Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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219
FXUS63 KGRR 221928
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
328 PM EDT Mon May 22 2017

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

.SYNOPSIS...
Issued at 328 PM EDT Mon May 22 2017

An upper low over the Great Lakes will keep the chance of rain in
the forecast for the next few days. Wednesday night into Thursday
looks like the highest chance of rain and that`s mainly south of I-
96. Temperatures will be near to slightly below normal this week.
Warmer weather is expected for the Memorial Day weekend.

&&

.SHORT TERM...(This evening through Wednesday night)
Issued at 328 PM EDT Mon May 22 2017

Forecast concerns deal with pcpn trends through the period. Regional
radar shows a decaying area of showers extending from southeast
Wisconsin through northern Missouri. This area of light rain was
moving east but struggling as it encountered drier air. We kept a
low chance of rain in the grids tonight, but we`re not expecting
much.

A sfc low will move toward Lake Michigan Tuesday as the upper trough
edges closer to Michigan. This will increase chances for rain
Tuesday afternoon . Li`s fall below 0c Tuesday and models show 500-
1k j/kg MUCAPE so we added a slight chance for thunder too.

A deeper low is progd to move north toward the state Wednesday. This
is when we`ll see the highest chance for showers/storms. The LLJ
increases during the day, but pwats remain fairly low. Thus heavy
rain isn`t expected.

.LONG TERM...(Thursday through Monday)
Issued at 328 PM EDT Mon May 22 2017

Still some scattered showers expected on Thursday, especially east
of highway 131, with upper low lingering over the eastern Great
Lakes Region. Would not even rule out a few isolated showers on
friday but ridging is shown to be moving in, so probably a
predominately dry day.

At this time, Saturday looks to be the best day of the holiday
weekend. Sfc ridging should lead to light winds, and H8 temps near
12C suggest highs in the mid to upper 70s. Currently the guidance is
keeping the warm frontal related convection south of the state on
Saturday.

Precipitation potential appears to increase on Saturday night and
Sunday due to the approach of the next H5 trough/upr low from the
west/northest. ECMWF/GFS differ on handling of this feature over the
second half of the holiday weekend, with the ECMWF more progressive,
so confidence is low regarding precipation potential and coverage,
and if/how much it cools off heading into Memorial Day.

&&

.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 153 PM EDT Mon May 22 2017

The main aviation issue this afternoon is the winds as we will
continue to have gusty west winds of 15 to 25 knots through early
evening. Sfc wind speeds will drop below 10 knots after 00z.

Rain showers are expected to push in rapidly from the southwest
later today and tonight, particularly north of a line from AZO to
LAN. Rain will be most persistent/heaviest at MKG and GRR, and
MVFR cigs/vsbys should develop at these terminals by 06Z tonight.
There is even a risk of some IFR later tonight, especially at MKG.

Meanwhile, farther southeast, JXN is expected to remain VFR
tonight into Tuesday with little or no rain. The AZO/BTL/LAN TAFS
are sort of tricky since they`ll be on the srn edge of the lower
MVFR/IFR cigs later tonight and could go either way - or
fluctuate between VFR and MVFR once the rain moves in.


&&

.MARINE...
Issued at 328 PM EDT Mon May 22 2017

We cancelled the small craft advisory a few hours early. Web cams
reveal little in the way of white caps and buoys are generally aob 3
ft. This suggest that mixing is struggling over the water.

&&

.HYDROLOGY...
Issued at 125 PM EDT Mon May 22 2017

River systems in Southern Lower Michigan are running above normal,
while river levels in Central Lower Michigan are around normal.
Tonight through Thursday, unsettled weather will bring up to an inch
of rain. This should keep levels elevated, but not expecting
flooding to result. The following forecast is based on observed and
forecast 24 hour precipitation.

&&

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

$$

SYNOPSIS...04
SHORT TERM...04
LONG TERM...Meade
AVIATION...Meade
HYDROLOGY...63
MARINE...04



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