188 FXUS65 KCYS 070511 AFDCYS Area Forecast Discussion National Weather Service Cheyenne WY 1111 PM MDT Thu Oct 6 2022 .UPDATE... Issued at 745 PM MDT Thu Oct 6 2022 The cold front has accelerated its push towards the Laramie range in the last few hours, with GOES satellite imagery showing the low-cloud deck moving into the Sidney area as well as northern Laramie county. This is a few hours ahead of most hires guidance, which warranted some minor tweaks to the forecast. Dropped temperatures for the next few hours and also nudged the winds up immediately behind the front. The faster southwestward progression of the front has also boosted confidence in the cloud-deck intersecting the terrain near the I-80 summit, which lead to the issuance of a Dense Fog Advisory through Friday morning. Showers have also begun to develop near the North Platte River Valley, with some lightning strikes already observed. Expect this activity to expand and continue through much of the overnight as isentropic lift supports continued redevelopment in a similar area through about 12z. && .SHORT TERM... (This evening through Friday night) Issued at 355 PM MDT Thu Oct 6 2022 KEY MESSAGES: 1) Scattered showers and isolated thunderstorms possible overnight Thursday night across the central and northern Nebraska panhandle and portions of east central Wyoming. 2) Areas of fog possible in areas that receive precipitation Thursday night/early Friday morning. Fog that does develop will impact morning commute, clearing by mid-morning. 3) Widespread chances of frost across all of southeast Wyoming and the Nebraska panhandle Friday night/early Saturday morning. DISCUSSION: The main story this afternoon through tonight is the cold temperatures with the passing cold front and scattered showers with isolated thunder possible. Temperatures behind the cold front are currently sitting in the 40s, creating a 20 to 25 degree temperature gradient across our CWA this afternoon. Hires guidance shows scattered showers developing in the Nebraska panhandle and far east central Wyoming (east of the Laramie Range) late tonight and slowly moving east overnight. Isolated thunder cannot be ruled out, however confidence is currently low. Portions of the Nebraska panhandle may receive up to 0.20 to 0.30 inches of rain, which will not help a ton with the drought deficit, but will make some short-term gains! With light winds and moist conditions following the showers, areas that received precipitation, may also see fog development early Friday morning. Areas west of the Laramie Range will remain mostly clear overnight with temperatures cooling to the low- to mid-30s by sunrise Friday morning. Due to these near-freezing temperatures, areas of frost are possible, especially in the valleys. Friday throughout the day will be dry and cool with highs in the 50s across southeast Wyoming and the Nebraska panhandle. There is higher confidence in frost and freeze development Friday night/early Saturday morning as the low temperatures then will be in the low- to mid-30s across all of southeast Wyoming and the Nebraska panhandle. Frost advisories are possible. .LONG TERM...(Saturday through Thursday) Issued at 235 PM MDT Thu Oct 6 2022 The extended forecast includes seasonal to slightly above average temperatures from this weekend into early next week, with a strong cold front bringing the high temperatures below normal potentially by mid-week. Precipitation chances look low at this time until we have the strong cold front bring the opportunity back in our favor by the middle of next week. This weekend will be pleasant as surface high pressure propagates across the Northern Plains to the southeast. Cold air aloft at 700mb will take its time to slide to the southeast along with the dome of high pressure. Morning temperatures are likely to bottom out in the 20s to middle 30s for a majority of the cwa, so we will monitor the forecast in the next 24 hours to see if any headlines are warranted with respect to Frost/Freeze criteria. With weak CAA being present, several areas will struggle to reach seasonal temperatures on Saturday. There will be a gradual trend of temperatures warming at 700mb from west to east as we transition into the afternoon hours of Saturday, with 700mb temperatures warming to near +5C. The lower boundary layer will mix these temperatures down to the surface on Saturday afternoon, resulting in daytime highs in the 60s for most areas, but much cooler air will remain present in the higher terrain where the highest peaks in the cwa will struggle to get out of the 40s. Sunday will be more of the same as pleasant conditions are expected across the area. A cut-off ULL will reside over the Baja California and Four Corners region for Sunday. There are some members of the model guidance that attempt to show this moisture scooting north into CO toward our southern forecast zones, primarily along the I-80 corridor of SE WY in the mountain terrain. Have kept PoPs out of the forecast in the event that we can get better Hi-res data sampling to sort this out. The most likely scenario that will play out is orographic enhancement resulting in a few sprinkles, and breezy winds. Daytime highs are forecast to be about 5 degrees warmer, with highs in the 60s to lower 70s, especially east of I-25 into the NE Panhandle. Monday-Wednesday continue to be a struggle for models to get a good handle on. Multiple shortwaves are progged at this time to either eject out of the Pacific Northwest to our northeast, a cut-off ULL parking itself over the California coastline between Monday- Wednesday, or a longwave trough bringing precipitation coupled with a strong cold front. The highest confidence we have is the cold front at this time. Surface high temperatures ahead of this cold front will be above average, with highs in the middle 60s to upper 70s for Monday and Tuesday. The highest daytime temperatures are likely in the NE Panhandle. The cold front will result in temperatures being on the order of 20 degrees cooler by Wednesday, should trends with model guidance on temperatures continue. The biggest change over the past 12 hours is that the extended model guidance for the GFS and EC model have backed off the precipitation opportunities quite a bit, but the Canadian model still hangs onto the rain showers for the cwa, with possible mountain snow showers. This trend has been present for several days where the models are struggling to be consistent, thus we will continue to monitor the forecast at this time. && .AVIATION...(For the 06Z TAFS through 06Z Friday night) Issued at 1108 PM MDT Thu Oct 6 2022 Cold front lays along the Laramie Range this evening. Upslope easterly winds across the Panhandle and eastern Wyoming plains will create widespread IFR/LIFR conditions through the morning hours. HRRR supports this and followed its guidance on the 06Z TAFs. Stratus could stick around through 18Z before lifting. && .FIRE WEATHER... Issued at 249 PM MDT Thu Oct 6 2022 No fire weather concerns through Monday due to well above critical humidity values and cool to cold temperatures. Areas of wetting rains possible in the Nebraska panhandle late Thursday night into early Friday morning. Next possible day for potential fire weather concerns is Tuesday. Concerns are limited and generally isolated to far southeast Wyoming and the southern Nebraska panhandle. && .CYS WATCHES/WARNINGS/ADVISORIES... WY...Dense Fog Advisory until 9 AM MDT Friday for WYZ106-116>118. NE...None. && $$ UPDATE...MN SHORT TERM...LK LONG TERM...BW AVIATION...GCC FIRE WEATHER...LK