FXUS65 KRIW 041131 AFDRIW Area Forecast Discussion National Weather Service Riverton WY 531 AM MDT Mon May 4 2026 .KEY MESSAGES... - The next weather system bring valley/basin rain and mountain snow for Monday and Tuesday with minimal impacts expected. - Colder temperatures through the week resulting in freeze watches to continue for lower elevations east of the Divide for Tuesday night being the coldest morning going forward. - Another system skirts across the north and east Thursday into Friday with additional precipitation chances expected (20-40%). && .DISCUSSION... Issued at 200 AM MDT Mon May 4 2026 IR currently depicts a closed low to the southwest near California as WV shows the PFJ dipping further south out of Canada and Montana into northeastern portions of the state. Current model trends continue the southward progression of the jet with a jet max of 120kts pushing into the next shortwave expanding across much of the CWA for Monday. This will drop a cold front through the area in the morning hours that will see cooler temperatures from Sunday around 10 to 15 degrees for afternoon highs. Otherwise, scattered rain showers expected with the front that will expand into the evening and overnight hours as the shortwave progressively moves across the CWA. Minimal impacts expected with any snow accumulations constrained to higher elevations even above mountain passes. Tuesday will see a more widespread mountain snow/valley rain effect as the aforementioned low to the southwest will embed into the positively tilted trough extending from the Dakotas. More ample divergence aloft expected, especially across the southern half of the CWA where QPF amounts could push over a quarter inch (60-70%) in some spots along the I-80 corridor of Sweetwater County and points south to the Colorado border. Otherwise, snowfall rates for the higher elevations will be greatest during the afternoon and into the evening hours. Minimal impacts expected to mountain passes (South Pass the only one to push advisory level amounts). However, with the warm temperatures ahead of this system and more of a longer duration time frame, any issuances were held off at this time for Tuesday and Tuesday night. However, a reinforcement of cooler air expected into Wednesday morning seeing a widespread below freezing event for basins east of the Divide. As such, freeze watches continue with this being the coldest morning of the week ahead. Additional precipitation chances with minimal impacts expected Thursday and Thursday night as the main trough exits to the east. This will give way to upper level ridging to build back in Friday and into the weekend with dry conditions and a warming trend expected. Northwest flow aloft extends through into early next week with a minor shortwave pushing to the northeast Saturday afternoon that might see some sporadic showers for the Bighorns and northeastern counties, but much of the activity will remain northeast. && .AVIATION /12Z TAFS THROUGH 12Z TUESDAY/... Issued at 530 AM MDT Mon May 4 2026 VFR conditions to start the period at all locations. A slow moving cold front is pushing through north to south through the morning hours already through COD/WRL turning winds more northerly. Winds will increase post frontal peaking at 18-25kts at all locations. Shower activity possible in the afternoon west of the Divide with the best chances for thunder at RKS after 20Z through about 00Z. More widespread showers at all locations after 00Z with deteriorating conditions there after through the overnight hours with MVFR ceilings likely, and even IFR for CPR/LND/RIW/RKS by 08-09Z. This will be through the end of the period into Tuesday morning likely to stick around for much of the day. Please see the Aviation Weather Center and/or CWSU ZDV and ZLC for the latest information on icing and turbulence forecasts. && .RIW WATCHES/WARNINGS/ADVISORIES... Freeze Watch from late Tuesday night through Wednesday morning for WYZ003>006-010-011-017-018-020. && $$ DISCUSSION...Lowe AVIATION...Lowe