Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 191753
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
153 PM EDT Wed Apr 19 2017

LATEST UPDATE...
Aviation

.SYNOPSIS...
Issued at 318 AM EDT Wed Apr 19 2017

Low pressure will track across Lower Michigan late tonight and
Thursday bringing a marginal risk of strong to severe
thunderstorms. High pressure will build in later Thursday with
fair weather into the weekend.

&&

.SHORT TERM...(Today through Friday)
Issued at 318 AM EDT Wed Apr 19 2017

Front stalls across the southern forecast area today and will
focus scattered showers there then return north tonight as sfc low
moves in from the west. Hi res models show showers increasing in
coverage after midnight as isentropic ascent strengthens ahead of
the low.

Instability and shear increase on Thursday and we will have to
watch convective trends as some strong storms could from across
central and eastern zones, which may destabilize enough by early
afternoon when cold front arrives.

The storms should be clearing the eastern zones during the evening
with drying rapidly occuring as the low departs to the northeast
and sfc ridging providing fair weather by late Thursday night.

.LONG TERM...(Friday night through Tuesday)
Issued at 318 AM EDT Wed Apr 19 2017

We continue to expect a fairly quiet period for the long term.
Especially considering how wet it has been this spring. There is
really only one chance of rain for the Mon night and Tue period.

A lingering upper trough over the area Fri will slip east of the
area on Fri night. Even though this trough is still in the area, the
long wave weather pattern has a ridge just WNW of the area which
will dominate. Also, a confluent flow and dry low level flow will
keep the area dry, yet a little cool.

Dry weather will hold overhead, and temperatures will stay fairly
stable over the weekend with slight moderation toward Mon. The long
wave ridge will move overhead, and looks to shunt the upper low
south of the area entirely over the weekend. Temps will not moderate
much as the flow will remain from the NNE which will funnel cooler
air from Canada into the area. The sunshine will temper the cool air
mass a bit.

We will see better warming take place on Tue and more so beyond this
long term period. This will also come with the only chance of rain
in the long term. The upper air pattern will return to a zonal flow
as the srn low over the weekend gets pushed east. A decent short
wave will emerge from the Rockies, into the Plains and help
establish a strong srly flow that will pump warm air up into the
area. The chance of rain will come at the leading edge of this
warmer air.

&&

.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 154 PM EDT Wed Apr 19 2017

Currently all TAF sites are VFR (as of 1745z) and for the most
part I expect it to stay that way this afternoon. There is an area
of showers an a cluster of thunderstorms from near MKE south to
CHI heading northeastward. There is also an area of MVFR cigs and
visibilities assoicated with this area of showers/thunderstorms.
I expect the thunderstorms to stay south of I-94 but I could see a
few showers between 19z and 23z across our taf sites as this area
moves through.

Early tonight I expect VFR cigs to prevail but after 06z a warm
front pushes northeast across the area and will see IFR cigs
spreads across the area. I also believe there will be showers
around between 09z and 16z but the thunderstorms should miss this
area. Even so thunderstorms are not out of the question so I put
VCTS at all taf sites tomorrow morning. The low clouds will last
through most if not all of the day.

&&

.MARINE...
Issued at 315 AM EDT Wed Apr 19 2017

Winds and waves will come close to small craft advisory at times
today though Thursday as low pressure tracks over Lake Michigan.
Strong to severe thunderstorms are possible tonight into Thursday
morning south of Whitehall.


&&

.HYDROLOGY...
Issued at 1118 AM EDT Wed Apr 19 2017

River levels have returned closer to normal in many locations but
still remain a little high for the time of year. Rivers are above
bankfull and falling at Ionia, Maple Rapids, and Eagle, while
Evart is above bankfull and rising. Rain totals Thursday in excess
of an inch are possible upstream of Evart, which may boost the
crest over the comping days. Croton may reach bankfull by Friday
also. More spotty rain totals are expected in the Grand and
Kalamazoo basins, which should have a limited effect on main stem
rivers. Smaller river basins that receive locally heavy rain
(including Eagle) would be susceptible to rise again.

&&

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

$$

SYNOPSIS...Ostuno
SHORT TERM...Ostuno
LONG TERM...NJJ
AVIATION...WDM
HYDROLOGY...CAS
MARINE...Ostuno



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