847
FXUS63 KGRR 291435
AFDGRR
Area Forecast Discussion
National Weather Service Grand Rapids MI
1035 AM EDT Sun Mar 29 2026
.KEY MESSAGES...
- Rain and Thunderstorms Monday Night into Tuesday Night
- Rain Chances Return Late Week into Weekend
&&
.DISCUSSION...
Issued at 305 AM EDT Sun Mar 29 2026
- Rain and Thunderstorms Monday Night into Tuesday Night
Monday Night into Tuesday Morning:
There is a Marginal Risk for strong to severe storms Monday night
into Tuesday morning. Southwest flow will be advecting moisture,
warm air, and with the low level jet convergence paired with
divergence from the upper level jet storms are expected to
develop Monday night. With the changing airmass instability will
be building with MUCAPE values around 1000 to 1500 J/kg and 40 to
50 knots of shear. Mid level lapse rates will be around 8 C/km.
Storms will be elevated and with the mentioned ingredients hail
will be the primary concern, but can`t rule out some stronger
winds, especially with 40+ knots just above the surface. Timing
would bring storms into the area after 8pm with the best chances
after midnight. There are differences on how long storms linger
into Tuesday morning. Depending on how fast the first round clears
will impact the severe potential Tuesday afternoon and evening.
Tuesday Afternoon into Tuesday Night:
Strong southwest flow continues ahead of the trough axis Tuesday
afternoon and evening. Overall the best chance for severe
thunderstorms looks to be in southern and southeastern portions
of the forecast area. This is due to a better potential for
surface based storms along with the orientation of the low level
jet and right entrance region of the upper level jet. However
some solutions keep a bit of CIN in the profile likely impacted by
how the initial round of storms play out. Instability will be
about the same with 40 to 50 knots of shear. CSU, NCAR`s AI NWP
Convective Hazard Forecast, and NSSL have been highlighting this
severe potential for days with the highest probabilities across
southern lower Michigan. Hail and damaging winds will be the
primary concern, but there will be a tornado potential for areas
that are able to become surface based.
Looking at the potential for some heavy rain, NBM probabilities
have increased for an inch or more in 24 hours. There are some
rainfall probability axis of 30 to 40 percent in portions of lower
Michigan depending on where storms track over the longest.
- Rain Chances Return Late Week into Weekend
Other than some lingering showers early Wednesday morning, dry
conditions are expected until our next shortwave trough moves
through the area during the Thursday to Friday timeframe. Taking a
look at the cluster analysis almost 50 percent of the GEFS members
are in a cluster that brings in the shortwave trough faster
resulting in rain chances earlier on Thursday, with the other
clusters a little slower trending toward Thursday evening into
Friday. This is represented by the NBM PoPs being higher across
much of the area (60 percent) Thursday night compared to during
the day on Thursday. Rain should be diminishing Friday as the
trough is progressive, but any dry break looks to be short lived
as a deeper trough moves through over the weekend. Again looking
at the cluster analysis, there are timing differences. The cold
front looks to move through Sunday bringing colder temperatures
and drier conditions, but there is a 20 percent chance showers
could linger into Sunday afternoon.
&&
.AVIATION /12Z TAFS THROUGH 12Z MONDAY/...
Issued at 636 AM EDT Sun Mar 29 2026
VFR conditions are expected today with southwest winds. Low level
wind shear will be present initially this morning and then
redevelop tonight.
&&
.MARINE...
Issued at 305 AM EDT Sun Mar 29 2026
Small Craft Advisory conditions continue from Holland and northward
with southwest winds gusting to 25 knots and waves 4 to 7 feet.
Southwesterly winds then become lighter with a lull in the high
waves through Monday. Monday night winds pick back up resulting
another chance for Small Craft Advisory conditions Monday night
into Wednesday. Southwest winds will shift to the northwest behind
the front Tuesday before winds become more offshore Wednesday into
Thursday.
Thunderstorms are expected at times Monday night into Tuesday
night and could be strong to severe with large hail and damaging
winds.
&&
.FIRE WEATHER...
Issued at 1034 AM EDT Sun Mar 29 2026
Based on latest guidance the dewpoints should remain in the 20s
this afternoon. So have adjusted the Dewpoints down to reflect
that. This also will drop the RH`s into the upper 20s this
afternoon. So expecting a drier day today. Winds should remain
around 10 mph with gusts of 20 to 25 mph possible.
Temps should drop off between 6 PM and 8 PM and RH`s should
recover through that time to above 30 percent and increase as the
evening continues.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...Small Craft Advisory until 5 PM EDT this afternoon for
LMZ846>849.
&&
$$
DISCUSSION...RAH
AVIATION...RAH
MARINE...RAH
FIRE WEATHER...Ceru
NWS GRR Office Area Forecast Discussion
