Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 012348

Area Forecast Discussion
National Weather Service Grand Rapids MI
748 PM EDT Sat Oct 1 2022


Issued at 748 PM EDT Sat Oct 1 2022

I have added more clouds to the overnight forecast, mostly in the
I-69 / I-94 area. We do have weak cold front coming through this
area overnight. After looking at the HREF, HRRR, RAP, NAMNEST,
GLAMPS models I have convinced myself we will see some low clouds
develop as this boundary moves from northeast to southwest across
our CWA after midnight. Seems the clouds will mostly be south of a
line from Alma to Ionia to South Haven. To some extent this is a
combination of night time cooling and moisture from Lake Huron.
Given all the dry air behind this front, the clouds should clear
by sunrise.

These clouds may limit how cold it gets in the area south of a
line from Alma to South Haven since the clouds will be over that
area a good 6 hours after midnight. So I increased the forecast
lows a few degrees in that area.


.DISCUSSION...(This evening through next Saturday)
Issued at 256 PM EDT Sat Oct 1 2022

Quiet weather continues under surface and upper ridging. A dry
cold fropa tonight ushers in cooler air for early in the week but
the bigger story will be the strong cold front on Wednesday into
Thursday with sharply colder weather and freezing temperatures by
the end of the week. Forecast thermal profiles show that there
could even be some snow mixing in to the rain showers by Thursday
night and this is reflected in the forecast.

Patchy frost and freezing temperatures are also possible Sunday
and Monday nights as Canadian high pressure ridge holds sway.


.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 748 PM EDT Sat Oct 1 2022

I was thinking at first this would a solid VFR forecast. Well that
worked until I started looking at the data. There is decent back-
door cold front coming through tonight. This will bring a period
of MVFR cigs across our I-69 and I-94 TAF sites after 06z.

This low cloud deck comes from the more moist air over Lake Huron,
where current dew points over mostly in the lower 50s. When that
air is pushed inland after sunset, it will condense into a low
cloud deck as it runs into the cooler air over southern Lower
Michigan at that point. We can thank the northeast wind below
6000 ft AGL for allowing this to happen. On the frontal boundary,
there will be stronger winds in the boundary layer. Winds kick up
to 30 knots between 2000 ft and 4000 ft in the 06z to 12z time
frame. So this all will cause a low cloud deck to form and be
pushed southwest.

Now this is a real cold front so there is drier air behind it but
that drier air will not get into our CWA till around sunrise. That
will clear the low clouds out so Sunday should be sunny with a
northeast wind in the 5 to 10 knot range.


Issued at 256 PM EDT Sat Oct 1 2022

Winds will be mostly offshore into early next week and waves
should be relatively light. Strong northwest winds can be expected
by late Wednesday as a powerful cold front moves through.




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