Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 181741
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
141 PM EDT Thu May 18 2017

LATEST UPDATE...
Aviation

.SYNOPSIS...
Issued at 240 AM EDT Thu May 18 2017

A low pressure system will track from Wisconsin through Northern
Lower Michigan today. A cold front associated with this system
will track through the region today. A few showers or
thunderstorms may accompany the passage of this feature. Strong
gusty winds today may occasionally top 40 mph. A large area of
high pressure then settles into Ontario for Friday. This fair
weather system will lead to dry conditions for much of the Great
Lakes region on Friday. Another low pressure system moves in for
the weekend leading to unsettled weather.

&&

.UPDATE...
Issued at 1134 AM EDT Thu May 18 2017

Convection allowing models like the HRRRX and the 3KM NAM both
pick up on the ongoing convection across Central Lower Michigan.
Confidence is fairly high on what they show for this afternoon,
which is the ongoing activity lifting into Northeast Lower
Michigan and much of the area remaining dry this afternoon. The
cold front begins to touch off convection in our far southeast CWA
this afternoon, but the bulk appears to be just south and east of
our area.

Wind advisory looks good with gusts up into the 45 to 50 mph range
this morning. Looking at BUFKIT profiles we should continue to see
advisory level gusts this afternoon.

&&

.SHORT TERM...(Today through Saturday)
Issued at 240 AM EDT Thu May 18 2017

The main challenge in the short term deals with how strong the
wind gusts will be today. It appears they will end up stronger
than currently forecasted.

Models are showing stronger winds at around 850 mb today...up over
40 knots. Combining this with the deeper mixing(to 850 mb) that
is forecasted...it looks like many locations will see surface
gusts over 45 mph later this morning and into the afternoon. Based
on this...will go with a wind advisory today for most of the CWA.

As for the thunder risk...models really do not generate much
convection today. We do destabilize through the morning...and the
axis of deeper instability persist along the I94 corridor through
the afternoon. Will keep a risk for thunderstorms going...but
overall POPs will remain low for the day. Given the strong wind
fields that will be in place...any stronger downpour could lead to
strong gusty winds at the surface.

Tonight through Friday....it looks mainly dry. Around Jackson
there could still be a storm through 01z to 02z...but overall the
focus for that looks further south.

A slow moving low pressure system approaches the Western Great
Lakes region from the southwest Friday night into Saturday. The
axis of instability and deeper moisture pivots into the CWA as we
go through the period. This supports increasing POPs and a rising risk
for thunderstorms.

.LONG TERM...(Saturday night through Wednesday)
Issued at 240 AM EDT Thu May 18 2017

The cold front associated with the low pressure system that will
be tracking through the Western Great Lakes region Saturday night
into Sunday will push through the CWA. Showers and thunderstorms
may result. The axis of instability tracks east of the CWA Sunday
afternoon. As a result I will diminish the risk for thunderstorms
then from west to east.

A cooler Canadian airmass arrives for Sunday night into Monday as
the low tracks eastward through Ontario. Will feature well below
normal temperatures.

Models are trying to develop a wave of low pressure on the surface
front Monday night into Tuesday. Then then track this system into
Michigan. If this happens...we could end up with a cool wet period
then. This is associated with the passage of a deep upper
trough...would support higher POPs.

&&

.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 141 PM EDT Thu May 18 2017

West and southwesterly gusts of 35-40 kts have been observed
throughout the area. Gusty conditions will continue to be an
issue through the remainder of the afternoon. Cigs look like less
of an issue with VFR/MVFR through the period.

A cold front that is currently over eastern Wisconsin will push
eastward into Lower Michigan this evening. A few showers are
possible along the front. However, the environment does not look
favorable for development. So, any shower activity would likely be
spotty and brief... hit-or-miss. Winds will shift out of the
northwest behind the front with gusts of 20-25 kts possible
through early evening. Wind is expected to slow to 10 kts or less
after sunset, becoming northerly into early Friday.


&&

.MARINE...
Issued at 240 AM EDT Thu May 18 2017

No changes to the marine headlines. Strong gusty winds will
continue as the cold front pushes through...supporting the SCA.


&&

.HYDROLOGY...
Issued at 1241 PM EDT Wed May 17 2017

Streamflow is currently normal for most sites. Although a few
storms may move through the region through Thursday, they won`t be
widespread enough to impact the main basins. Still looking at
basin average rainfall amounts this weekend of 0.50"-1.00". Can`t
rule out some locally higher amounts. That shouldn`t be enough
rain to cause more than some within bank rises, though above bank
rises can`t be ruled out. Additional rainfall is possible by the
early and middle portions of next week.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Wind Advisory until 8 PM EDT this evening for MIZ040-044>046-
     050>052-056>059-064>067-071>074.

LM...Small Craft Advisory until 6 AM EDT Friday for LMZ844>849.

&&

$$

UPDATE...Duke
SYNOPSIS...MJS
SHORT TERM...MJS
LONG TERM...MJS
AVIATION...JAM
HYDROLOGY...Hoving
MARINE...MJS



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