116 FXUS65 KRIW 110807 AFDRIW Area Forecast Discussion National Weather Service Riverton WY 207 AM MDT Thu Oct 11 2018 .SHORT TERM...Today through Saturday night Another trough over central ID will track over the state today, bringing another chance for snow over mainly northern portions. Widespread 3 to 6 inch amounts are still expected in the NW mountains. A half inch to 2 inches are expected in the western valleys and the Upper Green River Basin near Bondurant and Pinedale. Snow amounts will stay under 1 inch over the Bighorn Basin and portions of Johnson County, with 2 to 4 inch amounts in the Bighorns. Clearing and cold tonight, leading to a dry Friday due to brief shortwave ridging. Gusty winds will be possible near Cody tonight, as the 700mb temp gradient tightens along the foothills and a northerly push of the jet briefly moves overhead. The next system, which looks quite potent for areas along and east of the Divide, will move quickly in from the north Saturday. This system is currently moving over the Gulf of Alaska and will dive southward on the east side of the ridge over the Eastern Pacific, that has been in place for over a week (more or less). The system will continue southward over western Canada, arriving over the Northern Rockies Friday night. This system continues to trend along or west of the Divide, as it continues southward Saturday. Will continue to watch because it may have enough dynamics (strong QG forcing, cyclonic nose of the jet, frontal forcing, brief upslope and favorable dendritic growth zone temps) to produce advisory snow amounts east of the Divide. The upslope favored areas east of the Divide will be most favored, especially the Lander Foothills and southeastern end of the Bighorn Basin. It will also come through with a period of strong north wind of 25 to 40 mph. This system has the coldest air of the season. .LONG TERM...Sunday through Thursday Cold Canadian surface high pressure will build over the area Sunday behind Saturday's system. Isolated to scattered snow showers will linger across southwest Wyoming where some moisture and low level convergence will remain, especially along and near the west slopes of the Wind River Range. Otherwise, highs will struggle to break the freezing mark across east central and southern areas, with 30s to lower 40s across the western valleys and central basins. Mostly clear and cold conditions follow Sunday night with lows mostly in the teens, with some single digits in the western valleys. Medium range models are trending toward faster progression of upper ridge from the eastern Pacific into the western U.S. early next week, and thus diving a clipper system out of central Canada well east of the area Monday night and Tuesday. Thus, dry and gradual warming trend is expected Monday through Wednesday with upper ridge expected to be centered over the Rockies by midweek, H7 temps near 4c across Wyoming. Light winds will keep most areas from fully mixing out, so forecast keeps high temperatures on the cool side of MOS guidance with temperatures returning to near or slightly below seasonal normal values on Wednesday or most highs in the 50s. Medium- range models keep the upper ridge over the area beyond this extended period through next weekend which would continue to bring mainly dry and seasonably mild weather to the area. && .AVIATION...For the 12Z TAFS through 12Z Friday West of the Continental Divide...(KJAC, KRKS, KBPI, KPNA) Snow showers will occur in NW WY through 02Z with areas of MVFR conditions and some mountain obscuration. Scattered snow showers will develop in the remainder of the western mountains after 18Z and continue through 02Z with local MVFR conditions and some mountain obscuration. VFR conditions are forecast at the terminal sites through the period. East of the Continental Divide...(KCPR, KCOD, KRIW, KLND, KWRL) Local MVFR ceilings are expected through 18Z. KCOD airport will see some light snow at times through 21Z with MVFR to IFR conditions. Scattered snow showers will develop after 19Z and continue through 06Z Friday. Areas of MVFR conditions will occur along with some mountain obscuration. KCPR will see snow showers after 00Z until 06Z Friday with MVFR conditions at times. Conditions improve all areas after 06Z Friday as the snow showers end and clouds decrease. && .FIRE WEATHER... Snow showers will occur over northwest portions today, gradually ending late tonight into Friday morning. These showers will spread to the east and south through the day today. Winds will be light to moderate across the area. Friday will be dry, along with the mildest temperatures of the week. A strong cold front will quickly push southward across the state Saturday, delivering more snowfall to the area. Most of this will occur along and east of the Divide. && .RIW WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...LaVoie LONG TERM...Meunier AVIATION...Ross FIRE WEATHER...LaVoie