National Weather Service Weather Forecast Office

• Home
• Site Map
• News
• Organization
• Search for: NWS All NOAA 

000
FXUS63 KGRR 151939
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
339 PM EDT Mon Apr 15 2024

.KEY MESSAGES...

- Showers and Storms Tuesday Night into Wednesday Night

- Light Rain Chances Thursday Night

- Cool Down for the End of the Week

&&

.DISCUSSION...
Issued at 339 PM EDT Mon Apr 15 2024

- Showers and Storms Tuesday Night into Wednesday Night

Quiet weather will persist tonight and most of if not all of
Tuesday as high pressure drifts through the region. A warm front
approaches from the southwest late in the day on Tuesday and moves
squarely into the forecast area Tuesday night. The surface low
associated with the front will swing across the forecast area on
Wednesday with a warm sector likely pushing into southern portions
of the forecast area in the midday to afternoon hours. The active
weather is very much centered in the Tuesday night and Wednesday
forecast periods.

Tuesday looks to be dry with showers and likely embedded
thunderstorms moving in Tuesday evening. Forecast most unstable
CAPE values are not significant Tuesday night in the 400-800 j/kg
range. Expecting periods of rain with some rumbles of thunder
embedded. Not expecting severe weather and the SPC agrees with a
general thunder forecast.

Wednesday could be a bit more interesting, but there are caveats
with that statement. We are expecting a good amount of clouds and
rounds of precipitation Tuesday night lasting into Wednesday
morning. The clouds and rain will keep instability levels down a
bit, but the 3km NAM is showing 1,000-2,000 j/kg of most unstable
CAPE developing. a 30+ knot low level jet combined with a 40+
knot mid level jet produce deep layer shear around 40 knots
towards I-94. Expecting more rounds of showers and storms on
Wednesday, but with the chance of a few stronger storms. The way
Wednesday could over perform (severe weather) is if the
precipitation is a bit less coming into Wednesday and we get areas
of clearing in spots. Deep layer shear of 40 knots combined with
1,000+ j/kg of MUCAPE could certainly produce some severe weather.
Multiple fronts in the area and the potential for rotating storms
has our attention if the above caveats of less precipitation and
clouds come to fruition. The issue with severe chances on
Wednesday is less precipitation and clouds is not a good bet at
this time. Agree with the SPC marginal and we will see how things
evolve. With tonight`s model runs the event will be fully in the
HREF window which is obviously the gold standard in terms of
convective model forecasts. Showers move off to the east Wednesday
night as the low pulls away.

Rainfall totals look to be around an inch from this system which
should push a few sites to near or slightly above bankfull. That
said, we are not expecting much in the way of flooding issues.

- Light Rain Chances Thursday Night

A cold front will move through the area Thursday night to Friday
morning bringing renewed chances for light rain. Conditons should
turn dry after daybreak Friday as the front moves east. HIgh
pressure slides in behind that front resulting in dry conditions
through the weekend. Skies will begin to clear out Friday morning
with good chances for sunshine Friday afternoon through Monday.

- Cool Down for the End of the Week

The surface low that tracks through the area Tuesday and Wednesday
moves northwards into the Hudson Bay area on Thursday. 850mb thermal
trough settles in over the region on the backside of the low with
prolonged cold air advection through the weekend. 850mb temps bottom
out around -3C to -6C Saturday, resulting in peak afternoon surface
temps in the 40s to 50s. High pressure brings clearing skies this
weekend with radiational cooling dropping overnight temps to
freezing Saturday night and Sunday night.


&&

.AVIATION /18Z TAFS THROUGH 18Z TUESDAY/...
Issued at 133 PM EDT Mon Apr 15 2024

VFR ceilings and visibilities last through the forecast period
with dry conditions. Winds will be light and mainly from the west
this afternoon shifting northerly around 00z. Wind shift easterly
between 0z to 06z, and will increase after 10z Tuesday. Easterly
winds to 10 to 15 knots are expected Tuesday morning with gusts
to 20 to 25 knots. Wind will build into Tuesday afternoon and
evening as a system producing rain showers and storms moves
through the area.

&&

.MARINE...
Issued at 339 PM EDT Mon Apr 15 2024

A light wind regime will continue for the area tonight. High
pressure will remain in control one more forecast period before
things become more active. The ridge of high pressure moves off to
the east on Tuesday allowing for a strengthening easterly flow to
develop. 15 to 20 knot winds in the morning will be sub advisory,
but in the afternoon wind speeds increase. A small craft advisory
based on wind speeds will be needed for Tuesday afternoon, but an
increase to gales in the nearshore is possible. At this point
planning on holding off given offshore winds and borderline gales.
Envision the night shift will make the call on SCA vs Gale.

&&

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

&&

$$

DISCUSSION...Duke/Thielke
AVIATION...Thielke
MARINE...Duke