Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 101734
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
134 PM EDT Mon May 10 2021

LATEST UPDATE...
Aviation

.SYNOPSIS...
Issued at 314 AM EDT Mon May 10 2021

- Frost/Freeze Threat Through Wednesday Morning

- Low Risk for a Sprinkle/Light Shower Today and Tuesday

- Pattern Shift is Anticipated Next Week

&&

.UPDATE...
Issued at 1015 AM EDT Mon May 10 2021

We have issued a freeze warning for tonight for the entire area.
We wanted to give a little more lead time for everyone that needs
to protect any vegetation.

Tonight is one of those situations in which there will not
necessarily be a lot of frost. This is because the wind is
expected to stay up around 5 knots or so for the whole night and
keep things mixed. This will be more widespread cold temperatures,
versus a calm night where temperatures would be locally colder.

&&

.DISCUSSION...(Today through next Sunday)
Issued at 314 AM EDT Mon May 10 2021

-- Frost/Freeze Threat Through Wednesday Morning --

The setup for frost and freezing conditions tonight looks a bit
better than this morning, with colder readings of 28-32 expected for
the majority of the region (save for the western half of the
immediate coastal counties). This will likely necessitate a Freeze
Warning for most or all of our forecast area. Given a mid level
shortwave dropping through tonight I would expect NW winds to hold
up, making this more of an advective freeze as colder temperatures
aloft advect in. Similar case for Tuesday night/Wednesday morning,
though in both cases model soundings do indicate a low level
temperature inversion. I think low temps will be very similar to
tonight/Tuesday morning. In both cases I am still anticipating the
core fruit belt region along our lakeshore should escape a hard
freeze scenario. Further inland, it could be a close call. Take
precautions as necessary through Wednesday morning, and then we may
be out of this threat for good.

-- Low Risk for a Sprinkle / Light Shower Today and Tuesday --

Given the robust mid level troughing (upper low near Lake Superior)
and cold air advection over the Great Lakes today and Tuesday, can`t
totally rule out a sprinkle or light shower developing. These would
be minor and most places won`t get rainfall. Model soundings are
indicating cloud bases would be rooted near 850 mb with plenty of
dry air below, so virga may be a more likely scenario.

-- Pattern Shift is Anticipated Next Week --

There is growing confidence in next week being warmer and wetter
than we have seen recently. Normal highs by that time are around 70
degrees. It is looking likely that we`ll be near to above normal for
temperatures. Ensemble guidance is also hinting at a wetter stretch
setting up.

The ECE mean 500 mb height pattern becomes more conducive to a
wetter setup in the Midwest and Great Lakes. ECE mean precipitable
water content makes a distinct upward jump by the end of this
weekend and carries us all the way through next week potentially. We
have seen numerous model runs now of this being projected. Also
intriguing is the fact the deterministic runs of the GFS, GEM, and
ECMWF indicate a more active LLJ by early next week that could have
a fair shot of bringing up Gulf moisture into our region instead of
being shunted south of here, as has been the case so often this
spring. We`ll see how that pans out.

Ensemble guidance from the ECE, GEFS, and CMC shows growing support
for 1" or more of rain next week. The ECE probability of 1" or more
across our region is 50%-60% with the GEFS and CMC showing 60%-70%,
which is fairly impressive considering we are talking about the 7 to
14 day time frame. It is noted that roughly 1/3 of the ensemble
members from the combined grouping of ECE/GEFS/CMC have 2" or more
of rain. While these totals aren`t earth-shattering, they become
noteworthy when you consider that we scraped together only 1"-2" of
rain for the entire month of April. So, the bottom line is the odds
are tilting toward a warmer and at times wetter period for us next
week.

&&

.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 133 PM EDT Mon May 10 2021

We are dealing with some light rain showers south of the I-96
terminals out of the gate this afternoon. These will slowly end
from West to East through about 20z this afternoon. They are of
little impact with ceilings and visibilities remaining VFR. Skies
will clear out this evening, and winds will remain up around 4-6
knots through the night from the NW.

We expect diurnal cumulus to pop by late morning on Tuesday, with
a few light showers possible after 15z or so. These once again
should be of little impact with lots of dry air in the lower
levels. Winds will become a little gusty Tuesday afternoon with
gusts up to 20 knots likely away from Lake Michigan.

&&

.MARINE...
Issued at 314 AM EDT Mon May 10 2021

We`ll be able to cancel the SCA early this morning as conditions
have fallen below criteria. Expect waves to hold up in the 2 to 4
foot range today, however. Tuesday afternoon looks like a similar
case as NW winds pick up and we will likely be right back in the 2
to 4 foot range.


&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Freeze Warning from midnight tonight to 9 AM EDT Tuesday for
     MIZ037>040-043>046-050>052-056>059-064>067-071>074.

LM...None.
&&

$$

UPDATE...NJJ
SYNOPSIS...Hoving
DISCUSSION...Hoving
AVIATION...NJJ
MARINE...Hoving


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