Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 251713
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
113 PM EDT SUN SEP 25 2016

LATEST UPDATE...
Aviation

.SYNOPSIS...
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 18Z TAFS through 18Z Monday afternoon)
Issued at 107 PM EDT Sun Sep 25 2016

VFR weather to prevail with afternoon with a relatively dry
airmass in place. As a cold front pushes in from the west later
this afternoon and through the evening...the moisture will be on
the increase. This will support increasing shower activity. Some
instability will be present...especially near the
lakeshore...which could allow for a few thunderstorms. Ceilings
will lower as the moisture moves in...and MVFR conditions look
likely with IFR possible.  The main axis of rain showers should
push east of KLAN by 12z.

The wind will be on the increase as the front nears and pushes
through during the evening. Any shower or thunderstorm could
support locally higher gusts. Given the greater risk for a
thunderstorm near KMKG...I will feature gustier conditions there.

MVFR clouds look likely for Monday as the low levels remain moist
behind the front.


&&

.MARINE...
Issued at 330 AM EDT Sun Sep 25 2016

Guidance keeps wind speeds 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.


&&

.HYDROLOGY...
Issued at 102 PM EDT Sun Sep 25 2016

River levels are around normal for this time of year. Showers and
thunderstorms are expected tonight and lake effect rain showers are
possible Monday into Wednesday. Through Wednesday, over an inch of
rain is possible to the north and west of Grand Rapids with less
than a half inch to the south and east. Rivers and streams should
remain below bankfull through the week.

&&

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

$$

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



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