Area Forecast Discussion
Issued by NWS Cheyenne, WY
Issued by NWS Cheyenne, WY
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414 FXUS65 KCYS 191107 AFDCYS Area Forecast Discussion National Weather Service Cheyenne WY 507 AM MDT Thu Sep 19 2024 .KEY MESSAGES... - Dry conditions continue through the remainder of the week before precipitation chances return over the weekend. && .SHORT TERM /THROUGH FRIDAY NIGHT/... Issued at 245 AM MDT Thu Sep 19 2024 Rather quiet in the short term as the storm system, which brought windy conditions to the region yesterday, slowly moves northeast into Canada today. The next Pacific storm system, which will likely impact the Front Range this weekend, will still be drifting onshore across southern California through this afternoon. In between these systems, models indicate a shortwave ridge axis developing over southeast Wyoming and western Nebraska today and remaining over the area into Friday. Other than some fire weather concerns, minimal impacts are expected through Friday night as 700mb temperatures climb between 10c and 14c. Expect a slow warming trend today and Friday with highs pushing back into the mid 70s to mid 80s for southeast Wyoming by Friday afternoon, and mid 80s to low 90s for western Nebraska. Probability of precip will be near zero, and around 10 percent Friday night as the Pacific upper level low begins to track towards the Colorado/Wyoming border. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... Issued at 214 AM MDT Thu Sep 19 2024 Little changes for the forecast package during the medium range to extended outlook. Model guidance depicts multiple impulses of cooler Canadian air advecting toward our cwa from this weekend into early next week before we gradually begin to see an improvement in daytime highs. Deterministic model guidance remains for appreciable rainfall on Saturday and Sunday for the I-80 corridor east of the Laramie Range to help some areas with drought concerns. It will feel like fall this weekend as deterministic and ensemble model data remain in modest agreement for an impactful weather system to arrive. Lee cyclogenesis is anticipated as a mid-latitude cyclone/Colorado Low scenario evolves. A longwave trough is anticipated to have a slower trajectory over the Intermountain West into the High Plains, as a split-flow weather regime at H5 aloft occurs. The first measurable snowfall of the season is still modeled for elevations above 10,000 feet in the Snowy Range Mountains on Sunday. Temperatures will be chilly, especially on the eastern foothills and lower elevations of southeast WY. An upslope regime is anticipated to set up, translating to daytime highs in the lower 50s to low 60s from cloud cover and rain showers. Looked up the climatology for the day of 22 September for Cheyenne, and the record low-high maximum for that day is 40 degrees. It`s doubtful we will stay that cool, but it will most certainly be a day to have an extra layer on while outdoors. Depending on that surface low track, several drought-stricken areas could see beneficial rainfall between 0.5 and 1.0+ inches. Highest confidence for rainfall to persist is across the I-80 corridor east of the Laramie Range and east of the I- 25 corridor. The high plains will continue to see below normal temperatures early next week. The cut-off Upper level low (ULL) will slowly become absorbed into the mean steering flow again by Monday, with another weak cool front on its way towards our cwa. The cool air will spill down the spine of the Colorado Rockies via northwest flow aloft by Tuesday, keeping the region below normal for daytime highs. By the middle of next week however, upper level ridging will begin to amplify over the western CONUS. The upper level ridge will begin its trek towards the High Plains, and bring another opportunity for slightly warmer temperatures and dry conditions. && .AVIATION /12Z TAFS THROUGH 12Z FRIDAY/... Issued at 451 AM MDT Thu Sep 19 2024 VFR is expected for all terminals through the forecast period. Southerly to southwesterly winds will pick up by late this morning. Most terminals will see wind gusts of 15-25 knots through 0z this evening once the wind gusts pick up later this morning. After 0z wind gusts should transition to less than 10 knots, with east to southeast winds favored for terminals east of the Laramie Range. VRB winds between 6Z-12Z Friday are likely for most terminals. && .CYS WATCHES/WARNINGS/ADVISORIES... WY...None. NE...None. && $$ SHORT TERM...TJT LONG TERM...BW AVIATION...BW