Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 130000

Area Forecast Discussion
National Weather Service Grand Rapids MI
800 PM EDT Wed Aug 12 2020


Issued at 323 PM EDT Wed Aug 12 2020

- Very warm and dry through Friday

- Small chances for rain over the weekend

- Much cooler next week


.DISCUSSION...(This evening through next Wednesday)
Issued at 323 PM EDT Wed Aug 12 2020

-- Very warm and dry through Friday --

We will see similar weather like today, for the rest of the work
week. High pressure over the region this afternoon will slowly be
absorbed by a larger high up near Hudson Bay. The only change will
be a little bit more of an east wind. The air mass will not really
change with 850 mb temps only warming a degree or two through the
period. Also, dew points will go up slightly, but there is not a
good feed of moisture poised to move in immediately due to a lack of
flow from the Gulf.

-- Small chances for rain over the weekend --

There has not been much change in thinking from the forecast this
morning. Rain chances will increase this weekend, but do not look
likely at this time.

The first chance of a few showers and storms would be on Saturday
across the SE portion of the area. This chance is a result of a
southern stream system that tries to rotate back to the NW a little.
We will be fairly dry to start with, and will likely be on the
periphery of this wave rotating toward the area. Otherwise, it looks
like Saturday will be the warmest day of the stretch around 90.

The best chance of a few showers and storms will come very late
Saturday night and Sunday morning. We will see a cold front arrive
at that time and push through by early Sunday afternoon. The
ingredients are definitely not optimal for a widespread rain or
severe weather. The forcing is not very good, as the upper wave
supporting this front looks to stay north of the area. Also, a
frontal timing late at night, or in the morning hours is not
conducive to a whole lot of instability. Finally, the instability
will be limited without a good feed of moisture from the Gulf. The
chance for showers and storms looks a little better on the east side
of the state with a more favorable timing.

-- Much cooler next week --

We will see much cooler temperatures move in next week behind the
cold front that moves through early on Sunday. The upper air pattern
will feature large scale troughing over the Great Lakes region,
resulting from the large upper ridge over the western states. Right
now, we have a dry forecast. However, there is a small chance of a
few light showers with the upper cold pool nearby, and weak short
waves moving through the region. There will likely be a diurnal
component to them also.


.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 800 PM EDT Wed Aug 12 2020

VFR/CLR flight conditions continuing through Thursday evening.
Light to calm winds tonight becoming east at 7-10 kts by midday
Thursday. Exception will be at MKG where a northwest wind off the
lake is expected in the afternoon.


Issued at 323 PM EDT Wed Aug 12 2020

We expect that impacts for mariners will be minimal through
Saturday, before winds and waves are likely to pick up on Sunday.
Winds should generally remain below 15 knots through Saturday. The
only caveat to this is maybe some wind around 15 knots on Friday as
the gradient tightens a tad as a weak wave moves by to our south.
This will be an offshore easterly wind, so waves should not be
affected much.

The winds and waves increasing on Sunday will be behind a cold front
that will move through. These winds and waves look to linger into
Monday with colder air coming in.




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