Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 201808
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
108 PM EST Mon Feb 20 2017

LATEST UPDATE...
Hydro

.SYNOPSIS...
Issued at 323 AM EST Mon Feb 20 2017

More record setting warmth looks likely this week for Lower
Michigan. Highs will be in the 50s and 60s for much of this week.
Dry and quite a bit of sunny weather can generally be expected
through Wednesday. A quick burst of rain is expected late tonight
and Tuesday morning.

More rain is likely late Thursday and Friday as another system moves
into the area. Colder air will move in Friday night and Saturday.
This will change rain over to a little bit of light snow early
Saturday.

&&

.SHORT TERM...(Today through Wednesday)
Issued at 323 AM EST Mon Feb 20 2017

Our main challenge in the short term is dealing with max temps for
each of the three days. Actual readings have been overperforming
compared to model guidance the past three days. There is not much of
a challenge with the rain coming in for tonight/early Tue.

We are expecting that max temps today will once again overperform
compared to guidance, and likely eclipse daily records once again
for the third day in a row. We are expecting H850 temps to be about
3 degrees C warmer today compared to yesterday, and a SE wind to
avoid the cooler waters of Lake Michigan.

We are expecting that all areas will see around 0.25 to 0.50 inches
of rain from later tonight through Tue morning. The cold front out
across the Plains states early this morning is starting to draw Gulf
moisture northward ahead of it. There should be sufficient moisture
still as it crosses the area. There are some indications that
sufficient instability (elevated LI/s below 0C) will be present, so
we have added a chance of thunder to the forecast after 06z tonight.

Tuesday`s max temps are a little tricky with the rain/clouds early,
and with slightly cooler air moving in. We should see the sun come
out in the afternoon to help warm temps back up to around 60. The
chances of overperforming temps on Tue is a bit lower. Wed looks
like it could end up being the warmest day of the entire stretch.
Plenty of sunshine is expected once again, and H850 temps will surge
once again above +10C ahead of the next front in the series. If
there is enough mixing, we could be approaching 70 at southern
locations not downwind of Lake Michigan in a SW flow regime.

.LONG TERM...(Wednesday night through Sunday)
Issued at 323 AM EST Mon Feb 20 2017

It`s going to be an active weather pattern during the extended
period.

A weak low pressure system will move across northern michigan
Wednesday night and bring a slight chance of rain to the cwa. Most
likely though, given the weak dynamics and little support aloft, we
won`t see any pcpn. What it will do, though, is drag a weak cold
front through the cwa. The next storm upstream will ride northeast
along the frontal boundary and start to affect the cwa late
Thursday. Mixed rain and snow are possible south to around M-46
Thursday night with rain south of there. As the low gets closer, the
warm front will begin to lift north into Lower Michigan. Fairly
strong instability develops along/south of this front Friday.
Surface based Li`s fall to -2 to -4c by Friday afternoon south of I-
96 with weaker elevated instability north of there. We added thunder
to the grids Friday. Strong shear 40-60kts was noted across the cwa
as was 400-600 j/kg MUCAPE. Both the ecmwf and gfs show a strong
short wave support moving over the lake during the afternoon. This
system should have plenty of juice too with a 50kt llj moving across
the central cwa during the afternoon. Models prog the cold front
moving across the western cwa during the late afternoon which is
pretty ideal timing for storm development. We`ll keep a close watch
on this system.

Colder air will fill in behind this low as it moves away and snow
showers are expected over the weekend.

&&

.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 1243 PM EST Mon Feb 20 2017

VFR weather is to prevail through the evening...but conditions
will change overnight and Tuesday morning. Low level moisture will
be on the increase ahead of an approaching low pressure system.
This will raise the risk for low cloud formation...especially
after midnight. Then rain moves in and that should impact mainly
the western TAF sites later tonight. There could even be a few
thunderstorms around late tonight and early Tuesday. Low clouds
and drizzle could be widespread Tuesday morning with IFR and lower
impacts possible.

Will need to monitor the low level wind shear potential for
tonight as a low level jet moves in.


&&

.MARINE...
Issued at 323 AM EST Mon Feb 20 2017

We will be issuing a Small Craft Advisory for the entire nearshore
from this afternoon, through Tuesday morning. Winds come up this
afternoon ahead of the incoming cold front, and continue behind the
front a bit. There is some potential for Gale force wind, but we
think the warm air coming in over the colder waters will not allow
gales to reach the surface.


&&

.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 323 AM EST Mon Feb 20 2017

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

                  Today             Tue 2/21            Wed 2/22

Grand Rapids    61 - 1930           66 - 1930           67 - 1930
Lansing         59 - 1983, 1930     62 - 1930           66 - 1930
Muskegon        56 - 1983           58 - 1930           55 - 1930

The records are expected to be broken today and Wednesday.

Records will be approached on Tuesday depending on how much we can
warm after the rain moves out.

&&

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

&&

$$

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



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