Grand Rapids, Michigan 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

872
FXUS63 KGRR 211117
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
617 AM EST Thu Nov 21 2024

.KEY MESSAGES...

- Light snow today

- A Period of Rain Showers Sunday night through Monday night

- Seasonable temperatures and unsettled weather Tue and Wed

&&

.DISCUSSION...
Issued at 304 AM EST Thu Nov 21 2024

- Light snow today

The medium range models have done a splendid job with the track of
the surface low. Several days ago they showed the low developing
near western Lake Erie and then moving north across Lake Huron and
then west over the Straits. That`s pretty much what has occurred
with the low near the Straits currently. It should start making a
move to the southwest and then south soon.

Radar shows lake effect snow showers falling over the cwa with
synoptic snow farther north over northern Lower. We should start
to see the synoptic snow begin to move south within the next few
hours. Latest model trends, however, shows the bulk of the snow
remaining over the lake and west into Wisconsin. This will result
in reduced accumulations today. Still looking at an inch or two
this morning across the northern cwa before the low moves through
and subsidence behind coupled with a flip to offshore winds puts
an end to the snow. Most if not all of the lake effect snow
should be done by 1-2 pm.

Today will be chilly with highs in the upper 30s to lower 40s.

Once the surface low moves south this afternoon, ridging will nose
into the cwa tonight and Friday. We reduced PoPs tonight and
Friday with the drier air in mind.

- A Period of Rain Showers Sunday night through Monday night

There may be a lingering shower Friday night into early Saturday
with one more short wave clipping the area to the NE and some
possible light lake effect rain showers. Overall though
precipitation chances will be on the diminishing trend, and
completely ending by Saturday night. We will see dry conditions and
mild weather return briefly for Sunday with ridging at the sfc and
aloft traversing the area.

The most organized system in the longer term will be affecting the
area beginning on Sunday night and lingering through Monday night.
This system will be supported by energy being ejected by the current
massive Pacific NW storm ongoing. This energy lifts into the Upper
Midwest, and consolidates into a better upper system as it heads
toward the region.

The sfc front out ahead of this upper system will initially be
rather dry without sufficient moisture advection ahead of it. Some
rain showers are expected to eventually develop in the warm air
advection region of this system focused over Northern Lower later
Sunday night as some moisture arrives. Can`t rule out a shower
across our forecast area.

The better chance for precipitation with this system is actually on
the backside of the sfc low, and more associated with the upper wave
that will move in later Monday. The better forcing with the upper
wave, some moisture that advects in, combined with a boost from Lake
Michigan will bring in the better chances for rain late Monday and
Monday night.

- Seasonable temperatures and unsettled weather Tue and Wed

We see the more organized chances for rain move out by Tuesday, but
rain chances do not completely end. We do see some sfc ridging
building over the area behind the Monday system. However, the upper
level pattern becomes nearly zonal for a bit and brings some weak
short waves through. These short waves will not have much moisture
to work with, but just enough forcing and lake enhancement to keep a
small chance of rain showers in for Tuesday and Wednesday.
Temperatures will cool off a bit for Tuesday and Wednesday behind
the Monday system.

&&

.AVIATION /12Z TAFS THROUGH 12Z FRIDAY/...
Issued at 614 AM EST Thu Nov 21 2024

Low pressure has begun to turn south over northern Lake MI. Radar
shows an expansive band of light to moderate snow ahead of the
low moving south. We`ll see that snow move over the terminals
within the next several hours. Ahead of that band of snow, lake
effect snow showers have been falling, reducing visibilities to
less than 3 miles at time.

MVFR/IFR conditions will continue through the morning before the
low moves far enough south that the precipitation ends this
afternoon. Once the precipitation ends, we`ll see some improvement
in ceilings and visibilities.

&&

.MARINE...
Issued at 304 AM EST Thu Nov 21 2024

We made some changes to the headlines. The Small Craft Advisory
will remain in effect for all nearshore zones through 7 am. The
SCA will continue in the northern zone until 06z Friday.

The Gale Watch has been upgraded to a Gale Warning south of
Pentwater and will continue until 06z Friday.

Low pressure moving south over the lake will create low end gales
over most of the nearshore today before diminishing late tonight.
But the decrease may be short lived as another trough will move
south over the lake and tighten the gradient again Friday
afternoon.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...Small Craft Advisory until 7 AM EST this morning for LMZ844>848.
     Gale Warning until 1 AM EST Friday for LMZ844>848.
     Small Craft Advisory until 1 AM EST Friday for LMZ849.

&&

$$

DISCUSSION...NJJ/04
AVIATION...04
MARINE...04