FXUS63 KDTX 161910 AFDDTX Area Forecast Discussion National Weather Service Detroit/Pontiac MI 310 PM EDT Tue Oct 16 2018 .DISCUSSION... Temperatures in the low 50s accompanied by gusts near 30 mph within well-mixed southwest flow this afternoon. Surface obs reveal a weak cold front over northwest WI and central MN behind which temperatures are solidly in the 40s, except 30s beneath extensive stratus deck. A 140kt jet downstream of the amplifying western US trough will amplify the PV anomaly presently over Lake Winnipeg, strengthening the front and forcing it southeast through tonight. Minimal precipitation within the dry and weakly forced environment in advance of the front, the passage of which is forecast to occur roughly 10-15z from the NW to SE Wednesday morning. Amplifying wave will sweep across the peninsula in the wake of surface fropa, deepening convective depths over the lake just as cold air begins spreading into the area. Considered along with deep, albeit brief, dynamic support, increased pops solidly into chc category immediately in the wake of the front over central and western portions of the CWA where lake enhancement will be possible prior to veering of the wind profile after sunrise. Wednesday will otherwise be largely dry with minimal diurnal recovery, especially over the northwest two-thirds of the CWA, owing to a variable coverage of stratocu over the area (best chance for clearing in downslope areas) and ongoing cold advection. Temps will struggle into the low/mid 40s north of about M59 and will likely be falling everywhere by 18z. A few afternoon convective cores are plausible as the back edge of the trough moves through during peak heating. Any locally intense core could produce a few flakes along and north of the terrain after 21z, but coverage is forecast to be sparse and larger scale support will be waning by this time anyway. Maintained chc pops for -RASN in the Thumb to account for stray Superior-Michigan lake effect potential lingering into the evening. Expansive polar high translates off the Front Range into the Ohio Valley by Wednesday night. A secondary surface trough will bring renewed cold advection during the first half of the night further lowering 850mb temps to below -10C followed by an increased likelihood for decoupling during the second half of the night, especially over western portions of the area. This will be the final advertised freeze of the season as temps fall into the 20s over most of the area. Strongly confluent northwest flow aloft will ensure clear or mostly clear skies, save for some high cirrus, on Thursday while return flow around the gradually departing surface high lags until late in the day. Deep mixing within the resident cold airmass will set the stage for temps for an appreciable diurnal jump with highs forecast to touch 50 degrees within diminished westerly flow. Emerging return flow by Thursday night will support stagnant or rising temps, especially west of the ridgeline. A strong pressure gradient is expected to set up across the Great Lakes in response to low pressure centered over northern Ontario and a strong high pressure centered over Carolinas. As a response, breezy southwest flow gusting between 20 - 30 mph will help push temperatures into the 50s for a daytime high on Friday. Cyclonic flow will take hold late Friday into Saturday as an amplified upper- level trough digs in across the Midwest. This thermal trough will diminish h850 temperatures below the 0C mark and will also bring the chance for a cold lake effect drizzle Saturday morning and afternoon as CAA ramps up across the warmer Great Lakes waters. Additionally, mechanical mixing from the increase in cooler air aloft will allow gusts between 20 - 30 mph to persist during daylight hours. Uniform northwest from from the surface up to the mid-levels will continue to bring in cold, Canadian air, dropping h850 temperatures to an average of -7C by Sunday at 18Z. As a result, daytime high temperatures will be capped in the upper 40s to lower 50s Saturday and down into the low to mid 40s by Sunday. Upper-level flow will turn more zonal for the early part of next week which will moderate temperatures, capping highs in the low to mid-50s by Tuesday. On and off precipitation chances will be for the early-half of next week, however, too much discrepancy is noted between model runs at this time to pinpoint timing and location. && .MARINE... Northwest gales over the open waters of Lake Huron have settled down to around 30 knots during the early morning. The wind will now shift southwest and increase again into the 35 to 40 knot gale range through today affecting mainly Saginaw Bay along with central and northern Lake Huron. Gale Warnings remain in effect through this evening for Saginaw Bay and Lake Huron north of Harbor Beach. Small Craft Advisories remain in effect for all other marine areas through western Lake Erie. Gales subside to gusts around 30 knots by mid evening through the overnight as the pressure gradient relaxes in the vicinity of the cold front moving through the central Great Lakes. However, wind veers and strengthens Wednesday with northwest gales possible once again. Given the lengthy break tonight, and some uncertainty on timing and magnitude Wednesday, a Gale Watch has been issued for central and northern Lake Huron for Wednesday into Wednesday evening. High pressure then builds into the Ohio valley and southern Great Lakes for a short time through Thursday before the active weather pattern resumes with another strong cold front Friday night. && .PREV DISCUSSION... Issued at 1243 PM EDT Tue Oct 16 2018 AVIATION... Strong southwest flow (15-20 KTS gusts 25-30KTS) this afternoon ahead of a cold front, which will come through dry with the limited moisture in place, and expecting mainly just mid/high clouds through early evening. Good post frontal cold advection late this evening/tonight should allow for low VFR clouds to overspread southeast Michigan, with brief/transient high MVFR cig possible, especially if any isolated snow/rain showers develop with the steep low level lapse rates and Lake Michigan enhancement. West-northwest winds behind the front, with gusts aoa 20 knots during the daytime hours of Wednesday. For DTW...Strong southwest winds this afternoon, gusting 25-30 knots, will lose the gustiness toward near sunset, but still probably sustained 10-15 knots through most of the night and shifting to the west-northwest after 9z Wednesday. DTW THRESHOLD PROBABILITIES... * Medium to high for cig aob 5000 feet tonight and tomorrow. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...NONE. Lake Huron...Gale Warning until 10 PM EDT Wednesday for LHZ362-363-462. Small Craft Advisory until 10 PM EDT Wednesday for LHZ443. Gale Warning from 8 AM to 10 PM EDT Wednesday for LHZ361-463. Small Craft Advisory until 10 AM EDT Thursday for LHZ441-442. Gale Warning until 10 PM EDT this evening for LHZ421-422. Lake St Clair...Small Craft Advisory until 10 PM EDT Wednesday for LCZ460. Michigan waters of Lake Erie...Small Craft Advisory until 10 PM EDT Wednesday for LEZ444. && $$ DISCUSSION...JVC/AM MARINE.......SF AVIATION.....SF You can obtain your latest National Weather Service forecasts online at www.weather.gov/detroit.