FXUS65 KCYS 080501 AFDCYS Area Forecast Discussion National Weather Service Cheyenne WY 1101 PM MDT Sat Sep 7 2024 .KEY MESSAGES... - Warm and largely dry conditions are expected for much of the week ahead. A few isolated thunderstorms are possible Saturday afternoon. - With a slight increase in moisture aloft, the best chance of precipitation will occur on Wednesday, with mostly dry conditions for Tuesday, as well as Thursday through Saturday. && .SHORT TERM /THROUGH MONDAY/... Issued at 235 PM MDT Sat Sep 7 2024 Benign weather is expected over the next 48 hours as an amplifying ridge of high pressure aloft moves into the Intermountain West and into the Front Range. Current KCYS radar loop shows some weak convection trying to developing along a weak convergence boundary near the Laramie Range, but dewpoints have dropped into the 30s this afternoon, likely in response to the increasing subsidence and drier airmass aloft. Further east, light east to southeast winds continue with dewpoints in the 40s to mid 50s. A few thunder-showers are trying to develop at this hour, likely near the moisture gradient along the Wyoming/Nebraska border. Far eastern Wyoming and western Nebraska has the best chance to see a few thunderstorms late this afternoon and this evening, but high res guidance continues to back off on the overall coverage...with only a few cells across the southern Nebraska Panhandle. Kept POP around 15 percent for now, but may need to lower and remove weather this evening if activity struggles to develop. Upper level ridge axis will push over the area on Sunday. Warmer than average temperatures are expected over most of the forecast area with highs in the 80s, and a few locations near 90, mainly below 4500 feet. Believe there will be enough subsidence and dry air to greatly limit any deep convection, so kept POP below 10 percent. There is a subtle weak upper level shortwave that slowly moves southeast across the high plains, but with the drier air moving into western Nebraska along with considerable midlevel subsidence, do not expect this feature to produce anything more than a few showers near the mountains. For Monday, the upper level ridge axis is forecast to flatten by midday with westerly winds increasing slightly through the late morning and afternoon hours. Can't rule out a few thunder-showers along the Colorado border through the day, but coverage should be pretty limited. Monday will likely be the warmest day of the week with highs in the mid 80s to mid 90s across the forecast area...warmest east of the I-25 corridor. && .LONG TERM /MONDAY NIGHT THROUGH SATURDAY/... Issued at 148 PM MDT Sat Sep 7 2024 Monday night/Tuesday...Not as cool Monday night as the previous night as the airmass moderates. Low amplitude ridging aloft continues and with 700 mb temperatures near 14 Celsius, maximum temperatures will remain hot with highs around 80 degrees west of I- 25, and mid 80s to mid 90s east of I-25. With PW (precipitable water) values under 0.5 inches and warm temperatures aloft, convective chances appear minimal. Wednesday...As the ridge aloft moves off to our east, stronger southwest flow aloft develops, and with a shortwave trough aloft passage near peak heating, and PW values increasing to 0.7 to 1.0 inches, we anticipate scattered afternoon and evening showers and thunderstorms mainly west of I-25. Maximum temperatures will be slightly cooler with more cloud cover and precipitation coverage. Thursday...As a large scale trough aloft moves into the Great Basin states, southwest flow aloft will strengthen over our counties, with an attendant surface trough developing across eastern Wyoming. Warm temperatures aloft will limit convective development, though there may be enough mid level moisture to spawn isolated late day showers and thunderstorms. Friday...A more autumnal like pattern develops with a fairly potent shortwave trough aloft and its associated cold frontal passage early in the day which will likely dry out the airmass, keeping conditions dry and cooler, with breezy to windy conditions. Saturday...West southwest flow aloft continues and with PW values only from 0.4 to 0.6 inches, dry weather looks likely. Slightly warmer maximums with 700 mb temperatures near 12 Celsius. && .AVIATION /06Z TAFS THROUGH 06Z MONDAY/... Issued at 1054 PM MDT Sat Sep 7 2024 VFR conditions will be the rule tonight with a few showers and thunderstorms possible mainly near KSNY. The showers will most likely dissipate shortly after midnight with some patchy fog still possible along the North Platte River Valley. The upper level ridge will continue to keep its grip over the area during the next couple of days. && .CYS WATCHES/WARNINGS/ADVISORIES... WY...None. NE...None. && $$ SHORT TERM...TJT LONG TERM...RUBIN AVIATION...REC