876
FXUS63 KGRR 112336
AFDGRR
Area Forecast Discussion
National Weather Service Grand Rapids MI
735 PM EDT Thu Jun 11 2026
.KEY MESSAGES...
- Potential for severe weather remains for later this evening
- Much cooler Friday; Rain chances return late Saturday into Sunday
- Cooler and unsettled next week
&&
.DISCUSSION...
Issued at 304 PM EDT Thu Jun 11 2026
- Potential for severe weather remains for later this evening
There has been a lot said over the past few days regarding the
severe potential for tonight. That remains, but is still a little
uncertain just a few hours out due to leftover showers and storms
from last night trying to approach the area.
The synoptic scenario generally remains unchanged with lots of
dynamics still coming together over the area later this evening. The
main uncertainty comes with the showers and isolated storms slow to
diminish ahead of the main show, and the instability that can be
realized with the strong dynamics.
The showers and isolated storms are diminishing slowly as they
approach Lake Michigan. A bit slower than just about all of the
models have indicated. This is likely to delay the instability
advection over the area ahead of the strong short wave driving the
cold front through the region. An outflow boundary has settled over
Northern Illinois. This is becoming stationary and is about to be
pushed northward by the increasing low level jet ahead of the upper
wave and sfc front.
The bottom line is we expect plenty of instability to make it over
the area with up to around 2500 J/kg, highest across the SW corner
of the forecast area. The max instability will taper off as you head
further north and west.
Deep layer shear around 40 knots will work with the instability to
provide organization to the storms that are expected to line up
along the incoming cold front. Low level shear becomes very
favorable with the low level jet ramping up, especially across the
NW half of the forecast area. This along with backing winds at the
sfc provides quite some impressive hodographs that would support the
potential of isolated tornadoes along the QLCS.
Forecast soundings indicate that the further north you go, the more
of a stable layer is present. Further southwest, the stable layer is
quite shallow, partially because of the front approaching before we
lose too much instability, and partially because of the theta e axis
ahead of the front. The mid level winds are also strongest over the
western areas, leading to the best threat of strong winds. The best
threat of damaging winds reaching the ground, and possible tornadoes
will be there with the most shallow stable layer, with the threat
diminishing the further north and east you go.
The line should reach the Lake Michigan shore around 8-9 pm, and
then clear the forecast area 12-1 am, ending the threat once it
moves east. Some showers and storms may be possible with the wave
upper wave lingering. but the rich instability will be gone.
- Much cooler Friday; Rain chances return late Saturday into Sunday
We will likely see some residual clouds Friday morning, but these
will clear out quickly as ridging builds over the region. 850 mb
temps drop to around 12C Friday afternoon, which will support cooler
highs in the mid to upper 70s.
We will see the upper low over Canada then start to dominate the
weather over most of the Upper Midwest and Great Lakes. It will
bring a long wave trough down out of Canada late Saturday. This will
bring a sfc front into the forecast area Saturday evening. The front
is formidable itself, but then we will have a fairly strong short
wave ride along it, and bring another surge of energy to increase
the coverage of precipitation Saturday night and Sunday morning.
There is plenty of instability of around 1000 J/kg of MU CAPE ahead
of the front to support thunder. Shear is healthy too with the upper
jet near by, which helps support the marginal risk in place.
- Cooler and unsettled next week
Obviously the focus has been largely on the near term due to the
severe potential, so not much to say about the longer term period.
It can be categorized by long wave troughing/lower heights
dominating the region. This will result in much cooler temperatures
next week compared to this week. In addition, we will have short
waves moving through on the periphery of the upper trough. These
will bring periodic shower/storm chances to the area off and on next
week.
&&
.AVIATION /00Z TAFS THROUGH 00Z SATURDAY/... Issued at 213 PM EDT
Thu Jun 11 2026
The main change in this set of TAFs is to adjust the timing of the
next squall line currently moving across northern Illinois and
southern Wisconsin.
The main line of storms is expected to move through between 01Z and
06Z, and timing has been adjusted accordingly. Prevailing thunder
has been maintained at all sites, and TEMPO groups have been added
for higher gusts as the leading edge of the convection moves
through. IFR CIGs and visibilities are also included within the
TEMPO groups to account for the potential for heavy rainfall.
MVFR CIGs are expected overnight after the line passes, with VFR
conditions developing at most sites between 10Z and 14Z. Moderate
westerly winds will continue through 00Z Saturday, with skies
continuing to improve and cloud bases lifting to AOA 15kft AGL after
18Z.
&&
.MARINE...
Issued at 304 PM EDT Thu Jun 11 2026
We will leave the Small Craft Advisory and Beach Hazards Statement
as is for tonight and Friday. We saw winds and waves approaching
criteria earlier, but are now in a relative lull before the winds
increase again with the approach of the front this evening. Then
winds will shift to be from the WNW with cooler air coming in which
will build the waves again through the first part of Friday before
diminishing. Aside from the synoptic winds, thunderstorm winds could
gust much higher which would be accounted for with Special Marine
Warnings.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Beach Hazards Statement from 8 PM EDT this evening through
Friday morning for MIZ037-043-050-056-064-071.
MARINE...Small Craft Advisory from 8 PM this evening to noon EDT Friday
for LMZ844>849.
&&
$$
DISCUSSION...NJJ
AVIATION...Planz
MARINE...NJJ
NWS GRR Office Area Forecast Discussion
