Area Forecast Discussion
Issued by NWS Riverton, WY
Issued by NWS Riverton, WY
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445 FXUS65 KRIW 011715 AFDRIW Area Forecast Discussion National Weather Service Riverton WY 1115 AM MDT Sat Jun 1 2024 .KEY MESSAGES... - Isolated thunderstorms return to southern and western areas this afternoon and evening. - Monday and Monday night will be the most active day, with the best chance of showers and storms along with strong wind. - The warmest weather of the year moves in later next week, especially on Friday when the first 90 degree highs may occur. && .DISCUSSION... Issued at 256 AM MDT Sat Jun 1 2024 I would like to welcome you to June today. And, welcome you to the start of meteorological summer, which runs through August. And we are only 19 days from the start of astronomical summer, which begins on the June 20th, which is when the summer solstice occurs. And for the next week, we will have things that are found in a Wyoming summer, rather warm temperatures and a scattering of thunderstorms. The day will start dry today, although there could be some virga over southern Wyoming this morning. A few showers and storms will likely return to the area today, mainly over the western and southern half of the state this afternoon as a subtle shortwave moves through and a bit of mid level moisture creeps into the area. The chance of an afternoon or evening storm is small though, with a 1 out of 4 chance at the most. The main and probably only threat from any storm or shower would be strong wind gusts, given the inverted V sounding across the area. This could end up being a "Little Green Blob" day, with innocent looking showers producing strong wind gusts. Temperatures should be comfortably warm, averaging near to about 5 degrees above normal. A second shortwave then approaches for Sunday. With this one, the best forcing looks to be across northern Wyoming so the best chance of showers will be found here. Again, not a ton of moisture to work with, so coverage will be small again, generally around a 1 out of 3 chance in the mountains and 1 out of 5 in the lower elevations. And again, strong wind gusts will be the main threat with any shower or storm. This looks to be an earlier show though, with most convection out of the area by around 6 pm. The third and final wave will approach for Monday. This waves looks somewhat more potent, as it has a bit more moisture to work with and also better upper level support as an 120 knot jet will be associated with it. Chances for stronger storms look limited at this time though. There will be decent cloud cover across the area, limiting instability. The timing of the system is not ideal either for strong convection. The best upper level forcing also waits until nighttime to move through the area. With this though, we have kept the chance of thunder in the forecast through the night on Monday night. The main concern could end up being strong wind. This will be in the usual areas, mainly ahead of the system in the southwest flow areas like Casper and Rock Springs on Monday and Monday evening, and then switching to areas favored by northwest flow later Monday night and Tuesday like Greybull and Buffalo. The 700 millibar winds don`t look sufficient for high winds, but there is a 3 in 4 chance of wind gusts past 40 mph. As for fire weather concerns, humidity does not look that low, and green up should keep things from being too bad. Any lingering showers should end Tuesday morning. Following that, ridging should build in from the south and bring the warmest weather so far this year. Temperatures will rise on Wednesday and Thursday but the warmest day will be Friday when some of the warmer locations could see their first 90 degree highs of the year. The next chance of convection may move in for Friday, with some moisture and a spoke of energy in the form of a shortwave moves toward the area. Details on placement of the convection is obviously uncertain this far out. So, it looks like summer will arrive to the Cowboy State over the next several days. && .AVIATION /18Z TAFS THROUGH 18Z SUNDAY/... Issued at 1112 AM MDT Sat Jun 1 2024 Prevailing VFR conditions through the TAF period. Isolated showers and thunderstorms will be around this afternoon and early evening. The best chances (30% to 50%) occur at KLND and KRKS. Lesser chances (15% or less) occur at most other sites though. Given the lower chances, other sites do not have rain chance mentioned in TAFs. KCPR would be the most likely, with about 15% to 20% chances between roughly 23Z/Sat and 03Z/Sun. High-resolution models are very inconsistent with rain placement, so confidence is low at this time. These showers, especially in the vicinity of KCPR and KRKS (but could occur at most sites this afternoon) could bring strong outflows, the highest potential gusts being 40 to 50 mph. These winds will be the biggest threat through this evening. Some low rain chances (15% to 30%) move into western Wyoming between 06Z/Sun and 12Z/Sun, with KJAC being the potential impacted terminal there. 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... None. && $$ DISCUSSION...Hattings AVIATION...Wittmann