598 FXUS65 KRIW 091119 AFDRIW Area Forecast Discussion National Weather Service Riverton WY 519 AM MDT Sat Aug 9 2025 .KEY MESSAGES... - Quieter weather today, although elevated to near critical fire weather is still likely in Sweetwater and southern Lincoln Counties. - Warm and mainly tranquil weather is expected Sunday and Monday. - Hot temperatures return Tuesday along with increasing fire weather concerns, especially on Wednesday and Thursday. && .DISCUSSION... Issued at 300 AM MDT Sat Aug 9 2025 We are now entering a quieter period. We still have a few concerns today. The most immediate concern is the freeze warning for the western valleys. Daniel has already seen below freezing temperatures while or official sites, Big Piney and Pinedale, we sitting at 38 and 36 respectively. We will keep the freeze warning as is. The next concern is, once again, fire weather. However, things are more borderline today. WE will still have the low humidity, falling to under 10 percent in some locations. However, with the jet stream moving away, we will not have the jet forcing like yesterday and as a result, wind will not be as strong. Wind at the most likely locations, Sweetwater and southern Lincoln Counties, look borderline at this time, with only around 2 in 5 chance of wind gusts of 25 mph or more for more than 3 hours. So, we will not issue anything right now as an critical fire weather looks isolated at this time. Elevated fire weather is a near certainty though (greater than a 9 in 10 chance). Elsewhere, humidity is either too high and wind will not be strong enough. In addition, a weak system may bring a isolated showers and thunderstorms to northern Wyoming, mainly near the Absarokas. Moisture is limited though, so the chance is less than 1 out of 5 at any location. Tonight, cool temperatures are likely again but should run around 5 degrees warmer than last night so the chance of a freeze will be vastly reduced. Sunday and Monday look like mainly tranquil and seasonable days right now, with Monday the warmer day. Wind will remain light to moderate as ridging builds toward Wyoming so no fire weather concerns. Just enough moisture may return to Natrona County for an isolated afternoon thunderstorm, but the chance is less than 1 out of 5. Monday at this point looks completely dry. Fire concerns begin to ramp up again on Tuesday as the ridge gets flattened and flow turns more southwesterly. This will raise temperatures and bring more gusty breezes. Near critical fire conditions are possible as early as Tuesday, but Wednesday and Thursday still look like the most likely days of concern with increasing wind. Temperatures will become hot again with widespread highs in the 90s both Tuesday and Wednesday in the lower elevations East of the Divide. An approaching cold front for late in the week may then provide some relief from the heat but exact timing is still in question. As for any precipitation, Tuesday looks dry at this point. Increasing moisture may bring isolated convection Wednesday through Friday. However, most of the moisture is of the mid level variety and most showers and storms would likely not produce much rain. && .AVIATION /12Z TAFS THROUGH 12Z SUNDAY/... Issued at 518 AM MDT Sat Aug 9 2025 VFR conditions prevail across all terminals through the TAF period. Clouds will begin to gradually make their way into the area this morning. SCT-BKN FL150-200 will build in from the west through the morning becoming BKN-OVC by the afternoon. A few showers will be possible during the afternoon and evening. However, showers look to have little chance (10-20%) to impact any terminals. If they were to near terminals, showers will likely be virga due to the overall dryness of the atmosphere. Showers may create some obscuration along central and northern mountain ranges at times this afternoon and evening. Winds are expected to increase in the afternoon with all terminals seeing breezes around 10 to 15 knots. Stronger gusts of 20 to 25 knots may be possible at terminals west of the Divide and at KCPR. Winds decrease by the late evening into the early morning hours Sunday. Around the same time clouds should begin to break up becoming SCT-FEW at FL150-200 by the end of the TAF period. Please see the Aviation Weather Center and/or CWSU ZDV and ZLC for the latest information on smoke, icing, and turbulence forecasts. && .FIRE WEATHER... Issued at 300 AM MDT Sat Aug 9 2025 Elevated to near critical fire weather remains likely this afternoon in Sweetwater and southern Lincoln Counties. Relative humidity remains critical, but wind looks borderline for critical fire weather. Elsewhere, either wind will remain light to moderate or relative humidity will remain above critical levels. Few concerns are expected Sunday and Monday before fire weather concerns return for the middle of next week. && .RIW WATCHES/WARNINGS/ADVISORIES... Freeze Warning until 8 AM MDT this morning for WYZ025-026. && $$ DISCUSSION...Hattings AVIATION...Dziewaltowski FIRE WEATHER...Hattings