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000
FXUS63 KGRR 060731
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
331 AM EDT Thu May 6 2021

LATEST UPDATE...
Synopsis/Discussion/Marine

.SYNOPSIS...
Issued at 329 AM EDT Thu May 6 2021

- Rain showers today and Friday

- Concerns for frost and freezing temperatures the next six nights

&&

.DISCUSSION...(Today through next Wednesday)
Issued at 329 AM EDT Thu May 6 2021

- Rain showers today and Friday

Shortwaves dropping through the longwave trough over the Eastern
CONUS will prompt a few rounds of showers the next few days. The
first shortwave will slowly push surface low pressure across the
Ohio Valley today, spreading rain showers across the area into the
evening. Latest RAOBS across the region show very dry air in place
which must first be overcome, and we will continue to see quite a
bit or virga or just sprinkles until deeper moisture arrives just
ahead of the shortwave trough axis. Even as the slug of "heaviest"
rain pushes west to east across the area during the morning and
afternoon, we are still only looking at rain amounts between roughly
two and three tenths of an inch. Bottom line, no issues from the
rain are expected.

Additional upper waves will cause a surface trough dropping through
Michigan Friday to deepen, and eventually eventually close into a
low per latest guidance. This will bring another round of showers
tomorrow. With the system now looking a little stronger, models are
showing a modest amount of instability building by afternoon for
areas roughly east of US 131. This could be just enough to support a
few thunderstorms, especially towards areas like Lansing, Jackson
and Mt Pleasant for the late afternoon and evening. Rain amounts
will again be light, with most places on the west side of the State
receiving less than one-quarter of an inch.

- Concerns for frost and freezing temperatures the next six nights

An extended period of cooler weather with chilly overnight
temperatures is expected tonight through Tuesday night. Will have to
closely assess potential for frost and freezing conditions each of
the next six nights, with lows forecast to mainly fall into the 30s
each night. For tonight, it looks like we will stay above freezing
outside of isolated and known colder spots north of US 10.
Temperatures will however fall to the mid 30s, when we normally
become concerned about frost. With one system exiting and another
hot on its heals, and potentially even beginning to spread showers
into northern portions of the area by daybreak, the window for clear
skies may be too short for frost formation. Frost/freeze headlines
are not planned at this time, but cannot rule out patches of frost
forming overnight before clouds increase. Friday night is more of a
concern with lows forecast to drop into the upper 20s (mainly
Central Michigan) to low 30s. Skies will be clearing, but winds may
stay up just enough to lessen potential for frost formation. Lows
look to range generally from the low to mid 30s Saturday night
through Tuesday night.

&&

.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 143 AM EDT Thu May 6 2021

Surface low pressure passing south of the area will begin to
spread light rain showers into the area early this morning. Dry
air currently in place will initially keep ceilings and
visibility at VFR, before we see conditions deteriorate to MVFR
from west to east after 12Z. By afternoon and evening, there is
decent chance for each terminal to see several hours of IFR
ceilings. Improving conditions can be expected during the evening
and early overnight hours. Winds are expected to stay under 10
knots over the next 24 hours.


&&

.MARINE...
Issued at 329 AM EDT Thu May 6 2021

Winds will be fairly light through late tonight, keeping wave
heights low. Winds will pick up out of the northwest behind a cold
front early Friday morning, then remain out of the north and
northwest into Saturday. Low-end Small Craft Advisory conditions are
possible Friday afternoon and evening, but confidence is not high.
After light winds and waves Saturday night, north winds will
increase again Sunday into Sunday night. Gusts look to remain near
to below 20 knots, and the northerly direction should keep the
higher waves over the extreme southern portion of Lake Michigan, and
likely south of St Joseph.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
LM...None.
&&

$$

SYNOPSIS...HLO
DISCUSSION...HLO
AVIATION...HLO
MARINE...HLO