textproduct: Detroit/Pontiac

KEY MESSAGES

- A Freeze Warning remains in effect this morning for most of Southeast Michigan as lows drop into the mid 20s.

- Very dry conditions are expected this afternoon with relative humidity values dropping to around 30 percent.

- Temperatures warm back toward normal Tuesday, climbing well above normal through the rest of the workweek.

- Widespread rain chances increase again by Friday.

DTW THRESHOLD PROBABILITIES

* None.

PREV DISCUSSION

Issued at 238 AM EDT Mon Apr 20 2026

DISCUSSION...

The center of low-midlevel high pressure will push from NW Wisconsin this morning to the western basin of Lake Erie by this evening. For today, the forecast area will be located within the eastern flank of the high pressure in a favorable zone for anticyclonic flow trajectories and system relative isentropic downglide. Outside of some isolated lake effect cloud in vicinity of Lake Huron, the forecast area will largely experience low sky fraction. 850mb temperatures in the -9 to -13C range will limit highs in the 40s, some 12 to 15 degrees below normal. Notable item is very low RH, likely falling into the 20s to low 30s percent range.

Trough axis gets shoved eastward tonight allowing for moderated airmass with rapid surface dewpoint recovery (Tds of upper 40s to near 50) by Tuesday evening. Initial stage of synoptic scale warm advection could support possible sprinkles in the 10-14z time window Tuesday morning. Elevated activity but there is at least some evidence that the lower levels will dry to saturate. Southwest winds of 15 to 25 mph are expected by late morning and early afternoon as the large wavelength upper level ridge expands eastward across North America. A feature to key on will be a relatively narrow higher thetae plume that will advect through portions of northern Indiana and across far southern Lower Michigan by the evening. Model signal has been fairly persistent in enough 900-800mb moisture to support a few hundred J/kg of MUCAPE and possible high based shower activity for areas south of Detroit after 22z Tuesday. Mass centroid to surface based high pressure in Canada passes east of the longitude/meridian here for Southeast Michigan Tuesday night. The combination of increasing anticyclonic flow trajectories at the surface and a marine release off of the cold Great Lakes will allow a shallow cold front to slip south of Southeast Michigan. Therefore, expecting cooler conditions on Wednesday especially for those locations near Lake Huron. Lakeshore areas may struggle to reach the 50s.

High amplitude ridge then leads to high predictability for considerable warming Thursday and Friday. Highs are expected to be in the 70s depending on north to south extent. High solution variance continues to exist next weekend as a very complex upper level pattern is being advertised. There has been a ton of agreement in suggesting closed low/cutoff low potential upstream over the Great Plains and Upper Mississippi River Valley. Progression of any cold or occluded fronts will have a major impact on the sensible weather forecast. Most up to date timing of the cold front is late Friday night or Saturday. Duration of precipitation is very much in question Saturday and Sunday.

MARINE...

Gusty northwest wind will continue to subside through the morning as high pressure eases in from the west today. Small Craft Advisories remain in effect along the southern Lake Huron nearshore waters until late morning as wave heights will take time to diminish. The center of the high passes over the central Great Lakes this afternoon and evening with southerly return flow commencing tonight as the high departs east. Stronger south to southwest wind will spread over the region Tuesday morning into the early afternoon, and another round of Small Craft Advisories will be possible. Overlake stability will prevent much of the higher magnitude wind from reaching the surface, but a period of gusts to 20 to 25 kt looks likely between 4am and 2pm. A cold front then settles southward across the region late in the day, bringing a chance of showers and thunderstorms by Tuesday night, mainly in the south. Weaker wind follows on Wednesday as the pressure gradient relaxes again.

DTX WATCHES/WARNINGS/ADVISORIES

MI...Freeze Warning until 11 AM EDT this morning for MIZ053-060>063- 068>070-075-076-082-083.

Lake Huron...Small Craft Advisory until 10 AM EDT this morning for LHZ421- 441>443.

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