Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 231908

Area Forecast Discussion
National Weather Service Grand Rapids MI
307 PM EDT Mon Apr 23 2018

Synopsis/Short Term/Long Term/Marine/FireWeather/Hydro

Issued at 307 PM EDT Mon Apr 23 2018

The dry weather that has been in place since last week will come to
an end tonight. Light rain showers will move in from south to north
tonight, and will remain possible into Wednesday. Cooler weather can
also be expected after this afternoon.

A brief break in the rain chances will occur Thursday, as we will be
in between systems. Another system will move in by Friday, bringing
rain chances to the area for Friday and Saturday. Quieter weather
will return late in the weekend and early next week.


.SHORT TERM...(This evening through Wednesday)
Issued at 307 PM EDT Mon Apr 23 2018

Our main focus of the forecast is on the rain chances coming in
tonight, and how long they stick around. We have added some rain
chances in for Wednesday as the 00z ECMWF trends for rain to stick
around longer have continued for the new 12z run.

Very dry air mass in place this afternoon (RHs 15 to 30%) will keep
the area dry into this evening. Upper low across TN this afternoon
will slowly rotate to the NE through Tue. Broad deformation with the
upper low and moisture being advected to the NW ahead of the low
will bring some rain showers in overnight tonight.

The heavier rain showers with the upper low will stay SE of the
state. However, the moisture wrapping back into our area will be
acted upon by another upper trough that will dive in over the area
from the NW. This interaction will keep the showers in over the area
on Tue, and now into Wed.

The reason the showers are lingering over the area longer is the
upper trough diving in from the NW is showing signs of closing off
over the area. This will then slow the progression of the system
down. The system should not get stuck over the area too long as yet
another upper trough pushes in, and keeps the pattern somewhat
progressive. This should allow for the rain showers to end
gradually through the day on Wed.

.LONG TERM...(Wednesday night through Monday)
Issued at 307 PM EDT Mon Apr 23 2018

A low pressure system will swing south from Canada and then east
over the Great Lakes Region Thursday night and Friday. This will
bring a chance of rain showers, possibly with some wet snow flakes
over Central Lower Michigan and points north. No impacts are
expected due to precipitation, and no other weather should occur in
the long term.

Cooler than normal conditions are expected behind the low over the
weekend with temperatures returning to near normal early next week.
Normal highs are in the lower 60s with lows around 40 degrees.


.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 127 PM EDT Mon Apr 23 2018

As the low pressure system nears from the south...this will cause
the clouds to thicken up and lower. This will take some time the airmass is currently very dry. Thus this evening
and more so tonight...we will feature MVFR conditions arriving
from the south...and eventually some showers. Current the computer
models are showing widespread IFR/LIFR developing late tonight
into Tuesday morning. Given the dry conditions near the surface
right now...I did not go quite that low. Will need to monitor


Issued at 307 PM EDT Mon Apr 23 2018

Quiet conditions into Tuesday with lake breezes expected for the
remainder of this afternoon and Tue afternoon. Next possible
headline needed will be Tue night into Wed with a tightening
pressure gradient expected. This bout of windier conditions will
likely be mostly an offshore component, so waves will be limited a


Issued at 307 PM EDT Mon Apr 23 2018

Warm and dry conditions will persist into the evening tonight,
before some relief will arrive by Tue. The relief will arrive in the
form of higher dew points and some rain for most of the area. This
should limit fire danger some for a few days with cooler weather


Issued at 307 PM EDT Mon Apr 23 2018

Five Flood Advisories remain on the area rivers as of this morning.
River levels are cresting up north where snow melt from Northern and
Central Lower has allowed for some runoff. The snow has pretty much
entirely melted in the Muskegon basin, so river levels will start
coming down.

For all areas, rain is expected tonight into Wed. Basin averages
should be mostly under quarter of an inch, with everybody expected
to stay under half an inch. This over a period of time should not
cause any rises on the rivers this week.




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