Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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056
FXUS63 KGRR 221930
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
330 PM EDT Fri Jun 22 2018

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

.SYNOPSIS...
Issued at 330 PM EDT Fri Jun 22 2018

Showers and a small chance of a thunderstorm will persist into this
evening for areas mainly along and south of I-96. Rain chances will
then diminish overnight. Additional showers will develop over inland
locations on Saturday with an outside chance of a rumble of thunder.
Additional showers will remain possible across the north Saturday
night and early Sunday before they come to an end.

A dry day is expected on Monday as we will be in between systems.
Another good chance of rain will move back in for Tuesday and linger
into Wednesday.

&&

.SHORT TERM...(This evening through Sunday night)
Issued at 330 PM EDT Fri Jun 22 2018

Our main focus of the short term is dealing with rain trends and
convective chances through Sunday.

Band of showers continues to persist south of I-96 this afternoon,
moving a little slower than expected to the north. This is likely
due to the fact that dry air continues to eat away at the rain where
it is light enough. Where it is raining, some heavier downpours are
definitely still occurring. We are expecting the rain to diminish in
coverage and move NE as the entire upper low opens up and begins to
lift to the NE. The thunder chance will remain probably into mid-
evening, before we lose the limited diurnal instability available
with the abundant cloud cover.

We are expecting most areas to see mainly dry conditions for the
first portion of the day. There will be a couple renegade showers
lingering in the morning. During the afternoon hours, we will see a
lingering sfc trough over the area become enhanced some as the
inland areas warm up some and lake breezes form. The models are in
good agreement in setting up a sfc trough/convergence band near U.S.-
131 and then turning toward the sfc low near Detroit. These will be
mainly showers with little heating with plenty of clouds in place.
There could be just enough for an isolated storm, especially across
the south.

The showers from the diurnally enhanced trough on Sat will diminish
Sat evening. Additional showers will become possible across the
north Sat night as yet another short wave moves across Central and
Northern Lower. The showers will linger into Sun morning, before the
wave moves out Sun afternoon and clearing takes place.

.LONG TERM...(Monday through Friday)
Issued at 330 PM EDT Fri Jun 22 2018

Next week will start off dry with high pressure in place on Monday
both at the surface and aloft. The week become a bit more active
fairly quick with the chance for showers moving in late Monday
night. The showers are associated with an upper low moving through a
progressive pattern across the northern tier of states. This upper
low will move through the Great Lakes region Tuesday and Wednesday
bringing a fair amount of rainfall. Thunderstorms are quite possible
given some instability as dew points rise back up into the 60s ahead
of the system.

A brief respite from rainfall will come Wednesday night into
Thursday before another round of showers and storms potentially as a
warm front lifts into the area Thursday night and Friday. Saturday
we may transition into the warm sector with a southwest flow taking
shape.

The general trend on temperatures will be to above normal as 500mb
heights rise through the period. The forecast has upper 80s by the
end of the week.

&&

.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 141 PM EDT Fri Jun 22 2018

Low pressure lifting from Indiana to Southeast Michigan will bring
a deterioration in aviation conditions to all terminals over the
next 24 hours. The main impacts will be occasional chances for
rain showers, occasionally accompanied by heavy rain and a fast
reduction to visibility, and a period of IFR conditions tonight
through mid-morning Saturday. The more southern terminals (AZO,
BTL, JXN, LAN) may also see a period of LIFR after about 09Z
tonight. There is also a small chance for a thunderstorm (highest
along the I-94 corridor) but confidence was not high enough to
include in the 18Z TAFs. While there will be at least a continued
chance to see a shower at any terminal over the next 24 hours,
potential this afternoon will be greatest south of GRR, then shift
northward towards GRR, LAN, and MKG in the late afternoon and
evening after some drier air is overcome. Ceilings will begin to
lift Saturday morning as winds shift northwesterly on the
backside of the low and usher in some drier air.

&&

.MARINE...
Issued at 330 PM EDT Fri Jun 22 2018

We do not anticipate marine headlines being needed over the next few
days. A general offshore flow will continue for the nearshore waters
through much of the weekend. It will be a bit breezy the remainder
of today into tonight. The flow looks to be light enough Saturday
and Sunday that a lake breeze will develop in the afternoon and
early evening hours for a few hours.

&&

.HYDROLOGY...
Issued at 1108 AM EDT Thu Jun 21 2018

River levels are running near normal, and are steady or slowly
falling. No flooding is expected.

Periods of rain will be possible today through Saturday. Scattered
to numerous showers and thunderstorms may develop. Generally expect
less than an inch of rain, with locally heavy rainfall possible with
the storms. This may result in localized flooding where storms form
and train over the same locations.

&&

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

$$

SYNOPSIS...NJJ
SHORT TERM...NJJ
LONG TERM...Duke
AVIATION...HLO
HYDROLOGY...63
MARINE...NJJ



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