440
FXUS63 KGRR 141906
AFDGRR
Area Forecast Discussion
National Weather Service Grand Rapids MI
306 PM EDT Fri Aug 14 2026
.KEY MESSAGES...
- Showers and Storms Saturday into Sunday
- Cool and Dry through beginning of the week
- Showers and storms possible mid next week
&&
.DISCUSSION...
Issued at 306 PM EDT Fri Aug 14 2026
- Showers and Storms Saturday into Sunday
There have been some shifts in the trends for tomorrow`s incoming
system. Today, the showers and storms continue to stream through
Illinois and Indiana. This trend was expected to shift northward
but there is some question to what extent.
An upper level vort max is still shown to move through Lower
Michigan tomorrow, This would create some afternoon into early
evening convection along and southward of the I 94 corridor. This
is highlighted in the SPC Day 2 convective outlook. Latest Model
soundings through the Kalamazoo region so lapse rates only 5 to 6
C/km with a mid level inversion tomorrow that could stifle any
convection. Some of the ensembles do show some weak shear Saturday
evening that shifts to the north and could allow some showers and
storms along the I 96 corridor Saturday evening. So scattered
showers and storms are possible, there is the possibility any
convection remains to the south.
The overall trend continues to show a shift of stronger
convection southward. There remains a chance for increased
precipitation through the south and given the moisture aloft,
any showers could by heavy, with QPF of over an inch of rain
possible.
There is a deeper upper level trough with mid level
support moving through early Sunday. While there is less moisture
with that system and it comes in overnight into early Sunday, it
currently has the better CAPE and shear. While not huge, there is
1500 J/kg of MU cape and Lapse rates towards 7 C/km. This is with
the frontal boundary and propagates through between 15Z to 21Z
Sunday. So there remains a multitude of questions with the systems
this weekend, there remains several chances for showers and
storms across lower Michigan until Sunday evening but the trend
shows a lower potential.
- Cool and Dry through beginning of the week
There is good consistency that this front moves through Sunday
night with drier, cooler northwesterly flow into Monday.
A large upper level low over Canada will dominate the pattern
through the next week. It should form into a closed low over
Hudson Bay through mid week.
This will keep temps at to below normal with the region dry.
- Showers and storms possible mid next week
The previously mentioned upper level low will drive a short wave
trough through the region and a corresponding low through the
Great Lakes midweek. Currently there should be an elongating front
associated with with warm air advection out ahead of it. There
remains some position and timing questions. It could remain
further north and/or come in later. But Wednesday into Thursday
could see some decent convection.
&&
.AVIATION /18Z TAFS THROUGH 18Z SATURDAY/...
Issued at 115 PM EDT Fri Aug 14 2026
Visible satellite shows some cu over the southern terminals and
mainly high clouds along the I-96 terminals. Clouds will lower
overnight as low pressure moves toward the state. Included some
light rain at AZO late in the period, but don`t think it will
reach BTL nor JXN by 18z. A better chance of light rain will
arrive across the southern terminals after 18z. Look for MVFR cigs
to develop late in the period.
&&
.MARINE...
Issued at 303 PM EDT Fri Aug 14 2026
The only marine concern is the potential for showers and storms
Saturday through Sunday. Flow should remain offshore with a wind
shift into Sunday. There is an increase in winds/waves Saturday
night into Sunday. However, the gradient doesn`t seem to support
any winds/waves that would reach criteria.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...None.
&&
$$
DISCUSSION...Ceru
AVIATION...04
MARINE...NJJ
NWS GRR Office Area Forecast Discussion
