Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 271926

Area Forecast Discussion
National Weather Service Grand Rapids MI
325 PM EDT Thu Jul 27 2017

Synopsis/Short Term/Long Term/Marine

Issued at 325 PM EDT Thu Jul 27 2017

There will be a slight chance of a shower or storm this afternoon,
and Friday morning/afternoon as a wave of low pressure moves through
the area. Most areas will remain dry.

Then from late Friday through mid-week next week, a dry period is
expected for the area. Temperatures will start out cool Friday into
Saturday. A gradual warming can then be expected, with temperatures
becoming very warm and humid by next Wednesday. The next chance for
appreciable rain will likely hold off until at least next Thursday.


.SHORT TERM...(This evening through Saturday night)
Issued at 325 PM EDT Thu Jul 27 2017

Forecast challenges are pretty much limited to rain chances through
tomorrow afternoon. After Friday, we should see high and dry
conditions through the end of the short term Saturday night.

We have seen the cold front slip south of the CWFA this afternoon,
as evidenced by the low level winds having become from the NNE at
all sites. Even with the front having moved through, there is a
decent amount of residual moisture holding in place. This moisture
is starting to mix out, and a dew point boundary seems to be
slipping south. This dew point boundary could touch off a
shower/storm through sunset across the srn portion of the area.

We have left the chance of a shower or storm for the ern half of the
CWFA for Fri through mid-afternoon. This is the result of the strong
amplifying wave diving SE into the area late tonight. This wave will
be encountering a lot of dry air, and will not be hitting peak
heating well for our area. The trough axis will be about clear of
the area by 18z Fri, favoring SE MI for better coverage of
showers/storms. It still could pop something prior to 18z in our

After that wave passes east on Friday, we will see dry conditions
persist through Sat night and well beyond. A nice upper ridge
located just to our NW will provide plenty of subsidence for the
area, keeping our area dry. Temps will be slightly cool on Sat with
a NNE flow continuing to filter in from Canada.

.LONG TERM...(Sunday through Thursday)
Issued at 325 PM EDT Thu Jul 27 2017

This next week, the first week of August, will be a great week to
Vacation in Southwest Michigan.  The weather will be nearly idea for
almost any Michigan sort of outdoor activity expect possibly storm
chasing as I do not expect any storms most of next week.

We have a rather persistent western upper level ridge that may build
some during the middle of next week as a system currently over
northern Siberia digs into the eastern Pacific trough and boots out
a system that digs into the same trough early next week from western
Alaska. With a western ridge, of course there has to be a down
stream eastern trough. That trough is centered near the East Coast,
so any precipitation assoicated with system digging into that
eastern trough will largely be east of Michigan.

Another key aspect to our weather next week is the split flow
pattern.  There is persistent and yet distinct northern stream jet
mostly near or north of the Arctic Circle.  That means the truly
cold air stays up in the arctic and will not be visiting Michigan
any time soon.

Also, since the really cold air stays in the Arctic, the truly hot
air or even the warm and humid air Gulf air will stay away from
Michigan since western ridge will trap the hot and dry air over the
western states and flat eastern trough will keep the warm and humid
Gulf air closer to the Gulf States.

That leaves Southwest Michigan with high pressure Monday through
Wednesday with little chance of meaningful precipitation. That
system from Siberia, that kicks out the Alaska system, will send
some shortwave energy from the Alaska system into the eastern trough
in the Thursday time frame. This will bring another weak cold front
into the area with the risk of a few spurious showers (not much Gulf
moisture to work with and most of the dynamics would be north of

Bottom line... great for vacationing or most other outside


.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 118 PM EDT Thu Jul 27 2017

There is a narrow band of MVFR ceilings assoicated with a slow
moving cold front near I-96 at 17z, this band of clouds will slip
south over time but by the time it reaches the I-94 TAF sites
ceiling should be VFR. I expect skies to clear across the area
this evening then cumulus clouds are expected Friday.


Issued at 325 PM EDT Thu Jul 27 2017

We are looking at mixed conditions out on the nearshore waters
through Saturday. Winds will likely be up around 10 to 20 knots
through Saturday with a decent gradient remaining in place. We are
expecting a slightly offshore wind through the period that will keep
waves down a tad. These offshore winds will likely produce a
significant drop off of water temperatures at the shore due to
expected upwelling. Winds should drop off by Sunday as high pressure
moves overhead.


Issued at 100 PM EDT Thu Jul 27 2017

One to two inches of rain fell across a fair portion of Central
Michigan (along the US-10 and M-20 corridors) Wed and Wed night.
Given the mostly dry conditions over the last two or three weeks,
this rain was effectively captured by the soil and river rises
will be limited. The chance for substantial rainfall over the next
week is very low.




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