textproduct: Gaylord

KEY MESSAGES

- Rain/storms in play the next few days. Heavy rain and strong storms possible tonight through at least Thursday or Friday.

DISCUSSION

Issued at 358 AM EDT Tue Sep 1 2026

PATTERN SYNOPSIS/FORECAST:

Broad pattern has ridging over the CONUS/North America, particular, the eastern half...with +2 standard deviations from the mean upper ridge over Hudson Bay...and similarly anomalous southern stream ridge centered over the Mid MS Valley. A 554dm 500mb low is plowing its way through the ridge axis attm, currently spinning over central Manitoba, with a strong height rise/fall couplet across southern Canada associated with this...and very occluded 1000mb surface low smack dab beneath the upper low, with a surface cold front stretching down into the central Plains. Very warm and sticky ahead of this front, with dewpoints largely in the 70s across WI and much of northern Lower south of a stagnant stationary front stretching from western Lake Superior through the Straits and toward New York and the Mid-Atlantic; pwat on our 0z sounding was 1.66in. Lots of fog/low-clouds continue to hang out near and north of the stationary boundary across the Yoop and parts of the Straits/Tip of the Mitt. Very warm airmass in place, characterized by 700mb temps around +10- 12C, and freezing levels of 15kft on our 0z/01 sounding. Attm, low- level jet is stronger to our northwest nearer to the upper low, and to our southeast across SE MI. Approximately 2000J/kg CAPE on our evening sounding, with some minor CINH, which is generally representative of the region attm...the bulk of which is going untapped as of 4z, with little in the way of forcing in the region attm.

Upper low looks to track just to our north through Wednesday, weakening to some extent as it does so, dragging a boundary into the area and leaving it for a while. Upstream, broad upper low digs into the PacNW, resulting in ridge axis generally strengthening over the Central Plains/Upper Midwest later this week, which should bring warm advection and some potential convection to the Upper MS Valley through the end of the week. We should remain largely in the vicinity of aforementioned lingering baroclinic zone through the remainder of the week, and thus, hold onto the threat of periodic unsettled weather into the start of the holiday weekend -- much of which may be dependent on how early/late day convection evolves (i.e., higher uncertainty than usual). Some uncertainty in the evolution of the northern stream pattern across central Canada this weekend, depending on a lobe of energy crossing the top of the ridge, and whether or not the ridge is able to block northern Canadian energy from sinking southward into eastern Canada for early next week. This could mean the difference between a slightly warmer end to the Labor Day weekend...or a warmer and slightly more active one.

FORECAST DETAILS...

Rain/storm potential the next few days...With signals for the boundary to drape in today, and that PV max to slide by just to our north...not impossible there could be enough forcing around to pop something today. Relatively light low-level flow also suggests lake breezes will come into play, particularly across northern Lower MI, which could play a role in boosting pop-up showers/storms, especially this afternoon. If we end up clearing out today, certainly possible the cap could be broken as well, with potential for 1500-3000J/kg CAPE here, given weak stability aloft. Think this idea will depend on what happens yet this morning, and there is some potential for activity to develop prior to 12z, though forcing will not be super great. Deep layer shear should pick up early this morning as the nose of the 500mb jet enters the region, and will remain at or above 40kts through the day...suggesting that anything that gets going will have support for organization. With the potential for that boundary to turn zonal this afternoon/evening...think upscale growth could be a concern. Deepest moisture may end up well to our south, across southern Lower today, and we may well tap into some drier air aloft that could limit shower/storm activity... but will still be close enough to warrant some beefier rainfall totals.

Better rainfall chances should come tonight into Wednesday as the low-level jet strengthens closer to our area, allowing for better support of nocturnal convection and moist advection off the zonal boundary likely to stall just to our south tonight and slowly drift back northward/northeastward Wednesday. Better instability parameters may remain near and south of M-72...which could result in most, if not all, the stronger storms staying south. However, appears we should still have around 40kts deep layer shear to work with...and another afternoon of upscale growth potential, with shear vectors parallel to the boundary; weak low-level flow again should support the idea of lake breezes and potential for localized convergence to enhance any storms. Other concern is that pwats should be on the rise again Wednesday, supportive of another increased risk of heavy rainfall/localized flooding potential across the area.

Boundary looks to wiggle back and forth across the area the next few days...and think this will keep the threat of heavy rain in play into at least Thursday, if not longer. Thunderstorms will also remain in play, with the warm/unstable air mass in the vicinity and some better deep-layer shear at times to support a threat for stronger, more organized activity from time to time...but will depend on how far north/south that boundary fluctuates through the next couple days...perhaps into Friday/Saturday as well, pending the evolution of energy riding the ridge later this week. This latter idea is again supportive of activity developing along the upstream perimeter of the ridge axis and could track into the Upper Great Lakes...so will need to keep an eye on it as well. Fluctuating boundary will also keep some portions, particularly near and south of M-72/M-55, more likely to stay warmer and more muggy through the period, with lesser dewpoints likely across the EUP going forward.

AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/

Issued at 640 AM EDT Tue Sep 1 2026

Fog will burn off through the morning, followed by partly to mostly sunny skies with conditions improving to VFR by the afternoon. Some increasing high and mid level clouds expected this evening with an afternoon pop-up shower/storm possible. Generally light winds expected through the period with chances for FG/BR development yet again tonight into Wednesday morning.

APX WATCHES/WARNINGS/ADVISORIES

MI...Dense Fog Advisory until 9 AM EDT this morning for MIZ086>088- 095>098. MARINE...Dense Fog Advisory until 2 PM EDT this afternoon for LHZ345>347. Dense Fog Advisory until 2 PM EDT this afternoon for LMZ341- 342. Dense Fog Advisory until 2 PM EDT this afternoon for LSZ321- 322.