229
FXUS63 KGRR 152156
AFDGRR
Area Forecast Discussion
National Weather Service Grand Rapids MI
556 PM EDT Fri May 15 2026
.KEY MESSAGES...
- Round of storms expected overnight
- Another round of storms late Saturday night/Sunday morning
- Stronger storms expected both Monday and Tuesday
&&
.DISCUSSION...
Issued at 310 PM EDT Fri May 15 2026
- Round of storms expected overnight
Strong to severe thunderstorms are expected to erupt this
afternoon and evening across Western Iowa. These storms will roll
east and push out over Lake Michigan in a weakening state after
200am. A round of likely sub severe storms will move into Western
Lower Michigan off the lake around 400am. The storms will sweep
east and out of our area including the Highway 127 corridor by
800am or 900am. Some light rain will linger into the day on
Saturday ending from west to east in the afternoon. Wind will be
the main threat overnight with wind gusts to 45mph or so possible
over the lakeshore counties. Could envision needing a few Special
Marine Warnings or Special Weather Statements.
- Another round of storms late Saturday night/Sunday morning
After the showers and storms press off to the south and east on
Saturday an effective boundary will be located in that direction.
A warm front will push northward into and through the area late
tonight and on Sunday. While the low level jet is on the weaker
side during this time frame the moisture surge is not trivial.
Expecting showers and storms as the warm front pushes northward
through the area. Models are not bullish at all on precipitation,
so this time frame is lower confidence.
- Stronger storms expected both Monday and Tuesday
Better chances for severe weather exist on both Monday and
Tuesday. Monday`s event looks to occur during the afternoon and/or
evening associated with a strong low level jet (LLJ) and what
appears to be a MCV from upstream convection. It is early to be
nailing down timing of such a feature, but the 35-45 knot LLJ and
moisture surge of +15C dew points point towards a higher threat.
SPC agrees with a day 4 slight risk.
There may be a break in the convective activity Monday night into
Tuesday morning, but the LLJ remains strong leading one to
believe storms may continue through the night. Another round of
storms is likely then on Tuesday ahead of the main cold frontal
passage during the afternoon and evening. The front is strong with
a healthy dew point gradient across it. Lift from the front alone
will be enough to drive convection some that could be strong. as
Monday and Tuesday get closer we will better fine tune threats.
PWAT values increase to around 1.75 inches especially on Monday
and Tuesday which will make heavy rain a distinct possibility. The
good news is rivers have receded significantly from last months
rainfall so we have room in the rivers for absorb rises.
Expecting heavier swaths, but forecast rainfall amounts are mainly
in the 0.50 to 1.25 inch range. Localized short term flooding is
possible in spots given PWAT values that are off the charts for
this time of year.
&&
.AVIATION /18Z TAFS THROUGH 18Z SATURDAY/...
Issued at 552 PM EDT Fri May 15 2026
Mid cloud deck continues to persist across the region with gusty
south easterly winds. Those winds are slowly subsiding with some
clearing of the skies.
A weakening system moving in from the west will bring a chance
for showers/storms late tonight after 08z. Have prob30s for TSRA
at most TAF sites in between 09 to 13Z from West to east. Some
lingering showers will be possible. Expect periods of MVFR cigs
and vsbys as the system approaches and shortly after its exit.
Along with this system will be a low level jet which could bring
some LLWS to all TAf sites in between 08 to 12Z. Winds between
015KFT and 2KFT should be approx 25045kts.
VFR should again dominate tomorrow afternoon with mid deck clouds
and gusty winds out of the southeast through the afternoon.
&&
.MARINE...
Issued at 310 PM EDT Fri May 15 2026
A Small Craft Advisory is in effect through 500am Saturday as
strong south winds will continue into tonight. Winds along the
lakeshore at this time are gusting towards 30 knots. We expect
winds and waves to settle some overnight with waves falling below
4 feet by daybreak. A more slack gradient will set up for
Saturday into Sunday. So for the weekend better conditions are
expected, although there will be rounds of thunderstorms.
&&
.FIRE WEATHER...
Issued at 310 PM EDT Fri May 15 2026
After coordinating with the Michigan DNR, we will not issue a Fire
Weather Watch for Saturday across Central Lower Michigan. First, it
appears criteria may be close but not fully met. It will be warm
with highs in the 80s, winds look to potentially be just shy of
criteria in the 10-20 mph range and RH will be just above criteria
as well dipping into the lower 30s percent. Secondly and more
importantly, the DNR is mainly worried about the jackpine forest
of Northern Lower Michigan based on conditions they monitor. An
increased fire danger is expected across much of the area on
Saturday with Central Michigan being the closest to criteria.
Fully met criteria will occur north of our area.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...Small Craft Advisory until 5 AM EDT Saturday for LMZ846>849.
&&
$$
DISCUSSION...Duke
AVIATION...Ceru
MARINE...Duke
FIRE WEATHER...Duke
NWS GRR Office Area Forecast Discussion
