470 FXUS65 KRIW 170400 AFDRIW Area Forecast Discussion National Weather Service Riverton WY 1000 PM MDT Wed Apr 16 2025 .KEY MESSAGES... - A cold front across northern Wyoming will spread south overnight, slowing down towards the I-80 corridor. - Snow, rain, and wind will occur behind the cold front, with some isolated storms along I-80 Thursday afternoon before it pushes southward once again. - Winter Storm Warnings and Winter Weather Advisories are in effect for much of central Wyoming through Friday morning due to the snow and wind. - Snowy and windy conditions continue into Friday, lingering through the afternoon and evening, giving way to a dry Saturday. - Several weather systems will impact Wyoming from Sunday through next week. Temperatures will rebound to near normal by Sunday. && .UPDATE... Issued at 1245 PM MDT Wed Apr 16 2025 Snow/rain totals continue to be on track for the upcoming system with a bit of a hedge up for the Cody Foothills to Thermopolis along Hwy 120. As such, the winter weather advisory for that zone has been upgraded to a winter storm warning due to the colder than previously forecasted daytime temperatures and a bit stronger winds behind the cold front. The NAM Nest continues to be the more in lined model to current conditions following its track of timing of the onset of precipitation and FROPA. Some moisture continues to push in from northeastern Utah into Sweetwater County with a couple possible rumbles of thunder along the Colorado state line. CAPE values around 100-200 J/kg and a higher possibility as the area continues to warm. Near term this afternoon, winds continue to increase coupled with low humidity values, elevated fire weather continues to exist. This will diminish towards sunset with radiational cooling. FROPA will start into the far northern portions of the CWA around the sunset timeframe with initial storms possible what is left of the daytime heating. Otherwise, some rain/snow mix in the lower valleys initially before being just snow as the overrunning ahead of the FROPA ceases through the overnight hours. The question will become with temperatures Thursday afternoon and how close to freezing many of the basins below 6500 feet. Slight elevation difference can alter the temperature swings and what precipitation type it will be. For now, it seems temperatures will lean closer to freezing, and thus, more snow expected increasing confidence in the WWAs currently ongoing. Otherwise, precipitation eases some into the overnight hours into Friday and lingers across the Wind River Basin towards Casper and eastern Sweetwater through the afternoon hours. Beyond that, dry for Saturday with another system for Sunday into early next week with reinforced cooler air being more seasonable through much of the long term forecast. && .DISCUSSION... Issued at 234 AM MDT Wed Apr 16 2025 As is usually the case with warm temperatures during the spring, it can swiftly return back to cold in a matter of hours. Case in point is today`s weather shift. Today will start as a warm spring day, with highs soaring back into the 70s. Warm temperatures will in turn allow humidity levels to fall considerably. Gusty winds ahead of the next system will bring an elevated fire weather threat across lower elevations in the afternoon. Then the cold front blasts across the state Wednesday evening. Again, with dense cloud cover and CAA, temperatures Thursday will be 20 to 30 degrees colder than today, especially east of the Divide. The northerly winds will bring a favorable flow for overrunning and upslope precipitation Thursday and Thursday night. The main question remains how dominant ground temperatures and solar radiation will succeed in melting snow as it falls. With temperatures stuck in the low to mid 30s through the day, along with moderate snowfall rates, feel the probabilities remain high for significant accumulations in some lower elevations. Gusty north winds will also amplify any blowing snow issues, with lowered visibilities at times through the day. With the storm on the doorstep, have upgraded all watches to advisories or warnings for the day Thursday. Don`t let the warm temperatures today fool you! && .AVIATION /06Z TAFS THROUGH 06Z FRIDAY/... Issued at 1000 PM MDT Wed Apr 16 2025 West of the Divide...KBPI/KJAC/KPNA/KRKS Terminals Shortwave energy within a broad trough of low pressure dives toward southwest Wyoming by 12Z/Thursday, aiding the development of widespread precipitation between 12Z-16Z/Thursday. MVFR conditions and areas of IFR are anticipated across the region, developing last at KRKS around 18Z/Thursday as a vigorous cold front arrives. The cold front shifts the wind at KRKS to the east-northeast at 18-30kts producing localized blowing snow during the afternoon. The presence of a mid-level low allows for snow to continue through the afternoon, with the start of a downturn in precipitation coming 00Z-03Z/Friday. Mountains becoming obscured between 10Z-16Z/Friday. East of the Divide...KCOD/KCPR/KLND/KRIW/KWRL Terminals A cold front and accompanying wind shift are progressing south through the forecast area Wednesday evening. Upslope and overrunning moisture begin to overspread the region between 09Z-14Z/Thursday as an upper-level low takes shape just to the west of Wyoming. This low and an associated mid-level circulation over southwest Wyoming by Thursday morning will increase snowfall across the region between 12Z-16Z/Thursday. Right-entrance region jet dynamics will aid heavier snow during the late morning and afternoon hours, especially at KLND, KRIW, and KCPR where upslope flow is favorable. IFR conditions will be widespread during this timeframe and into the evening hours Thursday. Snow chances decrease late in the period at KCOD and KWRL, where MVFR may become more common after 00Z/Friday. Mountains becoming obscured between 08Z-14Z/Thursday across the entire region. 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... Winter Weather Advisory from 1 AM Thursday to noon MDT Friday for WYZ002-007>009. Winter Storm Warning from 3 AM Thursday to 3 AM MDT Friday for WYZ003-005. Winter Storm Warning from 6 AM Thursday to noon MDT Friday for WYZ010-011-016>020-022. Winter Storm Warning from 3 AM Thursday to noon MDT Friday for WYZ015. && $$ UPDATE...Lowe DISCUSSION...Straub AVIATION...CNJ