Area Forecast Discussion
Issued by NWS Riverton, WY

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000
FXUS65 KRIW 190629
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1129 PM MST SUN JAN 18 2015

.UPDATE...DRIER AIR OVERTAKING NW ZONES BEHIND SHORTWAVE WITH SNOW
MOSTLY ENDING OR BECOMING VERY LIGHT ACROSS THE ADVISORY AND
WARNING AREAS. ALL WINTER WEATHER HIGHLIGHTS HAVE BEEN CANCELLED.

&&

.AVIATION.../06Z ISSUANCE/

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

AN UPPER TROUGH MOVING ACROSS THE AREA TONIGHT WILL BRING ISOLD-
SCT MVFR -SHSN ACROSS THE SOUTH...MAINLY FROM VCNTY INTERSTATE 80
AND SOUTH AFFECTING KRKS-KCPR ROUTES. VFR CONDITIONS WILL PREVAIL
ELSEWHERE WITH DECREASING WIND SPEEDS THROUGH MONDAY MORNING.

ANOTHER UPPER DISTURBANCE IN NW FLOW WILL BRING ISOLD-SCT MVFR -SHSN
SE PRIMARILY ALONG AND EAST OF A VCNTY KCOD-KWRL-KCPR LINE AFTER 00Z
TUESDAY ALONG WITH SURROUNDING MTNS MOSTLY OBSCURED ABOVE FL8-9KFT.


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

DRIER AIR WILL PUSH IN BEHIND AN UPPER TROUGH ACROSS THE NORTHWEST
OVERNIGHT WITH IMPROVING CONDITIONS WHILE SCT MFVR SHSN MOVE ACROSS
THE SOUTHWEST...VCNTY AND SOUTH OF A KAFO-KPNA LINE THROUGH 9Z.
CLEARING ACROSS THE WESTERN VALLEYS WILL LIKELY RESULT IN SOME FOG
FORMATION PARTIALLY OBSCURING TERRAIN THROUGH MONDAY
MORNING...ESPECIALLY VCNTY KJAC.  ISOLD-SCT MVFR SHSN ARE LIKELY TO
LINGER VCNTY AND SOUTH OF INTERSTATE 80 THROUGH THE DAY MONDAY.  AN
UPPER DISTURBANCE WILL SPREAD SCT-NMRS SHSN INTO THE NORTHERN MTNS
LATE MONDAY AFTERNOON...INTO VCNTY KJAC MONDAY EVENING. SNOW
SHOWERS ARE NOT EXPECTED TO MAKE IT MUCH FURTHER SOUTH OF A VCNTY
KJAC-KDUB LINE MONDAY NIGHT WITH A DRIER AIRMASS/VFR CONDITIONS
PREVAILING ACROSS THE SW MONDAY NIGHT.

&&

PREV DISCUSSION... /ISSUED 143 PM MST SUN JAN 18 2015/

SHORT TERM...TONIGHT THROUGH MONDAY

WINTER STORM WARNING CONTINUES FOR THE TETONS WITH WINTER WEATHER
ADVISORIES FOR JACKSON HOLE AND YELLOWSTONE NATIONAL PARK THROUGH
5 AM MST MONDAY MORNING. HIGH WIND WARNINGS CONTINUE IN THE CODY
FOOTHILLS...SOUTHERN FREMONT AND NATRONA COUNTIES THROUGH 5 AM MST
MONDAY MORNING. PACIFIC TROUGH WILL PASS THROUGH LATE TONIGHT AND
MONDAY MORNING WITH DECREASING SNOW IN THE WEST AND OVERALL
DECREASING WINDS WITH A SHIFT TO THE NORTHWEST. SOME COOLING WILL
ALSO OCCUR BEHIND THE TROUGH. DO NOT SEE MUCH IF ANY
PRECIPITATION EAST OF THE CONTINENTAL DIVIDE OUTSIDE OF THE
BIGHORN MOUNTAINS.

LONG TERM...MONDAY NIGHT THROUGH SUNDAY

PATCHY FOG IN SOME PREFERRED LOCATIONS...AWAY FROM SW
ACTION...BETWEEN TUE AM AND SAT AM...WITH BETTER DAYS WED AND FRI
AM. GENERALLY FAIR/SEASONALLY COOL DAYS...COLD NIGHTS THRU MOST OF
THE EXTENDED.

BEGINNING OF FCST...TRANSITION FROM FLAT RIDGING TO SHALLOW NW FLOW
COMPLETED WITH THE HELP OF THE FIRST OF A FEW SWS THAT WILL RACE
INTO/THRU THE FA OVR THE NEXT COUPLE OF DAYS. THE FIRST WAVE MOVES
THRU MON NIGHT...DRAGGING PRECIP CHCS TO THE SOUTH AND EAST...OUT OF
THE STATE. AS AVAILABLE MOISTURE ALSO GETS SHUNTED OUT OF THE
STATE...THE NEXT FEW FLEETING SWS WILL NOT HAVE MUCH TO WORK WITH
AND WILL THEREFORE PRODUCE LITTLE IN THE WAY OF PRECIP/SNOWFALL BY
THE TIME THE TUE MORNING SW PLOWS THRU. ONLY VERY LIGHT SNOWFALL
EXPECTED OVER THE NW FA AND BIGHORNS...WHILE THE ERN FA GETS BRUSHED
BY THE TAIL END OF A QUICK MOVING CLIPPER FRONT...PRODUCING SOME
INCREASED GUSTY W/NW WIND THRU THE DAY TUE. NO HIGHLIGHTS EXPECTED
WITH THIS...WITH ONLY VERY SMALL CHCS FOR PRECIP IN THE
BIGHORNS...MAYBE. THE LAST OF THE SW DISTURBANCES...UNTIL WED NIGHT
ANYWAY...WILL RIDE THRU THE CWA TUESDAY NIGHT...MAINLY CLEARING OUT
THE SKY..LEAVING A FEW AREAS PRIMED FOR FOG PRODUCTION BY WED
AM...ESPECIALLY OVR THE JACKSON/STAR VALLEYS...UPR GREEN
BASIN...PORTIONS OF THE WIND RIVER BASIN...AND SRN BIGHORN BASIN
NEAR WRL.

WED THRU SUN...NW FLOW CONTINUES OVR THE FA WITH A TREND TOWARD
RIDGING BY THU...BEHIND ONE FINAL UPR SW TROF THAT WILL MOVE THRU
THE FA FROM N TO S LATER ON WED...WITH NOT MORE THAN SOME INCREASED
CLOUD EXPECTED ACROSS ERN WY. MDLS HOLD TOGETHER IN SIMILAR FASHION
THRU FRI MORNING...AHEAD OF THE NEXT UPR (GFS) DISTURBANCE TO MOVE
INTO AND THRU THE FA DURING THE DAY FRI. NOTHING MUCH WILL COME OF
THIS WAVE IF IT HAPPENS AS IT WOULD TAKE A BIT OF WORK TO GET ENOUGH
MOISTURE BACK INTO THE CWA UNDER THE PREVIOUS RIDGE DRY CONDITIONS
TO GET PRECIP/SNOW ON THE GROUND...SO ONLY VERY LOW END
POPS...SHIFTING ACROSS THE ERN CWA FRI NIGHT AS (POSSIBLY) ANOTHER
CLIPPER MOVES THRU.

MDL DIFFERENCES BEYOND FRI NIGHT MAKE THE REST OF THE FCST AMBIGUOUS
AT BEST...WITH SIGNIFICANT SPATIAL AND TEMPORAL DIFFERENCES REARING
THEIR HEADS. GFS CONTINUES MORE BULLISH WITH RIDGE AND EWD
TREND...KEEPING BETTER MOISTURE NORTH AND EAST OF THE FA UNDER MORE
NRLY FLOW. THE EURO KEEP THE FA UNDER NW FLOW AND THE RIDGE FURTHER
WEST...ALLOWING SOME MOISTURE TO WORK ITS WAY OVR WY. HOWEVER...ALL
LR MDLS KEEP THE STRONGEST PORTION OF UPR LVL FORCING TO THE EAST OF
THE CWA THRU THE END OF THE FCST. SO PLAYING ABOUT A 60/40 SPLIT
BETWEEN EURO/GFS ATTM...WITH SOME PRECIP CHCS INCREASING ACROSS THE
FA FROM SAT THRU SUNDAY...BUT WITH PROBS KNOCKED WAY BACK FROM WHAT
THE EURO WOULD PRODUCE.


FIRE WEATHER...

TEMPERATURES WILL REMAIN ON THE COOL SIDE WITH FAVORABLE RELATIVE
HUMIDITY WITH WIDESPREAD SNOW COVER OVER MOST OF THE AREA.  SNOW
WILL CONTINUE ACROSS THE WESTERN MOUNTAINS AND STRONG SURFACE WINDS
OVER AND NEAR THE EAST SLOPES OF THE MOUNTAINS AND THROUGH THE
WIND CORRIDOR FROM ROCK SPRINGS TO CASPER. GENERALLY MIXING
HEIGHTS WILL BE LOW. THE WINDS SHOULD BE STRONG ENOUGH TO PRODUCE
FAIR TO GOOD SMOKE DISPERSAL IN THE AFTERNOON IN THE FOOTHILLS OF
THE MOUNTAINS. PLEASE REFER TO THE WINTER STORM AND HIGH WIND
PRODUCTS FOR MORE DETAILS IN YOUR AREA.  WINDS WILL DECREASE
THROUGH MONDAY.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
HIGH WIND WARNING UNTIL 5 AM MST MONDAY WYZ003.

&&

$$

UPDATE...AEM
SHORT TERM...C.BAKER
LONG TERM...BRAUN
AVIATION...AEM
FIRE WEATHER...C.BAKER







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