Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 191927
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
325 PM EDT Mon Jun 19 2017

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

.SYNOPSIS...
Issued at 325 PM EDT Mon Jun 19 2017

Scattered showers and isolated thunderstorms will continue to
develop through Tuesday before fair weather returns Tuesday night
through Wednesday. Showers and thunderstorms are expected late
Wednesday night through Thursday night.

&&

.SHORT TERM...(This evening through Wednesday night)
Issued at 325 PM EDT Mon Jun 19 2017

Primary short term fcst concerns involve determining convective
potential tonight through Tuesday and for late Wednesday night.

Sufficient instability has developed for showers and isolated
convection to continue to develop late this afternoon and evening.
Scattered convection over our se fcst area will continue to drift
slowly east and out of our area with a westerly flow lake shadow
resulting in dry wx over most of our fcst area for the next
hour or two.

However rgnl radar trends suggest that scattered showers and
isolated storms currently over eastern WI and western Lake Michigan
will move into our fcst area very late this afternoon through this
evening. This notion is supported by 3km nam and hrrrx higher
resolution guidance.

Scattered showers and isolated convection will develop again on
Tuesday. However tomorrow`s environment will be different with
little to no instability but stronger shear. Overall we expect
even less coverage of convection tomorrow but isolated stronger
storms may potentially contain gusty (but sub severe) winds.

Fair weather will return late tomorrow night through Wednesday
evening as a high pressure ridge builds in. However showers and
thunderstorms will develop early Thursday morning fueled by
forcing from a vigorous llj.

.LONG TERM...(Thursday through Monday)
Issued at 325 PM EDT Mon Jun 19 2017

Thursday and Thursday night look rather active with the potential
for some stronger storms and/or heavy rainfall.

Some type of MCS should be impacting the area Thursday morning with
a strong low level jet aimed directly at us, so will carry likely
PoPs. Typically in this setup a weakening trend of the convection
will take place by noon as the low level jet weakens, but if the low
level jet can be sustained through the day or if new diurnal
development fires on residual outflows/MCVs from the earlier
convection, we could have clusters of storms around all day long.

Then on Thursday night the sfc cold front is shown to sink slowly
south through the area. Scattered to numerous storms will continue
to be possible along/ahead of this front within axis/pool of PWATs
close to 2 inches and sfc dew pts around 70 sitting over the area.

As the sfc cold front settles southward on Friday, we should dry out
in the afternoon and probably remain relatively quiet Friday night
and Saturday. It looks like the front could try to bulge north again
on Saturday night and Sunday as a wave moves along the front, but
confidence in this scenario is low. The whole weekend could
potentially end up being dry with cooler/drier air mass gradually
filtering in from the northwest.

&&

.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 156 PM EDT Mon Jun 19 2017

Will carry thunder in the TAFs through about 20Z east of GRR/AZO.
After 20Z, most of the convection near BTL/LAN/JXN will have moved
off to east as the westerly flow continues to send stable lake MI
air farther inland. Any shower/tstm could create IFR or lower
conditions, possibly even with some small hail, but these would
probably be very brief based on the small cell size noted on
radar.

More tstms are floating east from Wisconsin, but these should
tend to weaken as the come across lake MI. Will therefore only
carry VCSH into the evening hours before all of this activity
weakens with sunset.

Otherwise VFR tonight into Tuesday morning. Gusty west winds this
afternoon diminishing to 5-10 kts tonight, but increasing/becoming
gusty again after 14-15Z Tuesday. More widely scattered
showers/isolated storms will likely develop on Tuesday,
particularly in the afternoon.


&&

.MARINE...
Issued at 325 PM EDT Mon Jun 19 2017

Wave heights of 2 feet or less are forecast late this afternoon
through tonight. Wave heights of 1 to 2 feet are expected again
Tuesday although some 3 footers are possible by late morning through
the afternoon. Conditions will be tranquil Wednesday. Winds and
waves may ramp up on Thursday and thunderstorms may pose a hazard to
mariners late Wednesday night through Thursday night.

&&

.HYDROLOGY...
Issued at 159 PM EDT Mon Jun 19 2017

Two to over three inches of rain fell this past weekend which is
leading to higher river flows. The Flat River near Smyrna may reach
bankfull by midweek, but is the only site expected to do so.
Scattered showers and a few thunderstorms will be possible today and
Tuesday with less than a quarter inch of rain expected on average.
Additional heavier rains will become possible once again Wednesday
night through Friday and should lead to additional rises.

&&

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

$$

SYNOPSIS...Laurens
SHORT TERM...Laurens
LONG TERM...Laurens
AVIATION...Meade
HYDROLOGY...63
MARINE...Laurens



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