Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 122023
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
324 PM EST Fri Jan 12 2018

LATEST UPDATE...
Synopsis/Short Term/Long Term/Marine/Hydro

.SYNOPSIS...
Issued at 324 PM EST Fri Jan 12 2018

Snow that spread across West Michigan earlier today has moved east.
Additional snow showers are expected through the weekend, mostly
near the lake shore due to a trough moving through and then another
low Monday. Saturday will be the coldest day of the next week with
highs in the teens. Then, 20s are expected most of next week.

&&

.SHORT TERM...(This evening through Sunday night)
Issued at 324 PM EST Fri Jan 12 2018

Forecast concerns deal with pcpn trends through the period.

As mentioned above, the snow has largely diminished as the pcpn
shield moves east out of the state. In its wake though, north winds
have produced light lake effect snow showers. However, given 15 dBz
echos or less, not much more than flurries have occurred. The
exception is near the Points where visibilities have fallen to 2-4sm
in light snow.

North winds in the boundary layer will continue to keep shsn near
the lake shore. By Saturday, they will begin to get a westerly
component to them and also get an assist via another upper trough
that will move across the Great Lakes. High pressure at the sfc
though will limit moisture content.

The better chance of snow will come Sunday afternoon and Sunday
night as another clipper moves through. Several inches of snow seem
possible along the lake shore and a headline may be needed.


.LONG TERM...(Monday through Friday)
Issued at 324 PM EST Fri Jan 12 2018

Models are in relative agreement and continue to show a mid level
wave digging down from the Canadian Prairies into the Great Lakes
Region Monday.  This system evolves into a closed low that slowly
drifts through the area through Tuesday. Typically these kinds of
systems lead to widespread impacts.  How much of an impacts is
somewhat uncertain...but the synoptic aspect of the low will support
accumulating snow for the region.  The atmospheric will be plenty
cold enough to keep the precipitation as all snow.  One uncertainty
will be the potential for a mid level dry slot to work in...which is
shown by the GFS at 00z Tue across the Kalamazoo to Jackson region.
It is hard to say this far out whether this will happen.  For now
will feature  high POPs and the potential for accumulations right
through Mon night.

As the system pulls away later Tuesday the lake enhanced band could
continue to impact the lakeshore region well into Tuesday night.

Overall the models show mid level height rises Thursday into Friday.
This will support a moderating trend to the temperatures.  If the
trends continue we may see well above normal temperatures by
Saturday.

&&

.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 1238 PM EST Fri Jan 12 2018

The band of snow is forecasted to keep pushing east of the TAF
sites this afternoon...slowly. Impacts will be seen mainly around
KJXN. Along the lakeshore...there will be some lake effect snow
showers...which could move into the KMKG region this afternoon.
Otherwise...a trend toward VFR is forecasted into Saturday. Local
gusts over 25 knots from the north are possible this afternoon.


&&

.MARINE...
Issued at 324 PM EST Fri Jan 12 2018

We canceled the gale warning and issued a small craft advisory. The
SCA will be in effect through 6 pm Saturday.

&&

.HYDROLOGY...
Issued at 324 PM EST Fri Jan 12 2018

The water from the snow melt of late has made it into the rivers
across the area and some minor river flooding is ongoing. The colder
temperatures that have moved back into the region will cause ice to
reform and solidify into next week. Therefore, additional flooding
is not expected and river ice will likely be locked down by the end
of the weekend. Will need to monitor rivers for potential ice jam
flooding.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
LM...Small Craft Advisory until 6 PM EST Saturday for LMZ844>849.

&&

$$

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



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