Area Forecast Discussion
Issued by NWS Riverton, WY
Issued by NWS Riverton, WY
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764 FXUS65 KRIW 181737 AFDRIW Area Forecast Discussion National Weather Service Riverton WY 1137 AM MDT Sat May 18 2024 .KEY MESSAGES... - Elevated to critical fire weather conditions are expected today for much of central and southern Wyoming with humidity below 15 percent and wind gusts of 30 to 40. - Elevated fire weather conditions continue on Sunday. - A stronger system will arrive Monday, bringing cooler and wetter conditions through Tuesday. Snow is expected in the mountains. && .DISCUSSION... Issued at 457 AM MDT Sat May 18 2024 A dominant westerly flow will become reestablished over the area today as yesterday`s shortwave departs. Temperatures will be a little cooler behind the associated front that has pushed south this morning, but still around 5 degrees above normal for most. It will be another breezy day, though not nearly to the extent of Friday. However, fire weather concerns will continue as humidity values again drop into the teens. With an even drier airmass overhead, humidity may approach 10 percent across central and southern basins this afternoon. Wind will quickly wane with sunset. The prevailing flow will become more southwesterly this evening as a trough deepens to our west. This will help bring in some Pacific moisture, and we may see a few showers across the area overnight and through Sunday morning as a leading shortwave crosses the area. This will be followed quickly by a stronger wave rotating through the broad trough during the afternoon. Additional showers and thunderstorms should develop through the evening as a weak cold front pushes east. However, the majority of the area will remain dry. With another robust pressure gradient setting up, wind will increase again for Sunday; widespread gusts of 30 to 40 mph are likely, especially across southern and central areas. This will also bring another day of elevated to critical fire weather conditions, though slightly higher dewpoints will keep humidity values a little higher than Saturday. On Monday and Tuesday the trough mentioned above is forecast to drop south and impact the area with widespread cooler temperatures and precipitation chances. There is still plenty of uncertainty with the evolution of this system and of course with the amount of available moisture, but there has been a notable upward trend with QPF recently. With the associated low placement across Wyoming on Tuesday, locations east of the Divide appear favored to pick up the most precipitation as upsloping is enhanced. Accordingly, the mountains here could see a decent snow event and may need winter weather highlights. Further ahead, guidance is favoring a continued active pattern with the next wave arriving in the Wednesday to Thursday timeframe. The forecast reflects this trend with generally cooler than normal temperatures and daily precipitation chances across the area through the end of next week. && .AVIATION /18Z TAFS THROUGH 18Z SUNDAY/... Issued at 1133 AM MDT Sat May 18 2024 VFR conditions through the day today, with only high cirrus across NW WY this afternoon. Wind gusts will again rise to 25 to 30kts this afternoon. Winds will decrease overnight, with most locations remaining L/V. Some light shower activity will try to spread into western and southern WY after 06Z tonight, but will have minimal impacts on local airports due to the light and isolated nature of the showers. && .FIRE WEATHER... Issued at 457 AM MDT Sat May 18 2024 Another dry and windy day will return elevated to critical fire weather conditions to most of central and southern Wyoming today. Wind will not be quite as strong as on Friday, but gusts of 30 to 40 mph are still expected for most of the area. Humidity again will drop below 15 percent for much of this area. Wind ticks up a bit again on Sunday as the surface pressure gradient tightens. There will be some isolated convection in the area as a shortwave pushes through, but the majority of the area will remain dry; elevated fire weather conditions will continue. Cooler and wetter conditions are expected for Monday and Tuesday as a stronger system arrives. && .RIW WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION...Myers AVIATION...Straub FIRE WEATHER...Myers