Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 212341
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
641 PM EST Sat Jan 21 2017

LATEST UPDATE...
Aviation

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

The glimpse of sunshine seen this afternoon will quickly give way
to more clouds through the remainder of the weekend. Rain chances
will increase as a system slides to our south east on Sunday.
Despite slightly cooler air moving in for the beginning of next
week, temperatures will remain above normal. Winter finally makes
a return for the later half next week with temperature back into
the 30s and the possibility for light snow.

&&

.SHORT TERM...(This evening through Monday night)
Issued at 329 PM EST Sat Jan 21 2017

The main concern in the short term will be fog tonight. We then
look forward to additional precipitation chances beginning late
Sunday into Monday.

Once today`s clouds and fog eroded over the southern half of the
area, temperatures responded quite well, rising into the upper 50s
and lower 60s. Those through central Michigan have not been quite
so lucky with low clouds and fog has held its own along a slow
moving boundary.

This boundary will play a role in weather as we head into tonight
and Sunday, as it begins to slowly return south and east as a
weak cold front. Fog is likely to develop once again, become
dense. As a result, a dense fog advisory will extend through
tonight and into Sunday.

A storm system passes well to our south and east, but this
aforementioned boundary may provide enough lift to result in
showers late Sunday into Monday. With temperatures well above
normal, much of it should be rain. Cooler air then moves in early
next week and while some guidance likes to suggest that we mix
with snow late Monday into Tuesday morning, vertical profiles are
not too impressive to support this idea. Anything that mixes in
will not amount to much, if anything.

.LONG TERM...(Tuesday through Saturday)
Issued at 329 PM EST Sat Jan 21 2017

Sfc low tracks across Lower Michigan on Tuesday night and Wednesday
with primarily rain across much of the forecast area, although there
will be a transition to snow on the back side of the low Tuesday
night and Wednesday. Cold air returns for Thursday with a period
of west flow lake effect snow showers, especially Thursday night
into Friday morning as trough moves through and inversion heights
increase.

Another trough or weak clipper arrives for Saturday and this could
bring light synoptic snows as well as increase the lake effect snow
showers.

&&

.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 634 PM EST Sat Jan 21 2017

Low clouds and dense fog are likely to return to the TAF sites by
06z tonight. The crossover temperatures are very elevated...which
supports the low cloud and fog formation. The low conditions
situated around KMOP and KRQB may very well build backwards into
KGRR...KMKG and KLAN. Aviators will need to monitor trends
closely given the risk for hazardous conditions.

The low level moisture is not forecasted to go away on Sunday like
it did today for the TAF sites. Thus the impactful conditions
are most likely to persist even into the afternoon.

&&

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

Areas of fog will develop tonight with some limited visibility
through Sunday morning. Fog will gradually lift through early
Sunday in the nearshore and by early afternoon over open waters.

Waves are generally expected to be 1-2 feet on a southerly wind
through the rest of today. Winds turn out of the north ranging
10-20 knots late Sunday. Wave heights push near 3 feet over the
southern end of the lake. That`s about the best we will do. No
real concerns exist for marine interests.


&&

.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 Sunday for MIZ050-056>059-
     064>067-071>074.

     Dense Fog Advisory until 10 AM EST Sunday for MIZ037>040-043>046-
     051-052.

LM...None.
&&

$$

SYNOPSIS...JAM
SHORT TERM...JAM
LONG TERM...Ostuno
AVIATION...MJS
HYDROLOGY...MWS
MARINE...JAM



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