Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 270600
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
200 AM EDT Mon Mar 27 2017

LATEST UPDATE...
Aviation

.SYNOPSIS...
Issued at 300 PM EDT Sun Mar 26 2017

The system that has been plaguing the area with cool, cloudy, and
wet weather this weekend will finally slowly move out through early
Monday. Before this moves out, another round of showers and embedded
storms will affect the area this evening. Another wave of low
pressure could bring some light rain to far Southern Lower Michigan,
late Monday afternoon and Monday night.

A quiet period looks to be in store for the Tuesday and Wednesday
time frame. Temperatures will be fairly seasonable to a little
warmer than average. Wet weather looks to return to the area
beginning Thursday, and lasting into next weekend once again.

&&

.SHORT TERM...(This evening through Tuesday night)
Issued at 300 PM EDT Sun Mar 26 2017

Our two main periods of interest in the short term are this evening
with the departing low, and then late Mon/Mon night with pcpn chcs
coming in with the next wave.

The more widespread rain/showers are currently moving north of the
CWFA as of 19z this this afternoon, with more scattered rain showers
coming in from Indiana. The widespread rain is out ahead of a wave
that looks to be rotating up the nearshore waters. The showers
across Indiana seem to be near the main front around the MI/IN
border.

We are expecting the showers in Indiana to move up in the area this
afternoon, with an isolated rumble of thunder not out of the
question to develop. Conditions are mostly cloudy to our south with
just a few small breaks in the overcast. The cold pool aloft and
warm/moist air advecting in is providing for marginal instability
moving in. Updrafts will not be very strong with thin CAPE profiles
in the forecast soundings. Shear is not very good either, so we
expect these to remain rather tame.

We will gradually see remaining showers rotate out of the area
tonight as the low moves east of the area. Winds in the lower levels
will be rather limited. The moist air mass and lighter winds will
likely allow for fog across the area.

We have chance for rain tapering off from south to north mainly
Monday night, however we are expecting the rain to be mainly south
of I-96. There is even a decent chance it could entirely stay near
or even south of I-94. The final answer will depend on how far south
the front ends up before the wave arrives and rides along the
front.

Once the wave moves by early Tue, we are looking at improving
conditions. Skies will slowly clear on Tue, with seasonable temps
returning with the sunshine.

.LONG TERM...(Wednesday through Sunday)
Issued at 300 PM EDT Sun Mar 26 2017

Thanks to our extended East Asian Jet feature (continues through
next week and well beyond that) we will continue to see a split flow
over North America.  The northern stream jet for the most part will
be well north in Canada and that will not allow much of the really
cold air south into the Great Lakes (I can not forecast snow). On
the other hand the active southern stream will also prevent any
prolonged period of warmer than normal temperature either.  What
this will mean is about every three days we get a major southern
stream shortwave to come through our area. That will bring Gulf
moisture north and this suggests significant rainfall each time too.
Since these systems are progressive, I would not expect any major
flooding issues.

Our next system in this wave train will be in the Thu/Fri time
frame. The ECMWF has been very consistent with this, in every run
since the 22nd at 12z it has had precipitation with this system over
all of Lower Michigan and the 12z run today is no exception. On the
other hand the GFS has been all over the place with this and the
GFSX has not been much different than the GFS. I will say the
ensemble mean of the GFS has been wetter over Michigan so that helps
the cause for believability that we will see rain from this system
late in the week over Southwest Michigan. At this point, just like
with the current system we do not really get deep into the warm air
so the thunderstorm threat seems low (could be elevated storms like
we got with this one). This far out in time, just when it actually
rains is an issue but it would seem any time between Thu and Fri
looks good now.  By the way the next event will be the following
Tuesday (plus or minus a day or two).

As we have been writing, temperatures will for the most part be near
normal.

&&

.AVIATION...(For the 06Z TAFS through 06Z Monday night)
Issued at 157 AM EDT Mon Mar 27 2017

The most likely scenario is that we`ll see cigs blow 1k feet
through this morning. There may be a few pockets along/south of
I-94 where cigs climb to 4k feet or so, but vsbys below a mile and
perhaps a quarter mile are possible if not likely through early
morning. We`ll see some improvement this afternoon.

&&

.MARINE...
Issued at 300 PM EDT Sun Mar 26 2017

No marine headlines expected for the next few days as winds should
remain at or below 20 knots. Typical stabilizing effects of the cold
water and warmer March temps should also limit wave generation.


&&

.HYDROLOGY...
Issued at 300 PM EDT Sun Mar 26 2017

Rainfall totals over the last couple days have ranged from a quarter
inch across western reaches of the Muskegon and Grand River basins
to a swath of 1 to 2 inches across central and eastern stretches of
the Grand River basin as well as central and western reaches of the
Kalamazoo River basin. Rises on area rivers are occurring, though
most should hold within banks. Some exceptions will be at Ionia,
Hastings, Eagle, and Holt where minor flooding may impact areas
adjacent to the river banks.

Additional rainfall later this upcoming week will likely hold many
rivers at higher than normal levels.

&&

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

$$

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


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