


Area Forecast Discussion
Issued by NWS Riverton, WY
Issued by NWS Riverton, WY
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677 FXUS65 KRIW 131104 AFDRIW Area Forecast Discussion National Weather Service Riverton WY 504 AM MDT Sun Jul 13 2025 .KEY MESSAGES... - A hot finish to the weekend with highs in the 90s widespread in the lower elevations East of the Divide. - Elevated to possibly critical fire weather is expected Monday afternoon. - The chance of thunderstorms increases Monday, with the best chance of storms on Tuesday and Wednesday. && .DISCUSSION... Issued at 306 AM MDT Sun Jul 13 2025 All in all, the reasoning in the forecast has changes little from yesterday. Northwest flow will continue to dominate today. Thicknesses continue to climb today though, so it will be a rather hot day today with widespread 90s in the lower elevations East of the Divide. Almost all areas will be dry as well. However, notice the modifier, almost. There will be a very subtle shortwave moving across the area this evening. And this may be just enough to bring an isolated shower or thunderstorm in and near the northern mountains. The chance is very small though, small with a capital S. We have some slight POPs in spots but the chance is at most 1 out of 6 with the vast majority of locations seeing nothing. Things start turning more active next week. A cold front will start approaching the area from the north. It will remain north of the area though, so it will be another hot day with temperature fairly similar to todays. We have two concerns. And it reminds me of one of my favorite songs from the 70s, Fire and Rain by James Taylor. Although starting Monday will should not see sunny days we thought would never end. We will start with fire. With the approaching cold front, the pressure gradient will tighten ahead of it and bring some breezy conditions. Humidity will be very low on this day, falling as low as 10 percent. This brings the possibility of elevated to critical weather into the forecast. Wind looks borderline though. The most likely place to see it would be across portions of Sweetwater, Sublette and Fremont counties in the afternoon. At this time, it is uncertain if we will get 3 hours of wind gusts past 25 mph for Red Flag criteria though. So, we will let the day shift take another look to see if any watches are needed and then we can upgrade tomorrow night if needed. Now for the rain, or more specifically thunderstorm part. Chances of storms will increase but mainly across the northern portions of the state. Chances here range anywhere from 1 in 5 in the lower elevations to 1 in 3 in the mountains. There is not a lot of upper forcing with on this day. However, what we do have are very large dew point depressions (as high as 60 degrees) and inverted V soundings with any afternoon convection being high based, strong wind gusts are possible with any shower or storm, although many may end up bring rain free. The chance of rain increases in the evening and at night as temperatures cool and the atmosphere moistens somewhat. Tuesday and Wednesday still look like the most active days. The models do agree on the northwestern half of the area and areas East of the Divide seeing the best chance of seeing showers and storms, with tapering chances further south. There are still disagreements though on the timing and rainfall amounts of the storms each day, with some models showing Tuesday as the most active day with the system more progressive. Others have it on Wednesday with a slower progression. So, there is still little confidence in the details at this time. Temperatures will be substantially cooler though, especially in northern Wyoming. Some guidance shows Buffalo remaining in the 50s on Wednesday. Don`t know if I believe that with it being the middle of July though. Some areas will be around 30 degrees cooler on Tuesday or Wednesday when compared to Sunday and Monday. Flat ridging should then control the weather for Thursday through Friday and bring near normal temperatures. A few storms may be around each afternoon but most areas should be dry. Above normal temperatures are then favored to return for next weekend. && .AVIATION /12Z TAFS THROUGH 12Z MONDAY/... Issued at 504 AM MDT Sun Jul 13 2025 VFR conditions through the period. Outside some afternoon cumulus or high cirrus, a mostly clear sky is expected through the TAF period. Winds will follow diurnal patterns. 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 306 AM MDT Sun Jul 13 2025 No fire concerns today despite low humidity as wind should remain light to moderate. A cold front approaching from the north will bring elevated to possibly critical fire weather Monday afternoon as breezy conditions develop ahead of it, with the the southern half of Wyoming having the greatest chance of critical fire weather. && .RIW WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION...Hattings AVIATION...Wittmann FIRE WEATHER...Hattings