Marine Weather and Tide Forecast for Harbor Beach, MI

DISCUSSION

Clear skies in the wake of a cold front are now seeing temperatures drop below the 40 degree mark across most of SE MI, where frost advisories remain in place. Patchy to areas of frost will be likely just prior to sunrise. Frost advisories will drop off at 8AM EDT where late April/early May solar insolation works to quickly warm temperatures up into the upper 50s to low 60s across the interior of the cwa, but in the upper 40s to mid 50s within the lake shadow under the influence of light northeast flow. High pressure brings dry weather today.

The upper-level wave leaving the four corners region will traverse into the Texas Panhandle into Oklahoma today which will aid in the development and modest strengthening of a surface low, projected to path over southern Michigan late tomorrow into Friday morning. This will initially pivot a strengthening llj across Michigan, enhancing theta-e advection, bringing the first opportunity for precipitation very late tonight through tomorrow morning. Initial forcing will be derived from the more focused low-level system-relative isentropic ascent. The low pressure then takes aim for Michigan late in the day on Thursday with the upper-level trough trailing just behind, then supporting broad-scale ascent driven by low-level frontogenetic forcing as the elevated frontal boundary stalls with the boost in differential vorticity advection associated with the pronounced mid- level vort max tomorrow afternoon and evening. This will result in increased coverage of showers through the afternoon.Showalter indices range from 0 to -1 highlighting the weaker elevated instability present which will bring the chance for embedded thunderstorms with all activity. The potential for multiple rounds of activity including embedded thunderstorms will bring the chance for elevated rainfall totals of 1-2+ inches, which at present time looks to align somewhere across the Flint/Thumb/Tri-Cities Region or farther north into northern lower Michigan. Please see the hydrology section for additional details.

Severe weather potential will be highly conditional on daytime recovery of any morning activity. Most of the model hi-res probabilities brings low chances to exceed 1000 J/kg SBCAPE by the later afternoon and evening hours, but the energetic jet profile aloft does support some shear conducive for strong to severe storm development. If destabilization is realized, all hazard types will be possible in the late afternoon and evening hours until a cold front sweeps through. Storm mode can range from pulse turning to more linear bowing segments with unidirectional wind direction above the near surface. Again this is highly marginal at this time and outside of the NAM, supporting evidence in hi-res output is on the lower side.

Uncertainty regarding precipitation trends increases greatly over the weekend into early next week surrounding evolution of the longwave pattern. The ECMWF/AIFS/EPS mean highlights a secondary trough that drops through the plains into the Ohio Valley Friday into the weekend, stalling and closing off with a deep ridge across the Atlantic blocking off open flow. This would bring additional chances for rain showers over the weekend into early next week as opposed to the more progressive GEFS solution which stalls the upper-level off the coast of New England. Will retain a low (20% or less) PoP values through this period until the aforementioned wave is sampled and better convergence within model output is observed.

MARINE

High pressure has expanded across the region overnight and will hold through the day. The next low pressure will develop over the Mid MS Valley Wednesday night and will lift through lower MI Thursday and Thursday night. The precipitation will begin Wednesday night ahead of the approaching warm front that will lift through Thursday with the cold front following overnight. The low will not be very strong but will be strengthening while lifting through the region. Wind speeds are not expected to be too elevated with a lack of cold air advection, holding mainly at or below 25 knots. Thunderstorms will be possible Thursday into the overnight. A second cold front will drop through the region on Friday but will be followed closely with an area of high pressure building into the area for the weekend.

HYDROLOGY

Arrival of a low pressure system will bring widely scattered to widespread showers with embedded thunderstorms on Thursday. Multiple rounds of thunderstorms capable of producing heavy downpours will bring the chance to see rainfall totals between 1 to 2 inches across Southeast Michigan, with the Flint, Tri-Cities, and Thumb region having the highest probabilities of seeing these elevated totals, pending the final track of the low pressure system. Rainfall totals in excess of one inch cannot be ruled out across the Metro region with any thunderstorms, but basin averaged rainfall totals are forecasted to range between a half-inch to an inch. Highly localized flooding in low-lying and/or flood prone locations will be possible.

PREV DISCUSSION
Issued at 1219 AM EDT Wed Apr 30 2025

AVIATION...

Light northerly winds carry through the early morning hours under VFR skies. The northerly flow will usher in Lake Huron low clouds towards sunrise, but current expectation is for any lower ceiling to hold east of any terminals. Have maintained at least a FEW to SCT mention to account for the lake moisture push. Winds continue to veer and then hold out of the southeast by later this morning.
Increasing high clouds encroach on Lower Michigan late in the TAF period with chances for rain coming after 06Z Thursday morning.

DTW THRESHOLD PROBABILITIES...

* None.



DTX WATCHES/WARNINGS/ADVISORIES
MI...Frost Advisory until 8 AM EDT this morning for MIZ047>049-053>055- 060>063-068>070-075.

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