Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI
Issued by NWS Detroit/Pontiac, MI
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566 FXUS63 KDTX 181945 AFDDTX Area Forecast Discussion National Weather Service Detroit/Pontiac MI 345 PM EDT Wed Sep 18 2024 .KEY MESSAGES... - Warm and dry weather prevails through the end of the week and likely through the weekend. - A weak cold front has a slight chance of reaching Lower MI with spotty light rain possible late Friday into Saturday. && .DISCUSSION... Ridging continues across the Great Lakes as the dominate upper level features remain stationary across the conus through at least Thursday. The upper level trough over the west coast releases a strong vort max while also reinforcing itself with a southward diving jet down the coastline. Meanwhile, the weaker upper low over the Carolinas continues to churn with little movement with the ridge wedged between these two features. Airmass remains relatively unchanged trapped under this ridge, but starting this morning there has been an influx of low level moisture which resulted in an enhanced cu field this afternoon. Continued easterly flow will keep dewpoints up in the upper 50s to 60 tonight which should lead to another round of fog in the morning. Big question is whether or not we`ll see any precipitation Friday into Saturday when the aforementioned upper level wave releases from the west coast and tracks northeast through the Midwest. The main vort max gets pulled northward into western Canada but the trough swings through the Great Lakes while pivoting to a negative tilt. The surface front looks to wash out moving into the dry and stable air of the ridge still in place, but there is an arc of vorticity and pretty good ribbon of theta e pushing across the area. We`ve seen several times this summer where the 700mb forcing is enough to squeeze out some showers even with deep dry layer several thousand feet thick to work against. Model soundings show some elevated instability (couple hundred J/kg) as well so a thunderstorm cannot be ruled out but scattered light showers would be more likely. So the NBM offers 20-30 POPs Friday and Friday night to account for this which seems reasonable. Weekend looks mostly dry once again but forecast does start getting more interesting as models want to dislodge the cutoff west coast low and release it across the conus. With the ridge still extending up along the MS River, and the stronger flow aloft within the dominate trough over Western Canada, expectations would be for this low to eject northeastward into the Midwest as early as Sunday. GFS and ECMWF differ on how connected the cutoff low is to the Canadian trough and thus how progressive it is across the Plains. Regardless, looks likes we can expect precipitation chances for the first half of the new week as the trough slowly works through the region. && .MARINE... High pressure remains in control through the end of the week which will continue to bring light winds. The next chance (30-40%) for rain showers or a thunderstorm will enter Friday night into Saturday morning as a weak cold front and upper-level disturbance moves over the Great Lakes. Otherwise, dry weather persists. && .PREV DISCUSSION... Issued at 1259 PM EDT Wed Sep 18 2024 AVIATION... Daytime heating has resulted in a scattered cumulus field early this afternoon while the light easterly flow supplies the low level moisture boost. Skies are expected to remain VFR, but cloud bases will settle right around 3-4 kft and an occasional BKN observation is possible. A return to mostly clear skies and light winds tonight will bring another round of patchy to locally dense fog development. Have tempo groups for MVFR VSBYs, but it will be possible to see lower VSBY restrictions before lifting around 13-14Z. Winds remain east-southeast and below 10 knots tomorrow with another round of diurnal cumulus with the lake moisture boost. For DTW/D21 Convection...No thunderstorms are forecast through this week. DTW THRESHOLD PROBABILITIES... * None. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...None. Lake Huron...None. Lake St Clair...None. Michigan waters of Lake Erie...None. && $$ DISCUSSION...DRK MARINE.......AM AVIATION.....AA You can obtain your latest National Weather Service forecasts online at www.weather.gov/detroit.