421 FXUS63 KDTX 301819 AFDDTX Area Forecast Discussion National Weather Service Detroit/Pontiac MI 119 PM EST Fri Dec 30 2022 .AVIATION... Steady moisture flux under south-southwest flow continues to bring in a stream of showers and low stratus from DTW to FNT. Low MVFR to IFR ceilings currently observed across the airspace will steadily lower to IFR through the afternoon as persistent rainfall saturates the sub-cloud layer. Still some uncertainty as to how quickly this saturation process occurs and the role that surrounding drier air may play. TAFs thus reflect the general trend for lowering cigs/vis through the evening. A cold front approaching from the west this afternoon shifts winds to westerly and eventually northwesterly overnight, while focusing moisture primarily between PTK and DTW as it stalls over Lake Erie. Development of a subtle inversion aloft and diminishing SW flow lends to LIFR cigs with potential for visibility restrictions given such moist near-surface conditions. Ceilings and visibilities begin to improve mid-morning Saturday as the front releases further east. For DTW... approaching frontal boundary stalls over Lake Erie this evening, with winds veering NW by tonight. Stratus lowers through the evening, although timing will be largely dependent on shower intensity overhead. Still a good signal in guidance for cloud bases to reach LIFR by early Saturday morning, with IFR visibility restrictions given the moist near-surface conditions. DTW THRESHOLD PROBABILITIES... * High for ceiling 5000 ft or less today and Saturday. * High for precipitation as all rain today and tonight. && .PREV DISCUSSION... Issued at 351 AM EST Fri Dec 30 2022 DISCUSSION... Key Messages: -Above average temperatures hold for one last day today before a cold front sags into the region. -Pockets of light rain/drizzle continue this morning, followed by steadier rainfall this afternoon into tonight, especially across the Metro Detroit to Ohio border area. -Additional rainfall possible mainly south of I-69 Saturday until the cold front clears the region. -Expectation remains that the area will be on the warm side of the next low pressure system Tuesday which provides additional rainfall and high temperatures approaching 60F. Pockets of light rain/drizzle seen thus far tonight continue into the morning hours as southerly warm sector flow promotes low level saturation under anemic ascent. Frontal boundary currently over the western Great Lakes reaches central MI around midday as its parent partial-sheared shortwave slides northeast into northern Ontario. This cold front is progged to slow if not stall out from the Saginaw valley down towards Kalamazoo leading to the development of a baroclinic zone over the majority SE MI. Generally lighter rainfall intensities expected through the late morning-afternoon timeframe given the weak nature of the cold front and lack of substantial upper level support. This changes going into the evening hours as the 120+kt jet streak shifts further northeast into northern Ontario/Quebec resulting in the establishment of right entrance dynamics over southeastern lower MI. Greatest PW (1"+) likely holds over NW OH this evening/overnight with a rapid decrease in moisture quality the further north/west you are (falling to 0.25"-0.5" over the Thumb/Tri-Cities) which will result in a stark NW-SE QPF gradient over the CWA... see hydrology section for more details. Height falls continue into Saturday as the deamplifying longwave trough over the Plains expands towards the Great Lakes supporting cyclogensis over the mid-Mississippi/Ohio Valley. Surprising amount of spread still exists in the 00Z deterministic runs in respect to the degree of eastward progression the front makes Friday night/early Saturday which leads to differing tracks of this developing surface low and associated rain showers. GFS/NAM solutions are the most progressive with the front clearing or nearly clearing the region by mid-Saturday morning which keeps the low track towards central/eastern OH leading to dry conditions most of Saturday. The ECMWF on the other hand is least progressive resulting in track over NW OH supporting persistent rain shower activity over the bulk of SE MI into Saturday afternoon (Canadian family is the middle ground between these two camps). For now have erred more towards the Euro/Canadian solutions have kept chance PoPs going through the midday period Saturday for all areas aside from the Tri- Cities/western Thumb. Areas north of I-69 could some wet/melting snowflakes mix in with rain AM Saturday however no accumulations expected. Regardless of outcome between the two camps, system/frontal boundary fully vacate the region by Saturday evening. Diffuse weak low pressure then lifts through the upper Great Lakes daytime Sunday. Light precip (rain/snow mix) could clip the area early Sunday, however the lack of accompanying moisture (forecast soundings struggle to reach saturation in the mid/low levels) and primary shortwave forcing holding north of the CWA will make it difficult for much to develop/reach the surface. Quieter weather briefly returns to start the next work week as upper flow turns zonal over the eastern half of the CONUS before a potent Pacific NW trough digs into the Desert Southwest. This mid/upper wave pivots into the central US by Tuesday spurring rapid cyclogensis across the southern/central Plains. How progressive this low is still carries considerable uncertainty owing to spread in the longer range solutions. That said, all current solutions (both deterministic and ensemble means from the EPS, GEFS, CMCE) favor an initial all-rain outcome with the low track to our west over upper Mississippi valley. A transition to wintry p-types on the backend can't be ruled out (seen in the Euro/CMC solutions). MARINE... Low pressure tracks from Lake Superior into Ontario this morning and drags a cold front across the region today. Southerly wind of 15 to 20 kt will veer to the southwest in its wake, then weaken heading into the evening hours as high pressure rapidly builds into the region. A few gusts to 30 kt will be possible over Lake Huron early, but extremely stable conditions will keep winds in check despite a strong wind field just off the deck. The front stalls out over Lake Erie tonight before an Ohio Valley low pressure system tracks along it and into the eastern Great Lakes by Saturday night. This system will veer winds to the north/northeast on Saturday at 10 to 15 kt, then back to the southwest by Sunday. Given the mild air mass, rain will be the precip type with these systems. HYDROLOGY... Rain expands in coverage this morning, becoming widespread south of I-69 by afternoon as a frontal boundary sags into the region. This rain continues into at least Saturday morning though some showers could linger into Saturday afternoon mainly over the easternmost areas. Greatest moisture (PWATs nearly 1 inch) resides toward Ohio with a sharp dropoff the further north you are (decreasing toward 0.25-0.5" over the Tri-Cities/Thumb). This is expected to lead to a stark gradient in potential rainfall amounts with areas south of a line from Howell to Sanilac seeing 0.5-0.75"... perhaps approaching 1" near the Ohio border, and areas to the north of said line seeing less than 0.25". Rises on area rivers can be expected, although flood potential ultimately rests on the extent of frozen ground and any ice blockages that may occur from this spell of mild temperatures since the rain will occur over an extended period of time. Additional rainfall likely arrives late Monday, possibly continuing into Wednesday. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...None. Lake Huron...None. Lake St Clair...None. Michigan waters of Lake Erie...None. && $$ AVIATION.....MV DISCUSSION...KDK MARINE.......TF HYDROLOGY....KDK You can obtain your latest National Weather Service forecasts online at www.weather.gov/detroit.