455
FXUS63 KGRR 212339
AFDGRR
Area Forecast Discussion
National Weather Service Grand Rapids MI
739 PM EDT Sat Mar 21 2026
.KEY MESSAGES...
- Dry through Tonight, Isolated to Scattered Showers Sunday
- Mostly Dry through Next Week, Chance (30-50%) for Showers Thursday
&&
.DISCUSSION...
Issued at 213 PM EDT Sat Mar 21 2026
- Dry through Tonight, Isolated to Scattered Showers Sunday
Ongoing cloud cover will gradually clear this afternoon. Ongoing
reflectivities on radar haven`t been reaching the ground due to dry
air toward the surface. Temperatures will warm into the 50s to mid
60s this afternoon within the southerly flow ahead of the low
pressure system currently over northern Minnesota.
It is with this low pressure system that we`ll see our next chance
for rain. Associated with the front that moves through Sunday will
be plenty of low to mid level frontogenesis along with positive
vorticity advection with precipitable water values around 0.9" south
of the front. However even with these variables there is some dry
air to work through. Soundings show this and PoPs are not overly
high as seen in the different model solutions. Therefore only expect
isolated to scattered showers with the best chances (40 to 50
percent) along and north of M-20 early Sunday morning and then south
of I-96 Sunday afternoon. There could be some elevated instability
as shown in some of the NAM soundings and in the NSSL Prob Thunder
product, if this is realized occasional lightning is possible.
The probability of a tenth of an inch or more is around 20
percent in the NBM ensemble and 20 to 40 percent in the HREF with
the best chances toward Jackson.
- Mostly Dry through Next Week, Chance (30-50%) for Showers Thursday
Looking ahead into next week we`ll be locked into northwest flow in
the upper level pattern with ridging to the west and a trough to the
east. Within this flow we`ll need to look for shortwave troughs
moving through. Warm air advection will give us a 20 percent chance
for some shallow showers Wednesday, otherwise better chances (30 to
50 percent) hold off with a shortwave trough moving through
Thursday. The probability of a quarter of an inch of rain or more is
only 20 percent, so amounts are expected to be light. Dry conditions
are then expected into the weekend.
&&
.AVIATION /00Z TAFS THROUGH 00Z MONDAY/...
Issued at 727 PM EDT Sat Mar 21 2026
VFR conditions will continue tonight, as SCT to BKN upper level
cloudiness continues to stream overhead from the NW. Per latest
model guidance, still anticipate W-E oriented front to drop
southward overnight, turning winds from S/SW to N late tonight
/roughly between 08-12Z/.
In advance of frontal passage, TAFs include LLWS through about
08Z, a result of strong WAA just above the surface and modest
cooling/decoupling at the surface, along with a strengthening
surface pressure gradient.
Behind the front Sunday, expect lowering ceilings, likely
reaching into MVFR category by afternoon /2-3 kft/, along with a
steady N/NE flow. A few showers possible, mainly in the afternoon,
though restrictions should be minimal. Based on latest model
output, will only include PROB30 at JXN terminal, though it can`t
be precluded at all TAF sites.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...Small Craft Advisory from 2 PM Sunday to 11 AM EDT Monday for
LMZ844>846.
Small Craft Advisory from 8 AM Sunday to 5 AM EDT Monday for
LMZ847>849.
&&
$$
DISCUSSION...RAH
AVIATION...Smith
NWS GRR Office Area Forecast Discussion
