Expires:No;;383280 FXUS65 KRIW 260351 AFDRIW Area Forecast Discussion National Weather Service Riverton WY 951 PM MDT Thu Apr 25 2024 .KEY MESSAGES... - More widely scattered rain showers and isolated thunderstorms this afternoon and evening. - Main system pushes through Friday night and into the weekend with ample mountain snow and low valley rain. - Warming trend and mainly dry next work week with another system late week and into the following weekend. && .DISCUSSION... Issued at 1236 PM MDT Thu Apr 25 2024 IR currently depicts the deep trough over the western CONUS with cooling cloud tops through the CWA advecting in from the southwest. Radar shows a much more sporadic day ahead with widely scattered rain showers and some isolated thunderstorms. This will continue through the afternoon and early evening hours before subsiding with radiational cooling and the eventual FROPA of a cool front. This is pushing into northwestern portions of the state and will slowly move southeast throughout the remainder of the day. Temperatures behind it are not much cooler around 10 degrees from yesterday, but more seasonable in the days ahead over the weekend. With these rain showers and thunderstorms, there is enough instability of DCAPE to see some gustier outflows for southern counties and those east of the Divide from Wind River Basin to the I-25 corridor. Updraft is not strong enough to see any type of hail growth or potential for anything severe at this time. The prone area with the best potential will be well east of the CWA into far reaches of the state in eastern Wyoming and points southeastward. Otherwise, a decent rain fall, even for the higher terrain expected for the rest of today with the better bullseye further east from Casper to Buffalo dependent on where any showers/storms entrain upon one another. This first initial shortwave off the main low coming in from the Pacific northwest overnight into much of Friday. Initial waves of snowfall to the higher terrain of the Absarokas and Bighorns expected by mid afternoon spreading to the Winds by the evening. Fairly slow moving over the weekend, substantial snowfall expected with the Winds the highest amounts up to 1.5 to 2 feet with other ranges up to a foot possible. The better dynamics and 700mb trough orientation looks to set up off the Absarokas to the Winds with the highest probabilities over 18 inches of 80-90 percent. Over 12 inches with a 60-70 percent probability elsewhere at this time. Regardless, winter highlights have been issued to cover these ranges. Minor accumulations with little to no impacts with the warmer temperatures for lower areas west of the Divide. Liquid precipitation is expected for the lower valleys east of the Divide where the southern counties to be the possible winners for the weekend. All areas need the moisture, but especially this area. However, a minor flooding impact is possible and something to keep an eye on where up to an inch is possible. QPF amounts have come down as expected being a more progressive than expected system. Less than half an inch for other points to include the Wind River and Bighorn Basins, as well as along the I-25 corridor. Confidence on the liquid precipitation amounts are not as high as the snow, being more of medium confidence at this time as models are not in great agreement with one another. Beyond the weekend, expect a warming trend and mainly dry conditions for next work week as upper level ridging builds in with increasing convergence aloft. Back to above average temperatures and some windier days ahead for next week but hopefully this overall system's QPF amounts helps to alleviate any fire weather concerns in the more long term. Beyond that, long term models and outlooks show another GOA low pushing down that could affect the CWA by next weekend hopefully to bring in more of the much needed moisture. && .AVIATION /06Z TAFS THROUGH 06Z SATURDAY/... Issued at 950 PM MDT Thu Apr 25 2024 A very active weather pattern continues through the next 24 hours. An area of rain showers will develop from the Bighorn Basin down to Natrona County tonight/early Friday morning. Rain chances increase at KCOD/KWRL/KCPR terminals near/shortly after sunrise, so have prevailing -SHRA at that time. For other terminals it will remain dry tonight with more convective showers developing late Friday morning/early Friday afternoon across the area. For now have -SHRA for most terminals Friday afternoon, but -TSRA may be added with the next TAF issuance if confidence is high enough. There will be thunderstorms, but the exact location/timing is too difficult to pinpoint at this time. A more widespread -RA will develop Friday evening from KRIW/KLND terminals down to KRKS/KBPI/KPNA terminals. For KCPR/KWRL terminals showers exit to the southwest by mid- afternoon Friday. MVFR conditions are likely (70%) at KCOD by 10Z/Fri as low clouds develop and hang around through Friday afternoon. Improvement should occur at KCOD late Friday afternoon/Friday evening as clouds begin to lift and -SHRA shift to the southwest. For most terminals VFR conditions will prevail through the TAF period. Mountain obscuration will increase Friday afternoon and be prevalent Friday evening. Have VCTS at KRKS Friday afternoon and included a variable gusty wind to account for thunderstorm downdrafts/outflows. && .RIW WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory from noon Friday to 3 PM MDT Saturday for WYZ002. Winter Storm Warning from 6 PM Friday to 9 PM MDT Saturday for WYZ015. && $$ DISCUSSION...Lowe AVIATION...Rowe