089
FXUS63 KGRR 121900
AFDGRR
Area Forecast Discussion
National Weather Service Grand Rapids MI
Issued by National Weather Service Detroit/Pontiac MI
200 PM EST Thu Nov 12 2026
.KEY MESSAGES...
- Showers lingering into the evening along and south of I-96
- Lake-effect rain and snow showers along the immediate lakeshore
mainly north of Pentwater
- Quiet and mild weather early next week
&&
.DISCUSSION...
Issued at 200 PM EST Thu Nov 12 2026
Batch of persistently moderate rain showers has slowly nudged
westward to a Holland to Kalamazoo line. Radar estimates in excess
of an inch are common (values are probably slightly inflated due
to melting layer effects). The forcing is associated with ascent
at the terminus of the broad deformation axis associated with the
departing cyclone over the Lower Great Lakes. The cyclonic branch
of the deformation conveyor continues to support a steady moderate
rain. This forcing is expected to wane in the next couple of
hours as the flow finds a new balance state, while a second pulse
of forcing over east-central Lower Michigan takes over for a brief
time before also weakening.
The incoming cold airmass has also activated Lake Michigan. A
steady-state northerly flow will maintain the deep lake-effect
bands well offshore - with exception near Big Sable point, where
the primary band will flirt with the shoreline. Current CAM
guidance wavers - but keeps it offshore most of the night into
Friday. Otherwise, lake-effect from Lake Huron will try to squeeze
a couple bands toward the southwest that may graze eastern Ingham
and Jackson Counties, but prospects for any meaningful
precipitation in the form of snow are very low.
As the flow gains a slight west component late Friday and Friday
night, the main band structure over Lake Michigan will wander to
this side of the lake - likely bringing a rain/snow mix along
portions of the immediate lakeshore. If high enough intensity is
maintained, then a period of all snow may occur - bringing minor
accumulations to parts of Mason and Oceana Counties. Additional
residual light snow shower activity from the Grand Traverse area
may make inroads along and north of US-10.
The airmass begins to moderate Saturday night and Sunday,
deactivating the big lake. The high amplitude upper-level ridge
poised over the western CONUS will become the dominant weather
governor for a good portion of next week - with mild and quiet
conditions expected, once again.
&&
.AVIATION /18Z TAFS THROUGH 18Z FRIDAY/...
Issued at 1217 PM EST Thu Nov 12 2026
Concentrated area of showers will affect KGRR, KAZO, and KBTL this
afternoon - while scattered showers linger around the other
terminals. Near surface moisture is higher across center Lower
Michigan, thanks to contributions from Lake Huron. Ceilings
continue to respond hovering at low MVFR or IFR - with the
exception being MKG, where subsidence has eroded the cloud field
some. Rather persistent pattern this afternoon will start to dry
out after sunset - as the main low exits east. Lake-effect off of
Lake Huron will maintain lower clouds for LAN and JXN. Expecting
the showers (both rain and snow) will remain east. Otherwise,
steady northerly flow will hold into Friday - with plenty of VFR
clouds.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...Small Craft Advisory until 7 PM EST Friday for LMZ844>849.
&&
$$
DISCUSSION...Mann
AVIATION...Mann
NWS GRR Office Area Forecast Discussion
