Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 180537

Area Forecast Discussion
National Weather Service Grand Rapids MI
137 AM EDT Wed Apr 18 2018


Issued at 318 PM EDT Tue Apr 17 2018

Low pressure will track just south of Lower Michigan on Wednesday
night bringing rain and snow. Some light accumulations are
possible during the morning commute on Thursday.


Issued at 857 PM EDT Tue Apr 17 2018

I trended the forecast towards more cloud cover for the overnight
hours. Satellite trends show a fairly solid deck of clouds for all
but the South Haven to Kalamazoo area. The flow weakens as it
veers to the north then northeast overnight. Thus these colder
lower clouds may persist for much of the night. Based on the
greater cloud coverage...I did raise temperatures slightly.

UPDATE Issued at 808 PM EDT Tue Apr 17 2018

I did allow the small craft advisory to expire. Conditions are
likely marginal near South Haven for the next hour or two. Will
likely need another headline by Wednesday night.


.SHORT TERM...(This evening through Thursday night)
Issued at 318 PM EDT Tue Apr 17 2018

A brief period of fair weather tonight and Wednesday before sfc
low spreads rain and snow into western zones on Wednesday
afternoon, which spreads east during the evening.

Surface low tracks just south of Lower Michigan with an area of
mid-level frontogenetical forcing passing over the forecast area
for Wednesday evening then moving off to the east Thursday
morning as the closed upper low opens up and is absorbed into a
large upper trough across eastern Canada. Model soundings show
rain or mixed rain and snow change over to all snow by midnight
for most places with accums expected to be an inch or less most
places by the time the precip ends Thursday morning.

Snow accumulations still expected to be an inch or less with sfc
temperatures being marginal and a slushy coating possible on the
roads for the Thursday morning commute. Conditions will improve by
Thursday afternoon as snow ends and temperatures rise above

.LONG TERM...(Friday through Tuesday)
Issued at 318 PM EDT Tue Apr 17 2018

We will see a long period of fair weather with temperatures slowly
rebounding from far below normal to near normal under surface and
upper ridging. Height falls begin early next week but any
precipitation should hold off through Tuesday.


.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 131 AM EDT Wed Apr 18 2018

MVFR ceilings are favored overnight as low-level moisture remains
locked in place under an inversion, which will continue to lower
slightly towards daybreak as weak ridging expands into Southwest
Michigan. Flow will turn off the lake by 08-10Z, which could allow
some breaks to develop. Confidence in ceilings scattering out is
low. Low pressure tracking through the Ohio Valley will spread
precipitation and lower clouds into the area by late afternoon and
evening. Rain is expected to move into the area between 20-22Z,
then change to snow after sunset (about 01Z). This should drop
ceilings vis to MVFR or IFR. Northeast winds will also begin to
gust up to 20 knots in the evening.


Issued at 318 PM EDT Tue Apr 17 2018

Winds and waves will be decreasing this evening and the Small
Craft Advisory should be coming down at or before 8 PM.


Issued at 1122 AM EDT Tue Apr 17 2018

River levels are above normal in Southern Lower Michigan and around
normal in Central Lower Michigan. The significant precipitation over
the weekend has led to rising river levels across the area. With
only a few tenths of precipitation expected Wednesday into Wednesday
night and nothing else until next week, rises are still expected to
continue for the next several days. Minor flooding near river banks
is still possible.




LONG TERM...Ostuno
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