FXUS65 KREV 042146 AFDREV Area Forecast Discussion National Weather Service Reno NV 146 PM PST Wed Dec 4 2024 .SYNOPSIS... * Strong valley inversions continue at least into the start of the weekend with areas of freezing fog redeveloping each night. * Expect near seasonable temperatures outside of valley areas impacted by fog and low clouds. * No significant storms are on the horizon through mid-month, but a slider system could help erode the inversions by late weekend. && .DISCUSSION... Hi-res ensemble guidance, as well as blended guidance, continue to generate simulations that show little change to the current status quo weather-wise as the current upper level blocking pattern persists across the western CONUS, and splits the westerlies. GOES-West derived infrared imagery confirms this current forecast assessment as well. Looks like this continuing period of stagnant conditions under a cold dome of high pressure will continue through the remainder of the week into Saturday as well. Therefore, look for little deviation from the current forecast the next few days. This includes a continuation of cold overnight lows under clear skies, lighter winds, strengthening overnight inversions, and a continuance of air quality issues, especially in the more urbanized areas between Reno and Carson City. Also, denser patches of freezing fog will continue overnight across the Honey Lake Valley corridor of Highway 395 from the NV/CA state line to Susanville, that includes portions of Highway 36 and 44. This freezing fog projection also includes areas along highway 447 from Wadsworth to Gerlach, which includes areas around Pyramid Lake, and portions of the I-80 corridor from Fernley to Trinity Junction. Later this weekend starting overnight Saturday into Sunday morning, the trailing west edge of a weak cold front will become embedded in the upper ridge aloft, and sneak across the Sierra into the Great Basin backdoor-like. Areas north along the CA-NV-OR border will also have a 15-20% chance for precipitation late Saturday into Sunday as well. Following close behind, a deeper short wave system will take advantage of the now opened synoptic door, and push southeast "Inside slider-like" through northeast CA into Nevada later Sunday into Monday. The combination of these two features with the second system producing greater upper forcing, and stronger northwest breezes, will allow for better mixing into western Nevada valleys that mixes-out the stagnant conditions and enables dissipation of persistent freezing fog across the region. All other areas across the Sierra into western NV will remain dry, but a few degrees colder the first part of next week and colder air briefly filters into the region. Blended guidance also projects a slight upward trend in temperatures by mid-week that remains mostly seasonal through the remainder of next week. On a side note, extended ensemble simulations show a low confidence projection for an impending pattern change starting later next week. Although this projection carries a decent amount of uncertainty, it is something that will be tracked. More on this to come! -Amanda && .AVIATION... * Strong valley inversions will persist at least through Saturday morning. There is a good chance for areas of haze and minor reductions to slantwise visibility continuing for area terminals during the afternoon hours. Otherwise, western NV terminals outside of known areas of freezing fog will remain VFR with light winds continuing through the week. * Look for areas of morning freezing fog and low stratus to persist across the Honey Lake Basin, and the area around Pyramid Lake which stretches north through the Black Rock/Smoke Creek Deserts, and south to Fernley during the overnight hours. The freezing fog potential will still be high for KSVE and KTRK from 10Z to 17Z with periods of IFR/LIFR conditions in reduced visibility. There is also a less than 10% chance of KRNO and KRTS seeing some visibility reductions due to morning freezing fog as well. * Look for an end to stagnate conditions, and areas of freezing fog Sunday and Monday. Weak systems aloft will work their way across northeast CA into western NV, and bring an increased chance for W- NW breezes into the region. -Amanda && .REV Watches/Warnings/Advisories... NV...Freezing Fog Advisory from 8 PM this evening to 11 AM PST Thursday NVZ004-005. CA...Freezing Fog Advisory from 8 PM this evening to 11 AM PST Thursday CAZ071. && $$