575 FXUS65 KCYS 241709 AFDCYS Area Forecast Discussion National Weather Service Cheyenne WY 1009 AM MST Thu Dec 24 2020 .SHORT TERM...(Today and Friday) Issued at 401 AM MST Thu Dec 24 2020 Mountain wave activity and strong 700mb flow will assist in propagating winds at the surface across east Laramie County and Kimball/Cheyenne Counties in the Nebraska Panhandle. This shortwave looks promising on HiRes models such as RAP and HRRR as the agreement of 55-60 MPH gusts possible in the areas above. There is a small line of temperature advection positioned across I-25 and with the decrease in cloud cover, it is not out of the question that winds will mix down for these areas until 21Z this afternoon thus a High Wind Warning will continue for these counties until 2pm today. Wind prone areas will continue as gradients support up to 70 MPH until Friday 11 AM. A tale of two seasons plays for our CWA as diurnal heating into afternoon will bring our high temperatures across the region above normal for areas east of I-25 and areas west of I-25 will expect average temperatures in the mid 20s-30. This clearly displays our temperature advection in our region as low temperatures into tomorrow morning follow the same story: higher temperatures of mid to upper 20s east of I-25 and lower temperatures of teens west of I-25. Wind chills of single digits are possible for areas west of I-25 Friday morning. Dry conditions prevail tomorrow morning and afternoon bringing near critical fire weather conditions in the western Nebraska Panhandle with high temperatures reaching the upper 50s. A warm holiday for the entire region! .LONG TERM...(Saturday through Wednesday) Issued at 401 AM MST Thu Dec 24 2020 An exiting upper-level ridge will quickly transition to a near zonal upper-level flow with a series of shortwaves pulsing through it. This will lead to a period of gusty days both Saturday and Sunday leading to above normal temperatures east of the Laramie Range; temperatures in the 50s are expected Saturday afternoon across the High Plains. While winds continue to effect the region Sunday, a cold front will pass through the area, associated with a weak upper level trough and some moisture advection. Temperatures will drop into the 30s regionwide, with snow showers forecast for the mountains at first, then spreading across areas north of the North PLatte River Basin. This isn't a particularly moist system, with only a few inches expected in the mountains, a dusting expected elsewhere. Temperatures remain cold next week as a closed low transitions eastward and across the region, bringing temperatures down into the 20s Tuesday as the cold airmass really filters in. While closed low systems are notoriously hard to forecast, at this point it looks like most of the moisture associated with this system will be kept south of the WY-CO border, unfortunately. Still, the region will get another shot at moisture as the system passes. Will continue to monitor this system in the coming days. Behind it, winds will threaten the region once more, with wind highlights likely for Wednesday as the system exits east into the Plains. Quieter weather expected by Thursday as another shortwave ridge builds into the Intermountain West. Temperatures are expected to remain in the 20s and 30s for the duration of the week. && .AVIATION...(For the 18Z TAFS through 18Z Friday afternoon) Issued at 1010 AM MST Thu Dec 24 2020 VFR conditions expected to remain across all terminals through the forecast period. Main concern will be for LLWS in Southeastern Wyoming and strong winds as mountain wave activity brings west and northwesterly winds. Strong wind gusts along the wind prone areas of southeastern Wyoming expected to continue through Friday morning. Moderate to strong wind guests are also expected to remain across the Nebraska Panhandle, before calming down later this evening. OVC to BKN VFR ceilings continue for the Panhandle, but should start lifting out by this afternoon. && .FIRE WEATHER... Issued at 401 AM MST Thu Dec 24 2020 No major fire weather concerns today and tomorrow. Mountain wave activity is increasing winds for this morning and afternoon in the Nebraska Panhandle and southeastern Wyoming. Minimum RHs in southeastern Wyoming are too high for fire weather concern especially with the amount of moisture still lingering from the frontal system and possibility of blowing snow. Areas of the western Nebraska Panhandle trend close to critical fire weather conditions with fuels ready and minimum RHs ranging from 26-30 percent today. With wind gusts up to 60 MPH possible in Kimball and Cheyenne county, fire weather concerns are elevated but RHs are too high for warning criteria. Additionally, minimum RHs drop to 15-20 percent Friday afternoon but winds decrease significantly without mountain wave activity to assist; also winds aloft are less likely to reach the surface. && .CYS WATCHES/WARNINGS/ADVISORIES... WY...High Wind Warning until 11 AM MST Friday for WYZ106-110-116-117. High Wind Warning until 2 PM MST this afternoon for WYZ118-119. NE...High Wind Warning until 2 PM MST this afternoon for NEZ054-055. && $$ SHORT TERM...AW LONG TERM...AB AVIATION...MD FIRE WEATHER...AW