Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 251155
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
741 AM EDT Fri May 25 2018

LATEST UPDATE...
Aviation

.SYNOPSIS...
Issued at 256 AM EDT Fri May 25 2018

High pressure will bring fair weather today then weak low
pressure will spread some clouds and the chance for showers and
thunderstorms tonight into Sunday.

&&

.SHORT TERM...(Today through Sunday)
Issued at 256 AM EDT Fri May 25 2018

Forecast issue in the near term is timing and coverage of showers
and thunderstorms from this evening through early Sunday.
Continuity was kept with the preceding forecast in keeping it dry
through 00Z though there may be a slight chance across the far
northwest fringe of the forecast area late this afternoon.

The chance for precip will reach the southeast zones by late
tonight and persist through Saturday night as weak upper
troughing moves through.

Instability and shear are marginal so no severe storms are
expected but PWATS increase to about 1.5 inches tonight and
Saturday and isolated heavy downpours are possible.

.LONG TERM...(Sunday night through Thursday)
Issued at 256 AM EDT Fri May 25 2018

Very warm and rather humid weather will continue through the long
range forecast period and medium range guidance trends look even
warmer (actually hot) for Memorial Day with potential for many
locations inland from Lake Michigan to reach the upper 80`s to lower
90`s.

In fact 00Z mex guidance has a 92 max on Memorial Day for KGRR with
ECMWF numbers looking hot as well. Given guidance trends we raised
the max temp fcst by a few degrees for Memorial Day.  Fair wx is
forecast as there will be no real forcing mechanism for convective
initiation to occur in spite of increasing aftn/early eve
instability.

A high pressure ridge will continue to bring fair and warm wx
Tuesday through Wednesday. There is potential for an upper level
system to bring a chance of showers and storms by Thursday. In
addition to that system as we have been discussing for several
nights now there is a chance that some remnant subtropical
moisture/showers could move in from the south by Thursday. This
notion is supported by the 00Z ECMWF.

A medium range guidance consensus suggests heavier rain would stay
south to se of our fcst area but it is noted that some guidance
including the ECMWF trends favor a more northward progression of
showers into our fcst area by late week.

&&

.AVIATION...(For the 12Z TAFS through 12Z Saturday morning)
Issued at 741 AM EDT Fri May 25 2018

VFR conditions will prevail through tonight. Some light showers are
expected after 00Z but conditions should remain VFR. Winds will be
south to southwest 5 to 10 knots.

&&

.MARINE...
Issued at 256 AM EDT Fri May 25 2018

Wind and waves should remain relatively light through the weekend
with a chance of thunderstorms tonight through Saturday night.

&&

.HYDROLOGY...
Issued at 300 PM EDT Thu May 24 2018

No hydrology issues expected over the next week, and likely beyond.
Any rainfall expected over the next week will be spotty at best, and
thus not cause impacts on the rivers and streams. The higher levels
currently on the rivers and streams will only fall through next
week.

&&

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

$$

SYNOPSIS...Ostuno
SHORT TERM...Ostuno
LONG TERM...Laurens
AVIATION...Ostuno
HYDROLOGY...NJJ
MARINE...Ostuno



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