Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 141741
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
1241 PM EST Sun Jan 14 2018

LATEST UPDATE...
Aviation

.SYNOPSIS...
Issued at 330 AM EST Sun Jan 14 2018

Lake effect snow showers will impact the shoreline again today,
before a more widespread light snow develops tonight and continues
on Monday. Most locations will see an inch or so tonight and
another inch or two on Monday. The Monday morning commute could
feature slick conditions.

Additional snow showers are expected Monday night and Tuesday,
with the potential for several inches of lake effect snow around
South Haven. Cold air will stay with us through midweek then a
warmup will occur toward the end of the week with highs next
weekend up around 40.

&&

.SHORT TERM...(Today through Tuesday)
Issued at 330 AM EST Sun Jan 14 2018

Localized snow accumulations of an inch or two are possible today
along the lakeshore, particular in the Muskegon and Grand Haven
areas. The low level flow continues to back, and good convergence
is progged along the coast (maximized near MKG around Noon) as
the southwest flow over Lk MI interacts with the overnight land
breeze.

Inversion heights today are relatively low around 5K ft, so the
snow should not get too out of hand. The coastal snow showers are
expected dissipate later today and this evening while lifting
north as the low level flow turns more southeasterly due to
apching synoptic system.

Really no change regarding the widespread synoptic light snow
tonight related to the warm advection/isentropic lift component of
the approaching low. A rather deep DGZ is progged but the
lift is meager. Only about an inch of snow is expected overnight,
but it may still be enough to make for a slick Monday morning
commute considering the cold sfc temperatures of 10-15.

On Monday the ocnl widespread light snow continues as the upper
low drops into Wisconsin and a shortwave and the sfc occlusion
pivot into the area from the southwest. The sfc occlusion/trough
is shown to set up in a west-east fashion across srn lwr mi on
Monday night into Tuesday and highest pops and additional light
snow amounts will be with the enhanced convergence along this
feature.

The big wild card in later periods is if and where the heavy mid
lake convergence band decides to come onshore. The northern end of
this band is expected to head toward Door County/Green Bay Sunday
night and Monday due to easterly flow north of the sfc low.
However there is some indication that the srn end of it will come
onshore around South Haven Monday night and Tuesday. This will
need watched since some impressive snowfall rates could develop
if/where/when it comes onshore.

.LONG TERM...(Tuesday night through Saturday)
Issued at 330 AM EST Sun Jan 14 2018

Lake effect snows will continue Tuesday night, but then should
gradually diminish Wednesday.  The flow should be NNW which will
favors western Allegan and Van Buren Counties to see the steadiest
snows, with lighter snows from U.S. 131 and west.  Mainly another
inch or two, localized 4 inches in western Allegan and Van Buren.

A pattern shift occurs Wednesday night and this should last into
next weekend.  The upper flow becomes more zonal, with surface high
pressure centered over the TN Valley Thursday.  This high moves to
the Carolinas by Friday night.  This brings a SW low level flow over
the Great Lakes region and H8 air around 0C pushes in. The models
are in much better agreement on this as compared to last night`s
runs. Daily high temps should moderate each day in this set up,
warming from the low 20s Wednesday, to around 40 by Saturday.  For
the most it looks dry in this period too, until perhaps Saturday
when we see a cold front move into the upper Midwest.  This may
bring some rain, possibly mixed with snow north.  Even higher
chances of rain should move in early next week as the front arrives.
Cold air and a change back to snow appears to not occur until Sunday
night.

&&

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 1238 PM EST Sun Jan 14 2018

The band of heavy snow that impacted KMKG was moving northward
with time and should be north of the TAF site by 19z. There are
still some residual snow showers offshore that will need to be
monitored as they may approach the TAF site in the next hour or
two. Otherwise...for the remainder of the region the patchy MVFR
clouds should give way to VFR conditions this afternoon.

Next up the an area of snow that will be spreading in from the
west tonight. This will be a longer duration event. IFR looks
likely to develop tonight and then persist through much of Monday.

&&

.MARINE...
Issued at 330 AM EST Sun Jan 14 2018

We have considerable ice in the nearshore area, especially south
of Whitehall, so no small craft advisory issued despite
increasing southerly flow today.


&&

.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...None.
LM...Small Craft Advisory until 5 PM EST Monday for LMZ844>849.

&&

$$

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


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