Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 160509
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
1209 AM EST Thu Nov 16 2017

LATEST UPDATE...
Aviation

.SYNOPSIS...
Issued at 330 PM EST Wed Nov 15 2017

Rain showers will continue to scatter out a bit through early this
evening. The showers will then mix with and/or change over to some
snow showers by midnight before diminishing Thursday morning. Some
isolated locations could see a dusting of snow overnight, however
most areas will not see accumulating snow.

We will see a break in the weather on Thursday and early Friday
before additional rain will move in with the next developing system.
The rain will be around later Friday into Saturday before it changes
over to some snow late Saturday.

&&

.SHORT TERM...(This evening through Friday night)
Issued at 330 PM EST Wed Nov 15 2017

Our focus is on the transition of p-types/potential for any snow
accums tonight, and then the timing of the pcpn over the area on
Fri/Fri night ahead of the next system.

The more widespread rain activity has given way to more showery type
of weather with less coverage this afternoon. This will remain the
case for the next few hours as the first short wave pushes right
across the heart of the CWFA. We will likely see a brief break in
the showers, or even some drizzle with the DGZ becoming unsaturated,
before they perk up again with the approach of the second short wave
currently near the Arrowhead of Minnesota.

Some colder air will filter in behind the initial short wave this
evening. This will start to mix in a little snow to any showers
toward midnight. We could see a few brief moderate snow showers
during the early overnight hours as over lake instability becomes
sufficient for lake effect/enhancement, and the short wave lifts
inversion heights for a short time. Some isolated locations could
see a dusting of snow under the better snow showers. We do not
expect this to be widespread as there seems to be a good chance
temps remain above freezing for the entire night.

Once the short wave exits after 06z, the upper jet will be lifting
out of the area Thu morning. This combined with a lack of a
saturated DGZ will limit shower activity, even with sufficient over
lake instability.

We will see a break in the weather then from Thu morning through Fri
morning with the upper ridge moving overhead. Then, we will see a
strong surge of moisture transport move into the area Fri afternoon
with the lead short wave moving in on the backside of the ridge.
Rain will develop/move in, and continue through Fri night. There is
a small chance of elevated thunder across the srn portion of the
CWFA late Fri night.

.LONG TERM...(Saturday through Wednesday)
Issued at 330 PM EST Wed Nov 15 2017

Model/ensemble consensus is for our deepening low pressure system to
track across southeast lower Michigan on Saturday then deepen
further as it tracks northeast from there Saturday night. Current
indications are for a half inch to an inch of rain on Friday night
and Saturday, with the main risk of thunderstorms and excessive
rainfall probably passing just south of Michigan.

Northwest winds will pick up on the back side of the low later
Saturday into Saturday night, and as the cold air rushes in we will
see rain showers change to snow showers. We could see some minor
accumulations on the grass Saturday night and early Sunday before
the system pulls away.

Quiet weather is expected on Monday and Tuesday as ridging and warm
advection impact the region, with milder highs in the 40s. Current
indications are that this quiet pattern will continue through the
peak holiday travel period on Wednesday.

&&

.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1145 PM EST Wed Nov 15 2017

MVFR conditions are anticipated overnight with cloud bases in the
1.5-2.5 kft agl range and snow flurries overnight. It will remain
windy overnight with west to northwest winds of 15 to 25 kts with
gusts to near 30 kts.

Any lingering flurries or sprinkles should taper off during the
mid to late morning hours Thursday but mainly MVFR conditions will
continue through the afternoon and evening due to low clouds.

&&

.MARINE...
Issued at 330 PM EST Wed Nov 15 2017

Gale warning continues to look justified, with winds coming up over
the next few hours. This will continue through early Thu morning
before we see winds slowly diminish on Thu.

We are looking at two additional periods of possible gales, one Fri
ahead of the front, and again on Sat behind the front.


&&

.HYDROLOGY...
Issued at 330 PM EST Wed Nov 15 2017

So far Wednesday rainfall totals have reached a quarter to half inch
in the Kalamazoo and Grand river basins, and a half to one inch in
the Muskegon and upper Saginaw basins. Minor river level rises will
occur due to the already saturated soil, but above-bankfull rises
are unlikely (except for the Sycamore Creek at Holt). Another half
to one inch of rain is likely Friday night into Saturday, and this
may push some flood-prone rivers above bankfull.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
LM...Gale Warning until 8 AM EST Thursday for LMZ844>849.

&&

$$

SYNOPSIS...NJJ
SHORT TERM...NJJ
LONG TERM...Meade
AVIATION...Laurens
HYDROLOGY...CAS
MARINE...NJJ



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