367 FXUS63 KOAX 111113 AFDOAX Area Forecast Discussion National Weather Service Omaha/Valley NE 513 AM CST Sun Dec 11 2022 ...Updated Aviation Forecast Discussion... .DISCUSSION... Issued at 245 AM CST Sun Dec 11 2022 Key Messages: - Areas of dense fog in the river valleys of extreme southeast Nebraska and southwest Iowa through 10 AM today. - Rainfall totals of 0.5 to 1.0 inches are expected in eastern Nebraska and southwest Iowa between Monday afternoon and Tuesday. - Light snow is possible (10 to 30% chance) in the region Tuesday night into Thursday. At 245 AM, the axis of an upper level ridge and an area of surface high pressure were centered along the Missouri River. These features were leading to clear skies and strong radiational cooling. Areas of dense fog were ongoing in southwest Iowa and extreme southeast Nebraska where the combination of surface moisture and radiational cooling were just right. A Dense Fog Advisory was in effect for these areas. Today & Tonight: Proximity to the surface high (light winds), strong radiational cooling and surface saturation will continue to produce areas of dense fog in southwest Iowa and far southeast Nebraska this morning. Visibilities should be lowest in the river valleys due to cold air drainage. Fog could linger past sunrise, perhaps as late as 10 or 11 AM in southwest Iowa. More persistent southeasterly winds should limit fog formation elsewhere this morning eastern Nebraska (Lincoln and Omaha). Surface pressure gradients will tighten today as lee troughing develops in the High Plains. As a result southerly winds will gradually strengthen today. Sustained winds of 10 to 15 mph and gusts in the 20 to 30 mph range are expected by mid afternoon. WAA from the southerly flow will keep temperatures above normal today. Expect highs near 50 along the NE/KS border and upper 40s in Lincoln and Omaha. Areas of fog will be possible again tonight before low level moisture deepens enough to make the transition to low clouds. If fog occurs it would most likely be between midnight and 5 AM. Widespread Rainfall Monday Into Tuesday: A 40 to 60 kt low level jet will develop from Texas to Dakotas Monday, ahead of a strong upper level trough advancing east from the Rockies. The jet will drive moisture from the Eastern Pacific and Gulf of Mexico northward, increasing PW values to around 1.0 inch in eastern Nebraska and southwest Iowa by Monday night. This moisture should combine with strong isentropic lift to generate a north to south oriented band of precipitation over the Plains by Monday evening. CAM soundings show a significant amount of moisture and lift in the surface to 700 mb layer between noon and 6 PM Monday, so it wouldn't be surprising if light drizzle or rain got going in eastern Nebraska during the afternoon. However the heaviest rainfall should occur Monday night and Tuesday morning and may be divided into two bands. Band one with the isentropic lift and band two as the primary surface low lifts into Nebraska on Tuesday. Though CAPE profiles are anemic, lift will be very strong, and it wouldn't be surprising if there were a couple rumbles of thunder (especially Tuesday morning). Severe weather appears unlikely at this time. Rain totals continue to look significant, and our going forecast favors amounts of 0.5 to 1.00 inches by Tuesday evening. Gusty winds may approach or exceed Wind Advisory criteria (gusts to 45 mph) on Tuesday with the strong southerly flow ahead of the surface low. Current guidance (10th to 90th percentile) from the NBM suggests peak gusts in the 35 to 50 mph range. The NBM has a tendency to underestimate with stronger systems, and our forecast hedges towards the higher end of this guidance. The track of the surface low will be key to temperatures through Tuesday. The majority of 00Z guidance keeps us in the warm sector through sunset Tuesday. This would favor highs in the 40s and 50s Monday and Tuesday. Should the low track slightly further south or east, then there could be a potential for colder temperatures to sneak into northeast Nebraska and this could pose a snow risk Tuesday. This appears to be a low probability (< 20%) risk at this time. Cooler Temperatures & Snowfall Tuesday night Through Thursday: Ensemble guidance is in better agreement this morning with all three of the 00Z ensembles (GEFS, EPS and CMCE) tracking the surface low eastward Tuesday night into Thursday. As this occurs temperatures should fall below freezing Tuesday night and remain near or below freezing through Thursday. Thus snow would be the favored precipitation type. Ensemble means suggest 48 hour snow totals of a trace to 2 inches in the region, with the best snow potential occurring Thursday. There may be some potential for higher totals if a deformation zone gets going (as suggested by the 00Z ECMWF). For now however this isn't the most likely outcome. Thoughts On Next Weekend: The upper level trough should shift towards the East Coast by next weekend, allowing northwesterly flow to prevail across the Plains. This would suggest a colder weather pattern for the upcoming weekend. Note the strong lean towards below average temperatures in the CPC 6 to 10 Day Temperatures Outlook (60-80% chance of below average). For the time being significant precipitation appears unlikely (< 10%) next weekend. && .AVIATION...(For the 12Z TAFS through 12Z Monday morning) Issued at 508 AM CST Sun Dec 11 2022 VFR conditions at all our TAF terminals this morning, though there is some freezing fog down around the confluence of NW Missouri, SW Iowa, and SE Nebraska. This fog should burn off by around 15Z. VFR conditions expected through the rest of today into tonight with southeast winds increasing this morning to around 10-15 kt and holding through the rest of the TAF period. We'll see increasing clouds after 06Z Monday with an approaching system. Cigs will be lowering through the early morning hours with MVFR to IFR cigs possible Monday morning. && .OAX WATCHES/WARNINGS/ADVISORIES... NE...Dense Fog Advisory until 10 AM CST this morning for NEZ093. IA...Dense Fog Advisory until 10 AM CST this morning for IAZ080-090- 091. && $$ DISCUSSION...Albright AVIATION...McCoy