Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 051808
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
108 PM EST Tue Dec 5 2017

LATEST UPDATE...
Update

.SYNOPSIS...
Issued at 305 AM EST Tue Dec 5 2017

A strong cold front will push east of the region today. Strong
gusty winds will usher in a much colder airmass behind this front.
Lake effect snow showers will be on the increase as we go through
the remainder of the week as an arctic airmass moves in.

&&

.UPDATE...
Issued at 100 PM EST Tue Dec 5 2017

I am strongly considering a Winter Weather Advisory for my Lake
Shore Counties from late tomorrow afternoon into Thursday
afternoon. Seems the models have slowed down when the significant
snow happens but there is still lift in the DGZ. The largest snow
amounts will be in Mason, Lake, Allegan and Van Buren Counties.
There is a time window when the cloud layer wind is from the west
to northwest so some of the I-94 to I-96 counties would see some
accumulation but I do not think it would be enough for and
advisory. The other reason to do this is this is the first event
of the season were I think there will be measurable snow and it
will impact the morning drive Thursday morning.

&&

.SHORT TERM...(Today through Thursday)
Issued at 305 AM EST Tue Dec 5 2017

Based on the forecasted wind profiles and mixing heights
today...many areas in the CWA should see gust up around 40 knots.
The wind will happen in waves. One with the frontal passage early
this morning...then as the mixing height increases during the
daylight hours...another surge in the impactful winds should
occur.

I don`t see much potential for accumulating snow today into the
start of Wed. Strong winds will carry any snow showers well inland
limiting the intensity as well. That changes as we go through
Wednesday and more so Wednesday night into Thursday. The
continued veering winds will become more west northwest with
increasing low level directional convergence. The speeds will also
decrease somewhat. Thus accumulating snow should become more of
an issue then.

.LONG TERM...(Thursday night through Monday)
Issued at 305 AM EST Tue Dec 5 2017

A long wave upper trough will result in colder than normal weather
into early next week.

The ecmwf and gfs are similar in their solutions late this week
through the weekend. A series of short waves will carve out a deep
upper long wave trough over the Great Lakes which will funnel cold
air into the state. The cold air, in turn, will help to create lake
effect snow showers due to the significant instability over the
lake. There was little change to the forecast as the models have had
a good handle on this cold snap.

Snowfall will generally be light but persistent during the period
and accumulate the most along and west of US-131. Accumulations of 3
to 6 inches are possible from Thursday night through Saturday night
along the lake shore.

Highs will mostly be in the 25 to 30 degree range Friday and
Saturday before warming into the lower to mid 30s Sunday and Monday.

&&

.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1254 PM EST Tue Dec 5 2017

The main aviation weather item the next 24 hours will continue to
be the wind. The strong winds will continue through 03z or so this
evening at which time it will lose its gustiness at most sites.
Southwest winds of 20-40 knots will continue through the remainder
of the afternoon, with a tapering off away from Lake Michigan
between 00z and 03z. Overnight, inland TAF sites will see the wind
diminish to a sustained 13 knots or so. Winds will pick up again
after daybreak on Wednesday increasing into the 15 to 25 knot
range.

As far as clouds and weather, the MVFR ceilings should lift to VFR
this afternoon. Clouds will even tend to scatter out a bit this
evening and into the overnight hours. Ceilings will return towards
12z Wednesday when lake stratocumulus redevelops around 3,500ft.
There will be a few snow showers around this evening between 21z
and 03z. A better chance for snow showers will be developing
during the midday hours of Wednesday.


&&

.MARINE...
Issued at 305 AM EST Tue Dec 5 2017

Will maintain the Gale Warning. All sites along the lakeshore
are currently well withing the gale range. The pressure gradient
and mixing remain favorable for the gale force winds to continue
well through tonight.


&&

.HYDROLOGY...
Issued at 1257 PM EST Mon Dec 4 2017

Precipitation will fall as rain through tonight before colder air
rushes in behind a strong cold front and precipitation transitions
to snow. Total rainfall from this morning through Tuesday morning is
expected to range between 0.25 and 0.70 inches, which will not be
enough to cause significant rises on rivers and streams. Totals
exceeding 0.5 inches will most likely occur along and north of I-96.
A few thunderstorms may develop late this evening and overnight.
These would produce locally heavier rainfall amounts, and could
result in water ponding on roadways and low-lying areas.

Precipitation from Tuesday afternoon into the weekend will fall as
snow as temperatures remain below freezing. High snow-to-liquid
ratios will result in some snow accumulations (especially near the
lakeshore), but no significant liquid-equivalent accumulations.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Wind Advisory until 7 PM EST this evening for MIZ037>040-043>046-
     050>052-056>059-064>067-071>074.

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

&&

$$

UPDATE...WDM
SYNOPSIS...MJS
SHORT TERM...MJS
LONG TERM...04
AVIATION...Duke
HYDROLOGY...HLO
MARINE...MJS



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