701
FXUS63 KGRR 011137
AFDGRR
Area Forecast Discussion
National Weather Service Grand Rapids MI
637 AM EST Sun Nov 1 2026
.KEY MESSAGES...
- Light rain possible early today
- Dry conditions into Monday
- Wetter conditions Tuesday into the weekend
&&
.DISCUSSION...
Issued at 244 AM EST Sun Nov 1 2026
- Light rain possible early today
An area of precipitation has dissipated as it moved east across
southwest Lower MI. However, some models, such as the HRRR,
suggest that another batch of light showers could move northward
into extreme southwest Lower MI later this morning, possibly
affecting that area with another round of light rain. Cloud bases
remain high and a dry sub-cloud layer, as noted on the 01/00Z DTX
sounding, will limit precipitation accumulations. We expect
predominantly dry conditions from this afternoon onward.
- Dry conditions into Monday
Satellite shows a sharp upper trough off the west coast with
downstream ridging over the intermountain west. This ridge will
move eastward and be positioned over the western Great Lakes by
Monday afternoon, resulting in synoptic subsidence for our region
up through this time. Based on this, it is not surprising that more
recently available ensemble and deterministic NWP suggests Monday
could be predominantly dry for southwest Lower MI with precipitation
holding off until Monday night or Tuesday, while better chances
remain west and north of the area.
- Wetter conditions Tuesday into the weekend
Chances for rain grow substantially starting late Tuesday.
As a side note regarding Tuesday, highs are expected to reach the
lower 70s, which is about 20 degrees above normal for this time
of year. Even Wednesday will be making a run close to 70 degrees.
Total QPF for the coming week looks a bit less impressive overall.
For example, a sampling of available medium range ensemble guidance
(GEFS/ECE/Canadian) shows only about a 50 percent chance of accumulating
an inch or precipitation between now and Friday evening.
However, there is one important caveat regarding rain potential
later this coming week. There is growing consensus that a cutoff
low will form in the Wednesday timeframe somewhere over the
midwest. ECE mean 500 mb height forecasts show this, which indicates
surprisingly good positional and temporal consistency among the
ensemble members. This low develops from the aforementioned upper
wave, which by this time will be poised to cross the Mississippi
River. During the cutoff process, there is the possibility for
mid-level deformation and attendant fgen to materialize somewhere
downstream of the upper low, which could in turn produce localized
amounts of much greater than an inch of rain towards the latter
part of the week. It was interesting to observe in the QPF box and
whisker plots the presence of significant outliers indicating
this possibility.
So the takeaway is that rainfall amounts for the first part of the
week have relatively good predictability with low potential for
overperforming. The latter half of the week, on the other hand, has
much less predictability with a small chance of significant
rainfall in a concentrated area.
&&
.AVIATION /12Z TAFS THROUGH 12Z MONDAY/...
Issued at 628 AM EST Sun Nov 1 2026
Probability for VFR conditions at all terminals:
through 18Z - 95 percent
through 00Z - 90 percent
No changes to previous thinking. Radar does show light
precipitation entering far southwest Lower MI, but like previously
observed precipitation overnight, it is quickly dissipating as it
proceeds northeast. CAM guidance, such as the HRRR, predicts this
scenario to continue in the short term and for precipitation to
diminish overall into the late morning. Prior to this, however,
it`s not out of the question that KAZO could get a sprinkle with
this activity. But, given observed associated cloud bases at or
above 8000 feet AGL, no visibility or ceiling restrictions would
result.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...None.
&&
$$
DISCUSSION...TJT
AVIATION...TJT
NWS GRR Office Area Forecast Discussion
