Area Forecast Discussion
Issued by NWS Riverton, WY
Issued by NWS Riverton, WY
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999 FXUS65 KRIW 100417 AFDRIW Area Forecast Discussion National Weather Service Riverton WY 1017 PM MDT Sun Jun 9 2024 .KEY MESSAGES... - Showers and thunderstorms will continue this afternoon and evening, most numerous across the northern half of the area. Strong wind gusts and brief, heavy rain are the main concerns with this activity. - Monday will see continued isolated showers and thunderstorms. - Warmer and drier conditions expected Tuesday through most of the week. Elevated river and stream levels will continue. && .DISCUSSION... Issued at 236 PM MDT Sun Jun 9 2024 Scattered showers and thunderstorms are ongoing across much of Wyoming in response to the arrival of a shortwave trough riding along the upper level ridge. This activity is expected to expand eastward through the afternoon with the best coverage across the northern half of the area. With both Pacific and Gulf of Mexico moisture advecting into the area, there will be fairly decent moisture available for convection (107% of normal per 12Z sounding at RIW). Accordingly, instability will increase through peak heating, with MLCAPE values generally peaking in the 500-1000 J/kg range (with some caveats - such as the Bighorn Basin which will miss out on deeper theta-e advection). The best environment will be across eastern portions of the area which will see MLCAPE rise to the 1000-1500 J/kg range. Given the well-mixed boundary layer, strong, gusty winds are the main concern, though large hail can`t be ruled out with any stronger storms. As the current convection wanes this evening, another shortwave will push into western Wyoming. This will bring another round of showers and thunderstorms overnight, most focused on northern and western portions of the area. This round could bring a little more rain accumulation, though this is very dependent on individual cell locations. A quarter to half an inch is not out of the question from any one cell, though most of the area will see much less. This activity will wane by sunrise. Monday will see additional showers and thunderstorms develop in the afternoon as the next wave clips northern Wyoming. Accordingly, most of the activity will be focused on areas east of the Divide. Strong wind will be the primary concern again, with a lower hail threat as well. Otherwise, an increased surface pressure gradient will make for a gustier west to northwest wind for most of the area Monday afternoon. Further ahead, weak ridging to fairly zonal flow will take over. Accordingly, warmer and drier conditions are favorable Tuesday through at least Thursday. Ensemble cluster guidance is hinting at increasing troughiness by the weekend. && .AVIATION /06Z TAFS THROUGH 06Z TUESDAY/... Issued at 1012 PM MDT Sun Jun 9 2024 VFR conditions to start the period for all TAF sites with mid level ceilings across the CWA. Ongoing rain showers and a few isolated thunderstorms exist to start the period that should stay east of LND and pass CPR to its west and northwest. Confidence low on any on station, so kept out of TAF completely. Otherwise, some breezy winds will decrease behind these aforementioned storms becoming less than 10kts through the late morning. Expect winds to increase to 18-25kts for all TAF sites after the 17-19Z time frame with daytime heating before diminishing towards sunset around 01-03Z with nighttime cooling. The only rain chances will be with JAC associated with wrap around moisture from the ongoing trough with some off and on light rain in the cooler air between 13-16Z. Otherwise, no other weather elements for much of the period and into the next several days. Please see the Aviation Weather Center and/or CWSU ZDV and ZLC for the latest information on smoke, icing, and turbulence forecasts. && .RIW WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION...Myers AVIATION...Lowe