315
FXUS63 KGRR 281851
AFDGRR
Area Forecast Discussion
National Weather Service Grand Rapids MI
251 PM EDT Sat Mar 28 2026
.KEY MESSAGES...
- Thunderstorms Move in Monday Night through Tuesday Night
- Rain Chances Return Late Week into Weekend
&&
.DISCUSSION...
Issued at 251 PM EDT Sat Mar 28 2026
- Thunderstorms Move in Monday Night through Tuesday Night
After dry and mild days in store Sunday into Monday, there are
two main periods of concern for thunderstorm potential, the first
being late Monday night into Tuesday morning (SPC Day 3 Marginal
Risk) and then again later Tuesday afternoon into early Tuesday
night. For the first period, a classic nocturnal elevated storm
setup will likely take shape across WI/MI late Monday night,
possibly as early as midnight and then lasting into early Tuesday
morning. As has been discussed, a robust and ideally oriented LLJ
straight off the Gulf will advect in low level moisture at 50 to
60 kts and converge over a warm front draped across central Lower
MI. Sufficient CAPE above 850mb on the order of 1000-1500 J/kg
will support hail potential (also supported by mid level lapse
rates of 7- 8 C/km). The 12z RRFS shows a plausible scenario with
some elevated convection moving through during the 12am-8am
Tuesday timeframe. One thing to watch will be whether any residual
mixed layer instability remains in place. The RRFS and GFS
indicate there may in fact be a few hundred J/kg of MLCAPE
remaining but MLCIN could also be a hindrance. While hail will be
the main threat, some wind damage can`t be ruled out if MLCAPE
lingers given such strong wind fields in place just off the
surface.
Depending on when morning convection exits and to what extent our
region destabilizes, organized convection may develop along and
ahead of a strong cold front slated to move through Tuesday evening
into Tuesday night. Given strong low and mid level jets, severe
weather may occur with even modest mixing. NCAR`s AI-based NWP
Convective Hazards Forecasts continue to favor a threat for severe
weather across Lower MI should this scenario materialize, with
some AI models showing rather concerning severe probabilities
in our region. This will have to be fine tuned over the next
couple of days as the setup and threat become clearer. Outside of
thunderstorms, Tuesday looks like a fairly windy day with some
30-40 mph gusts possible.
- Rain Chances Return Late Week into Weekend
Ensemble guidance is favoring a break in precipitation on
Wednesday but with increasing odds for rain moving back in
as early as Thursday. GEFS/ECE mean 500 mb heights and vorticity
indicate a shortwave in SW flow moving our direction by Thursday.
In spite of chilly temperatures in the 40s, this anticipated
shortwave will help draw up higher PWAT values into the region. A
chance for showers will return to the forecast and can`t rule out
a period of a wintry mix (less likely at this point). A more
potent shortwave may arrive by next weekend bringing the risk for
more rain and thunderstorms.
&&
.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 112 PM EDT Sat Mar 28 2026
IR loops shows high clouds advancing toward the terminals from the
northwest. Expect sct-bkn cirrus throughout the period.
&&
.MARINE...
Issued at 251 PM EDT Sat Mar 28 2026
Another SCA will be in place starting 5pm this evening from
Whitehall to the north and then adding Holland to the north
starting at 10pm this evening. This occurs as S/SW winds over the
lake increase and hence wave activity will also be increasing.
Waves look to decrease late Sunday afternoon into the evening.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...Small Craft Advisory from 10 PM this evening to 5 PM EDT Sunday
for LMZ846-847.
Small Craft Advisory until 5 PM EDT Sunday for LMZ848-849.
&&
$$
DISCUSSION...Hoving
AVIATION...04
MARINE...Hoving
NWS GRR Office Area Forecast Discussion
