228
FXUS63 KGRR 241753
AFDGRR
Area Forecast Discussion
National Weather Service Grand Rapids MI
153 PM EDT Sun May 24 2026
.KEY MESSAGES...
- Fog Likely Tonight, Locally Dense Fog Possible
- Warmup into Wednesday With Low Rain Chances Mid-week
- Dry and Cool Late Week
&&
.DISCUSSION...
Issued at 152 PM EDT Sun May 24 2026
- Fog Likely Tonight, Locally Dense Fog Possible
Rain showers and isolated thunderstorms associated with an occluded
front crossing the area should exit by early evening. Concern then
develops for fog overnight given low-level moisture from today`s
rain. Winds subside and skies begin to clear as high pressure
moves in tonight, with a favorable environment for fog development
resulting. Signals are present in guidance that pockets of
locally dense fog could develop depending on the extent of
clearing overnight and to what extent any sunshine today can mix.
Climatology suggests that given a strong sun angle in late May,
widespread dense fog is unlikely, matching the picture guidance
shows. We will continue to monitor trends going into tonight.
- Warmup into Wednesday With Low Rain Chances Mid-week
West Michigan sets up on the periphery of a large scale ridge
starting later Monday into Tuesday with the development of an omega
blocking pattern over the central CONUS. 850 mb temps warm into the
mid teens Celsius resulting in highs in the 80s. There are two low
chances of rain for the first half of the week. First is Monday
where convergence off Huron may pop an isolated shower across our
northeast CWA. Confidence is low, with PoPs 10% or less. Second is
Wednesday with the arrival of a backdoor cold front. Moisture
quality is marginal so only light precipitation is expected. Medium
range model guidance suggests enough MUCAPE will be present thunder
to be in play.
- Dry and Cool Late Week
The post backdoor cold frontal environmnet will be slightly cooler
than the first half of the week, with highs in the upper 70s likely.
Comapred to yesterday, guidance has trended twoards the warmer
solution with 850mb temps in the low teens. The omega blocking
persists with a surface ridge in place across the region. This keeps
the forecast dry for the later portions of the week.
&&
.AVIATION /18Z TAFS THROUGH 18Z MONDAY/...
Issued at 1224 PM EDT Sun May 24 2026
Several challenges for the aviation forecast this afternoon into
tonight. The confidence in timing the thunderstorm arrival into
LAN and JXN is good, with occasional lightning and temporary IFR
heavy rain being reported in Southwest Michigan. There is little
to no lightning in the few hours of rain that will follow the up-
front thunderstorm, so expecting to hold on to MVFR to tempo IFR
cig/vis in the rain and remove the TS after it spends about an
hour passing through the remaining aerodromes.
The back edge of low clouds is crossing Lake Michigan, and mostly
clear skies are present in Wisconsin and Illinois. Latest models
lend less confidence in VFR late this afternoon and evening, as
there may be scattered to broken cumulus on either side of 2,000
feet hanging on through sunset. Then a brief clearing is possible
from sunset which should give way to fog development overnight.
The timing of fog onset will be difficult to pin down as it
depends on how much each location can dry out prior to sunset, but
this nonetheless is a good setup for fog tonight with lingering
lower atmospheric moisture, light winds, and clearing skies late
in the evening.
&&
.MARINE...
Issued at 152 PM EDT Sun May 24 2026
Primary concern for marine interests is the potential development
of fog across the waters tonight. Ample low-level moisture paired
with a approaching high pressure system looks to calm winds
enough for fog development overnight. Climatologically, the cooler
waters favor fog development, which is also supported by model
guidance. As a result, will be issuing a Marine Dense Fog Advisory
from late this evening through mid Monday morning.
As for winds and waves, Time/Height wind overviews suggest largely
that light winds and sub-advisory waves are expected over the next
several days. Winds in the 1-3kft range look to approach 30-35 kts
later Monday into Tuesday, however the strong warm air advection in
place suggests these winds won`t mix down. Other than the
aforementioned Marine Dense Fog Advisory, headlines are not
anticipaited over the next week.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...Dense Fog Advisory from 10 PM this evening to 10 AM EDT Monday
for LMZ844>849.
&&
$$
DISCUSSION...Thomas
AVIATION...CAS
MARINE...Thomas
NWS GRR Office Area Forecast Discussion
