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Area Forecast Discussion
Issued by NWS Riverton, WY
Issued by NWS Riverton, WY
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359 FXUS65 KRIW 160846 AFDRIW Area Forecast Discussion National Weather Service Riverton WY 246 AM MDT Tue Jul 16 2024 .KEY MESSAGES... - Seasonable temperatures across the Cowboy State today with isolated showers and thunderstorms possible this afternoon. - Gusty outflows of 30-40+ mph will be possible once again nearby any developing storms. - Near seasonable temperatures and daily chance for afternoon showers and thunderstorms look to continue through the remainder of the week. && .DISCUSSION... Issued at 245 AM MDT Tue Jul 16 2024 Yesterday was quite the eventful and unsettled day across the Cowboy State, especially in parts of Fremont and Natrona Counties. Widespread showers and thunderstorms developed during the early afternoon. A robust storm moved through the central CWA starting in Lander and moving all the way into Casper. Severe wind gusts were recorded in Lander with the airport recording a gust of 66 mph. This storm produced widespread strong wind gusts of 55+ mph which led to some downed trees and power lines in parts of Fremont County. Fortunately, things are looking much quieter this morning with a few lingering weak showers moving through parts of the CWA. Similar to yesterday temperatures are expected to be warm but seasonable with highs in the low to upper 80s and highs in the low 90s across parts of the Bighorn Basin. Showers and thunderstorms are possible once again this afternoon but are expected to be more isolated in nature and remaining mainly across central and western parts of the CWA. A weakening area of high pressure will continue to retreat to the south for the first half of the week. This is largely due to a longwave trough digging across the central CONUS, bringing with it an active northern stream that aids in suppressing the high to the south. As a result of this shift, westerly/northwesterly flow is expected to develop, which will aid in funneling moist pacific air into the region. PWAT values are forecast to remain above normal over the next few days with amounts ranging from 0.75 to 1.00 inches. This flow combined with daytime heating and Pacific moisture will create daily chances for showers and thunderstorms. The main concern with any convection will be strong gusty outflows and brief heavy downpours. Soundings for today are showing a drier overall profile compared to Monday with a lower dewpoint depression. This means that some storms may be capable of producing outflow winds but weaker in nature compared to yesterday. Storms will likely be able to produce isolated outflows of 30 to 40 mph with a few gusts near 50 mph possible. One thing to monitor will be upper steering flow today as models are indicating a rather stagnant flow. This would lead to storms stalling over one place or moving very slowly. Due to the above normal PWAT values there is some concern for heavy downpours over a brief period of time in the locations where storms develop. CAM`s are showing most of the convection being limited to the high elevation mountain ranges in the central and western part of the CWA. There are some models showing these storms being able to move off the mountains but due to the drier sounding profiles, storms will likely weaken quickly over lower elevations. Overall, showers and thunderstorms are possible this afternoon but will be more isolated and restricted mainly to higher elevations. This does not mean some lower elevations will not see a shower or two. The best chance for showers in the lower elevations look to be along the eastern slopes of the Wind River Range, western valleys, and the Green River Basin. Precipitation chances in these locations range from 20-40%. Thunderstorms are looking very isolated, with the areas mentioned before having the best chance of seeing some with a 10-30% chance. The majority of the CWA will likely remain dry today but there is still the concern for some strong outflow winds developing from the storms over the higher elevations. Showers and thunderstorms will gradually dissipate by the evening with a few lingering showers possible into the early morning Wednesday. Due to the suppression of the high to the south and the development of the potent northerly stream, unsettled weather is expected to occur daily through the Wednesday. Pacific moisture along with westerly/northwesterly flow will create daily chances for afternoon showers and thunderstorms. Temperatures will also remain around seasonable values with highs in the 80s to low 90s. The second half of the week still has a lot of uncertainty as models differ on the possible outcomes. Models are starting to lean towards the high south of the region being pushed west over the Great Basin for the second half of the week. This will leave Wyoming sandwiched in between a large upper level low over the Hudson Bay and the upper level high along the West Coast. Overall, temperatures look to remain warm but still around seasonable values. Unsettled weather will prevail through the remainder of the week with daily chances of afternoon showers and thunderstorms. && .AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/... Issued at 938 PM MDT Mon Jul 15 2024 An isolated shower or thunderstorm remains possible over northern Wyoming, especially in vicinity of KWRL until around 09Z. VFR conditions are generally expected, though MVFR conditions are likely if showers/thunderstorms move directly over or near TAF sites. Some mid-level clouds will remain overnight and move southward before sunrise. As the storm- producing weather system moves eastward, some northerly flow will move into sites east of the divide and increase Tuesday afternoon. WNW winds will increase west of the divide. Isolated showers and thunderstorms are expected over the southern Absarokas and Wind Rivers and other mountain areas during the afternoon with sites across central and southern WY the most likely to see isolated storms. Most convection on Tuesday should end by around 04Z. 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... Air Quality Alert until 1 PM MDT this afternoon for WYZ010-023- 024-027. && $$ DISCUSSION...Dziewaltowski AVIATION...Hattings