Area Forecast Discussion
Issued by NWS Riverton, WY

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441
FXUS65 KRIW 131855
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1155 AM MST SAT FEB 13 2016

.UPDATE...

ISSUED WINTER STORM WARNING FOR TETON AND GROS VENTRE MOUNTAINS
AND WINTER WEATHER ADVISORIES FOR THE REST OF THE WESTERN
MOUNTAINS AND VALLEYS FROM 5 AM SUNDAY MORNING TO 5 PM MST MONDAY
AFTERNOON.

.SHORT TERM...TODAY THROUGH MONDAY NIGHT

AN APPROACHING WAVE AND ASSOCIATED COLD FRONT WILL APPROACH THE
AREA THIS MORNING...AND MOVE THROUGH THE AREA THIS AFTERNOON AND
EVENING. ADDITIONAL MOISTURE WILL BE FOUND WITHIN THIS SYSTEM TO
PRODUCE SNOWFALL OVER THE WESTERN MOUNTAINS AND INTO THE VALLEYS
THROUGH THE DAY. AS THE WAVE MOVES THROUGH THE AREA...IT IS
ANTICIPATED TO BRING SOME PRECIPITATION ACROSS AREAS EAST OF THE
CONTINENTAL DIVIDE...BUT TEMPERATURES ACROSS THE AREA WILL HELP TO
KEEP THE LOWER ELEVATIONS PRECIPITATION AS RAIN DURING THE
AFTERNOON AND EARLY EVENING. AS TEMPERATURES LOWER...CONVERSION TO
SNOWFALL WILL BE POSSIBLE.

OTHER THAN PRECIPITATION...THE FRONT WILL RESULT IN GUSTY WIND
ACROSS THE AREA. THE CENTRAL MOUNTAINS AND BASINS LOOK TO EXPERIENCE
THE STRONGEST WINDS OUT OF THIS APPROACHING SYSTEM. AS THE FRONT
MOVES THROUGH THE AREA THIS EVENING IT WILL HELP WIND TO RELAX.

MOISTURE WILL CONTINUE TO MOVE ALONG THE NORTHWEST FLOW TO KEEP
SNOWFALL OVER THE NORTHWESTERN MOUNTAINS AND VALLEYS FOR THE NEXT
COUPLE OF DAYS. MOISTURE HAS A DECENT PUSH SUNDAY AND INTO
MONDAY...WITH SOME INCREASED ACCUMULATION ANTICIPATED ACROSS THE
WESTERN MOUNTAINS. BY MONDAY MORNING NEW SNOWFALL ACCUMULATIONS OF 3
TO 5 INCHES WILL BE WIDESPREAD ACROSS THE WESTERN MOUNTAINS...WITH 6
TO 7 INCHES POSSIBLE OVER THE TETON AND GROS VENTRE RANGES. THE
WESTERN VALLEYS WILL SEE POSSIBLE NEW ACCUMULATIONS OF 1 TO 3
INCHES. THIS MOISTURE PUSH WILL BE EVALUATED WITH UPCOMING MODEL
SOLUTIONS TO SEE IF ANY WINTER RELATED HIGHLIGHTS WILL BE
NECESSARY.

.LONG TERM...TUESDAY THROUGH SATURDAY

RIDGE AXIS TO THE WEST GRADUALLY SHIFTS EWD TUE INTO WED. BY
00Z...THU BOTH THE ECMWF AND GFS HAVE THE AXIS CENTERED RIGHT OVER
CENTRAL WYO ALONG WITH THE H7 THERMAL RIDGE. TEMPS WILL CONTINUE
TO WARM TUESDAY INTO WEDNESDAY. WEATHER BEGINS TO CHANGE THURSDAY
AS SYSTEM APPROACHING THE KAMCHATKA AREA RIGHT NOW MOVES ACROSS
THE PACIFIC AND INTO WESTERN WYOMING EARLY THURSDAY AND THEN
MOVING EAST ACROSS THE REST OF THE AREA LATER THURSDAY INTO
THURSDAY NIGHT. SYSTEM IS STILL MOVING THROUGH THE MEAN RIDGE SO
IT MAY WEAKEN/OR SPLIT MORE THAN SHOWN BUT STILL PRODUCE SNOW FOR
THE WEST ESPECIALLY AND WIND FOR THE MTNS AND CENTRAL WYOMING.
KEEPING THE IDEA OF INCREASING WINDS WED NGT...PEAKING ON THURSDAY
WITH POTENTIAL FOR HIGH WINDS IN CENTRAL WYOMING DEPENDING ON HOW
MUCH WEAKENING OCCURS WITH THIS SYSTEM AS IT HITS THE RIDGE. TEMPS
EACH OF THE DIVIDE COULD BE TRICKY THURSDAY DEPENDING ON THE
TIMING OF THIS TROUGH. COULD STILL BE QUITE WARM...ESPECIALLY ERN
HALF. SYSTEM EXITS QUICKLY WITH HEIGHTS REBUILDING FRIDAY INTO
SATURDAY WITH VALLEY/BASIN INVERSIONS REDEVELOPING. NOT AS STRONG
AS PAST WEEKS...ESPECIALLY EAST OF THE DIVIDE WITH MOST OF THE
SNOW GONE BY THEN AFTER ANOTHER WEEK OF WELL ABOVE NORMAL TEMPS.
MODELS DIVERGE ON A SYSTEM RIGHT AT THE END OF THE MEDIUM RANGE
PERIOD WITH THE GFS KEEPING MOST OF THE ENERGY SOUTH AND THE ECMWF
SHOWING A SYSTEM RACING ACROSS MONTANA ON SATURDAY. STRENGTH OF
LONGWAVE RIDGE AND ITS PROXIMITY WILL LIKELY KEEP THIS SYSTEM FROM
HAVING A HUGE IMPACT ON OUR AREA SO WE ONLY HAVE SLGT CHANCES IN
THE WRN MTNS. TEMPS IN THE MIXED AREAS WILL COOL A LITTLE WITH
THIS SYSTEM WHILE THE BASINS/VALLEYS MAY NOT SEE A BIG CHANGE AS
THEY MIX OUT MORE BUT ALSO HAVE LIMITED WARMING POTENTIAL WITH
COOLER AIR ASSOCIATED WITH THE TROUGH. OVERALL...ONE MAIN SHOT OF
SNOW OUT WEST THURSDAY WITH MOST AREAS CONTINUING TO SEE ABOVE
NORMAL TEMPS THROUGH THE PERIOD WITH WEDNESDAY BEING THE PEAK WHEN
50S AND EVEN A FEW 60S ARE POSSIBLE EAST OF THE DIVIDE WITH MAINLY
UPPER 30S TO NEAR 50 WEST. AS NOTED LAST NIGHT...H7 TEMPS ARE
FORECAST TO BE IN THE +3 TO +4 AT H7 IN CENTRAL WYO WED
AFTN...SIMILAR TO WHAT WE SAW FRIDAY BUT WITH LESS SNOW COVER.

&&

.AVIATION.../18Z ISSUANCE/

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

A COLD FRONT WILL PUSH ACROSS THE AREA 18Z-21Z BRINGING WIDESPREAD
MVFR TO IFR CEILINGS AND VISIBILITY REDUCED IN SNOW AND FOG
OBSCURING MOUNTAINS. THESE CONDITIONS WILL IMPACT VICINITY KJAC
AND KAFO AND MAY SPREAD EAST TOWARDS KPNA.

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

A COLD FRONT WILL PUSH ACROSS THE AREA 18Z-21Z 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 WEST WINDS WITH AREAS OF LOW LEVEL WIND
SHEAR WILL OCCUR VICINITY MOUNTAINS KCOD...KLND AND KBYG.

.FIRE WEATHER...

PERIODS SNOWFALL IS EXPECTED OVER THE WESTERN MOUNTAINS AND VALLEYS
FOR THE NEXT FEW DAYS. A COLD FRONT WILL MOVE THROUGH THE AREA
TODAY...WITH WIND SHIFTS ANTICIPATED AS WELL AS PERIODS OF GUSTY TO
BREEZY WIND.  SUNDAY AND INTO MONDAY LOOKS TO PRODUCE THE MOST
ACCUMULATION...WITH SOME ACTIVITY ANTICIPATED TO MOVE EAST OF THE
DIVIDE...MAINLY ACROSS NORTHERN WYOMING. DAYTIME TEMPERATURES WILL
KEEP ACTIVITY AS RAIN THROUGH THE EARLY EVENING...WITH CONVERSION TO
SNOWFALL POSSIBLE WITH DROPPING OVERNIGHT TEMPERATURES. LIGHT
SNOWFALL WILL CONTINUE THROUGH MONDAY....MAINLY OVER THE WESTERN
MOUNTAINS AND VALLEYS.

&&

.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.

HIGH WIND WARNING UNTIL NOON MST TODAY FOR WYZ003.

&&

$$

SHORT TERM...C.BAKER
LONG TERM...SKRBAC
AVIATION...C.BAKER
FIRE WEATHER...BRANHAM



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