889
FXUS63 KGRR 251836
AFDGRR
Area Forecast Discussion
National Weather Service Grand Rapids MI
236 PM EDT Wed Mar 25 2026
.KEY MESSAGES...
- Brief Window for Strong to Severe Thunderstorms Thursday
- Below Normal Temperatures Friday and Saturday
- Potentially Unsettled Weather Next Week
&&
.DISCUSSION...
Issued at 236 PM EDT Wed Mar 25 2026
- Brief Window for Strong to Severe Thunderstorms Thursday
Overall, there is a short period of concern for a few thunderstorms
to potentially reach strong to severe levels Thursday late afternoon
through evening across extreme southern Lower MI (roughly 4pm-9pm),
but the better setup for severe weather will likely take shape
across IL/IN/OH. Details are as follows.
As has often been the case this month, a surface warm front will
be located near or just south of the I-96 corridor Thursday
afternoon. A 40kt LLJ will develop during the day and converge
across northern IN and near the MI/IN border. Between 12z-18z,
low-mid 50s dewpoints will advect in southern Lower MI while 60+
dewpoints will be confined to south of the MI/IN border. Given
mediocre low level moisture, it`s not surprising that it will be
struggle to obtain a few hundred J/kg of either SBCAPE or MUCAPE
in our region. For the I-96 corridor, most likely we are just
looking at some late afternoon and evening showers with perhaps a
rumble of thunder. Further south, 12z HRRR guidance shows a few
hours of 7-8 C/km mid level lapse rates near the I-94 corridor
from 19z-22z. If any cells can develop in that region there may be
some hail.
Taking a 12z HRRR sounding near our southern border over Berrien
County at 22z shows 0-3km shear of nearly 70 kts but 0-3km CAPE of
zero and CINH of -300; MUCAPE is shown to be around 800 J/kg. Unless
1) convectively driven gravity wave interactions occur to tap some
stronger winds above the stable layer or 2) significant enough
precip loading occurs via downward momentum of hail and liquid
water, it`s unlikely that damaging winds of 60 mph or greater will
materialize in our southern region and are more likely to occur near
and south of the MI/IN border. The same holds true for a more
supportive environment for tornado development being across northern
IN based on the latest 12z HREF 2-5km updraft helicity swaths and
associated STP values of 1-2 there, coupled with supporting Nadocast
projections of higher tornado percentages near and south of South
Bend, IN.
- Below Normal Temperatures Friday and Saturday
Temperatures will tank Friday after cold frontal passage and 850mb
temperatures drop from about +10C Thursday to around -10C Friday.
Highs will range from the mid 30s to low 40s both days which is
about 10 to 15 degrees below normal for late March.
- Potentially Unsettled Weather Next Week
Global ensemble data is in good agreement regarding a synoptic
pattern change by the early to middle portion of next week.
ECE/GEFS/CMC ensemble mean 500mb heights and vorticity indicate a
shift from a dominant ridge across the SW U.S. to an orientation
more across the SE U.S. as deep upper troughing begins to set up
across the West Coast. This places the Great Lakes in a region of
deeper southwest flow and already there are signs of anomalous PWAT
values surging into the region by Tuesday or Wednesday. Depending on
frontal positioning, this could lead to a rather wet pattern heading
into the midweek period.
&&
.AVIATION /18Z TAFS THROUGH 18Z THURSDAY/...
Issued at 208 PM EDT Wed Mar 25 2026
VFR weather is expected the remainder of the afternoon and most of
if not all of tonight. Ceilings drop to MVFR and IFR around
daybreak on Thursday. South winds are in place across the entire
area at 18z with a cold front situated well to the northwest of
the area over the Northern Plains. Over the next 24 hours, the
front will drop southward and push into Southwest Lower Michigan
Thursday morning. The front is on the move due to a strong area of
high pressure advancing southward from Canada.
VFR ceilings and visibilities are expected through 10z tonight.
After 10z a rapid development of MVFR and quickly to IFR is
expected. By 13z to 14z all 6 TAF sites should have ceilings
below 1,000 feet and visibilities in the 3-5 mile range. It
appears much of the rain with the front will hold off until just
beyond the valid time of these TAFs, 18z to 18z.
A gusty south wind of 10-15 knots with gusts over 20 knots can be
expected through 00z or so. After 00z, the winds should drop into
the 7-12 knot range.
&&
.MARINE...
Issued at 236 PM EDT Wed Mar 25 2026
Increasing southerly flow over Lake Michigan this afternoon has
led to an uptick in waves and there are whitecaps visible on
Manistee webcams. A Small Craft Advisory is in place from
Whitehall to the north into late tonight with waves peaking in the
2 to 5 foot range this evening. Another SCA will be needed for
much of the nearshore waters Thursday afternoon into Thursday
night.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...Small Craft Advisory until midnight EDT tonight for LMZ848-849.
&&
$$
DISCUSSION...Hoving
AVIATION...Duke
MARINE...Hoving
NWS GRR Office Area Forecast Discussion
