Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 201450

Area Forecast Discussion
National Weather Service Grand Rapids MI
1050 AM EDT Thu Oct 20 2016


Issued at 330 AM EDT Thu Oct 20 2016

Low pressure tracking through the Ohio Valley today will bring
occasional rain, mainly to areas south and east of Grand Rapids.
North winds will usher in colder temperatures for tonight through
Saturday, along with some lake effect rain showers along the Lake
Michigan shoreline. Milder temperatures will arrive for second half
of the weekend.


Issued at 1050 AM EDT Thu Oct 20 2016

Made some minor changes to the forecast to address the NW edge of
the pcpn shield. Dry low level air winds out to the NW so not
expecting any rain NW of a AZO-Y70-AMN line. Trimmed the POPs from
this area. Also extended the likely POPs over the far SE CWA, near
JXN, into the evening hours as the pcpn should only very slowly
move out of this region.


.SHORT TERM...(Today through Saturday)
Issued at 330 AM EDT Thu Oct 20 2016

Not much change to the going forecast as guidance continues to show
most persistent rain impacting areas south and east of a AZO-LAN
line today. Mid level FGEN forcing will result in occasional banded
look to the rainfall, possibly resulting in non-uniform rainfall
totals and narrow corridors of locally higher amounts.

In general will have categorical pops around JXN tapering to only
chance around GRR, and a dry forecast north and west of GRR.
Actually areas north and west of GRR could get some filtered
sunshine today with only high clouds expected, and that could lead
to warmer highs than currently forecasted.

Setup still looks good for scattered lake effect rain showers as
deep upper trough and -2C H8 air impacts the region later tonight
and Friday. However the low level flow remains quite northerly
through the event which will limit the showers to immediate coast.
The Ludington and Pentwater areas should be most impacted by the
lake effect tonight and Friday.

Departure of the upper trough and incoming surface ridging will lead
to a diminishing trend to lake effect Friday night. Some frost
appears likely inland from the lakeshore as skies clear.

.LONG TERM...(Saturday night through Wednesday)
Issued at 330 AM EDT Thu Oct 20 2016

A ridge of high pressure will remain in control of the weather
pattern Saturday night and will bring fair wx with seasonable
temperatures. A brief warming trend in temperatures will occur on
Sunday as winds become southerly.

A mid level wave will move in from the northwest Sunday and may
bring just a few light rain showers or sprinkles to our far
northeastern fcst area. However dry and mild wx will prevail across
most of our area.

A cooler airmass will move back in behind that system for early next
week. However temperatures will moderate Wednesday as strong
southerly winds develop out ahead of a low pressure system that will
move from the central Plains states to the upper midwest. This
system will bring potential for some showers by midweek.


.AVIATION...(For the 12Z TAFS through 12Z Friday morning)
Issued at 748 AM EDT Thu Oct 20 2016

Predominately VFR conditions are expected today and tonight with
cloud bases at or above 4000 ft, although periods of MVFR
cigs/vsbys are possible south and east of GRR today related to the
areas of rain moving through.


Issued at 330 AM EDT Thu Oct 20 2016

Will issue small craft advisories as north flow increases today,
continuing through Friday evening. Will start the advisory this
morning north of Whitehall, then over the rest of the nearshore area
after 2 pm.

Waterspout potential exists with any lake effect showers per
waterspout nomogram with water to 850 mb temp difference around 19C
and convective cloud depths of 8000 ft or so.


Issued at 319 PM EDT Wed Oct 19 2016

Despite rivers running above normal to well above normal through
much of Southwest Lower Michigan, improvement is expected to
continue for a majority of the sites. The lingering question this
afternoon is in the far southeastern corner of the forecast area,
near Jackson. Rainfall tonight into Thursday has the potential to
total between 0.25-0.50 of an inch. These amounts are fairly run-of-
the-mill, but given recent ground saturation, results closer to 0.50
of an inch may lead to within bank rises in that area, especially on
small streams.

Aside from the rainfall mention tonight into Thursday, the next 5-7
days is void of any large impact events. Flooding is not anticipated.


LM...Small Craft Advisory until 8 PM EDT Friday for LMZ848-849.

     Small Craft Advisory from 2 PM this afternoon to 8 PM EDT Friday
     for LMZ844>847.



LONG TERM...Laurens
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