Area Forecast Discussion
Issued by NWS Cheyenne, WY
Issued by NWS Cheyenne, WY
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851 FXUS65 KCYS 300549 AFDCYS Area Forecast Discussion National Weather Service Cheyenne WY 1149 PM MDT Mon Apr 29 2024 .KEY MESSAGES... - Increasing precipitation chances tonight into early Tuesday with a cold frontal passage. Accumulating snowfall possible for the Sierra Madre and Snowy Ranges, especially above 8000 feet elevation. - Strong winds likely with and behind the front across the Laramie Range Tuesday morning. Gusts up to 60 mph possible. Additionally, dry downsloping winds could result in critical fire weather conditions Tuesday afternoon for portions of the North Platte River Valley. - Active extended forecast period with multiple rounds of rain and snow showers with occasional thunder possible daily through the rest of the week. && .SHORT TERM /THROUGH TUESDAY NIGHT/... Issued at 233 PM MDT Mon Apr 29 2024 Latest GOES WV imagery an upper level trough over the PacNW that will continue to move towards our CWA bringing chances for precipitation and strong winds. Overall seeing a warm day across southeast WY and western NE with temperatures so far reaching the upper-50s to mid-60s east of the Laramie Range and mid-50s farther west. However, gusty west winds and SCT to BKN cloud cover will continue through the afternoon as the shortwave ridge axis shifts to the east today. Hi-res guidance shows showers beginning to increase across Carbon Co early this evening, but will increase in coverage closer to midnight as the cold front currently analyzed over eastern ID near the WY border begins to move through the CWA. Most of the area will likely see ptype remain as rainfall, however elevations above 8000 feet could see accumulated snowfall. This will most likely be confined to the Sierra Madre and Snowy Ranges that could see up to 6 inches overnight. Precipitation will continue into early Tuesday morning before quickly moving off to the east with the frontal boundary that will be in play for potential severe thunderstorms in eastern NE in the afternoon. Additionally, strong winds appear likely with and immediately behind the frontal passage Tuesday morning. Downward omega fields still look to be strong across the Laramie Range. Westerly 700mb flow aloft increases to 40-45 kt, but has been on a slight downward trend over the last 24 hours with the GFS with hi-res guidance mostly showing sub-warning level gusts. In-house guidance has also been showing this slight downward trend in high wind probabilities and gust estimates for wind-prone locations. NBM probabilities of exceeding 55 mph still remains over 50% for most of the wind-prone locations across southeast WY, especially across the Central Laramie Range. Regardless, this bora wind setup could still lead to brief periods of localized wind gusts near 60 mph so have decided to keep the High Wind Warnings/Watches going across the area. With these westerly downsloping winds, dry conditions are likely across the adjacent foothills and plains into portions of the NE panhandle. However, there is uncertainty on if the post-frontal temperatures will be warm enough for a prolonged period of critical fire weather conditions with 700mb temps changing the most across east-central WY and the northern NE panhandle. Fire Weather Watches remain in effect for areas near Torrington and Scottsbluff. Temperatures Tuesday afternoon look to be 5-10F degrees cooler than Monday, but still reaching the low-60s east of the Laramie Range. && .LONG TERM /WEDNESDAY THROUGH MONDAY/... Issued at 233 PM MDT Mon Apr 29 2024 An active pattern in the long term with multiple disturbances ejecting through the forecast area, resulting in near daily chances of precipitation and near-normal temperatures. The long term period starts with an upper-level low sweeping east across the northern Rockies and into the Northern Plains between Wednesday and Thursday. Due to the low being north of the forecast area, our main impacts will likely be gusty winds and cooler temperatures with low precipitation chances. The mountains have the best chance at accumulating snowfall, but rain becoming snow cannot be ruled out at lower elevations, especially along and west of the I-25 corridor Wednesday night. This low is quickly followed by a shortwave entering the forecast area Friday, increasing precipitation chances once again. Precipitation type is still somewhat uncertain, but it will more than likely be snow in the mountains and rain at lower elevations with possible thunderstorms in the High Plains. Saturday finally brings a ridge of high pressure that will increase high temperatures back to above-normal through Sunday. The ridge will also keep conditions dry through the weekend. && .AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/... Issued at 1141 PM MDT Mon Apr 29 2024 A weather disturbance and cold front will sweep across the terminals early this morning, ushering in scattered showers and some lower ceilings until mid morning today. Wyoming TAFS...At Rawlins, occasional showers and fog will occur until 10Z, reducing visibilities to 3 miles and ceilings to 1500 feet. From 10Z to 14Z, ceilings will be near 6000 feet, then clear skies will prevail. Winds will gust to 35 knots. At Laramie and Cheyenne, ceilings from 8000 to 12000 feet will occur until 13Z, with occasional showers at Laramie and ceilings near 3000 feet until 11Z, then skies will become clear at the terminals after 14Z. Winds will gust to 45 knots after 10Z. Nebraska TAFS...Ceilings will range from 8000 to 15000 feet until 14Z, with occasional showers, then skies will become clear after 14Z. Winds will gust to 40 knots after 09Z. && .CYS WATCHES/WARNINGS/ADVISORIES... WY...Fire Weather Watch from Tuesday afternoon through Tuesday evening for WYZ433. High Wind Warning from 6 AM to 6 PM MDT Tuesday for WYZ106-107- 116-117. High Wind Warning from 3 AM to 6 PM MDT Tuesday for WYZ110. High Wind Watch from 9 AM MDT Tuesday through Tuesday afternoon for WYZ118. NE...Fire Weather Watch from Tuesday afternoon through Tuesday evening for NEZ435-436. && $$ SHORT TERM...MB LONG TERM...LEG AVIATION...RUBIN