Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 161523
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
1023 AM EST Mon Jan 16 2017

LATEST UPDATE...
Update

Updated to move up the start times of the headlines and boost pops
over the southeast cwa. Considered adding the southern row of
counties to the headlines, but temps are already in the lower 30s
there and should move above freezing by 17-18z; we`ll continue
with the SPS for the southern row. From I-96 northward, a mix of
sleet and freezing rain will continue to progress northeast
through noon.

.SYNOPSIS...
Issued at 306 AM EST Mon Jan 16 2017

A low pressure system will track from Texas today through Michigan
on Tuesday. This system will result in a wintry mix of
precipitation for the region that changes to rain as some warmer
air tries to move in. An area of high pressure then moves in for
Wednesday.

&&

.UPDATE...
Issued at 1019 AM EST Mon Jan 16 2017



UPDATE Issued at 813 AM EST Mon Jan 16 2017

The forecast was updated to reflect a high probability of
precipitation this morning given the reports from the ASOS
observations. AMDAR sounding from GRR this am does show a rather
deep warm layer...so less of a risk for snow as well.

&&

.SHORT TERM...(Today through Wednesday)
Issued at 306 AM EST Mon Jan 16 2017

Challenging forecast today and tonight as far as timing and type
of precipitation. The main culprits is the dry airmass that is in
place and surface temperatures that will hover around freezing
for a period this afternoon and tonight as steadier and heavier
precipitation moves in.

We will issue winter weather advisories for much of the region.
The band of precipitation upstream across IL and NRN IN is mostly
aloft at this time. This is forecasted to move into southwest
lower MI this morning and early afternoon. Tough call as to how
soon and what type the onset will be. However the main type across
southern parts looks to be ZR or R depending on the surface
temperature...while further north a mix looks likely. Icing seems
to be the main risk given the warm layer that moves in today.
The window for ZR looks shorter for the southernmost counties so
we did not include them in the headline. This is is from South
Haven to Jackson. It is possible that if they do not warm up above
freezing as quickly as forecasted...the may need to be
incorporated into the headline. Up to a quarter inch of ice looks
possible further north. Fortunately the wind does not look that
strong at this time...mostly under 15 knots. A small risk exists
for even heavier amounts of ice if surface temps end up rising
above freezing slower than expected. So close monitoring is
needed for today and tonight.

.LONG TERM...(Wednesday night through Sunday)
Issued at 306 AM EST Mon Jan 16 2017

A mild period is expected for the end of the week and into early
next week.  H8 temps hold from +4C to +7C throughout the long term.
This should keep temps well above normal for this time of year,
with daytime highs mainly 45 to 50.

The overall pattern that should bring this persistent warm air into
the Great Lakes is a rather stagnate one.  Upper troughing remains
fairly stationary over the center of the nation, leading to deep
southerly flow over the Eastern U.S.  A couple of weakening waves
spin off of this trough and head toward us, but they run into an
upper ridge and weaken further.  A few rain showers may occur
Friday, then another higher chance into Sunday.  Otherwise the
January warmth will come with relatively dry conditions.

&&

.AVIATION...(For the 12Z TAFS through 12Z Tuesday morning)
Issued at 633 AM EST Mon Jan 16 2017

Impacts will be on the increase at the day progresses for
aviators. A wintry mix should start the precipitation off this
morning. Eventually the sites will go to rain...but that may not
happen til tonight on for a few of the sites.

Ceilings and visibilities will lower through the day. By tonight
LIFR looks likely. That will persist through well into Tuesday
morning.


&&

.MARINE...
Issued at 306 AM EST Mon Jan 16 2017

Despite a low pressure system moving in...the wind values are
forecasted to remain relatively low with an offshore component. As
a result...not headlines are planned with this issuance.


&&

.HYDROLOGY...
Issued at 122 PM EST Sat Jan 14 2017

Rivers are running above normal across the area due to rain, melted
snow and ice jams. The Grand River at Robinson Township has an
active warning for minor flooding. Multiple sites also have active
advisories. A period of colder than normal temperatures through the
weekend may allow river ice to thicken. Next week looks warmer than
normal with highs possibly reaching the 50s. This could melt the
river ice and allow the rivers to flush out.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Freezing Rain Advisory until 2 AM EST Tuesday for MIZ050-056>059-
     064>067.

     Winter Weather Advisory until 9 AM EST Tuesday for MIZ037>040-
     043>046-051-052.

LM...None.
&&

$$

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



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