607 FXUS65 KRIW 101945 AFDRIW Area Forecast Discussion National Weather Service Riverton WY 145 PM MDT Wed Oct 10 2018 .SHORT TERM...(This evening through Saturday) Issued at 115 PM MDT Wed Oct 10 2018 Storm system performing about as expected today with snow winding down after a messy morning along I80 and over southern Lincoln County. Snowfall reports still coming in but many areas had 2 to 4 inches with some higher amounts around Kemmerer and the Bear River Divide area. Gusty northeast winds of 35 to 40 mph also made for some extra reduced visibility and cold wind chills. Not much of a break across the state between systems as the next trough to our northwest will start spreading snow into NW WY this evening with widespread 3 to 6 inch amounts expected in the high country with 1 to 3 inches across the lower elevations from the Jackson Valley north to YNP. Lapse rates steepen quite a bit Thursday so as this trough moves eastward and somewhat merges with a colder northern piece, we will likely see snow showers moving across the lower elevations in the afternoon and evening. Could see a few heavier snow showers, so we'll need to see how this sets up, especially off the Owl Creeks, Bridgers, and Bighorn mountains. Clearing and cold Thursday night leading to a dry Friday with brief shortwave ridging. 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 through southern Alaska and will ride over our ridge just off the west coast and then plunge southward through western Canada before arriving Saturday. This system will likely track along the continental divide or just west of it. This track will have to be watched closely because the trend has been a little further west meaning heavier snow in central WY vs further east. GFS 5-wave pattern is slowly pushing off to the east favoring a slightly further eastward shift but trend has been the opposite. So we need to watch it closely because it may have enough dynamics (strong QG forcing, cyclonic nose of the jet, frontal forcing, and brief upslope) and favorable dendritic growth zone temps to produce advisory snow amounts east of the divide along the track. 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. More on this system in the coming days. .LONG TERM...(Saturday night through Wednesday) Issued at 145 PM MDT Wed Oct 10 2018 Saturday night will see the remaining effects of the strong Canadian storm moving through the area. Snow will likely continue that evening from the eastern slopes of the Wind River mountains eastward to Casper, and taper off between midnight and 6am Sunday. Models are in good agreement with this system so far. Temperatures look to be quite chilly behind this system as 700mb temps below -10C will move over most of the area. Sundays highs will only be in the 30s. Clouds will be partly cloudy to mostly clear by Sunday evening so that Monday morning lows will drop down to about 20F or colder for most of the area. Cool northwest mid- level flow is expected for Monday and Tuesday with afternoon highs reaching the low to upper 40s. High pressure builds over the northern Rockies Tuesday and Wednesday causing another Canadian system to slide into the northern plains rather than following the previous storms track. The 00Z ECMWF had the system skirting eastern WY for possible impacts in northern Johnson county and the Bighorns, but the GFS and 12Z ECMWF are keeping it well to the east. Wednesday will see continued warming as 700mb temps climb back to +5C. Cloudiness from the southwest will increase Wednesday afternoon due to a weak low pressure system over the UT/AZ border region. && .AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon) Issued at 1145 AM MDT Wed Oct 10 2018 A storm system is currently moving though southern Wyoming this afternoon and has brought or will bring light to moderate amounts of snow to the southern third of the state. As the storm moves eastward this afternoon, snow will taper off from west to east and conditions should improve. Scattered showers with some low clouds are also impacting the rest of the forecast area. General IFR to MVFR conditions will be improving to MVFR to VFR by 00Z. Gusty northeast flow will continue as well across south central WY through 00Z/Thu. The exceptions are KJAC, KPNA, and KCOD where increasing snow showers will develop this afternoon over northwest WY and continue until just after 06Z/Thu. MVFR to VFR conditions will prevail overnight with MVFR ceiling returning after 15Z/Thu due to a secondary disturbance moving through the state. Wind on Thursday will be west to north and all TAF sites will see isolated to scattered showers. Please see the Aviation Weather Center and/or CWSU ZDV and ZLC for the latest information on icing and turbulence forecasts. && .FIRE WEATHER... Issued AT 115 PM MDT Wed Oct 10 2018 Another storm system spread snow across the northwest this evening, continuing at times through Thursday. A few of these snow showers will move east of the divide Thursday afternoon and evening. Areas of gusty east wind this afternoon will become gusty west winds in the western mountains Thursday. Friday will be dry along with the mildest temperatures of the week with many areas on both side of the divide managing to warm up to the 50s. A strong cold front will plow south across the state Saturday delivering more snowfall to the area. Sunday will be cool and dry. && .RIW WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory until 3 PM MDT this afternoon for WYZ014- 015-024-030. && $$ SHORT TERM...Skrbac LONG TERM...McDonald AVIATION...McDonald FIRE WEATHER...Skrbac