536
FXUS63 KGRR 132005
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
305 PM EST Thu Nov 13 2025

.KEY MESSAGES...

- Breezy and mild Saturday as high reach into the lower 60s
  despite cloudy/mostly cloudy skies, along with a chance of
  light rain showers.

- Cooler and breezier for Sunday as westerly winds gust 30-35 mph.

- Dry weather to start next week.

&&

.DISCUSSION...
Issued at 305 PM EST Thu Nov 13 2025

A pronounced warm advection pattern begins tonight as an amplified
upper level ridge axis (with 500 MB heights in the 564-568 DAM
range) builds over Lower Michigan through Friday night. This will
set the stage for a notably warm Saturday.

Despite the WAA aloft, the dry low levels and decoupled surface
winds tonight suggests mins falling to around freezing. However, an
elevated warm front at 700 MB and mid deck of clouds may provide
just enough of a blanket effect to hold minimums in the mid 30s.

A solid southwest low level jet (~40 knots) will develop,
transporting both milder air and significant low level moisture from
the Southern Plains. The NAM is most aggressive with the surface
moisture, lifting dew pts into the mid 50s on Saturday. The NAM also
indicates sufficient depth of saturation to support light rain or
drizzle due to waves of isentropic ascent and low level convergence
(frontogenesis) as a cold front tracks through in the afternoon. If
the cold front were to be slower and low level moisture were leaner
(as suggested by some regional ensemble members), temperatures could
approach daily maximum records for Nov 15, which occurred in 1990
(GRR-68, LAN 69, AZO-70).

Post frontal cold advection to occur Saturday night through Sunday
night, with 850 MB temps looking to settle into the negative mid to
upper single numbers, despite the heart of the cold air tracking
through the Eastern Great Lakes. Strongly confluent upper level
northwest flow with subsidence and the resulting dry airmass is not
expected to lead to any lake effect activity over southwest Lower
Michigan however.

Pronounced surface ridging underneath the confluent flow on Monday
will lead to dry but cool weather (40s for highs). Will have to
watch an upper level wave being ejected out of the Four Corners
region, which could impact our weather late Monday night-Tuesday.
However, current indications is the system will end up tracking just
south, through the Ohio Valley. This is due to the  upper level
low/trough over eastern Canada holding and deflecting the system, as
the confluent upper level flow persists over the Central Great
Lakes.


&&

.AVIATION /18Z TAFS THROUGH 18Z FRIDAY/...
Issued at 1155 AM EST Thu Nov 13 2025

Minimal wx concerns for aviation with VFR expected. West winds
gusting to 16-20 knots this afternoon will relax and become
southwest with nightfall. Ceilings around 10,000 feet are
expected overnight.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...None.

&&

$$

DISCUSSION...SF
AVIATION...CAS