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FXUS63 KGRR 160545

Area Forecast Discussion
National Weather Service Grand Rapids MI
145 AM EDT Mon Sep 16 2019


Issued at 300 PM EDT Sun Sep 15 2019

- A few lingering showers and patchy drizzle tonight

- Above to much above normal temperatures this week

- Fair weather most of the week


Issued at 915 PM EDT Sun Sep 15 2019

It would seem to me the low clouds will have a hard time clearing
out tonight due to the light winds and cyclonicly curved low 
level winds behind the departing storm system. The nighttime 
microphysics satellite loops show the clearing over WI heading 
this way. However several runs of the RAP model show the low 
clouds just hanging in there overnight. There is some suggestion 
in the model sounding that the clouds may try to break up some 
after midnight but even if they do we have light winds below 2000 
ft on the model sounding and the air is rather moist. Both the RAP
and the NAM show dense fog moving south like a frontal boundary 
from north of I-96 by 5 am to I-94 by 8 am. Given there is a 
trailing weak cold front behind the departing system that does 
make sense. Given the amount of low clouds I am not so willing at 
this point to put out a dense fog advisory tonight but it would 
not be totally out of the question either.

The light winds tonight into mid morning Monday will make it hard
to mix out the low clouds and fog Monday so it maybe that the
skies will not clear much till early to mid afternoon.

Another issue is there actually are a few showers near I-94
associate with that departing system. These will not be
thunderstorms but just light rain showers. They should be out of
the area by midnight or so. The RAP 00z run shows the 1000/850
moisture transport (weak through it is) into our I-94 counties
till around midnight. After that the moisture transport is focused
on northern IN and OH.  

So my bottom line is scattered showers this evening south of 
Grand Rapids to Lansing, extensive low clouds into Monday morning 
and fog, locally dense near I-94 toward sunrise. 


.DISCUSSION...(This evening through next Sunday)
Issued at 300 PM EDT Sun Sep 15 2019

A few light rain showers and patchy drizzle will linger tonight
due to extensive lingering low level moisture and as a mid level 
trough moves through early Monday morning. Fair wx is forecast 
Monday through mid to late week as an upper level ridge will gradually
build in and amplify over the Great Lakes region. 

Temps will undergo a slow moderating trend through the upcoming
week and average around ten degrees above normal for this time of
year early in the week. By mid to late week temps will average
close to 15 degrees above normal for this time of year with high
temps in the upper 70s to lower 80s and min temps mainly in the

A consensus of latest medium range guidance suggests that fair and
unseasonably warm wx will continue late in the week with the next
chance for rain likely not coming until next weekend. 


.AVIATION...(For the 06Z TAFS through 06Z Monday night)
Issued at 144 AM EDT Mon Sep 16 2019

A difficult aviation forecast, especially through mid morning with
low clouds in place, and the potential of fog to develop.

Low clouds are in place over much of the area, with some breaks
opening up. More clearing of the lower clouds is occurring down 
south, with just small breaks at the I-96 terminals. We expect
that the low clouds along I-96 will persist through mid morning.
This will likely lead to less fog and IFR development. 

Down along I-94 with more clearing, there is a better chance for 
fog development with the lights winds and moist air mass in place.
We expect that IFR will be likely as long as clearing persists.

Lower clouds and moisture will then lift and mix out gradually
during the daylight hours today. Locations should go VFR after
noon EDT or 16z. 

Fog looks likely again tonight, but it will come after this
forecast period is valid.


Issued at 510 PM EDT Sun Sep 15 2019

Looking at surface and marine observations around the area and
also beach cams, it is safe to allow the Small Craft Advisory and
Beach Hazard Statements to expire, so I did.




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