FXUS63 KDTX 090339 AFDDTX Area Forecast Discussion National Weather Service Detroit/Pontiac MI 1139 PM EDT Thu May 8 2025 .KEY MESSAGES... - A Freeze Warning is in effect tonight and Friday morning for Midland and Bay counties and a Frost Advisory for the rest of southeast Michigan outside of metro Detroit. - High pressure brings dry weather Friday and Friday night followed by a stray shower Saturday morning. - A steady warming trend is the weekend weather highlight as afternoon highs climb back into the 70s Saturday and Sunday. && .AVIATION... High pressure over the northern Great Lakes will make a gradual southward expansion tonight and Friday. Very dry air associated with this high will sustain clear skies tonight and Friday. Nighttime cooling will support light northeast winds tonight. Winds will turn northerly with the onset of daytime heating with speeds increasing to near 10 knots. For DTW/D21 Convection... No convection is forecast through the TAF period. THRESHOLD PROBABILITIES... * None. && .PREV DISCUSSION... Issued at 400 PM EDT Thu May 8 2025 DISCUSSION... High pressure building down from northern Ontario brings an air mass cold enough for frost/freeze concerns late tonight and Friday morning. Conditions this afternoon and evening set the stage as gusty NE surface wind diminishes after steady low level cold and dry air advection. This along with the loss of daytime instability maintains clear sky tonight and Friday morning while northerly surface wind decreases further below 5 knots as prime radiational cooling promotes decoupling from a lingering gradient. Colder members of the guidance range are favored in this scenario which point to several hours of temperatures around the freezing mark toward the Tri Cities. Areas of frost are expected across the rest of SE Mi where ground temperatures still make it too close to call in favor of colder outcomes. The exceptions are in and around metro Detroit and downriver locations where low temperatures hover near 40 through sunrise. Full early May sun quickly lifts temperatures off chilly morning lows Friday morning, however the day starts with the surface ridge still to our north and the low level thermal trough overhead. Temperatures are then kept in check by a lingering north wind that becomes strongly lake breeze modified in the afternoon and evening. Highs in the lower to mid 60s inland from Lake Huron are at or slightly below normal for early May. The next low pressure system tracks across Canada Friday night and pulls a wavy cold front into Lower Mi Saturday morning. There is a well-defined but low magnitude moisture axis ahead of the front that is capable of a few showers as the wind shift settles slowly through Lower Mi. Timing is slow enough for a temperature rebound into the 70s and a daytime instability component followed by a pronounced lake breeze release into Saturday evening. This leads to a cool Saturday night/Sunday morning period, however the inbound high pressure brings more of a Pacific air mass and not much temperature change for Sunday. The high moves quickly eastward by Monday opening up SW wind and warmer temperatures to start next week. Given the mid/upper ridge building overhead, guidance highs in the lower 80s look reachable Monday afternoon. MARINE... Post cold-frontal north to northeast flow will continue to produce elevated wave heights across Saginaw Bay through the Lake Huron shoreline through the evening hours where Small Craft Advisories remain in place until tonight. High pressure to then build over the Great Lakes tomorrow and will hold through the weekend. This will bring several days of mostly dry weather in addition to calm to light winds through the weekend. The only slight chance for showers will be late tomorrow night to Saturday morning over northern Lake Huron, along an elevated frontal boundary. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...Freeze Warning until 9 AM EDT Friday for MIZ047-048. Frost Advisory until 9 AM EDT Friday for MIZ049-053>055-060>063- 068>070-075-082. Lake Huron...None. Lake St Clair...None. Michigan waters of Lake Erie...None. && $$ AVIATION.....SC DISCUSSION...BT MARINE.......AM You can obtain your latest National Weather Service forecasts online at www.weather.gov/detroit.