textproduct: Marquette

KEY MESSAGES

- It will be very warm and humid today though the heat index will remain below heat advisory criteria. Be sure to stay hydrated and have a way to cool off.

- There is a marginal risk (<15% chance) for strong to severe thunderstorms today over the southern U.P., some of which could produce small hail and damaging winds.

- Temperatures will be closer to average for the holiday weekend along with notably drier air as dew points fall back into the 50s to low 60s.

DISCUSSION

Issued at 315 AM EDT Fri Jul 3 2026

Early this morning upper air analysis and water vapor imagery showed an upper level high pressure over the Ohio River Valley extending east to Virginia and the Carolinas. The ridge had flattened out with zonal flow over the northern US. A weak disturbance in the flow was bringing isolated showers and thunderstorms over western Lake Superior and the far northern Keweenaw. Elsewhere it was dry, with clear skies over the western U.P. and partly to mostly cloudy skies in the east. It remained warm and muggy with temperatures in the 60s to near 70.

Today will be very warm and humid again with highs in the mid 80s and dew points in the upper 60s. A lake breeze will develop near Lake Superior early this afternoon cooling temperatures near the shore back into the 70s. The lake breeze boundary will surge inland later this afternoon as high pressure builds into Ontario, shifting the flow to a more northerly direction. Showers and thunderstorms will develop along the boundary as it moves south. The air ahead of the boundary will be unstable, with mlcape of 1000-1500 J/kg and a weakly capped environment. Shear is rather lacking though with mainly less than 25kt except closer to 30kt over the southern U.P. The main threat over the northern U.P. will be heavy rainfall and gusty winds. Over the southern U.P. where shear is higher some of the storms could become stronger with small hail and damaging winds. SPC guidance has a marginal risk (<15% chance) for severe storms over the southern U.P.

The rest of the holiday weekend, temperatures moderate some as an approaching low pressure system causes flow to shift out of the northeast, but highs still range in the 70s to lower 80s and lows in the 50s. This system does also bring a potential for another batch of showers and storms later Saturday into Sunday, but with some of the deterministic and ensemble guidance favoring a storm track more to our south, thus far our best chances are closer to the WI border. Still, we aren't looking a washout with QPF topping out around a quarter of an inch for most; that said, where storms do occur, heavier amounts would be possible. Temperatures trend warmer again into next week as ridging recovers, and though drier weather is favored, diurnal instability presents almost daily chances for some convection.

AVIATION /12Z TAFS THROUGH 12Z SATURDAY/

Issued at 724 AM EDT Fri Jul 3 2026

A short period of MVFR at IWD and SAW is expected this morning before fog and/or low stratus mixes out. Thereafter expect light winds and VFR conditions through the early afternoon. As a lake breeze boundary shifts inland late in the afternoon scattered thunderstorms are expected to develop, which could affect SAW and IWD. Any storms will be capable of IFR conditions, mainly due to vsby restrictions. Storms will diminish in the late evening with VFR conditions thereafter. CMX should stay VFR through the TAF period.

MARINE

Issued at 215 PM EDT Thu Jul 2 2026

Afternoon satellite reveals at least some lingering patchy fog over the lake today, particulary between the Keweenaw and Isle Royale and closer to the international boundary. Webcams indicate that this is dense at times. With a humid airmass in place, patchy fog remains possible through tonight. Otherwise, additional weak waves may bring more storms out over the lake through the holiday weekend, though confidence is low. Weak gradient flow will result in light winds, below 15kts through the weekend, with the exception of stronger winds in the vicinity of thunderstorms.

MQT WATCHES/WARNINGS/ADVISORIES

Upper Michigan... None. Lake Superior... None. Lake Michigan... None.