Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 270409
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
1209 AM EDT Sat May 27 2017

LATEST UPDATE...
Aviation

.SYNOPSIS...
Issued at 330 PM EDT Fri May 26 2017

Showers and isolated thunder will move across areas mainly along and
south of I-96 tonight.  Some areas south of I-94 could pick up as
much as a half inch of rain. Then as we open up the holiday weekend,
Saturday will be dry and comfortable, with highs in the 70s. However
a more widespread area of showers and storms will arrive late
Saturday night, that will linger into Sunday evening.  All areas
should see a quarter to a half inch of rain in this period.

More widely scattered showers and storms will be possible Memorial
Day into Tuesday, before we dry for much of the rest of the week. We
will stay at or slightly below normal next week, with most daytime
highs in the upper 60s to mid 70s.

&&

.SHORT TERM...(This evening through Sunday night)
Issued at 330 PM EDT Fri May 26 2017

An MCS will slide east across Southern Lower MI tonight.  Then a
break from the rain will occur Saturday, for the best day of the
holiday weekend.  Then another period of showers and storms moves in
by late Saturday night and continues on and off Sunday and Sunday
evening.

MCS was located over North Central IL as of 19Z and is expected to
track east, then east southeast tonight.  The jet dynamics and best
instability remains to our south.  So only expect showers on the
north end of the MCS, with embedded thunder.  Much of the rain will
stay along and south of I-96, with only hit and miss pcpn north.  A
period of moderate to heavy will be possible along the I-94 corridor
where some areas may see up to a half inch of rain.  However any
severe risk will stay well to our south.  I removed lowered POPs
toward daybreak as most of the pcpn should be east after 09Z.

Weak surface high pressure and upper ridging builds back into the
region for Saturday.  Will keep the forecast dry, however their
appears to be a fair amount of lingering low level moisture,
especially south.  For that reason I have gone with more clouds on
Saturday, but still most areas should see partly sunny conditions
into the afternoon.  Trimmed max temps to hold in the 70s, and
staying in the lower 70s for the cloudier SE CWA.

More showers and storms arrive late Saturday night as the upper
ridge moves east and a short wave moves into the upper midwest. This
wave eventually becomes an upper low into Sunday night.  A surface
front and low pressure arrives around mid day, so this should spread
a fairly widespread area of pcpn across the area.  Maintaining the
likely POPs.

.LONG TERM...(Monday through Friday)
Issued at 330 PM EDT Fri May 26 2017

A cooler and unsettled wx pattern will develop early next week as
the upper level trough digs and amplifies over the Great Lakes
region.

High temperatures Monday and Tuesday will reach the 60`s with fairly
extensive diurnal cloud cover and scattered instability rain
showers. Showers will be enhanced from time to time by several
shortwaves that will rotate around the base of the upper trough.

Temperatures should moderate a bit toward late next week as the
upper trough axis moves east of our region and h8 temps moderate.
High temperatures should reach the lower to perhaps middle 70`s by
Thursday. A high pressure ridge will build in and bring fair wx late
in the week.

&&

.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 1137 PM EDT Fri May 26 2017

Vfr conditions will continue at all the terminals through the next
24 hours. Lingering light rain showers and sprinkles at our
southern terminals at the moment will gradually taper off during
the early morning hours Saturday.

Vfr conditions will then continue Saturday with sct-bkn fair wx
cumulus development during the late morning and afternoon hours.
Winds will be out of the southeast at around 5-10 kts Saturday
except at KMKG where winds will shift to the southwest to west at
around 10 kts by midday.

&&

.MARINE...
Issued at 330 PM EDT Fri May 26 2017

Waves will be held to two feet or less through Sunday night.  This
leave the threat of thunder as the main concern for boaters this
holiday weekend.  Highest thunder chance will come late Saturday
night through Sunday afternoon.


&&

.HYDROLOGY...
Issued at 217 PM EDT Fri May 26 2017

River levels in the upper Grand and the Kalamazoo basins are
running above normal for late May while elsewhere the levels are
closer to normal. Rain totals generally under a half inch in
Southern Michigan Friday night, then across much of the area on
Sunday, will likely not be enough to produce flooding.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
LM...None.
&&

$$

SYNOPSIS...JK
SHORT TERM...JK
LONG TERM...Ostuno
AVIATION...Laurens
HYDROLOGY...CAS
MARINE...JK



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