEILINGS AND VISIBILITY REDUCED IN SNOW AND FOG
OBSCURING MOUNTAINS. THESE CONDITIONS WILL IMPACT VICINITY KJAC
AND AFO AND MAY SPREAD EAST TOWARDS KPNA. WHILE A BRIEF BREAK IN
THE SNOW AND LOW CLOUDS CAN BE EXPECTED 09Z TO 12Z... MORE SNOW
AND WIND WILL ENGULF THE WEST AFTER 12Z. MVFR TO IFR CONDITIONS
CAN BE EXPECTED AT THE AIRPORTS.

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

A COLD FRONT WILL PUSH ACROSS THE AREA 00Z-06Z BRINGING WIDESPREAD
MVFR TO IFR CEILINGS AND VISIBILITY REDUCED IN SNOW AND FOG
OBSCURING MOUNTAINS ALONG AND EAST OF THE CONTINENTAL DIVIDE
AND OVER THE BIGHORN MOUNTAINS. THE LOWER ELEVATIONS WILL REMAIN
VFR AT ALL AIRPORTS. STRONG NORTHWEST WINDS WITH AREAS OF LOW
LEVEL WIND SHEAR WILL OCCUR VICINITY MOUNTAINS KCOD...KLND...KGEY
AND KBYG.

FIRE WEATHER...

MOIST WEST FLOW FROM THE PACIFIC WILL BRING A PROLONGED PERIOD OF
SNOW SUNDAY THROUGH MONDAY TO WESTERN WYOMING.  SNOWFALL UP TO 20
INCHES IS EXPECTED IN THE TETON MOUNTAINS WITH UP TO A FOOT IN THE
REST OF THE WESTERN MOUNTAINS. THE VALLEYS ARE EXPECTED TO RECEIVE
6 INCHES AND MAY HAVE SOME RAIN MIXED WITH SNOW MONDAY AFTERNOON.
STRONG WEST WINDS OVER THE PASSES AND HIGH RIDGES WILL CAUSE
SOME BLOWING AND DRIFTING SNOW OVER TETON...TOGWOTEE AND SALT
RIVER PASSES. EAST OF THE CONTINENTAL DIVIDE STRONG WINDS ARE
EXPECTED TO CONTINUE. SNOW WILL SPREAD INTO THE BIGHORN
MOUNTAINS. MOST AREAS WILL HAVE LOW MIXING HEIGHTS AND POOR SMOKE
DISPERSAL...ESPECIALLY AREAS WITH SNOWFALL. THE WINDY AREAS ALONG
THE EAST SLOPES OF THE MOUNTAINS SHOULD MIX OUT ENOUGH FOR FAIR
TO GOOD SMOKE DISPERSAL.

RIW WATCHES/WARNINGS/ADVISORIES...
HIGH WIND WARNING UNTIL 6 PM MST THIS EVENING FOR WYZ003>007-010-
015>020-022.

WINTER WEATHER ADVISORY FROM 5 AM SUNDAY TO 5 PM MST MONDAY FOR
WYZ001-002-013-014-023>025.

WINTER STORM WARNING FROM 5 AM SUNDAY TO 5 PM MST MONDAY FOR
WYZ012.

$$

SHORT TERM...C.BAKER
LONG TERM...ALLEN
AVIATION...C.BAKER

RIW WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY FROM 5 AM SUNDAY TO 5 PM MST MONDAY FOR
WYZ001-002-013-014-023>025.

WINTER STORM WARNING FROM 5 AM SUNDAY TO 5 PM MST MONDAY FOR
WYZ012.

$$

UPDATE...AEM
SHORT TERM...C.BAKER
LONG TERM...ALLEN
AVIATION...C.BAKER

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY FROM 5 AM SUNDAY TO 5 PM MST MONDAY FOR
WYZ001-002-013-014-023>025.

WINTER STORM WARNING FROM 5 AM SUNDAY TO 5 PM MST MONDAY FOR
WYZ012.

&&

$$

SHORT TERM...C.BAKER
LONG TERM...ALLEN
AVIATION...AEM
FIRE WEATHER...C.BAKER


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