Portage, Michigan 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

264
FXUS63 KGRR 011855
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
255 PM EDT Fri Aug 1 2025

.KEY MESSAGES...

- Seasonable temperatures and less humidity next several days

- Low chances for showers or storms mid to late next week

&&

.DISCUSSION...
Issued at 255 PM EDT Fri Aug 1 2025

- Seasonable temperatures and less humidity next several days

High pressure and weak upper-level flow settling directly over
the Great Lakes region through early next week will keep the
weather tranquil. Lows will be slightly below normal and highs
near normal but warming a little day by day. Much more tolerable
humidity levels will remain as dew points stay below 60 until at
least Tuesday.

Northeast winds have brought in some cleaner air and improved the
air quality to moderate over the Lower Peninsula today. Unhealthy
AQI and 4 to 7 mile visibility smoky haze looms just west of Lake
Michigan toward Minnesota. Experimental model guidance and
forecasts from Michigan EGLE suggest near-surface smoke
concentrations in our area will increase on Saturday and may
linger into Sunday. The smoke will drift back in slowly under more
northwesterly 850 mb flow and also mix down from that level
during the daytime.

- Low chances for showers or storms mid to late next week

The high pressure center gradually slides east of Michigan next
week, and low-level flow turns more southeasterly to provide a
slight increase in temperatures and dew points. Ensembles are
generally on board with weak upper-level flow over the region with
a lack of significant shortwave troughs propagating through the
pattern. There is even split flow and a weak Rex block likely over
the Great Lakes midweek.

Mid to late week, the somewhat higher moisture in the air and
weaker influence of the departing high pressure system will allow
for slight chances of scattered showers or storms to pop up during
the day. With a lack of wind shear and driving upper-level
disturbances, these deep-summer "air mass" thunderstorms are
unlikely to be severe.

&&

.AVIATION /18Z TAFS THROUGH 18Z SATURDAY/...
Issued at 114 PM EDT Fri Aug 1 2025

High confidence in VFR conditions exists for much of the TAF
period with one key caveat. SCT mid-level clouds have been
observed and will dissipate after sunset with brief periods of
high based VFR cigs at LAN/JXN thanks to enhancement of moisture
from Lake Huron. The main concern for any sub VFR conditions
arrives mid to late Saturday Morning, when wildfire smoke mixing
down may send visbys into the 3-6SM range. Given that model
handling of smoke concentrations hasn`t been great in recent days
will not include restrictions in the TAFs but that will be
something to monitor. Expect predominantly northeasterly flow
under 10 knots, with the exception of MKG shifting to
northwesterly each afternoon due to the lake breeze.

&&

.MARINE...
Issued at 114 PM EDT Fri Aug 1 2025

No significant marine concerns over the next several days as high
pressure and weak gradient flow dominate the forecast. A brief burst
of wind is expected along the coast this afternoon associated with a
thermal low developing across the land, though with winds to only
around 15 knots 2-4 foot waves with a moderate swim risk is favored.
Water temps remain on the cool side thanks to upwelling due to
recent northerly flow. Water temps remain in the upper 50s at St.
Joseph and South Haven this afternoon.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Air Quality Alert until midnight EDT Saturday night for
     MIZ037>040-043>046-050>052-056>059-064>067-071>074.
MARINE...None.

&&

$$

DISCUSSION...CAS
AVIATION...Thomas
MARINE...Thomas