Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 210730
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
330 AM EDT Tue Mar 21 2017

LATEST UPDATE...
Synopsis/Short Term/Long Term/Marine

.SYNOPSIS...
Issued at 330 AM EDT Tue Mar 21 2017

It will become breezy this afternoon, with gusts to 35 mph.  However
it will be mostly sunny, with highs in the mid and upper 40s.  The
winds will diminish this evening, and with mostly clear skies,
temperatures will become quite cold tonight with lows of 15 to 20.
Wednesday will stay chilly, despite more sunshine, with highs only
in the 30s. Thursday will see increasing clouds into the afternoon.
A warming trend will begin Thursday with highs in the 40s.

The latter portion of the week looks wet.  Rain is expected to
arrive Thursday night and chances of rain may linger through
Saturday night.  Despite the rain temperatures will trend warmer,
with daytime temperatures expected to approach 60 Friday through
Monday.

&&

.SHORT TERM...(Today through Thursday)
Issued at 330 AM EDT Tue Mar 21 2017

Winds will increase today as a moisture starved short waves rotates
in by this evening.  This wave will usher in a rather chilly air
mass for tonight through Wednesday night.

Clouds and fog over the SE CWA is expected to erode and mix out
fairly quickly this morning.  Decided not to go with a fog advisory
as the areas of dense fog should mix out before daybreak, resulting
in limited impacts by morning commute time.  Of course we will
continue to monitor this closely.

Much of the day will be mostly sunny, but we will see cold advection
move in, ahead of this evening`s short wave.  This will bring NW
winds that will frequently gust to 35 mph near the coast much of the
afternoon and evening.  Even inland areas will see 30-35 mph gusts
at times this afternoon.  This cold advection will prevent the
normal diurnal trend, with highs mainly in the 40s, that should
occur in the early afternoon, with temps dropping thereafter.

The short wave swings through tonight with only some clouds moving
across Central Lower.  Otherwise -10C to -15C air drops in, and with
the mostly clear skies and diminishing winds we will see lows drop
to 15 to 20.  These temps will also be seen Wednesday night.  Wind
chill readings both nights toward daybreak will drop to 5 to 10F.
Very chilly early Spring mornings.  Meanwhile Wednesday highs will
only be in the 30s, under mostly sunny skies.

High pressure floats by late Wednesday afternoon, bringing return
flow by Thursday, allowing temps to get back into the 40s.  We will
see increasing clouds Thursday afternoon as Gulf moisture advances
northward.

.LONG TERM...(Thursday night through Monday)
Issued at 330 AM EDT Tue Mar 21 2017

The extended period opens up active and it stays this way almost
throughout. Cooler temperatures will erode to give way to a more
spring like pattern with precipitation chances through the weekend.

A closed upper low will be positioned well to our southwest late
Thursday into early Friday. However, as a warm front progresses
south to north through Lower Michigan, moisture will increase and
milder temperatures will advect in from the south. Lift in the mid-
levels will result in rain developing and overspreading the area
through early Friday morning.

Guidance continues to stall the surface boundary somewhere through
the northern half of the forecast area. While soundings continue to
look too warm for winter precipitation through much of the southern
half of Lower Michigan, far northeastern locations (e.g. Reed City
to Harrison) easterly winds could help keep surface temperatures
near freezing for the first couple hours at the onset of precip. A
brief period of light freezing rain is possible, but should not
amount to much.

Much of the rain lifts into northern Lower Michigan during the day
Friday with decreasing POPs further south. Areas south of I-96 may
even stay completely dry with temperatures rising into the 60s.

The closed upper wave and occluded surface low begins to track into
the Midwest Saturday. Gulf moisture continues to flow in from the
south as it all presses into the Great Lakes. Chances for rain
increase once again Saturday and Sunday. Early flow at the surface
may allow just enough cool air to gradually work back into Lower
Michigan for a snow/rain mix or possibly all snow north of I-96.

Monday looks to be the best chance to dry out a bit. However,
another upper level wave moves in and models diverge on a solution.
While the going forecast is dry at the time, I wouldn`t bet on it
staying that way for long. The silver lining in is that temperatures
remain near or above normal.

&&

.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 157 AM EDT Tue Mar 21 2017

Low level moisture and clearing skies have resulted in fog that
is periodically sending vsbys down near 1/4SM at southern TAF
sites. Otherwise, we are generally hovering between 1-3SM. This
should only last for the next few hours or so. Better mixing is
expected to result in gradually improving conditions. MVFR and
VFR is expected to return through dawn Tuesday morning.

VFR conditions are expected through Tuesday. Winds will shift out
of the northwest and increase to 10-15 kts. Gusts of 15-25 kts
are possible through the afternoon. Mixing heights remain elevated
through the evening. Therefore, gusts of around 20 kts could
extend near/past dusk Tuesday evening.

&&

.MARINE...
Issued at 330 AM EDT Tue Mar 21 2017

Small craft advisory will go into affect at noon today as north
winds increase toward 30 knots.  Winds gradually let up late tonight
into Wednesday.

&&

.HYDROLOGY...
Issued at 140 PM EDT Mon Mar 20 2017

Generally 0.05 to 0.25 inches of precipitation fell Monday morning.
Scattered showers could produce similar amounts in portions of the
area this afternoon and evening. Flooding is not expected. Tuesday
through Thursday looks dry. Later this week and into next week,
there are indications of mild temperatures returning and several
rounds of showers and thunderstorms being possible.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
LM...Small Craft Advisory from noon today to noon EDT Wednesday for
     LMZ844>849.

&&

$$

SYNOPSIS...JK
SHORT TERM...JK
LONG TERM...JAM
AVIATION...JAM
HYDROLOGY...CAS
MARINE...JK


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