798 FXUS63 KDTX 012310 AFDDTX Area Forecast Discussion National Weather Service Detroit/Pontiac MI 710 PM EDT Thu Oct 1 2020 .AVIATION... A cold front now advancing across the Flint area will exit southeast of metro Detroit by 03Z. A decent push of post frontal low level cold air will occur. Enhanced low level mixing should thus support north-northwest winds of 10 to 15 knots or so into the overnight. There is a region showers along and immediately behind the surface cold front that are tied to lingering ascent from the associated upper level wave. These will rotate across Se Mi over the next couple hours, exiting to the southeast around or shortly after 03Z with the departure of the upper wave. Model soundings and area surface observations suggest a potential for some post frontal low cloud development. Suspect any lower clouds will be brief in light of post frontal dry air advection. There will also be enough of a northerly wind component to hold most of the lake clouds across the thumb region, opening up some clearing across the terminals. For DTW...A wind shift from the west to the northwest associated with the cold front is expected around 03Z. Another region of showers will also advance across metro Detroit over the next couple hours. .DTW THRESHOLD PROBABILITIES... * Moderate in ceilings at or below 5000 feet this evening. Low tonight and Friday morning. Moderate Friday afternoon. && .PREV DISCUSSION... Issued at 353 PM EDT Thu Oct 1 2020 DISCUSSION... Mid afternoon radar trends indicate showers and thunderstorms burning quickly through available instability. Cellular coverage and the pulsy nature of stronger updrafts reflects the overall lower convective potential compared to yesterday. Slower storm motion as a function of the weaker wind profile has also played into the convective mode. Forcing from the upper level circulation and surface trough maintain activity having a gradually decreasing trend in coverage and intensity as surface based instability becomes exhausted by early evening. The cold front helping to focus today's showers/storms moves through SE Michigan tonight. The colder air inbound post front takes low temperatures down into the mid and upper 30s while NW wind lingers at 5 to 10 knots through sunrise Friday. That wind speed is high enough to prevent frost development at interior locations where clouds have a chance of decreasing during the night. The typically colder regions of the Thumb are influenced by the additional warming effects of clouds and onshore wind direction off the warmer water of Lake Huron. The warming effect of the lake is also reflected in model soundings that show the boundary layer remaining well above freezing and capable of lake effect rain showers that linger through Friday morning. Inland locations experience dry weather but plenty of diurnal cumulus through Friday afternoon as high temperatures struggle to reach the lower and mid 50s. Diffuse high pressure settles over lower Michigan Friday night while broadly cyclonic flow and cold air aloft remain in place. The wind and temperature pattern support model RH depictions of diurnal cumulus Friday afternoon lifting into meaningful coverage of mid level clouds Friday night. This is combined with thickening high clouds ahead of the next short wave to make the low temperature forecast and potential for frost difficult to evaluate. These cloud trends are definitely something to monitor before getting too aggressive with low temperatures and frost potential heading into Saturday morning. Thickening high clouds occur ahead of the above mentioned short wave that continues approaching while surface high pressure departs eastward during Saturday. The system produces backing flow in the mid and upper levels that starts weak moisture transport during the day. Model plan view depictions of wind and theta-e suggest weak advection that may not be able to overcome dry air lingering in the low levels before evening. There is general agreement on the slower trend of saturation in QPF fields among today's mid range model solutions but it will be a close call. The upper level trough axis is still more over the Midwest than Great Lakes by Saturday night but is able to influence forcing with increased SW flow through the mid levels. The orientation of the mid level theta-e gradient also becomes more SW-NE while contracting through Sunday morning. This is a good sign of implied mid level Fgen downstream of the 500 mb trough to enhance the vertical motion response prior to arrival of the trough itself. The rapidly improved organization in these features is worthy of at least scattered to numerous coverage of showers late Saturday night through Sunday. The short wave feature producing the wet weather to finish the weekend carries the larger scale trough axis eastward by Monday. The upper level ridge moving in from central Canada brings surface high pressure for improved weather and a gradual warming trend. Highs return back toward normal by Tuesday before the next front arrives for the mid week period. MARINE... Afternoon observations verify moderate north wind developing on the north end of Lake Huron as cold front settles through the central Great Lakes. Wind speed remains around 20kts or less during the night while the long fetch over Lake Huron leads to high waves around the Thumb shoreline. Small Craft Advisories remain in effect tonight and Friday for these conditions. The colder air mass settles over the Great Lakes and lasts through the weekend keeping conditions unsettled with the potential for rain showers and waterspouts in Lake Huron lingering into the weekend. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...Lakeshore Flood Advisory until 4 PM EDT Friday for MIZ049-055-063. Lake Huron...Small Craft Advisory until 4 PM EDT Friday for LHZ421-441>443. Lake St Clair...NONE. Michigan waters of Lake Erie...NONE. && $$ AVIATION.....SC DISCUSSION...BT MARINE.......BT You can obtain your latest National Weather Service forecasts online at www.weather.gov/detroit.