Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 221629
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
1129 AM EST Sun Jan 22 2017

LATEST UPDATE...
Update

.SYNOPSIS...
Issued at 330 AM EST Sun Jan 22 2017

Dense fog will continue through the morning hours before lifting a
bit this afternoon. We could see a repeat of the fog tonight. An
area of low pressure will move from the plains into the Ohio Valley
today and tonight. The low will be responsible for spreading a few
rain showers into the Lower Michigan this afternoon and tonight. A
better chance for rain showers will exist on Monday slides by to our
southeast over Ohio and West Virginia. A brief break in the
precipitation will come on Tuesday before our next weather maker for
Tuesday night. Rain and snow is expected Tuesday night. Temperatures
will cool a bit each day as we head through the upcoming work week.
Highs today will rise into the 40s to near 50. By Friday, highs
should be back near the freezing mark.

&&

.UPDATE...
Issued at 1129 AM EST Sun Jan 22 2017

Although we expect some diurnal improvement with the fog, with the
inversion holding in place and the lack of much mixing, expect we
will see vsbsys lower again this evening into tonight. So have
decided to extend the fog advisory into Monday morning, ending at
10 AM.

The mixing does begin to increase late tonight over Southern Lower
and spreads north to Central Lower toward daybreak. This may be
enough to slowly improve vsbys toward daybreak, but feel it will
be a slow process, hence the 10 AM end time. In this regime,
Central Lower will probably hold on to the dense fog the longest.

Spotty light rain will also be around this afternoon, mainly along
and south of I-96. Max temps were trimmed back slightly due to the
dense clouds and fog.

&&

.SHORT TERM...(Today through Tuesday)
Issued at 330 AM EST Sun Jan 22 2017

The dense fog advisory looks solid with fairly widespread
visibilities of a quarter mile or less. Higher dew point air over a
cold ground is responsible for the fog as well as a continuing
melting of snow. We extended the Dense Fog Advisory through noon as
it looks like the fog will be slow to lift/improve today. We will
likely stay cloudy all day with some lingering fog even into the
afternoon. A low sun angle and abundant low level moisture should
equal a gray day. A repeat of some fog is likely again tonight
although we do have some wind in the lowest 1000ft, so it may not be
as dense.

Rain showers will begin to creep into the area tonight and increase
in coverage on Monday as the plains low moves into the Ohio Valley.
An inverted trough extending back into Lower Michigan from the south
will aid in precip production. Have chances for rain showers
increasing to likely (60 pct) on Monday afternoon. The rain showers
should taper off Monday night as the low pulls away to our
southeast.

Tuesday should be a lull in the precipitation before our next system
takes more direct aim on our area Tuesday night.

.LONG TERM...(Tuesday night through Saturday)
Issued at 330 AM EST Sun Jan 22 2017

A strong low pressure system will move ene into the Great Lakes
region Tuesday night and Wednesday and bring potential for mixed
pcpn Tuesday night followed by mainly rain for Wednesday except for
potentially heavy snow or a rain/snow mix across our northern fcst
area. This system will need to be monitored closely as a low track a
little further south would mean potential for significant snow for
portions of our fcst area.

Temperatures will return to closer to normal for this time of year
behind that system for late in the week in a nw flow caa pattern.
Scattered snow showers are likely late in the week as an upper level
trough builds in. H8 temps will be cold enough for lake effect snow
showers late in the week as well. A clipper system could also bring
more snow showers next weekend with another reinforcing shot of
colder air to follow.

&&

.AVIATION...(For the 12Z TAFS through 12Z Monday morning)
Issued at 655 AM EST Sun Jan 22 2017

Widespread VLIFR conditions are in place at 12Z on this Sunday
morning. The expectation is that the 1/2SM and below visibilities
and ceilings below 300ft will continue the bulk of the morning. We
are forecasting only a small improvement this afternoon to
ceilings around 600ft and visibilities potentially improving to
3/4SM to 1SM.

Tonight the dense fog will likely settle right back in and we
brought ceilings and visibilities back down once more. The bottom
line is widespread fog will continue the next 24 hours with light
winds.


&&

.MARINE...
Issued at 330 AM EST Sun Jan 22 2017

We will be issuing a marine dense fog advisory through midday in all
of our nearshore zones. Fog was expanding into the nearshore waters
as of 300am and expect the trend to continue the remainder of the
night. It may take a good portion, if not all of the morning for the
fog to improve to the point where navigation is possible.

In terms of winds and waves a light pressure gradient today will
keep things fairly calm. Tonight into Monday a north wind will
increase into the 10 to 20 knot range which will build waves into
the 2 to 4 foot range in the southern zones.


&&

.HYDROLOGY...
Issued at 329 PM EST Sat Jan 21 2017

While the initial flood wave on the Grand River has moved through
Robinson Township...a second rise in river levels is currently
working through Ionia and Lowell and will cause rises at Comstock
Park...Grand Rapids...and Robinson Township over the next few days.
Current thought is that this next rise will remain below flood stage
at the forecast points.

Rises continue on tributaries to the Grand...such as the Thornapple
at Hastings and Caledonia...Looking Glass at Eagle...and the Maple
River at Maple Rapids.  While some of this additional water will
travel through dams...this will keep levels on the Grand elevated
through at least the middle of next week.

Rainfall from the storm system Sunday night into Monday looks to be
less than one quarter inch for most locations.  While most of that
may end up as runoff...minimal impacts are expected from that event.
Another system will affect the region late Tuesday into Wednesday...
which will bring a colder airmass into the region.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Dense Fog Advisory until 10 AM EST Monday for MIZ037>040-043>046-
     050>052-056>059-064>067-071>074.

LM...Dense Fog Advisory until 10 AM EST Monday for LMZ844>849.

&&

$$

UPDATE...JK
SYNOPSIS...Duke
SHORT TERM...Duke
LONG TERM...Laurens
AVIATION...Duke
HYDROLOGY...MWS
MARINE...Duke


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