Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 211638
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
1238 PM EDT Fri Apr 21 2017

LATEST UPDATE...
Aviation

.SYNOPSIS...
Issued at 315 AM EDT Fri Apr 21 2017

High pressure will bring fair weather for the next several days.
The next chance for rain will not arrive until the middle of next
week when low pressure approaches from the west.

&&

.UPDATE...
Issued at 906 AM EDT Fri Apr 21 2017

I updated the zone forecasts to include the light rain showers
that were occuring around the area this morning. As I was driving
to work this morning it rained hard enough in places along the
road that I had to use my windshield washers and in some areas
the roads were wet from the rain falling. The showers are result
of shortwave with the coldest air aloft moving through the area.
All of this activity should move out of the area by early
afternoon as the core of the coldest air departs the region.

&&

.SHORT TERM...(Today through Sunday)
Issued at 315 AM EDT Fri Apr 21 2017

Some light showers early this morning across the northern zones
as upper trough axis moves through. Otherwise, fair weather
through the weekend as rex block and sfc ridging dominate the
weather in the Midwest-Great Lakes region.

Temperatures the next couple nights could dip close to freezing
across the southern half of the forecast area where fruit trees
have at least partially blossomed so we will have to look closely
at frost/freeze potential there. Light winds, very dry soundings
and clear skies should all help combine to produce prime
radiational cooling conditions, so the guidance mins were lowered
by a couple degrees across the forecast area for tonight and
Saturday night.

.LONG TERM...(Sunday night through Thursday)
Issued at 315 AM EDT Fri Apr 21 2017

The period begins with high pressure in control. We will remain
sandwiched between a washed out boundary over the northern Great
Lakes and a closed upper low passing over the Tennessee Valley.
Zonal flow develops Monday and should keep things dry through much
of Tuesday.

Warm air will begin to advect into Lower Michigan late Monday night
ahead of a surface low that eventually passes over Lakes Superior.
As this system continues to push northeast, a weak cold front will
trail behind it. The front never really makes it any further south
than central Lower. This may end up being a player on high temps
through the day Wednesday, but given the northwest trend in guidance
the last couple of days, I`d be comfortable keeping high temps in
the 60s. Any adjustment south could keep northern sections of the
forecast area in the 50s.

A second surface low takes shape over the Midwest and drives
northeast late Tuesday night into early Wednesday. The best chances
look to be favoring the NW corner of the forecast area, between
Grand Rapids and Ludington. Some of the convective parameters have
trended downward, as well. This may end up being another steady rain
with a couple of embedded thunderstorms. Given recent rainfall and
ground moisture, this will be something to watch with more rain to
contend with beyond Wednesday.

A weak cold front temporarily drop temperatures a few degrees on
Thursday. High pressure builds over the eastern conus into the day
Thursday, resulting in return flow and pushing the boundary back
north as a warm front. Yet another wave of rainfall is possible late
Thursday into Friday. Depending on how big of an influence the ridge
has late in the week, there is the potential to see high push well
into the 70s late next week.

$$

&&

.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 1238 PM EDT Fri Apr 21 2017

MVFR cigs prevail across the SW MI TAF sites early this afternoon
but the area of clearing is moving in from the north and
northwest. All taf sites should have VFR cigs by 21z and clear by
04z. Skies should remain clear into Saturday.

&&

.MARINE...
Issued at 315 AM EDT Fri Apr 21 2017

Winds and waves will gradually subside later today and the Small
Craft Advisory should be able to expire by this evening.


&&

.HYDROLOGY...
Issued at 1142 AM EDT Thu Apr 20 2017

Thursday morning rain totals surpassed 1 inch in Mason, Ottawa,
and northern Kent counties. Generally two thirds of an inch fell
upstream of Croton and one third fell upstream of Evart.
Expecting only a slight additional rise at Evart, while Croton
could reach bankfull on Friday. Looking Glass and Sycamore avoided
the heaviest rain while Maple caught some of it. While flood
stage being reached is not the most likely scenario, Looking Glass
appears to be the most vulnerable of all the rivers if it gets
repeated storms Thursday afternoon. Fortunately, dry weather is
expected Friday into early next week.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
LM...Small Craft Advisory until 11 PM EDT this evening for LMZ844>849.

&&

$$

UPDATE...WDM
SYNOPSIS...Ostuno
SHORT TERM...Ostuno
LONG TERM...JAM
AVIATION...WDM
HYDROLOGY...CAS
MARINE...Ostuno



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