Marine Weather and Tide Forecast for Howell, MI

DISCUSSION

An axis of deep moisture with connection to the Atlantic and Gulf is in place across Southeast Michigan. The PWAT on the 13.12z DTX raob was 1.40 inches and areawide surface dewpoints are in the 60s. The next few days, through midday Thursday, will be governed by moist adiabatic lapse rates that will bring periodic chances for showers and isolated thunder activity. The most favorable timing for convective development both today and Wednesday will be with daytime heating. Light easterly flow with low LCL heights limits much in the way of convective vigor. It is challenging to offer much temporal or spatial detail to the precipitation forecast as the EPS interquartile range of 24 hr QPF at all locations is less than 0.33 of an inch each of the next few days.

The arrival of the exit region to a strong pacific jet streak will cause geopotential height falls to impact Southeast Michigan Thursday night. Latest indications are that midlevel cooling will occur in advance of the upper level low to result in steep midlevel lapse rates exceeding 8 C/km. Recent model solutions have been converging on a UVV signal that suggests the best time period for thunderstorm activity will fall in the 03-07z time window.
Combination of the lapse rates with rich thetae/moisture from the surface to 5.0 kft agl is expected to result in very unstable conditions, CAPES of 2000-3500 J/kg. Despite the late evening to overnight timeframe, it is important to point out that confidence is increasing in this magnitude of instability owing to the lapse rates.
The uncertain aspect of the forecast is to what extent the near surface convective inhibition will erode which will impact both the coverage of activity and the potential for surface based impacts.
0-6km bulk shear magnitude is forecasted to increase to greater than 40 knots Thursday evening resulting in the potential for mesocyclones and supercellular storm organization. Will need to monitor forecast trends as this time period approaches. The latest Swody3 has the majority of the forecast area in a Slight Risk for severe weather.

Cool northwest flow is likely for next weekend as deep troughing remains in place over the Great Lakes. Depending on timing of successive cold fronts or lake breeze boundaries, the temperature forecast will be up for revision.

MARINE

A weak pressure gradient continues to maintain lighter southeast flow through the midweek period with bouts of isolated to scattered showers and possibly some embedded thunderstorms. A warm front will then pass over the Great Lakes late Thursday night into Friday, which will veer wind direction to the southwest and will bring some more elevated wind speeds and gust potential. Additionally, some more organized thunderstorms will be possible along the warm front, centered through Friday morning.

PREV DISCUSSION
Issued at 204 PM EDT Tue May 13 2025

AVIATION...

Moisture continues to advect into the region today from southeasterly flow on the north side of the large upper low spinning over TN/KY. CIGs largely lifted out of the IFR from the early part of the day but should hold MVFR through the afternoon before dropping again tonight. Scattered showers are redeveloping at press time and will continue through the afternoon. Will keep SHRA in for the next few hours to cover it without any more defining feature to lock onto for timing. Still an outside shot at an isolated thunderstorm or two this evening but coverage warrants watching and amending later if they look to target a taf site. Fog remains possible late tonight with models advertising combination of IFR CIGs and VSBYs. Showers will be possible again Wednesday as the upper low remains over the region.

For DTW/D21 Convection...
Potential exists for an isolated thunderstorm this afternoon and evening and again on Wednesday.

THRESHOLD PROBABILITIES...

* High in ceilings aob 5000 feet through the forecast.

* Low for cigs/vsby to fall below 200 ft and/or 1/2 SM early Wednesday morning.

* Low for thunderstorms this afternoon and evening.



DTX WATCHES/WARNINGS/ADVISORIES
MI...None.
Lake Huron...None.
Lake St Clair...None.
Michigan waters of Lake Erie...None.