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000
FXUS65 KRIW 301818
AFDRIW

AREA FORECAST DISCUSSION...UPDATE
NATIONAL WEATHER SERVICE RIVERTON WY
1117 AM MST SAT NOV 30 2013

.SHORT TERM...TODAY THROUGH MONDAY NIGHT

ANOTHER DAY OF MILD AND BENIGN WEATHER CONDITIONS EXPECTED FOR MUCH
OF THE AREA. LOWERING CLOUDS IN THE WEST WITH SNOW FLURRIES EXPECTED
IN THE NORTHWEST MTNS AS DIFLUENT FLOW AHEAD OF A JET STREAK DIVING
INTO THE PACNW INCREASES THIS EVENING. IN ADDITION...A WEAK
SHORTWAVE WILL TRACK TOWARD WYOMING TONIGHT WITH FLURRIES BECOMING
MIXED WITH AREAS OF LIGHT SNOW. BEHIND THIS SHORTWAVE...A QUICKLY
DEVELOPING ISENTROPIC UPGLIDE PATTERN DEVELOPS AND INCREASES AS THE
NW FLOW STRENGTHENS...THIS PATTERN SHOULD INCREASE SNOWFALL RATES
ACROSS YELLOWSTONE AND THE TETONS BY SUNDAY MORNING.

THE MOIST UPGLIDE PATTERN WILL CONTINUE INTO SUNDAY NIGHT WITH
INCREASING SNOWFALL RATES IN THE NW...QUICKLY SPREADING FURTHER
SOUTH AND EAST. IN ADDITION...WINDS WILL BEGIN TO INCREASE ACROSS
THE REGION RESULTING IN SIGNIFICANT BLOWING AND DRIFTING
SNOW...TRAVEL OVER WESTERN MOUNTAIN PASSES WILL BECOME INCREASINGLY
DIFFICULT IF NOT IMPOSSIBLE.

A LULL IS EXPECTED ON MONDAY IN ADVANCE OF THE UPPER LOW ITSELF BUT
THE SNOW RETURNS WITH A VENGEANCE MONDAY AFTERNOON IN THE
WEST...SPREADING EAST OF THE DIVIDE MAINLY AFTER 00Z TUESDAY WITH
THE ARCTIC FRONT...SPREADING SOUTH INTO THE CENTRAL BASINS MONDAY
NIGHT. WHEN SKIES CLEAR AFTER THIS STORM...THERE COULD BE A COUPLE
OF FEET OF NEW SNOW IN THE MOUNTAINS WITH MANY LOW ELEVATION AREAS
WEST OF THE DIVIDE AND IN FAVORED UPSLOPE LOCATIONS EAST OF THE
DIVIDE COULD SEE OVER 6 INCHES OF NEW SNOW. PLEASE KEEP AN EYE OUT
FOR ADDITIONAL WINTER STORM WATCHES AND WINTER WEATHER ADVISORIES
FOR MORE DETAIL REGARDING THE IMPACTS OF THIS STORM.

WINDS...EAST OF THE DIVIDE...THE WINDS WILL BE ON THE INCREASE
SUNDAY NIGHT AND MONDAY WITH LEE TROUGHING DEVELOPING AND INCREASING
MID LEVEL FLOW. THE WIND CORRIDOR AND THE CODY FOOTHILLS WILL SEE
QUITE A BIT OF WIND DURING THIS PERIOD...SOME WESTERLY 55 TO 65 KNOT
GUSTS ARE SHOWING UP AT 700MB...EASILY MIXING DOWN AT TIMES IN
FAVORED AREAS AND ACROSS HIGHER ELEVATIONS. WINDS IN THE MOUNTAINS
WILL BE STRONG AS WELL WITH GUSTS OVER 70 MPH COMMON AT THE SUMMITS.


.LONG TERM...TUESDAY THROUGH SATURDAY

...SNOW FOLLOWED BY FRIGID ARCTIC AIR TUESDAY AND WEDNESDAY...

AFTER SOME DEVIATION OVER THE LAST FEW RUNS...MEDIUM RANGE MODELS
HAVE REVERTED TO DROPPING CLOSED LOW WITH H5 -40C COLD POOL INTO
CENTRAL IDAHO ON TUESDAY AND LIFTING IT INTO THE NORTHERN HIGH
PLAINS ON WEDNESDAY.

ARCTIC FRONT IS EXPECTED TO BE SOUTH OF CPR-LND BY 12Z
TUESDAY...WITH RAPIDLY DEEPENING SURFACE LOW ALONG THE FRONT OVER
NORTH CENTRAL COLORADO TUESDAY EVENING.  THE FRONT WILL SPREAD LIGHT
SNOW NORTH TO SOUTH ACROSS CENTRAL WYOMING EARLY TUESDAY. STRONG
ISENTROPIC UPGLIDE SETS UP WITH UPPER SUPPORT TO PRODUCE HEAVIER
SNOW ALONG THE INTERSTATE 80 CORRIDOR INTO CENTRAL WYOMING...FROM
THE UPPER GREEN RIVER BASIN ACROSS FREMONT AND NATRONA
COUNTIES...TUESDAY AFTERNOON INTO WEDNESDAY MORNING. SNOW IS
EXPECTED TO TAPER OFF FROM WEST TO EAST THROUGH THE DAY WEDNESDAY
AS ARCTIC HIGH PRESSURE...H7 TEMPS -25C TO -28C ON ALL MODELS
RUNS...BUILD INTO AREA ON BACK SIDE OF UPPER LOW. FORECAST
CONTINUES TO TREND TEMPERATURES COLDER WEDNESDAY THROUGH FRIDAY
WITH HIGHS EXPECTED TO ONLY REACH THE SINGLE DIGITS WITH SUB-ZERO
READINGS IN THE MOUNTAINS ON WEDNESDAY...LOWS WEDNESDAY WITH
PARTIAL CLEARING FROM 10 TO 20 BELOW ZERO IN MOST LOCATIONS. MAIN
UPPER LOW WILL LIFT INTO EAST CENTRAL CANADA ON FRIDAY WITH HIGH
AMPLITUDE RIDGE REMAINING MOSTLY INTACT ALONG 140W. CROSS-POLAR
FLOW WITH EMBEDDED SHORTWAVES IS EXPECTED TO KEEP DEEP ARCTIC
AIRMASS ENTRENCHED ACROSS THE AREA THROUGH NEXT WEEKEND WITH
OCCASIONAL SHOTS OF FLUFF MAINLY ACROSS THE WESTERN MOUNTAINS.
HIGHS ARE EXPECTED TO REMAIN IN THE SINGLE DIGITS WITH LOWS MAINLY
IN THE 10 TO 20 BELOW ZERO RANGE THROUGH NEXT WEEKEND.

&&

.AVIATION.../12Z ISSUANCE/

EAST OF THE CONTINENTAL DIVIDE...
VFR CONDITIONS WILL OCCUR TODAY AND TONIGHT AT THE TERMINAL SITES.
SOME LIGHT SNOW WILL DEVELOP OVER THE HIGHER PEAKS OF THE ABSAROKA
AND WIND RIVER MOUNTAINS AFTER 21Z. THE LIGHT SNOW WILL INCREASE IN
COVERAGE AFTER 03Z WITH MVFR CONDITIONS NEAR THE MOUNTAINS. THE
LIGHT SNOW WILL CONTINUE THROUGH SUNDAY.

WEST OF THE CONTINENTAL DIVIDE...
LIGHT SNOW WILL DEVELOP OVER THE MOUNTAINS THIS AFTERNOON WITH MVFR
CONDITIONS AT TIMES THROUGH 00Z ALONG WITH MTN OBSCURATIONS. AFTER 00Z
SNOW WILL INCREASE OVER THE WESTERN MOUNTAINS WITH MVFR TO IFR
CONDITIONS PREVAILING THROUGH 12Z SUNDAY. AT THE KJAC AIRPORT LIGHT
SNOW IS EXPECTED BY 03Z WITH MVFR CONDITIONS PREVAILING THROUGH 12Z
SUNDAY. ON SUNDAY...MODERATE TO HEAVY SNOW WILL CONTINUE THROUGH THE
DAY SUNDAY WITH IFR/LIFR CONDITIONS EXPECTED AROUND KJAC AND MVFR
CONDITIONS EXPECTED AT KPNA/KBPI.

&&

.FIRE WEATHER...

VARIABLE MID AND HIGH CLOUDS WILL CONTINUE TO MOVE ACROSS WESTERN
AND CENTRAL WYOMING IN WESTERLY FLOW ALOFT. THE LOWER AIR MASS WILL
REMAIN STABLE WITH GENERALLY POOR SMOKE DISPERSAL TODAY. SOUTHWEST
WINDS OF 15 TO 25 MPH WITH OCCASIONALLY HIGHER GUSTS WILL CONTINUE
ACROSS EASTERN SWEETWATER COUNTY AND NATRONA COUNTY...AS WELL AS
ACROSS THE SHOSHONE NATIONAL FOREST LANDS INTO THE NEARBY FOOTHILLS
WITH SIGNIFICANT INCREASES IN WIND SPEEDS ON SUNDAY WITH MORE SNOW
EXPECTED ACROSS YELLOWSTONE AND TETON DISPATCH AREAS...SPREADING
EAST OF THE DIVIDE ON TUESDAY AND CONTINUING THROUGH WEDNESDAY.
&&

.RIW WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WATCH FROM LATE TONIGHT THROUGH LATE TUESDAY NIGHT
WYZ001-002-012-013-023>025.

&&

$$

SHORT TERM...ALLEN
LONG TERM...AEM
AVIATION...LIPSON
FIRE WEATHER...ALLEN