Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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811
FXUS63 KGRR 271810
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
210 PM EDT Sat May 27 2017

LATEST UPDATE...
Aviation/Hydro

.SYNOPSIS...
Issued at 330 AM EDT Sat May 27 2017

An area of low pressure will move from Central Illinois tonight
through southern portions of the Lower Peninsula on Sunday. Today
and Tonight will be fairly dry with increasing chances for
precipitation on Sunday. Showers and thunderstorms will accompany
the passage of the low on Sunday. Some of the storms could be on the
strong side on Sunday. Rain showers remain in the forecast for
Memorial Day as an upper low moves toward the region. Not a wash out
of a Holiday weekend, but we will see some rain. The driest day will
likely be today with the wettest occurring on Sunday. Highs will be
near normal for this time of year.

&&

.SHORT TERM...(Today through Monday)
Issued at 330 AM EDT Sat May 27 2017

Main focus in the forecast was on chances for precipitation,
beginning late tonight and persisting into Monday.

Shortwave ridging should keep us dry for the most part today after
some patches of light rain exit Southern Lower Michigan this
morning. Much of tonight will be dry as well with a low slowly
moving our direction from the Mid Mississippi Valley. Some light
rain showers are forecast by some of the short range models to be
pushing into Western Lower Michigan around 12z on Sunday.

All of the models move a low through southern portions of the state
on Sunday. Sunday looks to be our best chance for rain with multiple
upper shortwave`s affecting our area. Both showers and thunderstorms
look likely with convection allowing models like the 3kmNAM showing
MUCAPE values of 1000-2000 J/KG. Simulated reflectivity shows rounds
of showers/storms. 0-6km bulk shear values via the NAM12 are
forecast to be in the 40-50kt range so organized storms with the
threat of some severe weather exists.

Sunday night and Monday an upstream upper low gradually works our
direction with some diurnal showers anticipated. So, showers will be
more prevalent on Monday with Sunday night forecast to be fairly
dry.

A cooling trend will be noted through the Holiday weekend, with the
warmest day being today. Highs will reach the mid to upper 70s
today, cooling to around 70 on Memorial Day.

.LONG TERM...(Monday night through Friday)
Issued at 330 AM EDT Sat May 27 2017

Seasonably cool and unsettled wx will continue Monday night through
midweek with scattered rain showers through Wednesday with the upper
trough axis in place over the Great Lakes region.

Showers will be enhanced from time to time by several shortwaves
that will rotate around the base of the trough axis. These diurnal
showers will be most prevalent during the afternoon and evening
hours.

Fair wx will finally return late in the week as the upper trough
axis moves east of our region and a sfc high pressure ridge builds
in. Temps by Thursday and Friday will return to near normal for this
time of year with high temps in the lower to perhaps middle 70`s and
mins mainly in the 40`s to lower 50`s.

&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 210 PM EDT Sat May 27 2017

VFR conditions should prevail through Sunday morning. The
exception could be some MVFR with ceilings around 2500 feet early
Sunday. Winds will be below 10 knots and mostly variable through
tonight.

&&

.MARINE...
Issued at 330 AM EDT Sat May 27 2017

A slack gradient will be in place today resulting in light winds and
limited waves out on Lake Michigan. Tonight into Sunday a low will
move through the Southern Great Lakes with a veering wind from
southeast to southwest between this evening and Sunday evening. The
expectation is that winds and waves will remain below Small Craft
Advisory criteria during these two forecast periods as well. Sunday
night and especially into Monday, winds and waves will pick up and a
SCA may be needed for Monday. Southwest winds of 15-25 knots are
possible on Monday.


&&

.HYDROLOGY...
Issued at 210 PM EDT Sat May 27 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 around a half inch on Sunday will likely not be
enough to produce flooding. Occasional showers over the upcoming
week will be rather light.

&&

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

$$

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



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