Area Forecast Discussion
Issued by NWS Riverton, WY
Issued by NWS Riverton, WY
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864 FXUS65 KRIW 290450 AFDRIW Area Forecast Discussion National Weather Service Riverton WY 1050 PM MDT Sun Apr 28 2024 .KEY MESSAGES... - Scattered snow/rain showers continue across parts of western WY. Showers and thunderstorms look to develop and spread east during the afternoon and evening. - Showers dissipate during the overnight hours with a few lingering showers over western WY. - Winds increase Monday as a quick moving system works it way into western WY. Scattered showers and thunderstorms will be possible during the afternoon and evening. - Winds remain gusty through the first half of the week. The remainder of the week looks to be unsettled, with multiple chances for precipitation and cool below normal temperatures. && .DISCUSSION... Issued at 110 PM MDT Sun Apr 28 2024 The low that brought steady precipitation to parts of the state over the past few days has finally moves east into the Northern Plains. However, unsettled weather will remain over the region, as a weak shortwave trails behind the low and moves across the Northern Rockies today. Western WY currently is seeing some scattered snow showers mainly over parts of YNP. The remainder of the state can expect to see some periods of sun during the early afternoon, with highs nearing normal values. This afternoon and evening will see scattered showers and a (10-20%) chance for a few isolated thunderstorms to develop across the state. Central and northern portions of the CWA have the best chance to see some precipitation with a (30-60%) of seeing a brief shower. Sweetwater, Sublette, and Lincoln County look to likely remain mostly dry through the day today. Similar to yesterday winds will increase slightly this afternoon with most seeing breezy conditions. Parts of Sublette and Sweetwater Counties look to see the strongest winds with a (40-70%) chance of seeing gusts of 35+ mph. Showers dissipate overnight with a few showers lingering into the early morning hours Monday. Winds decrease after sunset light and variable overnight. Another weak shortwave sweeps across the PACNW and moves into the Northern Rockies by Monday afternoon. Showers look to develop by the late morning across western WY before gradually spreading east through the day. A few isolated thunderstorms will be possible across the state during the afternoon and evening, with most having a (10-20%) chance for a thunderstorm. The best chance (40-70%) for showers and thunderstorms looks to come during the late evening, as a cold front sweeps across the state. Dry air looks to be ahead of the front, which may create some concerns regarding strong outflow winds with any showers or thunderstorms that do develop. This is due to inverted V signatures that indicate the possibility for dry downbursts due to dewpoint depressions being 40- 50 degrees. Overall, winds look to increase Monday as the pressure gradient tightens due to the approaching shortwave. Currently models are showing a (40-80%) chance for most of the state to see gusts of 40+ mph during the day Monday. Weaker winds are expected in parts of the Bighorn Basin and Powder River Basin. Winds look to remain breezy after Monday, as the pressure gradient remains tight due to another system nearing for the second half of the week. Temperatures will briefly rebound for Monday, with near normal values for areas east of the Divide. Tuesday will be drier with an upper-level low staying north of WY. Showers will still be possible but look to be very isolated with chances remaining below (20%). The main concern for Tuesday with be near elevated fire weather conditions as a potent upper-level jet crosses over the area. This will aid in mixing down strong winds with wind prone areas seeing a (30-60%) of seeing 45+ mph gusts. RH values will also be rather dry with percentages around 20%. Temperatures do look to remain cooler than normal with highs around 5-10 degrees below normal. The remainder of the week is looking active with multiple quick hitting systems moving through the region. Mid week is looking interesting as an upper-level low develops over the PACNW and swings down across the Great Basin into Colorado. Models are showing some unseasonably cold air associated with this system. 700 mb temperatures for Wednesday into Tuesday show values of -5 to -10 degrees Celsius across the state. As the low sweeps to the south of the state a brief period of northeasterly upsloping looks possible. Snow would be possible across parts of the Absarokas, Wind Rivers, and Casper Mountain due to this favorable flow. There even looks to be a chance for some lower elevation snowfall during the overnight Wednesday into the early morning Thursday as snow levels fall below 5000 feet. Overall, there still is a lot of uncertainty for the upcoming week, as models have little grasp on the tracks and impacts for these systems. && .AVIATION /06Z TAFS THROUGH 06Z TUESDAY/... Issued at 1049 PM MDT Sun Apr 28 2024 VFR conditions prevail overnight, with relatively light winds. Winds begin to increase Monday morning, with gusts to around 30 knots by the afternoon for many sites. There is a possibility for higher gusts for KBPI, KCPR, KPNA, and KRKS, possibly to 35-40 knots; will have to reevaluate wind potential with newer model runs. Precipitation begins over western Wyoming around 18Z/Mon. As a weak cold front passes through, rain chances spread eastward through the day, reaching the Continental Divide roughly around 00Z/Tues. All sites have a chance of rain through the TAF period, but lower confidence for locations east of the Divide, so have left mention out for most locations for now. 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...Dziewaltowski AVIATION...Wittmann