Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 230528

Area Forecast Discussion
National Weather Service Grand Rapids MI
128 AM EDT SAT JUL 23 2016


Issued at 328 PM EDT Fri Jul 22 2016

The hot and humid weather will continue into Sunday before a cold
front comes through and brings relatively cooler and drier air
into the area. That relativity cooler air will last through next
week. The next chance for thunderstorms will be Sunday into Sunday
night. If your area misses out on that rain, the next chance would
be Wednesday into Thursday.


Issued at 1055 PM EDT Fri Jul 22 2016

Updated to add patchy fog to the forecast. Clear skies and calm
winds with dew points near 70 should promote some radiational fog
development. Latest gridded visibility guidance suggests under
1/2 mile possible, especially near lk mi and south of I-96.


.SHORT TERM...(This evening through Sunday night)
Issued at 328 PM EDT Fri Jul 22 2016

The main issues are the threat of thunderstorms on Sunday and just
how hot it will get Saturday. It does not look like we will have
high enough dew points to justify a heat advisory Saturday.

The passage of weak cold front through the area has brought much
drier mid level air into the area (as seen on the water vapor
image loops). A Canadian shortwave passing well north of the area
is helping to bring down the drier air. This dry air will prevail
over the area into Saturday evening. That will keep the chance for
thunderstorms below 10 pct through early evening Saturday.

That dry air will also allow for cooler lows tonight, with most
areas having lows in the 60s. On Saturday we do have a surge of
hot air later in the day. That should help bring our highs into
the lower to mid 90s. With dew points in the 60s, that will not be
hot enough for a heat advisory.

Our next chance for thunderstorms will be Sunday into Sunday
night. A northern stream system will push a warm front through the
area in the morning. That will bring the risk of thunderstorms.
Then the cold front will come through Sunday evening and that will
also have the threat for thunderstorms. There is good moisture for
this system but the best dynamics are north of the area once
again. On the up side, we do get the right entrance region of the
polar jet Sunday evening. That could help the cause of bringing
much needed rain to the area once again. The severe risk looks
marginal at best.

.LONG TERM...(Monday through Friday)
Issued at 328 PM EDT Fri Jul 22 2016

The beginning of the upcoming work week looks to be dry with surface
high pressure in place much of the time. A cold front will be
slipping off to the east of the area Monday morning with the high
centered overhead on Tuesday. Have a dry forecast in place for
Monday through Tuesday night. 850mb temps are still fairly warm on
Monday, so looking at highs well into the 80s despite the frontal
passage. 850mb temps do not change much into Tuesday either, so a
similar warm story that day as well.

Have small chances for showers and thunderstorms the remainder of
the week, from Wednesday through Friday. Wednesday and Wednesday
night a low pressure system will be traversing the area and these
periods are probably the best chances for rain in the long term. The
flow is fairly zonal with a shortwave swinging through the Great

Thursday into Friday the upper flow is more northwesterly with
another shortwave embedded in the flow. Moisture is a bit more
shallow in these periods, but cannot rule out some precipitation.
Temperatures should be closer to normal on Thursday and Friday.


.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 128 AM EDT Sat Jul 23 2016

The only expected impacts to aviation interests will be the
fog/stratus that is already starting to form across the area. We
expect that conditions will drop down to IFR and below at all of
the terminals by 09z this morning. The fog will quickly dissipate
after sunrise this morning.

We expect mainly clear skies once the fog burns off this morning.
There could be a few cumulus clouds floating around, but they
would not impact pilots. Winds will remain light under 10 knots.
KMKG will see a lake breeze kick in. The VFR conditions will
likely remain through 06z Sun. Showers and storms will become
possible from West to East after this fcst period after 06z Sun.


Issued at 328 PM EDT Fri Jul 22 2016

We will likely need a small craft advisory Sunday as we get into
the warm sector of the system moving through the area. Likely a
beach hazard statement will be needed too.


Issued at 1233 PM EDT Fri Jul 22 2016

Thursday rainfall amounts ranged from a tenth to three-quarters of
an inch across the whole area... a welcome sight for many.
Sunday`s thunderstorms will likely produce a similar range of
amounts, although locally higher amounts could occur if the storm
mode turns out to be more of a multicell cluster rather than
progressive linear like Thursday.


.GRR Watches/Warnings/Advisories...


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