Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 231719

Area Forecast Discussion
National Weather Service Grand Rapids MI
119 PM EDT FRI SEP 23 2016


Issued at 330 AM EDT Fri Sep 23 2016

A cold front will slip south of the area today which may touch off a
few showers especially across Southern Lower Michigan. The front
will become stationary just south of the Great Lakes and even though
mainly dry conditions are expected tonight, Saturday and Saturday
night it will likely provide a fair amount of cloud cover to the
area. Cooler and less humid air will begin to flow into the area
today as winds go northerly. Noticeably less humid air will be in
place for Saturday. The next good chance for rain will come Sunday
night into Monday as a cold front sweeps in from the west. Cooler
fall like air will flow in behind this front. Highs will be near
normals for this time of year today through the weekend in the 70s,
cooling into the 60s for mid next week.


Issued at 946 AM EDT Fri Sep 23 2016

Based on Kgrr/rgnl radar trends and a consensus of latest short
range guidance and sref pops we will raise pops for showers for
our southern fcst area today (south of I-96 and particularly south
to sw of KGRR). Scattered showers will continue to develop through
late morning into the afternoon mainly along and south of the I-94
corridor in closer proximity to the nearly stationary frontal
boundary that will eventually move a bit further south this
afternoon. Otherwise the remainder of the fcst looks good and will
remain unchanged.


.SHORT TERM...(Today through Sunday)
Issued at 330 AM EDT Fri Sep 23 2016

Limited concerns overall through the short term with a mainly dry
forecast in place. The cold front is somewhat ill defined at 07z,
but likely is situated somewhere near the I-96 corridor. No showers
were noted in Southwest Lower Michigan near the front. The front may
pass to the south of the area by midday with little fanfare by

Some instability lingers along the I-94 corridor with most unstable
CAPE values forecast to be around 1000 J/KG at 18z. Convection
allowing models are not bullish on precipitation let alone thunder,
so left thunderstorms out of the forecast. Have a 20 percent chance
for isolated showers in the forecast today. Lingered the 20 percent
chances across the far south this evening. Overall not expecting
much in the way of precipitation today or this evening as
convergence along the front should be pushing south of the area.
There is no low level jet support either.

Possibility for some patchy fog issues this morning, but overall not
expecting any issues as the northerly flow should advect in drier
air and mitigate the threat.

Dry weather is forecast from late tonight through Sunday morning as
high pressure noses into the area. Some mid clouds may trend skies
toward partly to even mostly cloudy at times during these forecast

On Sunday a cold front associated with an upper trough advancing
through the plains states will push showers into Western Lower
Michigan during the afternoon hours. Best chances will hold out
until Sunday night, but there will be some precipitation trying to
work in from the west late in the day.

.LONG TERM...(Sunday night through Thursday)
Issued at 330 AM EDT Fri Sep 23 2016

We will see an increase in rain chances at the beginning of the long
term Sunday night, after a break in rain chances for much of the
weekend. The upper ridge that will bring the dry weather to end the
short term will move east of the area toward Sunday night. This will
allow the nrn portion of the Wrn U.S. trough to approach the area.
This will push rain in ahead of the sfc front for Sun night and into

Some uncertainty remains for how long we see much cooler temps and
the threat for showers as the upper trough or low moves through the
region. The speed of this trough/low moving through will be
dependent on how much it closes off. There has been a slight trend
toward a less closed scenario, and slightly more progressive
solution. With this in mind, we have a chance of rain showers
gradually diminishing through Wed with the trough/low near the

We should then dry out for next Thu as long as the system does not
close off and get stuck over the region. Moderating temps aloft with
more sunshine will help sfc temps warm also back to near average


.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 115 PM EDT Fri Sep 23 2016

IFR impacts are forecasted to diminish as we go through the
afternoon as the low level humidity will decrease. MVFR is
expected to persist any drying will be limited. There will be some
showers around...mainly for KAZO and KBTL this afternoon. While
some instability will build...the risk for thunderstorms was too
low to include in the forecast.

I have added IFR conditions to the tonight forecast for many TAF
sites. The low level moisture increases again tonight. This could
lead to a period of low clouds and fog. Any fog or low clouds will
lift during Saturday morning.


Issued at 330 AM EDT Fri Sep 23 2016

Winds and waves will remain below Small Craft Advisory criteria
through the next couple of days. A front will slide south of the
lake today with high pressure building into the northern Great
Lakes. This will provide an off shore northeast and easterly flow.
Winds will generally be in the 10-15 knot range which given and off
shore flow should keep waves at 2 feet or less in the nearshore

On Sunday a southerly flow will increase ahead of an advancing cold
front. South winds may increase into the 10 to 20 knot range if not
even a bit higher. Therefore, Sunday may be our next time frame of
concern in regard to waves that may reach SCA criteria.


Issued at 1032 AM EDT Fri Sep 23 2016

Hydro concerns are minimal through the weekend, as little rain is
expected and river levels are around normal for the time of year.
Showers and thunderstorms are expected Sunday into Monday night with
additional rain possible Tuesday into Wednesday. Around 1 inch of
rain is expected and therefore rivers and streams should remain
below bankfull through the week.


.GRR Watches/Warnings/Advisories...


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