706 FXUS63 KDTX 210004 AFDDTX Area Forecast Discussion National Weather Service Detroit/Pontiac MI 804 PM EDT Fri Aug 20 2021 .AVIATION... VFR conditions through the remainder of this evening with mostly clear skies and light winds. Persistence rules during the early morning time frame with the potential for scattered ground fog development again. Periods of MVFR VSBYs will be possible in locations that see any fog development. MBS has seen the lower VSBY reduction lately, so will carry slightly lower VSBY there, but will keep it in the MVFR range for now. .DTW THRESHOLD PROBABILITIES... * None. && .PREV DISCUSSION... Issued at 241 PM EDT Fri Aug 20 2021 DISCUSSION... NEAR TERM / REST OF TODAY THROUGH TONIGHT As of 240 PM EDT...Quiet, but humid, afternoon continues across southeast Michigan as broad surface high pressure remains in place centered over the southern Lake Huron basin. Aloft, weak upper low continues to slowly drift eastward into the Mid-Atlantic region while sharp upper ridging folds over across the northern and central Great Lakes. As a result, mid and upper-level flow trajectories continue to become increasingly anticyclonic in nature which have helped in the stable weather trends ongoing across the region today. Forecast soundings continue to show increasing amounts of midlevel dry air moving in from the northwest along with increasing subsidence, which has helped to suppress the cu field so far this afternoon to more of a general scattered coverage in nature, with the exception being south of the I-96/696 corridor where a lingering bit of cyclonic flow remains. Dry weather will prevail through tonight outside of a rogue sprinkle or brief shower along any lake breeze convergence zones through roughly 6pm. High temperatures have the potential to overachieve in the mostly sunny conditions, but the suppressed boundary layer growth conditions will keep maxes topped out in the mid 80s for most, with isolated upper 80s readings. Tonight will be a muggy night once again with mid/upper 60s lows and saturated conditions towards daybreak promoting patchy ground fog/haze. SHORT TERM / SATURDAY THROUGH SUNDAY NIGHT Saturday will be another dry day as the region remains under the influence of the departing surface high pressure and folding upper ridge, and synoptic interactions between the Mid-Atlantic closed low and soon-to-be Hurricane Henri moving north up the eastern seaboard. Strong low pressure tracking northeast into northern Ontario will help progress a cold front eastward through the upper Midwest and mid-Mississippi Valley, with southwest flow increasing, albeit still on the lighter side, ahead of the boundary. The increased flow will help to transport slightly higher low-level moisture into the region with dewpoints making a run at 70 degrees region-wide. With another day of plentiful sunshine, degree of morning fog cover will determine how warm high temperatures get as virtually the same airmass will be in place from a thermal perspective, with the exception being a better mixed boundary layer. Opted to go slightly higher on max temps vs. model guidance with highs region-wide in the upper 80s, with around 90 in the Saginaw Valley and Detroit Metro regions. As the front approaches late Saturday night into Sunday morning, all indications are that it will have little dynamic forcing to work with as the parent low remains well to the north. Little convection is expected to accompany the front itself, but by Sunday afternoon, lingering surface trough coupled with peak daytime heating will provide more of a forcing mechanism for isolated to widely scattered thunderstorms. Severe thunderstorm chances will be low, but cannot rule out a strong thunderstorm with gusty winds due to a water loaded updraft. Ambient moist environment will promote efficient rain producing thunderstorms as well. Precip quickly comes to an end Sunday night with loss of daytime heating and arrival of inbound weak high pressure. LONG TERM / MONDAY THROUGH THURSDAY Upper ridging builds back into the region for early next week as 500 hPa heights build back above 588 dam resulting in continued sultry conditions. Monday and Tuesday will see a good potential for high temperatures to reach 90 degrees for a good chunk of the region as dewpoints remain around 70. Relief from the heat and humidity may arrive as early as the middle of next week as another cold front and possible complex of thunderstorms move in vicinity of the region. MARINE... Light southeast flow persists over the central Great Lakes for the rest of today as controlling high pressure gradually shifts east. Waves remain well below headline criteria (less than 2 feet) with no precipitation expected over the next 48 hours. Winds turn northwesterly with the passage of a cold front on Sunday with a minor uptick in wind speeds helping increase wave heights to 3 feet across most of the Huron basin. Locally higher gusts and waves are possible for the Detroit area waterways with any stronger afternoon thunderstorms. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...NONE. Lake Huron...NONE. Lake St Clair...NONE. Michigan waters of Lake Erie...NONE. && $$ AVIATION.....99 DISCUSSION...IRL MARINE.......KK You can obtain your latest National Weather Service forecasts online at www.weather.gov/detroit.