Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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741
FXUS63 KGRR 212328
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
728 PM EDT Fri Apr 21 2017

LATEST UPDATE...
Aviation

.SYNOPSIS...
Issued at 322 PM EDT Fri Apr 21 2017

As high pressure builds over the Great Lakes tonight, skies will
gradually clear and patchy frost is possible. Sunny skies are
expected through Monday before we see a chance of showers Tuesday.
Temperatures will slowly warm through the weekend.

&&

.SHORT TERM...(This evening through Sunday night)
Issued at 322 PM EDT Fri Apr 21 2017

Forecast concerns deal with frost potential tonight and Saturday
night.

Latest hi res vis loop shows quite a bit of closed cell cu covering
Lower Michigan and high clouds covering the southern cwa. As north
winds develop, it will take a while for the clouds to diminish. High
pressure building into the Great Lakes will start to clear the sky
late tonight and we could see some frost develop. Included frost in
the grids both tonight and Saturday night. Saturday and Sunday will
be mostly sunny with clear skies both Saturday night and Sunday
night.

Saturday will be coolest day with highs mostly in the 50s, then warm
to the 60s Sunday.

.LONG TERM...(Monday through Friday)
Issued at 322 PM EDT Fri Apr 21 2017

Next week, Monday through Friday will for the most part be warmer
than normal.  It will start out dry Monday into Tuesday then we will
have a series of systems move through the area starting Wednesday
bringing showers and more than likely thunderstorms Wednesday
through Friday and likely well beyond that. Later next week into
next weekend we could see some really strong thunderstorms.

The split flow upper air pattern will continue through next week and
that will keep the really cold air in Canada. Meanwhile another of
those East Asian Jet (EAJ) features develops by Saturday evening. By
Sunday evening it will stretches (around 40N to 45N) from near Japan
to near Northern California. The first jet core associated with this
latest EAJ crosses the dateline Monday and reaches the West Coast
(northern California and Oregon) by Tuesday evening. All of that jet
energy will dig a trough over Western Plains. Since there is more
than one jet core crossing the Pacific with this latest version of
the EAJ, that will help to keep the trough farther west and in so
doing prevent longwave trough from moving east much the second half
of next week.With that trough over the Western Plains, then of
course there has to be an upstream ridge. That will be over the
eastern 1/3 of the CONUS into the western Atlantic. This puts
Southwest Michigan on the eastern edge of the storm track for the
middle to end of next week. That being so, we will likely be very
warm, it would not surprise me to see highs in the 80s on a least
one or two day the second half of next week (this in not in our
grids at this point but just watch and see how that changes as we
get closer in time).

The lead wave crosses the Great Lakes Wednesday but that will minor
our as it tries to cross developing upper ridge over the eastern
CONUS. Even so we will likely see some showers (and maybe
thunderstorms (also not in the grids at this time) in the Wed time
frame. The more important system is in the Friday time frame. It is
ahead of that system we could see highs in the 80s Thursday. It
should be noted that since there is a series of jet cores coming on
shore even the system Friday will not be the "Big One" that will
wait till early in the following week. Still we could and likely
will see a period of showers and strong thunderstorms later Thursday
into Friday. Since all of the energy for these systems is still over
Eastern Asia and the western Pacific timing on all of this could
change some. If anything it would slow down.

So the bottom line is warm next week and likely wet toward the end
of the week with periods of thunderstorms. It may even seem summer
like.

&&

.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 728 PM EDT Fri Apr 21 2017

VFR conditions were across the region early this evening as skies
slowly clear and clouds lift. VFR is expected to be maintained
overnight and through Saturday.

Northeast winds will increase by early Saturday afternoon to
around 10 knots and continue into the early evening.

&&

.MARINE...
Issued at 322 PM EDT Fri Apr 21 2017

Wind and waves will continue to slowly decrease. Waves will fall
below advisory criteria around midnight.


&&

.HYDROLOGY...
Issued at 105 PM EDT Fri Apr 21 2017

Wednesday night to Thursday rain totals ranged from 0.5 to 1.5
inches across a majority of the area. As a result, several river
points are rising again, prolonging the high river levels
experienced for much of the season so far. Crests are not expected
to approach what has already occurred earlier this month.
Fortunately, the next chance of rain will hold off until late
Tuesday.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
LM...Small Craft Advisory until 11 PM EDT this evening for LMZ844>849.

&&

$$

SYNOPSIS...04
SHORT TERM...04
LONG TERM...WDM
AVIATION...JK
HYDROLOGY...CAS
MARINE...04



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