618
FXUS63 KGRR 190659
AFDGRR
Area Forecast Discussion
National Weather Service Grand Rapids MI
259 AM EDT Wed Aug 19 2026
.KEY MESSAGES...
- Low clouds and fog possible this morning, then partly cloudy
- Rainfall chances return Friday
&&
.DISCUSSION...
Issued at 259 AM EDT Wed Aug 19 2026
- Low clouds and fog possible this morning, then partly cloudy
Given the widespread precipitation we received last night, light
winds, and decreasing clouds, we can expect the development of low
clouds and perhaps fog early this morning. The extent and
severity of possible fog remain in question, but the best guess
now is that it would be patchy and only locally dense. Please see
the Aviation section of this discussion for additional details.
Any fog that manages to develop should dissipate relatively
quickly after sunrise this morning.
- Rainfall chances return Friday
As noted previously, we will be predominantly drty Wednesday and
Thursday. An approaching upper PV max approaches the western Great
Lakes Thursday night and guidance brings precipitation associated
with this disturbance into the area beginning early Friday. Going
into the weekend, we remain under the influence of broad longwave
troughing. Deterministic models had been consistently hinting at
the development of a vertically stacked low somewhere over the
western Great Lakes, but now the favored location for this to happen
is east of Lower MI, more towards the central Great Lakes. This would
result in a drier weekend forecast for our area than previously thought.
Not surprisingly, this forecast remains very much a moving target,
especially when dealing with cutoff lows, so the general takeaway
for now is to cautiously plan for generally unsettled conditions
this weekend. That said, it`s reasonable to expect that the next
couple of model cycles in the coming day or so will bring better
consensus/clarity for the weekend forecast.
&&
.AVIATION /06Z TAFS THROUGH 06Z THURSDAY/...
Issued at 139 AM EDT Wed Aug 19 2026
The first concern for this update was to adjust for the area of rain
about to clear the last of our terminals. We had already removed the
mention of thunder based on radar trends and a corresponding lack of
lightning detection in GOES GLM and the available lightning mapping
networks.
Another change was to introduce more pessimistic ceilings and
visibilities in low clouds and fog. Near-surface flow is
currently light and chaotic in direction thanks to the development
of a mesohigh with the heavier-than-expected precipitation that
occurred earlier. Although near-surface winds are expected to
reorganize into a generally northwesterly direction as the
mesohigh weakens and moves eastward, winds should nonetheless
remain light enough to limit mixing.
IR satellite indicates an area of clearing behind the rain that will
favor outgoing longwave radiation flux supportive of near-surface
cooling and fog development. The 06Z terminal package therefore
advertises a mix of low clouds and fog, but it could end up being
mostly fog with vertical visibility restrictions approaching the
LIFR range. Not yet confident enough about this to explicitly
mention in the TAFs, but it will be something to watch as we
approach the 09-10Z timeframe this morning.
The good news is that VFR conditions are expected areawide by 15Z
and this should continue through the day.
&&
.MARINE...
Issued at 259 AM EDT Wed Aug 19 2026
The highest reported waveheights in the nearshore area at this
time is at the Ludington buoy, which is down to 3.3 feet after
reaching 3.9 feet early Tuesday night. Based on buoy trends and
WW3 guidance, have cancelled the Small Craft Advisory early. The
next threat for hazardous waves arrives Friday afternoon across
our northern zones in response to persistent and moderately strong
winds from the south-southwest.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...None.
&&
$$
DISCUSSION...TJT
AVIATION...TJT
MARINE...TJT
NWS GRR Office Area Forecast Discussion
