Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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187
FXUS63 KGRR 210739
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
240 AM EST Tue Feb 21 2017

LATEST UPDATE...
Synopsis/Short Term/Long Term/Climate/Marine

.SYNOPSIS...
Issued at 240 AM EST Tue Feb 21 2017

Rain showers associated with a weak cold front will move through the
area through this morning. The showers will come to an end at most
locations by afternoon, and clearing skies can be expected.

We will see one more potential record warm day on Wednesday as
another surge of warmth will move up over the area ahead of the next
system that will pass through Wednesday night into Thursday. A much
stronger system will begin to move in late Thursday and on Friday.
This will bring more widespread rains and a few storms, some of
which could become strong.

Colder air will move in Friday night and Saturday behind the system.
This will change rain showers over to some light snow across the
area before they end on Saturday. Cooler weather can then be
expected through early next week.

&&

.SHORT TERM...(Today through Thursday)
Issued at 240 AM EST Tue Feb 21 2017

Our items of interest in the short term are rain chances for today
and again Wed night/Thu, and the potential for record max temps. No
real changes have been made to the fcst.

Band of rain showers to our west and southwest are slowly
progressing toward the area on schedule. Moisture transport is
holding its own supporting these showers, but will start to weaken
as it moves through the area. We are still expecting that they will
exit most of the CWFA by early afternoon. We should see the clouds
clear out and allow temps to warm back up into the 50s and 60s.

We should stay dry then for tonight and Wednesday, although we can
not rule out a sprinkle during the time frame. We will see the cold
front moving through today return north as a warm front later
tonight and Wed. Moisture is quite limited, so we are not really
expecting anything.

As we get into the warm sector on Wed, record highs will once again
be likely. SW flow will limit the heating potential a bit for areas
downwind of Lake Michigan. Areas further S and E will see much
better warming without the influence of Lake Michigan. The I-94
corridor will have a chance of touching 70 with H850 temps of around
10-11C nosing in.

Another cold front will push through prior to daybreak Thu morning.
The chances of rain are not zero with this, but moisture is rather
limited once again for the time being. This will change late Thu
afternoon and more so after the short term. The front will get hung
up once again as the main low approaches the area, and starts to
advect much better moisture from the Gulf over the front.

.LONG TERM...(Thursday night through Monday)
Issued at 240 AM EST Tue Feb 21 2017

Forecast concerns continue to deal with a fairly strong storm that
is progd to move across Lake Michigan and central Lower Michigan
Friday. Both the ecmwf and gfs show similar structure, track and
timing which is leading to higher confidence in the solution.

GFS ensemble mean shows a warm front moving north across the cwa by
12z Friday. The sfc low is progd to move from northeast Iowa at 12z
to northern Lower by 00z Saturday. A 50 kt llj will draw abundant
moisture north from the Gulf. As this moisture crosses the northward
moving warm front Thursday night, showers will develop. Across the
northern cwa where sfc temps will be aob freezing, some freezing
rain is possible. This could last for 6 hours or so before warmer
air arrives in the 12z-15z time frame.

Instability quickly increases with li`s falling to -4c or so by 18z
Friday. Strong dynamics with respect to lift such as the approaching
cold front, upper short wave, and the arrival of the left exit
region of the upper jet will provide favorable conditions for
convection. Shear values around 50 kts strongly point toward
organization. While this doesn`t look like a tornadic situation...
hodographs are rather meager... Friday afternoon could be our first
severe wx day of the year with strong wind the main threat and 16z-
24z the main time frame. It`s only Tuesday, so we won`t get too
carried away with this as the models will change some by Friday.

After the trailing cold front moves through late Friday, colder air
will flow into the state. H8 temps fall from -12c Saturday morning
to -16c by Sunday morning. We have snow showers in the grids.
Moisture appears limited with this situation so accums will be
limited.

&&

.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 1207 AM EST Tue Feb 21 2017

A weak cold front will move across Lower Michigan this morning.
Obs along the frontal boundary show IFR/MVFR conditions and we
expect those lower cigs/vsbys to develop after 10z. National radar
shows a long train of echos from Lake Superior south to the Gulf
and some of these showers will work their way up and through the
taf sites this morning. Skies will clear this afternoon, but
residual moisture near the ground may result in more fog
development tonight.


&&

.MARINE...
Issued at 240 AM EST Tue Feb 21 2017

We will need to hold on to the Small Craft Advisory for just a few
more hours this morning. Winds will be coming down, but waves will
take a little longer to come down sufficiently below the 4 ft
criteria.

There is a chance another advisory will be needed for the Wed time
frame. This will be just out ahead of the next frontal system that
will move through the area. We are not sure if the winds aloft will
be able to mix down. It is something worth monitoring.

&&

.HYDROLOGY...
Issued at 100 PM EST Mon Feb 20 2017

Basin average rainfall through tomorrow is expected to be ranging
from a couple tenths of an inch over the Grand and Kalamazoo River
basins to perhaps a half inch across the western reaches of the
Muskegon River basin. This rainfall should not lead to any
appreciable rises on the main stem rivers. More substantial
rainfall is possible Thursday night through Friday as a
strengthening storm system approaches the Great Lakes. The
placement of this heavier rainfall is still in question, but
models are indicating an inch or more possible where it does set
up. Both small stream and main stem river rises look likely if
this pattern holds.

&&

.CLIMATE...
Issued at 240 AM EST Tue Feb 21 2017

The records for our official sites through Wednesday are as follows:

                 Tue 2/21            Wed 2/22

Grand Rapids     66 - 1930           67 - 1930

Lansing          62 - 1930           66 - 1930

Muskegon         58 - 1930           55 - 1930

Our current thinking is that we will come up just shy of all of the
records for today. A little extra sunshine, and they could be
approached.

The records for Wednesday do look in jeopardy of being broken for
the most part. The most difficult one will be Grand Rapids, but it
will be close.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
LM...Small Craft Advisory until 11 AM EST this morning for
LMZ844>849.

&&

$$

SYNOPSIS...NJJ
SHORT TERM...NJJ
LONG TERM...04
AVIATION...04
HYDROLOGY...Hoving
CLIMATE...NJJ
MARINE...NJJ



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