044
FXUS63 KGRR 170810
AFDGRR
Area Forecast Discussion
National Weather Service Grand Rapids MI
410 AM EDT Sun May 17 2026
.KEY MESSAGES...
- Scattered showers and storms today with a warm front
- Threat for severe storms on Monday
- Additional severe storms possible Tuesday
- Quieter weather mid to late week
&&
.DISCUSSION...
Issued at 409 AM EDT Sun May 17 2026
- Scattered showers and storms today with a warm front
A warm front will lift northward through Southwest Lower Michigan
tonight bring in higher dew point air and associated instability.
By evening mid 60s dew points should be in place over much of the
area. MUCAPE values should surge into the 1500 to 2500 j/kg range.
Plenty of instability for storms with the trigger being the warm
front. CAMs are not overly bullish though on coverage which makes
sense given today`s convection will be located within an upper
ridge position overhead. Feel a few storms are possible this
morning with a slight increase in coverage this afternoon given
daytime heating. Severe weather is not out of the question today
and SPC rightly has us in a marginal threat. Deep layer shear is
actually quite strong due to a convectively induced mid level jet
that move in from the west today from strong storms in the Central
Plains this past evening. The stronger shear, moderate instability
and a warm front nearby make all severe weather hazards possible
today. Showers and storms should lift to the north/end this
evening as the warm front lifts northward and we lose daytime
heating.
- Threat for severe storms on Monday
The active weather pattern that begins today will continue into
Monday. Another round of showers and strong to severe storms are
possible on Monday. The SPC has Southwest Lower Michigan in a
slight risk for severe weather. A strong southwesterly low level
jet of 35-40 knots will be in place with another convectively
induced mid level jet moving through as well. The threat on monday
looks to be centered in the midday through afternoon hours as this
is when a MCV will likely be working through the areas from
overnight convection in the plains. MUCAPE values should increase
to around 2000 j/kg with deep layer shear on the order of 30 to 40
knots. Wind and hail look to be the main threats on Monday in the
open warm sector of the system.
- Additional severe storms possible Tuesday
Another round of storms and possible severe weather will occur as
a strong cold front sweeps from west to east through the area on
Tuesday. 30 to 40 knots of deep layer shear looks to be in place
once again with in excess of 2000 j/kg of MUCAPE ahead of the cold
front. Wind and hail will once again be threats during the
afternoon.
- Quieter weather mid to late week
Cooler and drier weather is expected overall mid to late week with
high pressure building in from the north. 850mb temperatures
actually dive towards zero C Wednesday from a peak around +18C
Monday night. Wednesday and Thursday certainly look dry, but there
is some model disparity out on Friday with the GFS and the ECMWF
at odds in regard to the pattern. The GFS has a low in the area
while the ECWMF has ridging.
&&
.AVIATION /06Z TAFS THROUGH 06Z MONDAY/...
Issued at 202 AM EDT Sun May 17 2026
A warm front will lift north through Southwest Lower Michigan
tonight, including through all of the TAF sites. The front may
touch off a few showers and storms this morning between 11z and
16z at KMKG and KGRR and then for all the TAF sites this afternoon
between 17z and 22z. For the most part VFR weather is expected to
prevail outside of some scattered showers and storms. The time
frame that this activity would impact any one of the TAF sites
will be limited. There is a chance for some MVFR ceilings at KMKG
for a couple of hours around 18z, but left this small chance out
of the TAF at this point. The front should be north of the TAF
sites this evening and expect quieter/VFR conditions after 01z.
Winds will generally be out of the south today with sustained
speeds of 08-12 knots with some gusts to around 20 knots.
&&
.MARINE...
Issued at 409 AM EDT Sun May 17 2026
Strong southerly flow will develop tonight and continue into the
early portion of the work week. For now we will cover the first 24
hours of the wind and issue a Small Craft Advisory from this
evening through Monday for areas north of Holland. The wind will
continue into Monday night and Tuesday and expand to the south of
Holland as well with time. So, as we move forward the SCA will
need to be expanded in time and also in area (to the south). Waves
will reach the 3 to 6 foot range north of Holland on Monday.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...Small Craft Advisory from 11 PM this evening to 8 PM EDT Monday
for LMZ846>849.
&&
$$
DISCUSSION...Duke
AVIATION...Duke
MARINE...Duke
NWS GRR Office Area Forecast Discussion
