Area Forecast Discussion
Issued by NWS Grand Rapids, MI

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS63 KGRR 251934
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
334 PM EDT Mon Mar 25 2024

.KEY MESSAGES...

- Rain showers tonight and severe storms possible Tuesday

- Dry and Cool Mid to Late Week but Some Sunshine

- Chance for Showers Over the Weekend; Seasonal Temps

&&

.DISCUSSION...
Issued at 330 PM EDT Mon Mar 25 2024

- Rain showers tonight and severe storms possible Tuesday

Confidence is increasing some that some severe weather will be
possible Tuesday afternoon.

Dry air below 10k ft with the low level flow still from the SE is
helping to keep any leading edge rain shower activity from being
much more than a few sprinkles this afternoon across the NW
counties. Warmer air is moving in well this afternoon with highs in
the 60s at many locations already, it just doesn`t have enough
forcing or moisture to allow it to rain yet.

The best forcing ahead of the incoming system is still west of the
area, with the low level jet supporting rain showers this afternoon
over WI. This low level jet will weaken over the next few hours as a
short wave over IA moves north away from the area. We can expect
rain to develop after midnight over our area from SW to NE as
another strong short wave lifts NE and ramps up another low level
jet overhead.

A low level jet like this would usually supply enough instability to
allow for some elevated storms. However, all of the guidance we have
looked at indicates not enough instability to justify a thunder
mention overnight at this time. Just a good soaking rain for a few
hours for all of the area. This are of rain will move out by sunrise
Tuesday, with another weak line moving through mid-Tuesday morning.
Winds then will pick up to gust between 30 and 40 mph in the warm
sector. We don`t feel a Wind Advisory is needed at this time.

This is when things could start to get interesting. There is good
agreement that all areas will see a break in the rain from late
morning to early afternoon. There is good agreement that temps will
warm into the 60s across the south where a brief area of clearing
will be possible, and 50s north where clouds will likely stay in. We
will see another short wave lift toward the area starting around 18z.

We expect that a scattered to broken line of convection will fire n
ear Chicago, and drive NE at a rapid pace with the strong upper
level steering winds. This line is expected to become more
widespread and intensify a bit as it encounters the better warmth
and moisture. MU CAPEs are forecast to increase to around 500-600
J/kg across the southern half of the area, with most of it being sfc
based. This, to go along with the strong mid-level winds will have
very good deep layer shear in place.

The uncertainty comes with do we realize the instability, and will
it overlap with the cold front and short wave. If it does, damaging
winds will be the most likely severe threat due to the strong wind
fields to start with. The storms will be more low topped with the
EQL around 500 mb/20,000 ft. There does look to be a small, yet
justified chance of a tornado mention. This comes with possible
embedded low topped supercells in the main line of storms. Hi-res
models are indicating some sort of weak sfc trough developing over
SW lower. What this does is it has the potential to back the sfc
winds a bit, creating better low level shear, in addition to the
very good deep layer shear and 0-3km shear with winds around 40-50
knots at 3-5k ft. The best chance of this would be south of I-96.

The storms should move out between 21 and 00z tomorrow evening,
leaving drier and cooler weather to move in behind the front.

- Dry and Cool Mid to Late Week but Some Sunshine

Upper troughing and cold advection in the wake of the Tuesday
system will yield cooler than normal temps Wed-Thu, although by
Friday we recover to closer to normal as the upper trough lifts
out. Guidance suggests we will see a fair amount of sunshine
despite some troughing aloft, thanks very dry air advecting in
from the west followed by eventual arrival of surface ridging.

- Chance for Showers Over the Weekend; Seasonal Temps

The pattern over the weekend will feature a mid level baroclinic
zone nearby and a fast/quasi-zonal flow aloft. Expectation is for
a couple fast moving/weaker systems to skirt the area providing
occasional risks/rounds of showers-- but confidence on the
timing/placement of these is low at this time.

Eventual development of a Hudson Bay High should promote dry
northeast low level flow which could lead to a light night/early
morning rain/snow mix in northern sections of the area if/when
any precip events occur Saturday through Monday. This should also
keep the sfc warm front suppressed south of MI most of the time,
resulting in near normal temps.

&&

.AVIATION /18Z TAFS THROUGH 18Z TUESDAY/...
Issued at 139 PM EDT Mon Mar 25 2024

The forecast period for the 18z package is starting off fairly
benign with VFR conditions, and some slightly gusty winds. We will
see the winds pick up this afternoon as we continue to heat up and
mix better winds down from aloft. Mid clouds will rule through
sunset, although a sprinkle can not be ruled out at KMKG. This
should not cause any restriction to conditions.

Winds will likely come down a bit overnight as we lose the daytime
heating. This will set all of the sites up once again for low
level wind shear. A core of wind of 50-60 knots at 2k ft and above
will move overhead this evening. Those winds will be from almost
the south, with sfc winds still from the SE. This will continue
until mid Tuesday morning.

We will see rain chances really increase after 04-06z from SW to
NE through the terminals. Right now, this just looks like rain,
with not really any instability to justify a thunder mention. The
widespread rain will move out from 10-12z Tuesday. MVFR conditions
are expected, with an isolated IFR report not out of the
question. MVFR ceilings will linger for a few hours with a couple
of scattered showers Tue morning into early Tuesday afternoon.

A line of broken storms will develop, and potentially start to
affect the KMKG and KAZO terminals just before the end of this
forecast period.

&&

.MARINE...
Issued at 330 PM EDT Mon Mar 25 2024

We are upgrading the Gale Watch to a Warning for later tonight
into Tuesday night for the entire nearshore, while keeping the
Small Craft Advisory from now until the Gale Warning starts.

Winds are picking up this afternoon as the gradient tightens up
ahead of the incoming system. The Gale may be a little marginal
for tonight given the offshore flow and the strong warm air
advection over the colder lake waters, but will still go with it.

The strongest winds will come on Tuesday just ahead of and just
behind the cold front moving through. Those winds will be onshore
and with cold air advection, so Gales are much more likely at that
time.

Small Craft Advisories will be needed after the Gales wind down a
bit. It may take until Thursday, or even Friday, to be able to drop
all headlines.


&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...Small Craft Advisory until 3 AM EDT Tuesday for LMZ844>849.
     Gale Warning from 3 AM Tuesday to 2 AM EDT Wednesday for
     LMZ844>849.

&&

$$

DISCUSSION...NJJ/Meade
AVIATION...NJJ
MARINE...NJJ


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.