Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 250730

Area Forecast Discussion
National Weather Service Grand Rapids MI
330 AM EDT SUN SEP 25 2016

Synopsis/Short Term/Long Term/Marine

Issued at 330 AM EDT Sun Sep 25 2016

Enjoy the mild weather today because a cold front passage tonight
will usher in more fall like weather for a few days. The front will
bring a band of rain showers tonight, followed by cloudy, breezy and
cool weather through mid week. Highs Monday through Wednesday will
be only in the lower 60s with scattered lake effect rain showers.


.SHORT TERM...(Today through Tuesday)
Issued at 330 AM EDT Sun Sep 25 2016

Latest guidance indicates showers will probably not reach western
lower Michigan until this evening, first reaching the coastline
around 7-8 pm then marching slowly east from there tonight.

Categorical pops are warranted for most of the area tonight as front
interacts with narrow axis of very high PWATs close to two inches.
Some locally heavy downpours and rainfall amounts near one inch are
possible, although the thunder threat/coverage remains questionable
as instability ahead of the front is shown to wane significantly
after 00z.

Brief dry slot is anticipated Monday morning after fropa, although
lake effect clouds and showers should be quick to form by afternoon
as H8 temps near 4C sweep across the warm lake waters. Showers will
be enhanced by PVA associated with digging upper trough.

With upper low closing off and remaining over nrn Grtlks region, and
continued low level cold advection/cyclonic flow, expect a prolonged
period of clouds with scattered to numerous showers. Showers will
continue to be occasionally enhanced at times as shortwaves pinwheel
around the upper low. Warm Lake temps around 22C with cold pool
aloft could generate a few tstms from time to time as well.

.LONG TERM...(Tuesday night through Saturday)
Issued at 330 AM EDT Sun Sep 25 2016

We will see the continuation of cool and unsettled weather across
the area linger into the beginning of the long term. It appears that
there will be a break in pcpn chances, before the upper low could
rotate back toward the area late in the week and next weekend
bringing additional chances of rain.

We have fairly high confidence in the showery and cool conditions
for Tue night and Wed. There is good agreement that the upper low
that will close off will do so close enough to the area that it will
have a direct impacts. These impacts will be be in the form of lake
effect showers and cloudy and cool conditions. Best case scenario
for temperatures will be that we will get into the 60s.

The various models indicate that the upper low should temporarily
rotate out of the area for at least Thu at this time. Upper ridging
will build in from the North and West and bring somewhat milder
temps for at least a day.

The uncertainty comes in then for Friday and Saturday. The Euro has
been fairly consistent over the past couple of days in rotating the
low back toward the area from the SE. We could potentially see bands
of showers/rain move in on via the NW flank of the low. It is at
least worthy of a low chance mention at this time. We can bump pops
up later if there is better consistency that occurs.


.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 155 AM EDT Sun Sep 25 2016

Much of the period for the 06z fcsts will be quiet with VFR
expected to rule. We will see some mid clouds float through this
afternoon along with some cumulus/stratocumulus around 4k ft.
Winds will become gusty for the wrn terminals with gusts of around
20 knots likely.

Clouds will thicken up after 00z tonight as pcpn ahead of the
front approaches the area. The chance looks best after about 03z
at KMKG, and then progressively later moving east. We believe that
VFR will likely rule as rain tries to make it to the ground. Some
lower conditions will become possible after this fcst period.


Issued at 330 AM EDT Sun Sep 25 2016

Guidance keeps wind speed just below gale criteria so no watch at
this time, but it will need monitored. Small craft advisories will
be needed, probably starting starting tonight and continuing through
at least Tuesday. Waves could reach 10 feet. Have maintained a
chance of waterspouts but this may be marginal with winds close to
35 knots at 850 mb.


Issued at 1140 AM EDT Sat Sep 24 2016

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. Up to around one inch of rain
is expected and therefore rivers and streams should remain below
bankfull through the week.


.GRR Watches/Warnings/Advisories...


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