textproduct: Detroit/Pontiac

KEY MESSAGES

- Chance (20-30%) of light showers both today and Friday.

- A stretch of well below average temperatures will persist into this weekend. This will bring potential for frost/freeze conditions each morning Friday through Sunday.

DTW THRESHOLD PROBABILITIES

* High for ceiling at or below 5,000 feet today, moderate tonight.

PREV DISCUSSION

Issued at 340 AM EDT Thu Apr 30 2026

DISCUSSION...

Closed upper low over Lake Superior deepens as it meanders eastward over the next 48 hours. Lower MI remains entrenched within cool cyclonic flow during this period, with 850mb temps near -3C this morning trending cooler toward -5 to -7C by Friday night into Saturday - these values in the bottom 10th percentile for this time of year. Pervasive overnight showers and drizzle will diminish in coverage this morning as PVA and height tendency progs trend neutral. Mostly cloudy skies follow for most of the day with high temps inching up to the low to mid 50s. The cold air aloft and late April sun angle steepen low-level lapse rates this afternoon to offer a chance of diurnally driven showers into this evening. There will be potential for some wet snowflakes or graupel to mix in given low wet bulb zero heights.

It will be a complicated setup for frost development tonight with low confidence on the degree of cloud cover after sunset. Loss of daytime heating will allow any diurnal showers/clouds to diminish this evening but then the next shortwave pivoting around the mean trough will renew mid-level moisture advection into the area which could limit radiational cooling. The gradient will be weak and sfc dew points falling to the lower 30s will allow temps to settle to near freezing within any prolonged clearing. Highest confidence for frost will be in the typical cooler spots of the Thumb and Saginaw Valley, and lowest confidence exists around Metro Detroit and south of I-94 which may see some showers move in late, associated with the shortwave. Will let subsequent shifts evaluate additional data and the need for any headlines tonight.

A corridor of height falls and PVA pass overhead on Friday, causing mid-level temps to lower and induce deeper diurnal mixing. This brings a higher coverage of convective showers during the daylight hours. Highs generally a degree or two cooler than today. Friday night into Saturday morning will present another window for frost/freeze potential with slightly higher confidence in this period given the cooler and drier ambient near-surface conditions.

Little support aloft for shower generation on Saturday and with less boundary layer moisture available, maintained a dry forecast for now. Similarly cool conditions continue with another round of frost/freeze considerations Saturday night into Sunday morning. Stalled troughing finally gives way to a shortwave ridge on Sunday with ensuing southwest flow supporting positive thickness advection and temperatures rebounding back toward 60. A weak clipper brings a chance of rain by late in the day. A broad upper low stays parked over northern Ontario early next week with deeper troughing setting up over the upper Midwest, favoring deeper southwest flow directing into the area. More seasonable temperatures look to be in store next week with potential for periods of wet weather.

MARINE...

The Great Lakes will remain under the influence of a slow moving upper-level low pressure system. This will bring periodic isolated to scattered shower chances through the end of the week, along with lighter winds under a more diffuse pressure gradient. Wind direction to generally hold from the northwest with stronger winds holding across northern lake Huron, where gusts around 20 knots will be possible.

DTX WATCHES/WARNINGS/ADVISORIES

MI...Frost Advisory from 10 PM this evening to 8 AM EDT Friday for MIZ047>049-053>055-061>063-069-070.

Freeze Watch from late Friday night through Saturday morning for MIZ047>049-053>055-060>063-068>070-075-076-082-083.

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