textproduct: Detroit/Pontiac

KEY MESSAGES

- Dry and cool through Friday.

- Rain returns by Friday night and continues into Saturday.

DTW THRESHOLD PROBABILITIES

* High for ceilings at or below 5000 ft this morning. Low this afternoon.

PREV DISCUSSION

Issued at 356 AM EDT Wed May 20 2026

DISCUSSION...

A surface cold front progressed across the area overnight and a strong marine augmented pneumonia front continues to surge south and west early this morning. An impressive 10 to 25 degree temperature drop has been observed behind this feature. The frontal inversion traps a stratus deck overhead early today, but this shows signs of giving way with time as drier air arrives from the north. Some sunshine looks likely across the north later today but high cloud remains more pervasive across the south. 850mb temps settle in the 1 to 3 C range today, carrying a much cooler day with highs in the lower to mid 60s. North to northeast flow off Lake Huron holds temps near the lakeshore in the 50s.

Upper jet streak entrance region overhead gains an increasingly anticyclonic orientation through the day, causing expansive high pressure to spread from the Midwest into the Great Lakes tonight. Another release of dense marine air spreads across the area late this evening and sends temps down into the 40s and dew points into the 30s. Could see some patchy frost Thursday morning in the cooler locales of the Saginaw Valley and Thumb if wind ends up going calm, but expectation is for the persistent northeast gradient and a veil of mid/high cloud to prevent widespread frost development.

Light wind maintains a northerly component through much of Thursday, holding temperatures in a similar range compared to today. Strong deep layer stability and mid-level dry air ensure dry conditions through the day and most of Friday. Slightly milder conditions are forecast Thursday night with more cloud cover in the vicinity.

Longwave trough over the High Plains helps direct a shortwave from the western Gulf coast toward the Great Lakes late Friday. The attendant surge of moisture brings relatively high confidence in widespread stratiform rain Friday night into Saturday, with a notable shift among the bulk of ensemble guidance toward a later start time - likely after sunset Friday. Placement of steadiest rain will be subject to the eventual track of low pressure and efficiency of warm conveyor moisture advection, but will note 12z LREF grand ensemble probabilities target southeastern portions of the area with a 50% chance to exceed 1 inch by Saturday afternoon.

Deep layer southwest flow ensues Saturday as the wave lifts through, with warm advection boosting temps back into the 70s to finish the holiday weekend. Another shortwave capitalizes on burgeoning instability to bring a chance of showers and thunderstorms Sunday afternoon/evening. A warming trend follows next week with good consensus among grand ensemble 500mb progs in depicting an omega blocking ridge setting up over Ontario by late week.

MARINE...

High pressure will fill in across the Great Lakes this morning and will slowly move across the region tomorrow before washing out across the Continental Northeast by Friday morning. This will bring dry weather through the midweek period. Northwest and north flow in the wake of a cold front will bring some slightly elevated winds across north and north-central Lake Huron with gusts 20 to 25 knots. A heightened wave field reaching the Thumb nearshore prompted a Small Craft Advisory this afternoon and evening. As the high pressure system moves over the Great Lakes on Thursday, winds will begin to veer to the northeast and will hold northeast-east through Friday. The next low pressure system is then expected to enter the Great Lakes late Friday into Saturday which will bring the next potential for showers and thunderstorms.

DTX WATCHES/WARNINGS/ADVISORIES

MI...None. Lake Huron...Small Craft Advisory from 4 PM this afternoon to midnight EDT tonight for LHZ421-441.

Lake St Clair...None. Michigan waters of Lake Erie...None.