Area Forecast Discussion
Issued by NWS Riverton, WY
Issued by NWS Riverton, WY
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633 FXUS65 KRIW 200412 AFDRIW Area Forecast Discussion National Weather Service Riverton WY 1012 PM MDT Thu Sep 19 2024 .KEY MESSAGES... - Dry and seasonal today and tomorrow. - A weak cold front moves through Friday evening, bringing a cool north wind shift. - Cool to seasonal through the weekend, with isolated (20%) rain chances for portions of southern Wyoming. && .DISCUSSION... Issued at 1238 PM MDT Thu Sep 19 2024 A very seasonal day today. Highs are in the 60s to mid-70s across the area this afternoon. Winds will be light, with gusts around 20 mph for the Wind Corridor (approx. South Pass through Casper). Some low clouds have hung around portions of northwest Wyoming. Of note is Jackson Valley, where mid-level clouds have kept the eroding sunshine from breaking up the lower clouds. Models have been struggling to resolve this. Would expect these lower clouds to erode by mid-afternoon as the sun becomes stronger. For Friday, temperatures increase a little, with highs in the 70s for most of the area. Not expecting any precipitation. Afternoon winds do increase, with 20 to 30 mph gusts for the Wind Corridor and portions of northwest Wyoming. Elevated fire conditions may occur for the Wind Corridor, but winds will be marginal, and critical RHs may not be widespread enough to warrant any highlights. A weak cold front pushes through in the evening. This shifts winds to the north and northeast, with a slight breeze and cooler temperatures. The cold front leaves Saturday cooler, with highs in the 60s. No strong signals for precipitation chances, but an approaching low to the south could bring an isolated (20%) shower for southern Wyoming areas. This low also brings a tighter pressure gradient, so gusty winds across the Wind Corridor of 20 to 35 mph. Models still track this low southeast of the CWA, so its impacts will be minimal to none through the weekend -cooler temperatures and isolated (20%) rain chances for southern areas. Sunday morning looks to have the coldest temperatures through the next week. Even so, Sunday morning lows look to remain in the middle 30s to around 40 degrees for lower elevation locations that have yet to hit freezing (mainly east of the Divide locations). The HREF has less than 10% chances for 32F or less Sunday morning. The low exits to the east Monday, allowing another trough to dip down into the state. There is some uncertainty with this low. The ECMWF brings a closed upper-level low, while the GFS keeps it an open trough as it passes through Wyoming. Continued cool temperatures and some precipitation chances are the main result in either case. High pressure looks to make a return for the middle and end of next week. This would favor warmer temperatures and less precipitation chances. Long range models are keeping these conditions until the start of October. && .AVIATION /06Z TAFS THROUGH 06Z SATURDAY/... Issued at 1010 PM MDT Thu Sep 19 2024 Light winds and mostly clear skies prevail overnight into Friday morning. During the early afternoon hours on Friday, typical 15 to 25 kt breezes will develop for many TAF locations. A cold front will push in from the north during the evening and early overnight, causing winds to shift to northerly and become gusty (see TAFs for more precise timing). An hour or two of 20 to 30 kt gusts are likely (60% chance) at sites east of the Continental Divide as the front passes, then decreasing to lighter northerly flow overnight into Saturday morning. && .RIW WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION...Wittmann AVIATION...VandenBoogart