Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 140958
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
316 AM EDT Tue Aug 14 2018

LATEST UPDATE...
Synopsis/Short Term/Long Term/Marine

.SYNOPSIS...
Issued at 316 AM EDT Tue Aug 14 2018

High pressure over the Ohio Valley will drift east today which will
enable a weak cold front to drop south through the state Wednesday.
As the front stalls out, low pressure over Missouri will ride along
the boundary toward Lower Michigan bringing showers and
thunderstorms late Wednesday and Thursday. A half inch to an inch of
rain is possible during this time. Conditions will dry out for the
weekend.

&&

.SHORT TERM...(Today through Thursday)
Issued at 316 AM EDT Tue Aug 14 2018

Forecast concerns deal with the convective potential through the
period.

High pressure over the Ohio Valley will drift east and a cold front
will start to move south through the UP into northern lower tonight.
We`ll see mostly sunny skies again today filtered through smoke
aloft from Canadian forest fires. The cold front looks like it will
wash out over central Lower tonight. Low pressure over Missouri is
progd by the ecmwf and gfs to ride northeast along the boundary
through southern Lower Thursday. Models are trending southeast with
the track of the sfc low and so areas north of I-96 might see
limited rainfall. Heaviest rain looks to be along the I-94 corridor
based on the low track.

Precipitable water values remain close to 2 inches Wednesday night
and Thursday and so any storms that develop could produce heavy
rainfall. Limited shear values point toward non severe storms.

.LONG TERM...(Thursday night through Monday)
Issued at 316 AM EDT Tue Aug 14 2018

Low pressure will be exiting the cwa at the start of the period and
high pressure will nose in from the northwest. Generally dry weather
is expected through the weekend before the next low develops in the
Plains and moves toward the state.

&&

.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 114 AM EDT Tue Aug 14 2018

Brief periods of mvfr/ifr fog may occur prior to sunrise at MKG,
otherwise vfr conditons are expected through the period.


&&

.MARINE...
Issued at 316 AM EDT Tue Aug 14 2018

No marine issues as winds and waves will remain favorable for small
craft today. Waves will increase to 1-2 feet tonight as a cold front
washes out over central Lake Michigan.

&&

.HYDROLOGY...
Issued at 246 PM EDT Mon Aug 13 2018

Stable rivers are expected through Tuesday. Beginning Wednesday,
runoff from showers and thunderstorms is expected to impact area
rivers and streams, particularly in areas that have had rain
recently. Drier areas will soak up the rain fairly easily and less
runoff will occur.

Of concern is the atmosphere`s capacity to produce high rainfall
rates Wednesday into Thursday with such high precipitable water
values and a southern Plains system moving toward Michigan, drawing
up Gulf moisture. Smaller rivers and streams may respond quickly to
locally heavy rain with some within bank rises and perhaps some out
of bank rises in spots, but there is uncertainty about this. Recent
localized heavy rainfall in Ingham County (2"-5" several days ago)
produced well-within bank rises on rivers and streams and no
flooding, though the threat for heavy rain amounts with this coming
system is over a larger area than that event. Still some question
marks about which river basin(s) will be most impacted.

Main stem rivers may rise as well but should hold within banks
unless widespread several inches occur across large stretches of the
basin (unlikely but certainly not out of the spectrum of
possibilities).

&&

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

$$

SYNOPSIS...04
SHORT TERM...04
LONG TERM...04
AVIATION...04
HYDROLOGY...Hoving
MARINE...04


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