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Area Forecast Discussion
Issued by NWS Riverton, WY
Issued by NWS Riverton, WY
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578 FXUS65 KRIW 171712 AFDRIW Area Forecast Discussion National Weather Service Riverton WY 1112 AM MDT Wed Jul 17 2024 .KEY MESSAGES... - Another day of seasonable temperatures with afternoon showers and thunderstorms. - Slightly above normal temperatures are expected to end the week along with daily chances for afternoon showers and thunderstorms. - Hazy and smokey skies may be a continuous occurrence as flow remains from the NW/N and more wildfires develop to our west and north. && .DISCUSSION... Issued at 317 AM MDT Wed Jul 17 2024 Warm but seasonable temperatures continue across the state today. Highs range from the low to upper 80s with the warmest temperatures in the Bighorn Basin as highs near the mid 90s. Showers and thunderstorms develop once again this afternoon with the best chances remaining over central and northern portions of the CWA. Strong outflow winds of 40+ mph will again be the main threat. Slightly above normal temperatures are expected for the later half of the week. Highs will range from the mid to upper 80s west of the Divide and low to mid 90s east of the Divide. Daily chances for afternoon showers and thunderstorms look to continue into the weekend. High pressure continues to sink southwest today, gradually making its way toward the Desert Southwest. This high looks to stay south of the region but will continue to funnel moisture into the area, greatly influencing daily diurnal convection. PWAT values are forecast to hover around 0.75 inches through the remainder of the week due to this moisture. At the same time, this flow will continue to push wildfire smoke in from the PACNW over the Cowboy State. While the concentration of smoke is not expected to create impacts, hazy skies are expected to continue through the remainder of the week. Today convection looks to remain across the upper two-thirds of the CWA, as the moisture and instability will be greatest here. Per usual the best chance for a strong thunderstorm is forecast to be over parts of Johnson County. This will be due to a east- southeast wind advecting in Gulf moisture. Overall, chances for precipitation today range from 20-45% with lower chances in parts of Lincoln, Sweetwater, and Sublette Counties. Thunderstorms will be possible across much of the same areas with most seeing a chance (15- 30%) this afternoon and evening. Gusty outflows of 40+ mph will continue to be possible from these storms, based off dewpoint depressions. Showers and thunderstorms will mostly dissipate by sunset, but a few weak lingering showers and storms may be possible into the early morning hours of Thursday. Temperatures will be about 5 degrees warmer across the CWA Thursday, as the high shifts eastward. Thunderstorms will develop between 20Z and 21Z as a result of a capping inversion. This convection looks to be more widely scattered across the forecast area, with the better chances occurring over the northern half. Strong outflow winds will once again be the main threat. By the end of the week, the high will have made its way into the Great Basin, shifting the upper level flow from northwesterly to northerly. This shift will likely improve the wildfire smoke being blow in from parts of the PACNW. However, there are some large fires beginning to develop to the north so while the flow may shift keeping western smoke away, smoke from northern fires may begin to blow into the state instead. Highs will be hot, but still seasonable. There will be greater chances for areas west of the Divide to be the hotter side, due to the aforementioned northerly winds occurring over areas east of the Divide. Diurnal convection will continue to be possible heading into the weekend as long as the high keeps funneling moisture into the region. Unfortunately, that moisture is forecast to start drying up as we reach the end of the weekend and into the start of next week. The end of the weekend into the start of the next work week is looking messy at this point with a lot of uncertainty. This is largely due to multiple large-scale features interacting with each other. Models currently show the high to our southwest remaining stationary over the Great Basin as an upper low sits over the Central Plains. At the same time, a strong upper-level low looks to try and make its way into the PACNW. The current forecast is looking like the high will be pushed even farther south as this next disturbance moves into the region sometime next week. This would possibly mean another week of unsettled weather, due to the influx of additional Pacific moisture. && .AVIATION /18Z TAFS THROUGH 18Z THURSDAY/... Issued at 1111 AM MDT Wed Jul 17 2024 Isolated showers and thunderstorms develop this afternoon. Due to the isolated nature, have either TEMPO or VCTS at sites. Overall, all locations have a 15% to 40% chance of a shower/thunderstorm today. Confidence is to low to include at KBPI or KPNA. KRKS has the least likely chance (less than 10%). The main threat from any convection is gusty outflow winds. The strongest storms could produce gusts over 40 knots, but most likely wind gusts would be up to 30 knots. Convection decreases this evening, leaving a mainly clear sky and lighter winds overnight. Some smoke still lingers across portions of the area, notably near KCOD. Some mountain obscuration is expected through the TAF period. 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...Dziewaltowski AVIATION...Wittmann