Portage, Michigan 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

853
FXUS63 KGRR 220517
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
1217 AM EST Sun Dec 22 2024

.KEY MESSAGES...

- Cold and calm night tonight

- Light accumulating snow Sunday night into Monday

- Mild and unsettled weather from Christmas into next weekend

&&

.UPDATE...
Issued at 949 PM EST Sat Dec 21 2024

Lake clouds are still in place south and west of GR and are not
really showing signs of leaving any time soon. This creates low
temperature challenges since current readings under the clouds
are holding between 20 and 25 whereas clear areas from GRR to the
north and east already have readings in the single digits.

Will keep the Min temp fcst as is, featuring zero to -5 north and
east of GRR and 10 to 15 to the south and west but the
location/movement of the stubborn lake strato-cu may lead to
warmer readings.

Additionally, if the lake clouds do not dissipate tonight they`ll
probably move farther inland early Sunday due to the backing H8
flow then lift northeastward Sunday afternoon in increasing SW
flow at H8. Coupled with the approaching mid clouds from the west
on Sunday, some locations may not see much sun.

&&

.DISCUSSION...
Issued at 239 PM EST Sat Dec 21 2024

- Cold and calm night tonight

Latest radar loop shows that just about all of the light lake effect
snow showers that were over the area earlier have now moved offshore
as of 19z. A few echoes remain over the southern lakeshore. We
should see the remaining snow showers move out over the lake as the
winds from the NNE move through the southern half of the forecast
area this afternoon.

The pattern is setting up for quite a cold night. Skies should clear
out quickly toward or just after sunset with the offshore flow. This
will only become enhanced as a land breeze sets up, with a weak
gradient inland. We have undercut model guidance temperatures for
most of the area. Some of the area across Central Lower will likely
drop below zero with the light winds, clear skies, and a recent
snowpack.

- Light accumulating snow Sunday night into Monday

The cold air mass tonight will recover a bit on Sunday, but will
still be a bit below average. Most of Sunday should be dry, except
maybe the far NW corner of the area that sees winds become from the
SSW, and a few flurries may drift onshore. Other than that, a partly
sunny day will be expected.

Clouds will be on the increase then Sunday night, with mainly snow
developing across most of the area early Monday morning. This snow
will be associated with one more northern stream clipper system that
will move through the area on Monday. This system does not look to
be as potent as the Thu night/Fri clipper. It does look like from
less than an inch across the south, to around 2-3 inches across the
U.S.-10 corridor is likely. Limited moisture return and the upper
system weakening as it arrives, will be why this system should be
weaker.

One other thing to watch out for is for a little bit of light icing,
mainly across the far southern counties as the air aloft will be
warm enough for some rain, but the sfc stays below freezing until
mid-afternoon.

- Mild and unsettled weather from Christmas into next weekend

Once the Monday system moves out, we will eventually transition from
the flow from the west/northwest, to the southwest by late on
Tuesday. The impetus for this pattern change will be a strong long
wave trough coming onshore over the Western U.S. coast.

This flow from the SW aloft and from the S at the sfc will help to
increase the moisture over the area. Initially, any short wave in
the flow will be rather weak. This combined with the moisture will
be enough to generate some chances for precipitation, but nothing
significant. The only concern with the precipitation from Tuesday
through Wednesday, would be some light icing where temps would be
below freezing, mainly overnight. This does not look like anything
significant, but could cause some minor travel issues overnight if
pcpn falls with temps slightly below freezing.

The better chance for more widespread rainfall will come next Friday
and Saturday. It is at that time that the better forcing with the
long wave trough will arrive with good large scale synoptic lift,
and better short waves ejecting from the parent trough. Moisture
should be plentiful by that time with a solid flow directly from the
Gulf. Also, temperatures will be plenty warm that p-type issues will
no longer be a concern.

&&

.AVIATION /06Z TAFS THROUGH 06Z MONDAY/...
Issued at 1217 AM EST Sun Dec 22 2024

VFR conditions will prevail through tonight. A deck of stratus
clouds near lake Michigan with ceilings around 3500 feet and tops
around 4500 feet will prevail until about 18Z before lifting and
thinning further. Winds will be east to southeast less than 10
knots.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...None.

&&

$$

UPDATE...Meade
DISCUSSION...NJJ
AVIATION...Ostuno