Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 160525
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
1225 AM EST Fri Feb 16 2018

LATEST UPDATE...
Aviation

.SYNOPSIS...
Issued at 330 PM EST Thu Feb 15 2018

Dense fog over the I-94 corridor will dissipate this evening as a
cold front moves through the state. The sun will return Friday as
high pressure moves overhead. Snow is expected Saturday afternoon
and evening as low pressure aloft moves quickly through the region.
Rain is expected early next week as a series of low pressure systems
move across Lower Michigan. Temperatures will rise into the 50s
Monday and Tuesday ahead of those low pressure systems.

&&

.SHORT TERM...(This evening through Saturday night)
Issued at 330 PM EST Thu Feb 15 2018

Forecast concerns deal with ongoing dense fog and precipitation
chances Saturday afternoon and evening.

Observations reveal widespread dense fog near the I-94 corridor.
Visibilities are at or below a quarter mile there. However, farther
north, visibilities are in the 4-5 mile range. We have discontinued
the dense fog advisory except for the southern row from Van Buren
county east and extended it there for another hour to 6 pm.

A cold front is moving across the lake at this time and will provide
the ending for the dense fog from west to east as it moves through.
H8 temps will fall from 4c this afternoon to -8c by 12z Friday. It`s
possible we could see a few lake effect snow showers over the
northwest cwa, but the air quickly dries out as high pressure moves
in and we should see quite a bit of sunshine by Friday afternoon.

Both the ecmwf and gfs show a compact short wave moving across Lower
Michigan Saturday afternoon. This system could produce 1-2 inches of
snow with a bit more possible along the lake shore before it moves
east Saturday night.

.LONG TERM...(Sunday through Thursday)
Issued at 330 PM EST Thu Feb 15 2018

Zonal flow aloft to begin the long term on Sunday quickly turns into
a deep southwest flow into Monday and Tuesday. The main story in the
long term is the potential for heavy rain early next week when we
are in the deep southwest flow pattern. Both the GFS and the ECMWF
are showing 1 to 2 inches of rainfall across the CWA early next
week. There is uncertainty still about where exactly a heavier axis
of rain would set up, but it should be in or near Southwest Lower
Michigan. The warm nose at 850mb`s moves into Lower Michigan as a
surface low rides through our forecast area. Periods of heavier rain
and potentially even a bit of thunder look possible from Monday
night into Tuesday. There will be a mix of rain and snow Sunday
night into Monday as the colder low level air erodes. The cold air
works back in on Tuesday night changing rain back over to snow.

Temperatures will be a bit of a roller coaster, with warming
southerly winds bringing 50s on Monday and Tuesday. We will cool
back toward normal into the 30s for highs on Wednesday and Thursday.

&&

.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 1225 AM EST Fri Feb 16 2018

MVFR ceilings along with MVFR vsbys in light snow was sagging
south from Northern Lower. This will cover the TAF sites by 09Z.
The snow will be brief, and some areas may not see any, but the
MVFR ceilings are expected to linger into the afternoon. Skies
will then clear from the north through mid/late afternoon,
producing VFR conditions that will continue into the evening.

Northwest winds will increase early this morning to 10 to 15
knots.  These winds diminish by late afternoon/early evening.

&&

.HYDROLOGY...
Issued at 1059 AM EST Thu Feb 15 2018

Snow water content in the Grand River basin is about 1.5 inches,
and about a half inch of it is expected to melt today. The
Looking Glass River near Eagle and Sycamore Creek in Holt may rise
out of bank over the next couple days in response to this
snowmelt. Ionia may do the same. Ice on the rivers will continue
to cause short term fluctuations. A low confidence of heavy rain
with a medium confidence of total snowmelt Mon to Tue will likely
keep river levels elevated with an outside chance of more
substantial flooding.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
LM...None.
&&

$$

SYNOPSIS...04
SHORT TERM...04
LONG TERM...Duke
AVIATION...JK
HYDROLOGY...CAS



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