Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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296
FXUS63 KGRR 161756
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
1256 PM EST Fri Feb 16 2018

LATEST UPDATE...
Aviation

.SYNOPSIS...
Issued at 305 AM EST Fri Feb 16 2018

A northerly flow of colder air will dominate the weather today.
Abundant clouds and a few snow showers will accompany the arrival
of this airmass. A large area of high pressure over the Central
Plains will build rapidly east today and tonight. This fair
weather system will dry our airmass out. Another cold front will
push in from the northwest later Saturday into Saturday night
possibly leading to some snow showers.

&&

.SHORT TERM...(Today through Sunday)
Issued at 305 AM EST Fri Feb 16 2018

The main challenge in the short term deals with the precipitation
potential. Overall not much risk today but an increased potential
for later Saturday into Saturday night.

Cold air advection was underway as the cold front pushes off to
the southeast. Soundings show a relatively dry airmass moving in
especially below the DGZ. Radar does show some echoes spreading
in from the southwest. Observation in IL/IA where the echoes are
show mid level clouds which happens to be where the DGZ is. Thus
the CWA will see abundant mid level clouds continuing to spread in
this morning. There is an outside chance for them to seed the
lower cloud deck here in MI...but it appears there is too much of
a dry layer to support anything over chance POPs this morning.

Mid level heights rise this afternoon and tonight as surface high
pressure tracks eastward up the OH Valley. Dry and cold weather is
expected.

Then for later Saturday into Saturday night a mid level trough
sharpens up as it moves in from the west. With increasing lift and
deepening moisture...the region will see some snow showers moving
in. The southwest low level flow out ahead of this system may
support lake enhanced moisture spreading into the region north of
Muskegon. Will feature the highest POPs there along with a
potential for minor accumulations.

.LONG TERM...(Sunday night through Thursday)
Issued at 305 AM EST Fri Feb 16 2018

A very wet system looks to be in store by Monday and lingering
through Tuesday night in some areas.

Good agreement in the models initially with deep southwest flow
pushing into the Great Lakes region Monday.  A surface boundary will
become parallel to this upper flow and rest from roughly Chicago to
Alpena.  Gulf moisture will continually be advected along this front
and periods of rain, occasionally heavy will move across the CWA.
The Monday and Monday night periods may see a half inch to one inch
of rain alone, with additional steady rains Tuesday into Tuesday
night.  However the Tuesday/Tuesday night rains seem more pegged for
the SE CWA as the front slowly sags SE through the two day period.
All and all, with the combination of the rest of the snow melting,
and this rain, hydro issues seem very possible from mid week onward.

One thing we will have to watch for, as this rain first arrives,
late Sunday night/early Monday, we may have some areas still below
freezing and a brief period of freezing rain will be possible a
couple hours either side of daybreak Monday.  Not expected too much
glaze, but it could coincide with the Monday morning commute.

Some model differences as to when the front finally clears, but it
appears it will be Tuesday night or Wednesday.  Cold air arrives for
Wednesday and Thursday.  Some areas may pick up snow late Tuesday
night/early Wednesday, but this is looking minimal, as drier air is
progged by late Wednesday into Thursday with high pressure building
in.

&&

.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 1256 PM EST Fri Feb 16 2018

Some MVFR ceilings remain across far Southern Lower Michigan with
VFR ceilings spreading in from Central Lower Michigan. The bottom
line is a continued improvement is expected this afternoon and
evening. By late afternoon, VFR weather should prevail. VFR
conditions are expected tonight and through 18z on Saturday.

Northwest winds of 10 to 20 knots are expected this afternoon.
Tonight the winds will turn southwest and decrease to below 10
knots. Winds will increase on Saturday from the southwest at 10 to
20 knots again.

&&

.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...MJS
SHORT TERM...MJS
LONG TERM...MJS
AVIATION...Duke
HYDROLOGY...CAS



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