603
FXUS63 KGRR 240558
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
158 AM EDT SAT SEP 24 2016

LATEST UPDATE...
Aviation

.SYNOPSIS...
Issued at 315 PM EDT Fri Sep 23 2016

Fair weather will return tonight through Saturday and most of Sunday
with seasonably mild temperatures. A cold front will bring rain and
perhaps a few thunderstorms Sunday night into early Monday. A cooler
airmass will move in behind the front from Monday night
through Wednesday.

&&

.SHORT TERM...(This evening through Sunday night)
Issued at 315 PM EDT Fri Sep 23 2016

Primary short term fcst concerns involve timing rain into our fcst
area Sunday night.

An isolated light rain shower or sprinkle is still possible into
this evening mainly along the I-94 corridor closer to the nearly
stationary frontal boundary that extends across far northern IN/OH.
Otherwise quite a bit of cloud cover will linger overnight and some
patchy fog may develop during the early morning hours Saturday.

High pressure anchored to the northeast of our region will bring
fair weather Saturday through most of Sunday. It will be
seasonably mild in spite of easterly winds Saturday with high
temperatures reaching the middle 60s to lower 70s. It will be a
bit milder Sunday as winds veer to the southeast to south. This in
conjunction with some sun will help to boost max temps into the
lower to middle 70s.

The cold front approaching from the west will bring rain showers
Sunday evening that will become more widespread late Sunday night.
Convective potential late Sunday night is fairly low due largely to
frontal timing and weak instability.

.LONG TERM...(Monday through Friday)
Issued at 315 PM EDT Fri Sep 23 2016

Models are in decent agreement in showing the cold front moving east
of the forecast area Monday morning.  Less of a risk for
thunderstorms exists as the main instability axis will be ahead of
this front.  With a post frontal airmass moving in during the day on
Monday the highest potential for measurable rain will be in the
morning.

Some differences show up for Monday night into Tuesday.  The GFS
wraps around considerably more moisture behind the departing system.
This occurs partly because the GFS is much cooler and the lakes add
moisture to this low pressure system.  The new High Res Euro is
still dry as it is not as cool and it keeps the low further north.
Will hold onto the low risk for showers Monday night into Tuesday
given the spread in the models.

Ridging moves in for Wednesday into Friday.  Thus any risk for rain
looks minimal.  A moderating trend to the temperatures will occur as
the ridge builds east for the end of the week.

&&

.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 158 AM EDT Sat Sep 24 2016

Our main aviation focus is on the lower cloud cover that is in
place, especially along I-94 early this morning. The cigs along
I-94 are in the 2-3k ft range. This is the back edge of the lower
cloud cover that plagued the area on Fri. This is fcst to slowly
sink south later this morning, and should be south of the I-94
terminals by 16z.

Once this cloud cover moves out, some diurnal cumulus will be
possible with mid clouds also floating by. This should generally
remain the case then through 06z tonight, with the diurnal clouds
dissipating around sunset. An E/NE wind will likely hold up
through the period.

&&

.MARINE...
Issued at 315 PM EDT Fri Sep 23 2016

Northeast to east winds in the 5 to 15 kt range through Saturday
will result in minimal wave heights mainly in the 1 to 2 foot
range. Winds will veer to the se to south and strengthen somewhat on
Sunday out ahead of an approaching cold front. This will result in
building wave heights to at least 2 to 4 feet and potential for
wave heights to flirt with small craft criteria by Sunday
afternoon.


&&

.HYDROLOGY...
Issued at 1032 AM EDT Fri Sep 23 2016

Hydro concerns are minimal through the weekend, as little rain is
expected and river levels are around normal for the time of year.
Showers and thunderstorms are expected Sunday into Monday night with
additional rain possible Tuesday into Wednesday. Around 1 inch of
rain is expected and therefore rivers and streams should remain
below bankfull through the week.

&&

.GRR Watches/Warnings/Advisories...
MI...None.
LM...None.
&&

$$

SYNOPSIS...Laurens
SHORT TERM...Laurens
LONG TERM...MJS
AVIATION...NJJ
HYDROLOGY...63
MARINE...Laurens