799 FXUS63 KDTX 191123 AFDDTX Area Forecast Discussion National Weather Service Detroit/Pontiac MI 723 AM EDT Sat Oct 19 2019 .AVIATION... Calm surface conditions with ridge of high pressure in place has resulted in an isolated area of fog over portions of Lapeer and Oakland counties. Relatively dry surface conditions with surface temperature/dewpoint spreads precludes more than just a patchy coverage of fog this morning. High clouds will be possible today and tonight with approaching trough. Otherwise, VFR conditions tonight with potential for shallow fog development 10-13Z Sunday morning. DTW THRESHOLD PROBABILITIES... * None. && .PREV DISCUSSION... Issued at 334 AM EDT Sat Oct 19 2019 DISCUSSION... Morning water vapor imagery provides a good look at the strong anticylonic mid-level flow and attendant subsidence which is supporting clear skies and calm wind over the Great Lakes this morning. Lead shortwave associated with incoming Pacific energy will lift well northwest of the area during the next 24 hours, taking the poorly organized batch of showers over the eastern Plains with it. In the meantime, the thermal profile will continue to moderate over yesterday as H85 temperatures rise into the upper single digits. Highs in the low 60s still appear quite reasonable given full insolation to start the day. Expanding high clouds over eastern MO/western IL lend support to model simulations of increasingly filtered sunshine by this afternoon as upstream cloud cover advects into Lower MI limiting potential for further warming. Essentially a persistence forecast follows for Sunday with just a couple extra degrees tacked on due to airmass modification. Altogether, the weekend will be characterized by variable clouds, light wind, and seasonable warmth. Deep PV anomaly coupled with the 145kt jet taking aim on the Pacific Northwest this morning is impressive on water vapor imagery. This represents the feature of interest heading into next week as it will trigger a lee cyclogenesis episode late Sunday into Monday followed by rapid deepening late Monday as dynamic forcing ramps up over the Upper MS Valley/northern Great Lakes regions. Northward moisture transport will not be optimal given how quickly the cyclone occludes, but the general consensus remains suggestive that a very modestly unstable warm sector will have the potential to push into the southern CWA late Monday. The NAM12 and 00z EC indicate a ribbon of around 200 j/kg CAPE, all focused in the lowest several hundred meters, nosing into the CWA coincident with 200-300 j/kg SRH - a fairly typical low predictability high shear scenario. Warmth on Monday will be muted by clouds and potential for precip to lift into the area during the day. Temperatures then fall back below average heading into the extended as the cyclone lifts toward Hudson Bay and anchors a mean longwave trough through day 7. MARINE... A weak surface ridge will persist over much of the Central Great Lakes this upcoming weekend. An increased southerly pressure gradient will result in southerly winds of 10 to 15 knots with gusts of 20 to 25 knots across central and northern Lake Huron. The gradient weakens on Sunday causing winds to become variable around 10 knots or less. Monday morning, winds ramp up out of the southeast as a low pressure system deepens and lifts northward into the Upper Mississippi River Valley and far western basin of Lake Superior. Winds through the rest of Monday will bring potential for gales with gusts at or above 30 knots over much of Lake Huron. Elevated winds above 20 knots persist into Tuesday with post frontal flow veering to the southwest. Conditions for Tuesday look to remain below gales at this time. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...NONE. Lake Huron...NONE. Lake St Clair...NONE. Michigan waters of Lake Erie...NONE. && $$ AVIATION.....CB DISCUSSION...JVC MARINE.......CB You can obtain your latest National Weather Service forecasts online at www.weather.gov/detroit.