Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 202350
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
650 PM EST Tue Nov 20 2018

LATEST UPDATE...
Aviation

.SYNOPSIS...
Issued at 323 PM EST Tue Nov 20 2018

Light snow accumulations mainly west of M-66 tonight could create
some slick roads through Wed morning. Below-normal temperatures
continue through Thanksgiving before a temporary recovery to
near-normal for the weekend. This Thanksgiving will likely be the
coldest since 2014 (if not a little colder), and for the date of
Nov 22nd it could be the 10th to 15th coldest on record.
Occasional breaks in the clouds through Friday will yield to
unrelenting cloud cover once again through at least the middle of
next week. A triple-header of low-pressure troughs Saturday
through Tuesday are poised to bring rain over the weekend changing
to snow at some point during the early portion of the workweek.

&&

.DISCUSSION...(This evening through next Tuesday)
Issued at 323 PM EST Tue Nov 20 2018

Alberta Clipper low passing through the northern Great Lakes
tonight will produce lake-enhanced light snow accumulations. The
heaviest snow is going to be focused within about 50 miles of
Lake Michigan, with greater amounts generally north. Still looking
at a dusting to 1 inch for most of us, but can`t rule out an
isolated 2 inches in Mason/Lake counties. With low temperatures
in the 20s away from the lake, plan for slick roads in some areas
Wed morning.

The upper level ridge that has been focused over the western
continent will progress eastward over the next few days. A surface
high and vertical subsidence late Wed into Fri will be main
feature of our weather, keeping the us mostly dry and skies
sometimes clear. The only fly in the ointment is light freezing
drizzle potential Thu night under warm advection before
temperatures climb above freezing late Fri morning. So far the NAM
and Canadian are the models advertising this potential the
strongest, and both have the greatest potential for fzdz over
Wisconsin but do extend it into areas northwest of GRR. Not
mentioning this in the forecast yet but it`s something to keep an
eye on for doorbuster traffic.

Sat looks fairly rainy (not excessively heavy) and milder as the
first of a series of troughs move through the region. The second
trough, either moving through on Sun or Mon, my start off as rain
but transition toward snow on the backside as cold air advects in
with the third trough, which settles into the longwave ridge over
the Great Lakes. While it could be cold enough to favor lake-
effect snow through midweek, the truly Arctic air will be held
closer to the pole next week.

&&

.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 650 PM EST Tue Nov 20 2018

Light snow this evening will bring areas of MVFR conditions with
ceilings 1500 to 2500 feet AGL. Conditions will improve Wednesday
morning. Southwest winds will gust over 20 knots at times this
evening.

&&

.MARINE...
Issued at 147 PM EST Tue Nov 20 2018

Increasing west winds will kick up waves hazardous to small craft
this evening, reaching 6 to 9 feet overnight with gusts to 30
knots. Winds will shift north and relax somewhat on Wednesday, but
high waves will continue through much of the day. Possible that
the waters near Muskegon could quiet down as soon as Wed afternoon
with wind becoming offshore. Small craft hazards will likely
return Friday with southerly winds.


&&

.HYDROLOGY...
Issued at 147 PM EST Tue Nov 20 2018

There are no hydrologic concerns through early next week. Light
snow today and tonight will not have an impact on river levels.

A series of low pressure systems will bring rounds of rainfall
this weekend and early next week. The rounds look to occur
Friday night into Saturday, and late Sunday into Monday before
precipitation changes back to snow by Monday evening. Rainfall
amounts do not look heavy enough to cause flooding concerns or
significant rises in rivers, creeks, and streams.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
LM...Small Craft Advisory until 5 PM EST Wednesday for LMZ844>849.

&&

$$

SYNOPSIS...CAS
DISCUSSION...CAS
AVIATION...Ostuno
HYDROLOGY...HLO
MARINE...CAS


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