Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 142343
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
643 PM EST Sun Jan 14 2018

LATEST UPDATE...
Aviation

.SYNOPSIS...
Issued at 320 PM EST Sun Jan 14 2018

An approaching clipper system will move across Michigan tonight and
Monday bringing widespread light snow beginning around midnight and
continuing through Monday. Generally 1-3 inches of snow is expected,
but a local accumulation of around 4 inches seems possible too.
Warmer weather is expected toward the end of the week as southwest
winds develop when high pressure moves across the Ohio Valley and
highs in the 40s are expected by the weekend along with some rain.

&&

.SHORT TERM...(This evening through Tuesday night)
Issued at 320 PM EST Sun Jan 14 2018

Forecast concerns deal with the approaching clipper.

Regional radar shows light returns moving across the upper
Mississippi Valley moving toward Lake Michigan and we expect light
snow to develop around midnight and then continue through Monday.
The sfc low is progd to move across Chicago Monday and then pivot
over I-94 during the afternoon. The occluded front that lifts north
into Lower Michigan will likely become a focus for the higher totals
in the range. Mainly looking at 1-2 inches north of I-96 and 1-3
inches south of I-96. It`s certainly possible that a few local
accums could be around 4 inches. This snow will affect the morning
and perhaps evening commutes and we issued a Winter Weather Advisory
along and south of I-96 from midnight tonight through 00z Tuesday.

The other thing to consider is that a dominant lake band of snow is
expected to develop north/south over the lake. Initially, this band
will move east over Wisconsin, but as the sfc low moves east, the
lake band will eventually drift out over the lake and perhaps clip
the southwest cwa Monday evening. The snow will diminish Monday
night, but some lake effect will develop near the lake shore Tuesday
as colder air moves over the lake.

Highs will remain below normal through the period...in the lower
20s.

.LONG TERM...(Wednesday through Sunday)
Issued at 320 PM EST Sun Jan 14 2018

The pattern starts off with warm air advection on Wednesday as the
mid level low pulls off to the east.  The low level flow will be
westerly at the surface which then backs southwest going into
Friday.  Thus...several days of moderating temperatures are
expected.  The moisture will be limited as the Gulf moisture remains
cut off from the region.  Mid to high level clouds will likely be
around as Pacific moisture spills over the ridge located to the
west.

Models are advertising a stronger low ejecting out of the Southern
Rockies next weekend.  Considerable differences exist which results
in highly variable potential impacts.   The GFS tracks a stronger
low through the CWA with heavy snow for northern parts of the CWA an
ice storm in the middle and heavy rain down south.  The High Res
Euro tracks the deepening low northward through WI on Sunday.  This
would leave the CWA in the warm sector with the main impacts being
rain/rivers with perhaps some thunderstorms.  Will maintain the
forecast of mostly rain...transitioning to snow as the low goes by.

&&

.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 643 PM EST Sun Jan 14 2018

VFR conditions will continue this evening then snow will begin
around 04Z at MKG spreading east and reaching LAN and JXN by 08Z.
Conditions will quickly go IFR at the onset of the snow and remain
there through Monday afternoon. Some LIFR is possible at times in
heavier snow bands. Winds will be southeast around 10 knots.

&&

.MARINE...
Issued at 320 PM EST Sun Jan 14 2018

A small craft advisory remains in effect through Monday afternoon.


&&

.HYDROLOGY...
Issued at 1215 PM EST Sun Jan 14 2018

Minor flooding ongoing at a few sites. Cold temperatures have lead
ice to reform and solidify on area rivers. Additional flooding is
not expected and rivers will likely be locked down through the week.
Will need to monitor rivers for potential ice jam flooding toward
next weekend, as warmer air is expected to return.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Winter Weather Advisory from 11 PM this evening to 7 PM EST
     Monday for MIZ050-056>059-064>067-071>074.

LM...Small Craft Advisory until 5 PM EST Monday for LMZ844>849.

&&

$$

SYNOPSIS...04
SHORT TERM...04
LONG TERM...MJS
AVIATION...Ostuno
HYDROLOGY...63
MARINE...04



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