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Area Forecast Discussion
Issued by NWS Riverton, WY
Issued by NWS Riverton, WY
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420 FXUS65 KRIW 160340 AFDRIW Area Forecast Discussion National Weather Service Riverton WY 940 PM MDT Mon Jul 15 2024 .KEY MESSAGES... - Scattered thunderstorms will produce brief heavy rain and gusty outflow wind of 35 to 45 mph through early Monday evening. - A secondary surge of northerly surface wind arrives Tuesday afternoon and evening. This will allow wildfire smoke to increase along the Interstate 25 corridor in Johnson and Natrona Counties. Oregon wildfire smoke will reach western Wyoming tonight and Tuesday. - Temperatures at or just above seasonal averages along with typical diurnal convection prevails much of the period. && .DISCUSSION... Issued at 143 PM MDT Mon Jul 15 2024 Scattered convection is ongoing as of 130 PM Monday across western and central Wyoming. The strongest storms and greatest areal coverage is across southwest Wyoming where a lack of cloud cover earlier today has allowed for better destabilization as mid-level lapse rates are ranging from 8-9C/km. Further destabilization is expected across central Wyoming through mid-afternoon as solar radiation has increased the past few hours. With precipitable water values topping 0.80 inches, these storms will be producing rain Monday afternoon and early evening. Temperature-dew point spreads favor wind gusts 35 to 45 mph with the stronger convection. CAMS show most of the stronger storms relegated to locations over Natrona and eastern Sweetwater Counties by 5-6 PM. Showers and isolated storms eventually develop over north central Wyoming late this afternoon. This activity tracks east-southeast through the evening, lingering longest in Natrona County. To the west, drier westerly flow aloft brings an earlier end to the convection this evening. However, western wildfire smoke, mainly from Oregon, is likely to filter into the region in this flow regime. Tuesday finds enough lingering mid-level moisture to trigger convection around midday. Orographics favor the Absaroka and Wind River Mountains for the best coverage Tuesday afternoon. Drier west- northwest flow aloft should limit convection in the basins east of the Continental Divide. Surface high pressure dropping south through the Northern Plains provides a secondary surge of northerly surface wind east of the Divide Tuesday afternoon. Wildfire smoke from southern Montana fires is likely to make a push farther south into central Wyoming along the Interstate 25 corridor in Johnson and Natrona Counties given this wind direction. Temperatures will be around seasonal normals with the exception of cooler readings in Johnson County. The north to northeast wind reaches Sweetwater County and points westward Tuesday evening, but speeds will generally be only 10 to 15 mph. Convection decreases in coverage early Tuesday evening leaving a clearing sky and seasonal temperatures overnight. The remainder of the week finds a building ridge across the Great Basin, which retrogrades closer to the West Coast late in the forecast period. For the most part, temperatures at or just above seasonal averages prevail through next weekend. Enough mid-level moisture remains trapped under the ridge to keep isolated/scattered diurnal convection in the forecast through at least Friday. As the ridge retrogrades, Wyoming may end up in northerly flow aloft with any southerly moisture surge possibly being tempered. Therefore, next weekend may end up a bit drier. && .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 Tuesday for WYZ010-023-024- 027. && $$ DISCUSSION...CNJ AVIATION...Hattings