Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 141122
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
722 AM EDT Sat Apr 14 2018

LATEST UPDATE...
Aviation

.SYNOPSIS...
Issued at 324 AM EDT Sat Apr 14 2018

A major winter storm will continue to impact this area into
Sunday. Today rain will change to freezing rain and sleet near and
north of I-96 with some thunderstorms possible today into this
evening. Gusty winds will increase the impacts of ice
accumulations today into Sunday morning. The area of ice
accumulations will spread south to the I-94 corridor tonight.
Some slightly warmer air moves into the area Sunday afternoon but
colder air follows Sunday night into Monday changing the rain,
freezing rain and sleet to snow. Some accumulations are possible.

&&

.SHORT TERM...(Today through Monday)
Issued at 324 AM EDT Sat Apr 14 2018

I have added a Winter Weather Advisory for tonight into Sunday
morning for the I-94 corridor since the cold air will spread into
that area by sunset. As a result all areas of our CWA will see
some impacts from this winter storm event. The greatest
accumulations of ice and sleet are expected north of I-96 and east
of US-131. Our Winter Storm Headlines will remain as is.

The storm is progressing largely as expected. There will be two
periods of precipitation. The first is the band of precipitation
on the warm side of the storm, north of the squall line passing
south of Michigan this morning. The second period of precipitation
will be tonight into Sunday and that is associated with the upper
low moving into the area. This will bring the coldest air with it
and all areas should be seeing some sort of frozen precipitation
by late evening. We get a break from the precipitation (more or
less) during the midday hours of Sunday as the dry slot moves
through with the upper level system. Sunday night into Monday the
cold side of the system moves in and likely all area will see the
precipitation change to all snow by early Monday morning. That
will continue into Monday afternoon. Some accumulations are
possible.

.LONG TERM...(Monday night through Friday)
Issued at 324 AM EDT Sat Apr 14 2018

A few residual snow showers will remain possible Monday night before
diminishing on Tue. These are the result of the upper trough
lingering over the area, and some lake effect with H850 temps around
-12C early Tue. The upper trough will exit, and H850 temps will
moderate, ending any ongoing lake effect.

There will be a brief break in the unsettled weather then later Tue
through early Wed, before more unsettled weather moves back in. The
upper low in the Gulf of Alaska will dig S, and eventually lift out
into the Plains and toward MI. This system will not be as wet due to
a lack of a direct flow out of the Gulf of Mexico. It will be a bit
more progressive compared to this weekend`s system, as yet another
strong upper low pushes into the Western US and keeps the pattern
moving. Milder air will move in for a short time out ahead of the
system.

Cooler air will filter in for the end of the week, and drier
conditions will eventually move in. The air will not be as cold
behind the Wed/Thu system as it will not be tapping the colder polar
air this time around. Any showers with the low should move out by
Fri. Ridging building in should bring drier and slightly cooler than
average temps for the end of the week.

&&

.AVIATION...(For the 12Z TAFS through 12Z Sunday morning)
Issued at 722 AM EDT Sat Apr 14 2018

Expect IFR conditions with ceilings and mvfr/ifr vsby with rain
and fog this morning and it will be very windy. It will be very
windy all day and tonight also. Winds may gust to near 50 knots at
times into this evening. By this afternoon the rain should change
to freezing rain at GRR and LAN by early afternoon. There should
then be a break in the rain, so then expect drizzle of freezing
drizzle into the evening before the second area of precipitation
moves in. This time through all TAF sites should be below
freezing. The I-96 TAF sites should have some sleet mixed with the
freezing rain.


&&

.MARINE...
Issued at 324 AM EDT Sat Apr 14 2018

Gales are expected into Sunday evening before the wind subsides.
So I have not changed those headlines.


&&

.HYDROLOGY...
Issued at 330 PM EDT Fri Apr 13 2018

Region still on track for widespread precipitation event over the
next 72 hours.  Models continue to show one to two inches in general
with isolated higher amounts.  While confidence is on the expected
amounts is high...the type of precipitation is uncertain and will
impact the speed at which area rivers are affected.  Recent model
trends have been to push the colder air farther to the south...
which could produce significant delays in runoff.

Current river forecasts have locations rising to between bankfull
and flood stage.  While this seems reasonable at this time...expect
later forecasts to hone in on a solution as the precipitation type
question is answered.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Winter Weather Advisory from 5 PM this afternoon to noon EDT
     Sunday for MIZ064-065-071>074.

     Winter Storm Warning from noon today to noon EDT Sunday for
     MIZ056>059-066-067.

     Winter Storm Warning until noon EDT Sunday for MIZ037>040-
     043>046-050>052.

LM...Gale Warning until 8 PM EDT Sunday for LMZ844>849.

&&

$$

SYNOPSIS...WDM
SHORT TERM...WDM
LONG TERM...NJJ
AVIATION...WDM
HYDROLOGY...MWS
MARINE...WDM



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