


Area Forecast Discussion
Issued by NWS Riverton, WY
Issued by NWS Riverton, WY
Versions:
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
483 FXUS65 KRIW 281732 AFDRIW Area Forecast Discussion National Weather Service Riverton WY 1132 AM MDT Sat Jun 28 2025 .KEY MESSAGES... - Gusty winds and low humidity brings another day of elevated to critical fire weather conditions this afternoon. A Red Flag Warning is in effect for portions of Natrona County/Zone 280 from noon to 9PM today. - Isolated to scattered thunderstorms are possible (from Sweetwater County to Johnson County) this afternoon and Sunday afternoon. This afternoon, any showers or thunderstorms will be capable of dry microbursts producing 50-60 mph winds. - Much of next week will feature above normal temperatures and a possible increase of convection, especially Wednesday and beyond. && .DISCUSSION... Issued at 248 AM MDT Sat Jun 28 2025 Compared to yesterday, we have some things that are similar and some things that are not. As for similarities, we will continue to have above normal temperatures, with most locations having high temperatures from 5 to as much as 12 degrees above normal. There will also continue to be a gusty breeze in many locations, although a little less than yesterday in northern portions of the area. And, we will continue to have low humidity across a good portion of the forecast area, although a bit higher than yesterday. And that leads to the question of the day. Do we need another Red Flag Warning for Natrona County? Humidity will still be critical, dropping down to close to 10 percent at times. Wind will also be gusty, but is borderline, with most areas having around 1 in 2 chance of gusts past 25 mph. But we do have a difference. That is an approaching shortwave and weak cold front that has a bit more moisture than the wave of yesterday. Most of the moisture is of the mid level variety, with soundings in most locations showing a very substantial inverted V signature. This includes at Casper, with dewpoint depressions approaching 60 degrees. As a result, any storms or even showers that form could cause dry microbursts with wind gusts around 60 mph. And with the possibility of lightning, this was the factor that tipped the balance to issuing the Red Flag Warning for this afternoon and evening. Much of northern Wyoming could have a shower or thunderstorm as well, but the chance of one at any particular location is only 1 out of 5. This also looks like a later show, with a few storms lingering in Johnson County after midnight before everything ends between 1 and 4 am. Fire concerns should be less tomorrow across most of the northern two-thirds of the area, with somewhat cooler temperatures and higher humidity moving in as flow turns north to northwesterly. Elevated to critical fire weather will continue across southern Wyoming though, with gusty wind continuing and humidity again falling below 15 percent. Another shortwave will bring a chance of a few showers and thunderstorms. There is more model disagreement in placement this day though. For the most part, we kept a 1 in 4 chance across portions of Johnson and Natrona Counties while keeping the rest of the area largely dry. Ridging then gradually builds over the area through the middle of the week, bringing a return to above normal temperatures but nothing out of the ordinary for late June / early July. Monday looks like a mainly dry and nice day with lighter wind and any isolated convection (1 out of 6 chance) limited to in and near the mountains. Coverage of storms may increase Tuesday and especially Wednesday as deeper moisture moves in from the south, with precipitable water values rising to as much as 150 percent above normal by Wednesday afternoon and a weak shortwave bringing some additional destabilization of the atmosphere. The end of the week looks to be the same with above normal temperatures and a scattering of showers and thunderstorms, with an average of a 1 in 4 to 1 in 3 chance each afternoon and evening. As per usual this time of year, the best chance will be in and near the mountains. && .AVIATION /18Z TAFS THROUGH 18Z SUNDAY/... Issued at 1131 AM MDT Sat Jun 28 2025 VFR conditions are expected through the period. A shortwave passing over Wyoming will kick off a few showers or thunderstorms this afternoon, most likely at KCPR where a TEMPO group is now in place. The main concern with this activity will be strong outflow wind gusts given the dry boundary layer. Large temperature/dew point depressions, as well as consistent CAM guidance, supports brief wind gusts of 40+ knots at KCPR during this period. KRKS also has a brief window for impacts as convection builds off the Uinta mountains this afternoon, but confidence here is lower and have kept in the PROB30 group. Any convection in the area will end by late evening, leaving mostly clear or scattered skies with calm wind overnight through Sunday morning. 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 248 AM MDT Sat Jun 28 2025 Another day of low humidity (as low as 10 percent) and gusty wind (gusts as high as 30 mph) will bring elevated to critical fire weather to approximately the southern two-thirds of the area, with a Red Flag Warning in effect for the lower elevations of Natrona County. Fire weather concerns should ease for central Wyoming on Sunday, but continue across southern Wyoming as humidity remains below 15 percent and a gusty wind continues. && .RIW WATCHES/WARNINGS/ADVISORIES... Red Flag Warning until 9 PM MDT this evening for WYZ280. && $$ DISCUSSION...Hattings AVIATION...Myers FIRE WEATHER...Hattings