Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 211156
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
756 AM EDT Mon May 21 2018

LATEST UPDATE...
Aviation

.SYNOPSIS...
Issued at 330 AM EDT Mon May 21 2018

Low pressure moving northeast from Missouri will bring widespread
rain and cool temperatures today and tonight. Clouds will linger
in the wake of this system on Tuesday then sunny and warm weather
is expected Wednesday and Thursday. Memorial Day Weekend starts
out warm and humid with scattered showers and thunderstorms, then
ends up dry for the holiday.

&&

.SHORT TERM...(Today through Wednesday)
Issued at 330 AM EDT Mon May 21 2018

Big slug of rain headed our way today as shortwave ejects
northeast from the Plains and draws up PWATs over 1.5 inches via
30kt low level jet. Will have categorical pops spreading in from
southwest to northeast this morning, then expect a persistent cool
rain this afternoon and evening which could even be heavy at
times once the higher h8 theta-e air arrives from the south.

Widespread rainfall amounts of one half to one inch are expected,
although some streaks of locally heavier amounts over an inch are
quite possible. MUCape progs argue against much coverage of tstms
this afternoon and evening, but will continue to carry a slgt
chance as some weak elevated instability does come through later
in the day and evening.

Heaviest/widespread rain departs after midnight, put expect some
lingering scattered showers and areas of drizzle/fog. Low clouds
will linger most of the day Tuesday, although some clearing may
develop later in the day especially over nrn and wrn sections.

Prospects for sunshine are much better on Wednesday (after patchy
morning stratus/fog dissipates) with drier air mass and sfc ridge
overhead.

.LONG TERM...(Wednesday night through Sunday)
Issued at 330 AM EDT Mon May 21 2018

Chances for rain aren`t great during the long term, but probably
highest over the northwest cwa. Initially, high pressure over
Michigan will drift east late Thursday. Developing low pressure over
the Plains will generate showers/storms along the Mississippi valley
as the LLJ strengthens. An upper trough moving across the northern
tier of states will push the sfc low eastward and the precipitation
ahead of it will move toward the cwa.

The highest chance of precipitation looks to be late Saturday as the
trailing cold front moves across the cwa, but pops will linger into
Sunday as the upper support moves through.

Highs through the period will be in the 76 to 81 range.

&&

.AVIATION...(For the 12Z TAFS through 12Z Tuesday morning)
Issued at 754 AM EDT Mon May 21 2018

Variable flight conditions exist this morning, ranging from VFR
to IFR/LIFR where areas of fog/stratus are present. Conditions
will trend toward predominately MVFR by afternoon everywhere as
rain becomes more widespread, then mostly IFR by later in the day
and this evening as the rain continues and is occasionally heavy.
Late tonight there will probably be quite a bit of LIFR
developing as cigs further lower and areas of fog/drizzle develop
behind the departing area of heavier rain.

&&

.MARINE...
Issued at 330 AM EDT Mon May 21 2018

May be dealing with areas of fog over Lake Michigan over the next
48 hours before high pressure delivers a drier air mass on
Wednesday. Otherwise winds and waves expected to remain below
advisory criteria.


&&

.HYDROLOGY...
Issued at 1127 AM EDT Sun May 20 2018

Many rivers especially in southern Michigan are running much above
normal for this time of year, with lowland nuisance flooding still
occurring at several points. Most river levels are falling.
Showers on Monday have the potential to produce around a half inch
of rain on average in southern Michigan, though it wouldn`t be
surprising if some locations picked up closer to an inch.
Depending on the basins where any heavier rain may fall, this
could prolong the nuisance flooding. The middle part of the week
will be dry, then rain chances return toward the end of the week.

&&

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

$$

SYNOPSIS...Meade
SHORT TERM...Meade
LONG TERM...04
AVIATION...Meade
HYDROLOGY...CAS
MARINE...Meade



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