Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 151713

Area Forecast Discussion
National Weather Service Grand Rapids MI
113 PM EDT Thu Mar 15 2018


Issued at 232 AM EDT Thu Mar 15 2018

A cold front will slip south of the region early this morning.
Northerly winds will strengthen today ushering in another cold
airmass. Some light snow showers will be possible. An area of
high pressure tracks eastward through Lower Michigan on Friday.
This fair weather system will provide the area with dry weather
and cooler than normal temperatures. Low pressure is forecasted to
track up the Ohio Valley Friday night into Saturday. Most of the
precipitation is forecasted to stay south of the Michigan Indiana
border at this time.


Issued at 1050 AM EDT Thu Mar 15 2018

Cold air flowing south behind a cold front is creating lake effect
stratocu which is spreading south across Lower Michigan. We
updated to reflect more cloudiness this afternoon and also kept
the slight chance of snow in the grids.


.SHORT TERM...(Today through Saturday)
Issued at 232 AM EDT Thu Mar 15 2018

Cold air advection is underway for most of the forecast area as
the cold front is now pushing through the I94 corridor. North to
northwest flow behind this system is shown to be mostly diffluent
at the surface today. This...combined with only shallow moisture
will likely limit the snow shower coverage.
temperatures try to warm up...some shallow cape is seen on the
forecast soundings throughout the county warning area. Typically
this leads to shallow convective clouds. A few of the relatively deeper
updrafts could touch off some snow showers as they reach into the
DGZ. The flow within the convective column increases today to 30
to 35 knots. As a result of this...any snow showers that do
form...will be brief as the cells will be moving along rather

High pressure moves in for Friday. Thus it looks dry with a decent
amount of sunshine. Continued below normal temperatures despite
the sunshine are expected.

Will need to monitor the track of the next low pressure system
Friday night and Saturday. The northern edge of the deeper
moisture will try to move into the I94 corridor. Currently most
model solutions keep this deeper moisture just south of this
region...but it will be a close call for some potentially
impactful weather. The temperatures on Saturday will largely be
determined by this system. If we end up with more clouds an
virga...high temperatures will be much lower than currently
forecasted. For now...will not stray too far from climatology. Given
that the system will be pulling away from the area in the
afternoon highs for the day will likely occur later in the day.

.LONG TERM...(Saturday night through Wednesday)
Issued at 232 AM EDT Thu Mar 15 2018

We continue to expect a quiet and mild period early in the long
term, that will transition to a cooler, and potentially more
unsettled pattern by the end of the long term.

The long term will see a continuation of the dry weather from the
short term, with temps warming a bit more for Sunday. The upper
ridge axis will re-establish itself over the Plains Sat night as
what is left of the Sat wave moves away from the region. Temps aloft
will moderate a bit more to allow for some 50s on Sunday, before a
backdoor cold front slips SW through the area and brings cooler air
in on Mon.

The attention then turns to the next system that will emerge from
the Plains early next week. The latest model trends show the
emerging Plains low staying south of the area, and eventually nrn
stream energy diving in over the region in its wake. We can say with
confidence that the upper pattern will likely revert back to an ern
trough as the amplified flow over the Pacific and North America
holds on, with the ridge centered over the Rockies. This will spell
a cool down for the area with chcs of pcpn remaining possible. The
details of how cold, how much pcpn, and what type of pcpn will
remain quite uncertain until we approach the period as upper lows
are very tricky.


.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 107 PM EDT Thu Mar 15 2018

Colder air flowing south over the lake is creating some stratocu
at the taf sites. Most of the clouds are vfr however some pockets
of mvfr are out there and may affect the northern taf sites this
afternoon. We expect ceilings above 3k ft tonight to scatter out
after sunset.


Issued at 1032 AM EDT Thu Mar 15 2018

River levels will continue to fall into next week. The Portage River
near Vicksburg is the only site remaining above flood stage and has
a history of falling very slowly. A dry weather pattern is expected
to continue into next week.




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