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183
FXUS63 KGRR 261520
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
1120 AM EDT Mon Jun 26 2017

LATEST UPDATE...
Hydro

.SYNOPSIS...
Issued at 330 AM EDT Mon Jun 26 2017

Another unseasonably chilly day is in store with highs only in the
60s and scattered rain showers. Temperatures will gradually moderate
after today, returning to closer to normal by mid to late week.
However the return of the warmer air will also result in showers
and thunderstorms with a risk of some stronger storms and locally
heavy rain.

&&

.SHORT TERM...(Today through Wednesday)
Issued at 330 AM EDT Mon Jun 26 2017

The last in a series of vorticity maxima/upper lows in the
anomalous northwest flow pattern arrives this afternoon. Expect
an increase in clouds and shower coverage as this feature drops
in, with thunder probabilities also creeping up by afternoon.

Since the shortwave arrival is coincident with peak heating, can`t
rule out a few isolated stronger cells today with strong gusty
winds and small hail. Freezing levels drop to 6500-7000 ft this
afternoon. The pattern is also supportive of cold air funnels as
the core of the cold air with H8 temps around 3C comes overhead
later today.

Shower coverage will decrease after sunset, then arrival of
surface ridging on Tuesday will lead to quieter weather
continuing into the first half of Wednesday. However the warm air
is quick to surge back in from the southwest later Wednesday as
low level jet cranks up to 50 kts over WI/IL in the afternoon.
Showers and tstms are likely north and west of GRR by late in the
day.

.LONG TERM...(Wednesday night through Sunday)
Issued at 330 AM EDT Mon Jun 26 2017

Active wx is anticipated mid to late week with potential for several
rounds of convection. A low pressure system will move east into the
upper midwest Wednesday night and bring the first round of showers
and storms.

Convection will develop on the nose of a strong 45-55 kt llj. This
in conjunction with increasing low level moisture and some weak to
moderate instability will set the stage for convective development.
Some strong to potentially severe storms are possible given this
synoptic setup and fairly strong deep layer shear.

Medium range guidance continues to show potential for a frontal
boundary to then stall out near our just south of our fcst area
Thursday through Thursday night. This would continue to focus
development of more showers and storms. Another low pressure system
will then move through our region Friday through Friday night and
bring more convection. A few showers may linger into Saturday before
a cooler and drier airmass advects in for later in the weekend.

&&

.AVIATION...(For the 12Z TAFS through 12Z Tuesday morning)
Issued at 752 AM EDT Mon Jun 26 2017

Diurnal cumulus clouds should become more widespread through the
morning, starting out with sct-bkn MVFR bases of 1500-2500 ft,
lifting to mostly bkn-ovc VFR levels around 3500 ft by noon.
Isolated showers this morning will become more numerous, with
tstms also possible in the afternoon/evening. Some small hail
could occur. West winds will be gusty today at 15 to 30 kts, and
possibly even some stronger gusts if a heavier cell moves through.
Winds will decrease below 10 knots tonight.


&&

.MARINE...
Issued at 330 AM EDT Mon Jun 26 2017

Cold advection and cyclonic flow similar to a fall pattern will
result in hazardous winds and waves today into the evening.
Arrival of the upper low this afternoon and even colder air aloft
will also the support the possibility of a few tstms and waterspouts.

After a calmer period on Lake Michigan Tuesday, winds and waves
will increase to hazardous levels again on Wednesday into
Thursday with southwest flow.


&&

.HYDROLOGY...
Issued at 1119 AM EDT Mon Jun 26 2017

River levels are trying to return to normal across the region...with
the Chippewa River at Mt. Pleasant and Pine River at Alma above flood
stage. Scattered showers and thunderstorms...which will develop as
an upper low moves over the state this afternoon...are not expected
to produce the areal coverage or intensity of precipitation needed
to slow the falling of the stages. Therefore...expect river levels
to continue to fall steadily over the next 24 hours.

Another round of potentially heavy rainfall will occur later
Wednesday into Wednesday night. Deep moisture returns to the
region...and bands of heavy rainfall may occur across central
portions of Lower Michigan. Rivers in Isabella and Gratiot
counties are especially vulnerable to excessive rainfall...and
significant rises would likely develop on the Pine and Chippewa
rivers should the heavy rainfall occur in these basins.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Beach Hazards Statement through this evening for MIZ037-043-050-
     056-064-071.

LM...Small Craft Advisory until midnight EDT tonight for LMZ844>849.

&&

$$

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