FXUS65 KRIW 160232 AFDRIW Area Forecast Discussion National Weather Service Riverton WY 832 PM MDT Thu Oct 15 2026 .KEY MESSAGES... - Partly cloudy to mostly clear skies will continue overnight under cool northerly flow. Temperatures will drop to the low 30s and into the 20s late in the night into Friday morning across western and central Wyoming. Freeze warnings have been issued for those areas that have not already had a hard freeze (less than 28 F) this season. - High pressure develops over the Intermountain West, bringing dry and mild conditions Friday and Saturday, with highs mainly in the 50s and 60s (and some 70s over parts of north-central WY). Breezy and gusty winds will develop from central into north-central WY, as well as over the eastern portions of the Absarokas. - A cool front will drape across northern WY on Sunday, decreasing temperatures somewhat, but not bringing any chances for precipitation. - Moisture increases from the southwest late Monday into Tuesday, bringing a chance (30 to 50%) of precipitation to western and southwest WY Tuesday afternoon through Thursday. && .UPDATE... Issued at 1200 PM MDT Thu Oct 15 2026 IR continues to show some scattered mid level clouds across eastern counties in wake of the previous storm system, diminishing and push further east into the mid afternoon hours. Temperatures will remain on the cool side, around seasonable to just below average for this time of year in mid October. Winds have increased for the remainder of the afternoon as leeside cyclogenesis has occurred off the northern Colorado Rockies, tightening the gradient through Sweetwater to Fremont and Johnson Counties (strongest up to 30 to 35 mph), and 20 to 25 mph elsewhere. There winds will diminish towards sunset with radiational cooling under mainly clear skies into the overnight hours. This will allow temperatures to drop below freezing east of the Divide, many a hard freeze around of below 28 degrees. The upgraded Freeze Warning goes into affect after midnight through 9AM Friday morning before temperatures rise there after. Warming and dry trend starts Friday afternoon and over the weekend into early next week as ridging builds in from the south and southwest with increased convergence aloft. The next system for Tuesday through Thursday next week still looking to push through but details a bit uncertain at this time, with newest model trends have back up on the QPF (both valley rain and mountain snow). Stay tuned for updated forecasts in the coming days as this system pushes near. && .DISCUSSION... Issued at 152 AM MDT Thu Oct 15 2026 The H5 trough continues to exit to the southeast, and is gradually taking the clouds and precip with it. As of current writing time, the only remaining light rain is confined to Natrona County, and continues to draw to the southeast as well. Most light rain should be complete by 6AM, but light sprinkles may continue on Casper Mountain for a couple more hours. Skies will clear through the rest of the day, and with good cold air advection still in place, highs will struggle to reach the 50s. This will be accompanied by a modest northerly breeze, making for a brisk autumn day. Areas across Johnson County will hold some more of the influence of the sfc low gradient, so winds will be higher through the day, gusting 30 to 40 mph through the afternoon. Watch for cross winds along the I-90 corridor. Winds will die off quickly after sunset as high pressure sweeps in. This sets the stage for the first freeze of the season for most of the state. Most areas will fall into the 20s for several hours tonight. The only inhibiting factor may be enough of a breeze in the Wind River Basin to mix things enough to limit the overall timing of the freeze, but this airmass is cold enough toovercome most of this. Freeze Warnings are in effect tonight across central Wyoming, where freezing temperatures have not yet been reached. The main pattern this weekend is a broad H5 ridge across the Rockies, bringing moderating temperatures and deflecting the storm track back into southern Canada. The main impact will be which way the winds are from. Winds Saturday will be from the southwest, bringing the warmer air back into the region. Sunday a weather system passes across southern Canada, switching winds back from the north. While no cold air will return with these winds, it will be enough to bring temperatures back to near normal around 60 degrees. The next weather impact across western Wyoming still looking to be sometime Tuesday, when the ridge is broken down by a trough along the Rockies, bringing more moisture back from the southwest. && .AVIATION /00Z TAFS THROUGH 00Z SATURDAY/... Issued at 402 PM MDT Thu Oct 15 2026 There is high confidence in dry conditions through at least 00Z Friday. Breezy north winds at KWRL are expected through 01Z, at the latest, before becoming 12kts or less. Winds at all other terminals are forecast to be light (12kts or less) the entire TAF period. There is a 10 to 20 percent chance of fog or low cloud development beginning around 12Z Friday at KJAC, KRIW, KRKS, KPNA, and KBPI. There is no mention in TAF at this time given the very low confidence. 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 Warning until 9 AM MDT Friday for WYZ005-006-010-011- 016>020-028>030. && $$ UPDATE...Lowe DISCUSSION...Straub AVIATION...Gerhardt