textproduct: Gaylord

KEY MESSAGES

- Rain chances return for the weekend...but probabilities/ evolution are in question (some areas may not see precipitation at all).

- Seasonably cool Monday through midweek.

DISCUSSION

Issued at 245 PM EDT Thu Sep 17 2026

Pattern Synopsis: North American pattern anchored by impressive 600dam 500mb high (+3 sigma height anomaly) encompassing much of the southern U.S. Split flow across the western U.S. between strong zonal flow across western Canada and a stalling upper low over California; Great Lakes under the influence of the southern branch of this split with a strong jest streak across northern Ontario/ Quebec. Low amplitude short wave crossing the upper Lakes today...part of a long (latent) PV filament that stretches from Quebec all the way back to the California upper low. West-east axis of deeper moisture rotating around the northern periphery of the southern U.S. anticyclone...from the mid Mississippi Valley east across the Ohio Valley and into the Mid Atlantic/southern New England. Also along the northern periphery the upper high stretches a surface front from New England back into the central Plains... serving as an unrelenting corridor of rainfall south and west of Michigan for the most part. Broad high pressure extends from central Canada across the upper Lakes and into Quebec.

Primary Forecast Concerns:

Rain chances return for the weekend...but probabilities/evolution are in question (some areas may not see precipitation at all): Looks like we will be able to squeeze out a dry day Friday; high pressure over Manitoba and ridging into the upper Midwest/Great Lakes this afternoon will propagate into northern Ontario Friday...increasing northeast boundary layer flow into northern Michigan. Mid/high clouds will thicken during the afternoon... precipitation shield across Minnesota/Wisconsin driven by isentropic ascent and entrance region jet forcing will spread across Lake Michigan by early Friday evening. But with convection likely developing across Iowa Friday afternoon/ evening where the low level jet intersects the warm frontal boundary...this may tend to allow the precip shield to propagate more southeast with time. The implication is that precipitation may be confined to about the southwest half of the forecast area Friday night/Saturday. This is definitely a trend to the south with this forecast...probabilities of exceeding 1 inch/24 hours through 0000Z Sunday around 40% across Manistee county and drops below 10% north of M-32. In fact current forecast will not carry PoPs north of a Charlevoix-Harrisville line through the weekend. Rain chances will linger south of M-32 into Sunday though anticipating a decreasing trend from north to south. Overall highest rainfall amounts Friday night through Sunday afternoon 0.50- 1.00 inch possible along-south of M-55.

Seasonably cool Monday through midweek: High pressure to the north of the Great Lakes through midweek should result in a preponderance of east/northeast boundary layer flow into Michigan through Wednesday. This will keep temperatures generally in the 60s from Monday through the middle of the week...which will be a few degrees below normal though we are beginning our foray into normal daytime highs in the 60s. Remnants of the upper low over California could bring some rain chances back to the region by midweek.

AVIATION /00Z TAFS THROUGH 00Z SATURDAY/

Issued at 720 PM EDT Thu Sep 17 2026

Mainly VFR conditions are expected across northern Michigan TAF sites through the issuance period. Patchy FG/BR development is possible late tonight/early Friday morning, especially across interior low-lying areas -- although FG/BR may result in VSBY restrictions for a brief time. Any FG/BR will quickly burn off after sunrise, bringing VFR conditions back to all areas. Weak/calm winds tonight will increase to around 5-10 kts out of the northeast on Friday.

APX WATCHES/WARNINGS/ADVISORIES

MI...None. MARINE...None.