Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 151200
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
700 AM EST Mon Jan 15 2018

LATEST UPDATE...
Aviation

.SYNOPSIS...
Issued at 330 AM EST Mon Jan 15 2018

A slow moving low pressure system will bring occasional snow
through Tuesday. Temperatures will moderate late in the week,
with highs in the 40s expected next weekend.

&&

.SHORT TERM...(Today through Wednesday)
Issued at 330 AM EST Mon Jan 15 2018

The only change to the existing advisory is to extend Allegan and
Van Buren counties through 7 AM Tuesday. Some heavier lake
enhanced snow showers may set up in these counties tonight.

Widespread, generally light, snow expected to persist today as
upper low currently over MN continues dropping to the south-
southeast. Some breaks in the snow may occur, especially this
afternoon, once the isentropic lift component is lost and some
mid level drying comes in from the southwest. However the sfc
occlusion pivots into srn lwr mi this afternoon and will keep the
ocnl light snow going - especially south of I-96.

For tonight that sfc occlusion becomes a pronounced sfc trough
situated from roughly South Haven to Lansing and will have a band
of likely pops with the low level convergence zone associated
with this feature.

Potential exists for some heavier localized snowfall rates to
develop in portions of Allegan and Van Buren counties along the
sfc trough axis and close to the sfc low. Also strong low level
FGEN forcing may develop in this area where much colder sfc air
from nrn Indiana/far srn lwr MI interacts with the milder lake
influenced air over these counties.

On Tuesday the sfc trough shifts slightly farther south and east
and the flow over Lk MI becomes more northerly or even north-
northeasterly. This should cause the heavier snow band over
Allegan and Van Buren tonight to migrate toward Berrien Co and NW
Indiana. Then on Tuesday night the flow backs which sends the
lake effect back into the coastal counties.

.LONG TERM...(Wednesday night through Sunday)
Issued at 330 AM EST Mon Jan 15 2018

The models show a bit of a blip in our warm up for late in the week.
A fairly impressive looking short wave is progged to move through
Thursday evening. This may bring some light snow with it, with
colder air behind it for Thursday night.

The cold should be brief, as the warm up should be in full gear as
the flow becomes zonal and a southwest low level flow brings +2-3C
air Friday and into the weekend.  Deep southwest flow gradually
develops, along with a cold front that approaches by Saturday night.
 The front should be a slow mover and could result in some decent
rains. Rain chances start on Saturday, but this looks rather light
with limited lift. But better chances of steady rains should move in
by late Saturday night and into Sunday as the front moves in.  The
models are not in good agreement by Sunday with a wave that moves
along the front. Depending on the timing/location of this wave will
be critical to the amount of rain we see and whether we will face
some hydro issues.

It appears colder air returns about Monday when the pcpn should
switch back to snow.

&&

.AVIATION...(For the 12Z TAFS through 12Z Tuesday morning)
Issued at 700 AM EST Mon Jan 15 2018

Widespread IFR vsbys will persist today as light snow continues to
impact the area. The snow should diminish in coverage and
intensity tonight leading to slightly improved vsbys, but the
arrival of the sfc low and occlusion into srn lwr mi should
promote some lower IFR cigs.

&&

.MARINE...
Issued at 330 AM EST Mon Jan 15 2018

No change to the SCA.

&&

.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 until 7 PM EST this evening for MIZ050-
     056>059-065>067-072>074.

     Winter Weather Advisory until 7 AM EST Tuesday for MIZ064-071.

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

&&

$$

SYNOPSIS...Meade
SHORT TERM...Meade
LONG TERM...JK
AVIATION...Meade
HYDROLOGY...63
MARINE...Meade


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