National Weather Service Raw Text Product

172 
FXUS63 KGRR 121742
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
1242 PM EST Fri Jan 12 2018

LATEST UPDATE...
Aviation

.SYNOPSIS...
Issued at 330 AM EST Fri Jan 12 2018

Arctic air returns to the region today behind a cold front and
will be with us into next week. Some roads will be slick for the 
morning commute as temperatures fall into the 20s and residual
moisture freezes up. Also a 1 to 4 inch snowfall is expected this
morning for areas south and east of a line from South Haven to 
Alma.

Lake effect snow will occur near Lake Michigan over the weekend
but no significant accumulations are expected. A more widespread 
snow is expected beginning Sunday night and continuing through 
Tuesday, with some light accumulations likely over most of the 
area.

&&

.UPDATE...
Issued at 1105 AM EST Fri Jan 12 2018

We trimmed most of the western counties from the advisory leaving
Gratiot and Ionia from the group that is scheduled to expire at 1
pm. The eastern group remains unchanged. 

Latest radar trends show the back edge of the pcpn slowly moving
east but will take several more hours until it clears the cwa.
Meanwhile, light snow showers in north flow can be seen on radar
over the west/northwest cwa, but accums will be limited to less
than an inch this afternoon. 

UPDATE Issued at 926 AM EST Fri Jan 12 2018

Increased snow amounts for east and southeast counties as the
banding continues. I did add inch per hour rates to the WSW. High
res models show the snow diminishing later this morning into the
afternoon.  No other changes at this time.

&&

.SHORT TERM...(Today through Sunday)
Issued at 330 AM EST Fri Jan 12 2018

No changes to the existing Winter Weather Advisory. Good lift and
FGEN forcing will be present this morning as upstream mid level
trough deepens and moves east. Also there is plenty of moisture to
work with as precip transitions quickly to snow, with 4-5 g/kg 
mixing ratios still noted on the 300K sfc from GRR to the south 
and east.

Snow could become briefly heavy at times during the morning commute,
and some localized 4-5 inch total accums cannot be ruled out 
within any of the more intense FGEN bands which set up south and 
east of GRR. The period of freezing rain and sleet in the 
transition zone is expected to be relatively brief this morning 
given the fast arrival of the cold air behind the front, and have 
raised total snow amounts a bit for the LAN/JXN/BTL areas. This is
supported by latest trends in the HRRR which are farther north 
and west with the snow this morning and show the banded nature of 
the snow. 

Most of the snow should be done by noon, but increasing northerly
winds could lead to some blowing snow lingering into the 
afternoon where accums occur. 

Things turn relatively quiet but cold after today. The lake 
effect snow over the weekend does not look too impressive since 
moisture is fairly shallow and inversion heights generally below 
5K feet. However there still may be some localized light 
accumulations west of Highway 131.

.LONG TERM...(Sunday night through Thursday)
Issued at 330 AM EST Fri Jan 12 2018

A stacked low is progged to be moving into the Western Great Lakes 
by early next week.  This will keep the region in the cold air, 
along with a prolong period of snow that should start late Sunday 
night and last until Monday night or Tuesday.  This system will also 
see some lake enhancement with H8 temps around -15C.  This will be 
mainly true once the low is to our east, by Monday night.  Snow 
amounts could be rather impressive, with 2-4 inches expected inland, 
and perhaps 6-9 inches for areas west of U.S. 131 by Tuesday 
morning.  Once this system is to our east another reinforcing surge 
of arctic air moves in for Tuesday and Wednesday. Lake effect snow, 
mainly hugging the coast should persist these two days.

By Wednesday night and Thursday temperatures should not be as cold 
as an upper ridge builds over the upper Midwest.  Surface high will 
also accompany the ridge, so it appears dry for this period.

&&

.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 330 AM EST Fri Jan 12 2018

Gales and freezing spray expected on Lake Michigan as arctic air 
pours in. 


&&

.HYDROLOGY...
Issued at 957 AM 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...Winter Weather Advisory until 7 PM EST this evening for MIZ059-
     066-067-073-074.

     Winter Weather Advisory until 1 PM EST this afternoon for MIZ052-
     058.

LM...Gale Warning until 4 AM EST Saturday for LMZ844>849.

&&

$$

UPDATE...04
SYNOPSIS...Meade
SHORT TERM...Meade
LONG TERM...JK
AVIATION...MJS
HYDROLOGY...63
MARINE...Meade