Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 231135
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
635 AM EST Fri Feb 23 2018

LATEST UPDATE...
Aviation

.SYNOPSIS...
Issued at 327 AM EST Fri Feb 23 2018

Our current weather pattern favors rain events about every other
day. This morning will start with an area of rain moving through
the area but it will be out of the area by early afternoon.
Areas near Route 10 may see a little freezing rain at the start
but it should change to all rain there by mid morning. Rainfall
amounts will be light.

High pressure briefly follows this system for tonight into
Saturday but a stronger storm will track west of the Great Lakes
Saturday night bringing a period of showers and isolated
thunderstorms. Skies should clear Sunday afternoon but it will be
breezy.

High pressure moves in for Sunday night into Tuesday but then the
next system follows but this time we have a stationary front
setting up so we could see periods of rain into Friday. It will be
much warmer than normal through this entire period.

&&

.SHORT TERM...(Today through Sunday)
Issued at 327 AM EST Fri Feb 23 2018

We have a risk of freezing rain mid morning as the rain area from
WI moves into Michigan but air temperatures will be marginal and
warming as the rain moves in. Thus I canceled the Winter Weather
Advisory for Mason and Lake Counties for this morning.

Today we have an occlude front coming through the area with an
narrow band of mid level moisture. It will rain across the CWA for
about 2 to 3 hours in any one place. The highest rainfall amounts
will be south and north of our area due to the system dynamics.
The 1000/850 moisture transport vectors suggest the heaviest
rainfall will be south of I-80 this morning. Even so I could see
around a tenth of an inch of precipitation in most places. Most of
the rain will be between 6 am and 11 am. Once the rain ends skies
will not clear all that quickly as the low level moisture will be
slow to move out.

Shortwave ridging and surface high pressure will give us some dry
weather till Saturday evening. Then the next system, coming out of
the Southwestern CONUS upper trough, goes negative tilt as it
moves into the western Great Lakes Saturday night. The upper jet
core crosses the Detroit area around midnight so once again, as
supported by the 1000/850 moisture transport vectors, the
heaviest precipitation will be south of Michigan. Due to the
negative tilt of the upper wave, we get just enough instability
that an isolated thunderstorm is possible, mostly near I-69
(closer to the upper jet). That system quickly moves through and
because it is much stronger it does have enough dry air behind it
to clear or at least mostly clear skies by Sunday afternoon. Still
there is not much cold air with this system either. Temperatures
will remain well above normal through Sunday.

.LONG TERM...(Sunday night through Thursday)
Issued at 327 AM EST Fri Feb 23 2018

The long term will be much warmer than normal with highs in the 40s
except Tuesday and Wednesday when we`ll see temperatures in the 50s.

The first chance of precipitation will come Tuesday night when low
pressure over eastern Kansas moves northeast. A stationary front is
progd to set u from near South Haven to Flint. Mixed rain and snow
will likely develop north of the front across the northern half of
the cwa and that`s where we have the highest pops. Precipitation will
diminish by Wednesday afternoon.

A stronger system is will affect the cwa Wednesday night and
Thursday. This system has a decent trailing short wave which should
mean more precipitation. It will also be occluded when it reaches
Lower Michigan so the warmer air should be pinched off to the
southeast. As the system moves past, the precipitation may end as
mixed rain and snow as colder air flows south Thursday night.

&&

.AVIATION...(For the 12Z TAFS through 12Z Saturday morning)
Issued at 635 AM EST Fri Feb 23 2018

Expect IFR conditions most of the day today and largely MVFR
tonight. The area of rain will cross the taf sites between now and
16z. That will help to lower visibilities to below 2 miles at
times in rain and fog. Temperatures are just warm enough to
prevent freezing rain this morning.

Once the rain moves out, and the front moves through, visibilities
should improve to 10SM but it will become breezy with winds
gusting to 25 knots at times. Even so the low ceiling are
expected through the afternoon. Ceilings should lifting to MVFR
by this evening and that should continue through the night.

&&

.HYDROLOGY...
Issued at 328 PM EST Thu Feb 22 2018

Water that ponded into low-lying areas and smaller rivers, creeks,
and streams is continuing to slowly make its way into the larger
rivers. Moderate to major flooding is expected to occur along the
Kalamazoo, Thornapple and Grand Rivers tomorrow into the weekend.
Water levels along the Grand River are expected to approach or
possibly exceed levels reached during the flooding in April of 2013.
Water levels along the Kalamazoo River, particularly near Comstock,
are expected to near levels that occurred in September 2008.

Please see the latest flood statement or river hydrographs for
details. Hydrographs are available by going to weather.gov/grr and
clicking on the "Rivers and Lakes" tab above the map.

A wintry mix of precipitation is expected late tonight through
Friday morning. This should not impact river levels or cause ongoing
flooding to worsen. Precipitation from a low pressure system over
the weekend will spread mostly rain into the area Saturday night and
Sunday. Amounts could exceed 0.25 inches, and could approach 0.50
inches near the Michigan/Indiana border. This may slow the receding
of waters and prolong river crests for rivers that crest over the
weekend. This precipitation is not yet accounted for in river
forecasts, as it is not expected to fall within 48 hours.

&&

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

$$

SYNOPSIS...WDM
SHORT TERM...WDM
LONG TERM...04
AVIATION...WDM
HYDROLOGY...HLO


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