Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 221917
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
315 PM EDT Fri Sep 22 2017

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

.SYNOPSIS...
Issued at 315 PM EDT Fri Sep 22 2017

Hot humid and predominantly dry weather will continue through
Monday. An isolated shower is possible through early this evening
east of US-131. However the vast majority of our area will have dry
conditions through the weekend into early next week. A cold front
will bring the next good chance for rain for most of our area late
Tuesday into Wednesday.

&&

.SHORT TERM...(This evening through Sunday night)
Issued at 315 PM EDT Fri Sep 22 2017

It will remain unseasonably hot and humid through the weekend with
sfc/upper ridging in place and persistent south to sw flow waa.
High temperatures will reach the upper 80`s to lower 90`s through
the weekend with a couple of middle 90`s max temps possible at
typically hottest/driest locations. Low temps will range from the
middle 60`s to lower 70`s. We will maintain mention of patchy fog
in the fcst during the early morning hours Saturday with the humid
airmass in place and very little boundary layer mixing at that
time.

A cu field has developed near to east of a line from Mt. Pleasant
to Allegan. Dry wx will continue across the vast majority of our
area through the rest of the afternoon and evening. However
an isolated shower or two and perhaps an isolated storm may
develop east to southeast of KGRR through the early evening hours
now that instability has increased. Overall convective potential
looks very low though due to lack of a forcing mechanism/boundary
to focus convective initiation.

.LONG TERM...(Monday through Friday)
Issued at 315 PM EDT Fri Sep 22 2017

A substantial shift is still expected next week in our weather
pattern. The upper ridge that is in place now will shift off to the
east on Monday and Tuesday replaced by troughing on Thursday and
Friday. 850mb temps start the work week in the +16 to +18C range,
but dive to as low as +3C later in the week.

Monday and Tuesday will continue to be warm and humid with highs
expected to be in the 80s. The frontal passage has trended earlier
in both the ECMWF and the GFS. The front is now east of the CWA in
both models by midday on Wednesday.

Chances for showers and storms look possible with the front from
Tuesday afternoon through Wednesday midday. The deeper moisture with
the front is forecast to move pretty quickly through the area so the
best chances for precipitation look to come Tuesday night and early
Wednesday morning.

Much cooler air will be in place for the last two days of the work
week, Thursday and Friday. Highs on Wednesday will likely be in the
70s, but only 60s are expected for Thursday and Friday. So, folks
that are not fond of this type of heat in September will be happier
by mid to late next week.

As for precipitation chances in the northwest flow/upper troughing
our model blends look a bit dry in my opinion for Thurs/Fri. I can
see needing to add more in the way of showery precipitation to the
forecast as the ECMWF is pushing multiple upper shortwaves through
our area during that time frame.

&&

.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 151 PM EDT Fri Sep 22 2017

Two items to keep an eye on the next 24 hours in regard to
aviation. The first will be the chance for some isolated showers
and thunderstorms at KAZO, KBTL, KLAN and KJXN this afternoon and
early evening. Best chances (albeit small) for precipitation are
between 19z and 01z. At this point given the isolated threat of
precipitation have only included VCSH wording. A few thunderstorms
are certainly possible however given the amount of instability
present today. Shower and thunderstorm chances should end by 02z
at the latest.

The next item of concern is some light fog late tonight. MVFR
visibilities of 3-5SM are possible at KAZO, KBTL, KLAN and KJXN
between 09z and 14z.

Otherwise expecting VFR weather the remainder of the time with
mostly clear skies. There will likely be some broken ceilings
though across South Central Lower Michigan this afternoon with
bases around 5,000ft.


&&

.MARINE...
Issued at 315 PM EDT Fri Sep 22 2017

Wind speeds and wave heights will remain minimal through the
weekend with south to southwest winds of around 5 to 15 kts and
wave heights at or below 2 feet.

&&

.HYDROLOGY...
Issued at 1054 AM EDT Fri Sep 22 2017

Rivers are running around normal to below normal for the time of
year. Meanwhile, the US Drought Monitor is indicating dry conditions
across Southern Lower Michigan. Isolated thunderstorms may develop
during the afternoon and early evening near I-69. Near-record warmth
is expected today through the weekend. The next chance for rain is
Wednesday. No river issues are expected through next week.

&&

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

$$

SYNOPSIS...Laurens
SHORT TERM...Laurens
LONG TERM...Duke
AVIATION...Duke
HYDROLOGY...63
MARINE...Laurens


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