989
FXUS63 KGRR 291843
AFDGRR
Area Forecast Discussion
National Weather Service Grand Rapids MI
243 PM EDT Wed Apr 29 2026
.KEY MESSAGES...
- Precipitation ending late tonight, then possible frost/freeze
- Afternoon showers Thursday and Friday, frost/freeze potential
- Unsettled early next week with greater rain chances
&&
.DISCUSSION...
Issued at 243 PM EDT Wed Apr 29 2026
- Precipitation ending late tonight, then possible frost/freeze
An extensive area of precipitation was crossing southwest Lower
MI early this afternoon and is expected to dissipate/exit by late
tonight. There is a well defined upper PV max driving this
precipitation. Additional precipitation is noted over WI with
separate and somewhat weaker upper PV support. However, CAM
guidance suggests this is chiefly forced by diurnal destabilization
and it will likely not make it into Lower MI.
After discussion with APX, decided to go with a freeze warning for
interior northern counties and a frost advisory extending south
towards I-96 overnight. There is a lot of bust potential with
this forecast because there are questions about how quickly we
will lose cloudiness overnight. Also, we will now be dealing with
a bit more soil moisture than before, meaning slightly more
resilience against falling air temperatures.
- Afternoon showers Thursday and Friday, frost/freeze potential
With a seasonably deep upper low over the western Great Lakes and
cold temperatures aloft, there remains the chance for at least
some afternoon showers, mainly over interior Lower MI, thanks to
diurnal surface insolation yielding favorable lapse rates for
moderately deep moist convection. Thunder is not expected per SPC
outlooks and instability progs.
Temperatures in the lower troposphere look to be colder Friday and
Saturday mornings. Additionally, there is greater potential for
clouds clearing at night. Hence, we expect a growing threat for
nighttime frost/freeze conditions as we go into the latter part of
the week and into the weekend.
- Unsettled early next week with greater rain chances
Guidance is coming into better agreement regarding a strong upper PV
max pivoting into the western Great Lakes on the periphery of a
broader upper low. This looks favorable chiefly for rain showers
given the arrival of best upper forcing in the morning hours when
conditional instability tends to be at its minimum.
As noted previously, we will see increasingly Gulf-sourced lower
tropospheric moisture as we move into the middle of next week. This
will allow conditional instability to develop and increase the
chances for thunderstorms. By late in the week, deep southwesterly
flow looks like it could set up somewhere over the eastern U.S. and
this will definitely need to be watched since both convective and
hydrologic hazards could be in play wherever this occurs.
&&
.AVIATION /18Z TAFS THROUGH 18Z THURSDAY/...
Issued at 142 PM EDT Wed Apr 29 2026
Light rain associated with an upper trough moving through the
region will continue to fall this afternoon before ending late in
the day. IFR cigs are expected overnight due to abundant low
level moisture. Some improvement is expected Thursday morning as
slightly drier air advects in from the west.
&&
.MARINE...
Issued at 243 PM EDT Wed Apr 29 2026
Waves could make a brief run to around 3 feet tonight over our far
southern marine zones. However, this is not terribly significant
and no concerns are noted at this time.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Freeze Warning from 2 AM to 9 AM EDT Thursday for MIZ038>040-045.
Frost Advisory from 2 AM to 9 AM EDT Thursday for MIZ044-046-051-
052-057>059-065-066.
MARINE...None.
&&
$$
DISCUSSION...TJT
AVIATION...04
MARINE...TJT
NWS GRR Office Area Forecast Discussion
