Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 011841
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
141 PM EST Wed Mar 1 2017

LATEST UPDATE...
Hydro

.SYNOPSIS...
Issued at 315 AM EST Wed Mar 1 2017

Low pressure will move east and colder air will arrive today with
rain changing to snow by the afternoon. Snow and gusty winds could
impede travel by this evening across central and northern Lower
Michigan. Lake effect snow showers will continue through the end
of the week.

&&

.UPDATE...
Issued at 1221 PM EST Wed Mar 1 2017

The winter wx advisory was unchanged and remains in effect until 9
pm for our northern fcst area. Moderate snow was falling at KLDM
and pcpn will quickly changeover to snow across the rest of the
area in the advisory due to brisk north flow caa. Snow may become
heavy at times due to strong mid level fgen forcing and
deformation zone processes.

We did tweak the snow amount fcst up a bit for our west central
fcst area including KGRR as a consensus of higher resolution
guidance suggests snow should increase very late this afternoon
through the evening. This notion is supported by upstream obs
trends in Wisconsin which indicate fairly widespread moderate to
heavy snow and rgnl radar trends.

&&

.SHORT TERM...(Today through Friday)
Issued at 315 AM EST Wed Mar 1 2017

Will keep the winter weather advisory across the north although
snow amounts were lowered based on model QPF trends. This is
looking more like 2 to 4 inches of snow rather than a 4 to 6 inch
event.

Colder air filters in from the northwest today and area of f-gen
snow should arrive for the afternoon across the north then moves
south and weakens during the evening. Impacts should be minor
although there could be some slippery spots on untreated roads as
temperatures drop well below freezing overnight.

Cyclonic flow and shortwave trough axis should allow for some
light accumulations of lake effect snow Thursday and Thursday
night. A clipper passes south of Lower Michigan Thursday night as
well and some f-gen snows could extend into the southern zones.

Lowered blended temps a bit Thursday and Friday as this still
looks to be a cold air mass with cold air advection continuing
through the period.

.LONG TERM...(Friday night through Tuesday)
Issued at 315 AM EST Wed Mar 1 2017

Friday night and Saturday look dry as high pressure at the sfc and
aloft moves over Michigan. As the high moves east Sunday, a warm
front will push north through the cwa and we may see a shower with
that. Otherwise, the next weather maker will be the development of a
low over the upper Mississippi Valley. Medium range models show a
strong short wave accompanying it. Southwest flow ahead of the
trailing cold front will push moisture northward and we`ll see
showers develop ahead of the cold front Monday and Monday night.
Colder air advecting south behind the system Tuesday may result in
some mixed rain and snow as the upper short wave passes through.

Highs through the period will be in the 40s and 50s.

&&

.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 1245 PM EST Wed Mar 1 2017

I expect and area of snow to cross the TAF sites between 19z-20z
at MKG and 00z at JXN. The snow will last 3 to 5 hours at any one
site. MKG and GRR should see 2-3 hours of moderate to heavy snow
(based on the HRRR and RAP models) from late afternoon into early
this evening. Since there will be strong northwest winds of 20 to
30 knots gusting 35 to 40 kts and temperatures will fall below
freezing before sunset, I would also expect blowing snow too.

All of this should be done by 06z then just MVFR cigs through
Thursday afternoon.

&&

.MARINE...
Issued at 315 AM EST Wed Mar 1 2017

Small craft advisory will be in effect today and tonight with
winds gusting to 30 knots at times.

&&

.HYDROLOGY...
Issued at 141 PM EST Wed Mar 1 2017

One to over two inches of precipitation fell over most of Southwest
Lower Michigan over the last couple of days and considerable rises
are occurring on area rivers. Only minor flooding is expected
through the weekend. Another system early next week may drop another
inch of rain and may lead to increased flooding problems through
next week.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Winter Weather Advisory until 9 PM EST this evening for
     MIZ037>040-043>045.

LM...Small Craft Advisory until 8 AM EST Thursday for LMZ844>849.

&&

$$

UPDATE...Laurens
SYNOPSIS...Ostuno
SHORT TERM...Ostuno
LONG TERM...04
AVIATION...WDM
HYDROLOGY...63
MARINE...Ostuno


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