Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 280051
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
851 PM EDT TUE SEP 27 2016

LATEST UPDATE...
Aviation

.SYNOPSIS...
Issued at 323 PM EDT Tue Sep 27 2016

A large area of low pressure over the central Great Lakes will
produce cool temperatures and showery weather during the next
several days. High temperatures will remain in the 60s through next
Monday.

&&

.SHORT TERM...(This evening through Thursday night)
Issued at 323 PM EDT Tue Sep 27 2016

Forecast concerns are tied to the movement of the upper low through
the period.

Not a lot of changes were made to the grids. Precipitation changes
will remain fairly high as the upper low continues to spin over the
state. Regional radar shows a large area of showers across northern
Wisconsin, the UP, and northern Lower and this area is slowly moving
south. The presence of the cool temps aloft will keep the region
unsettled and produce showers from time to time. Lake enhancement
will come into play also with h8 temps around 3c and lake temps
around 20s. It`s possible a few of the stronger cells could produce
thunder and we kept that in the grids. The low is progd to move
slowly south through the short term and continue to affect the cwa
into the long term. Temperatures will not increase much with the
upper low overhead and should remain in the 60s through the period.

.LONG TERM...(Friday through Tuesday)
Issued at 323 PM EDT Tue Sep 27 2016

Main focus for the extended forecast centers on occasional showers
with some breezy conditions possible on Friday with additional
chances for showers continuing into the weekend. Improving weather
conditions are anticipated after the weekend concludes.

The upper low that is currently moving into the region will be fully
cut off from the mid and upper level jets on Friday, leading to slow
propagation. The upper low will be in the process of migrating back
toward Michigan on Friday with more showers expected on the northern
periphery of the system. Solid low level NE flow coming off Lake
Huron and into the Grand River valley Friday will help boost wind
speeds a bit, likely above the current forecast of 10 to 20 mph.
Would not be surprised to see 20 to 30 mph at LAN and GRR with this
type of setup. Only a slight chance for thunder across our far
southern counties for Friday given very little instability. The
current forecast high temps may be too optimistic (mid 60s). Could
be closer to 60 if we trend wetter.

By Saturday, the upper low should be over central or northern
Indiana and Ohio. The surface low creeps into Michigan later in the
day, continuing the threat for showers. This actually continues into
Sunday as the system slowly moves over Lake Huron. Winds over the
weekend should be light given the proximity to the low center.

Mid level ridging Monday and Tuesday will help kick the system out
of the region and dry things out. The possibility exists for highs
well into the 70s on Tuesday as low level southerly flow potentially
brings H850 temps into the 10C to 13C range into Lower Michigan.

&&

.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 850 PM EDT Tue Sep 27 2016

VFR conditions are in place at all of the TAF sites at 00z. MVFR
ceilings are poised to the north across northern Lower Michigan
and portions of Wisconsin. These ceilings will try to work into
western Lower Michigan tonight. It appears MVFR conditions will
push in for a time overnight, but may retreat back to the west
with time. The showers are not restricting visibility too much and
therefore used VFR vsbys in the rain. Winds have already come down
from earlier today and light winds will continue through the
night.

Bottom line...we are expecting a push of MVFR ceilings this
evening and overnight, before they retreat west Wednesday morning.
Another push of MVFR ceilings will try to work in from the south
Wednesday afternoon. The rain will likely not affect visibility
too much.

&&

.MARINE...
Issued at 323 PM EDT Tue Sep 27 2016

We left the small craft advisory headline as is. Winds and will
decrease tonight. Waterspouts remain possible through Wednesday as
the upper low continues to sink south over the lake. A large lake
delta t combined with a deep convective cloud depth are contributing
factors.


&&

.HYDROLOGY...
Issued at 140 PM EDT Tue Sep 27 2016

River levels are around normal for this time of year. Lake enhanced
rain showers are possible through Wednesday. Rain showers continue
to be possible into Sunday. Rainfall totals into the weekend will
range from a half inch up to an inch and a half. Rivers and streams
should remain below bankfull through the weekend.

&&

.GRR Watches/Warnings/Advisories...
MI...None.
LM...Small Craft Advisory until 8 AM EDT Wednesday for LMZ844>849.

&&

$$

SYNOPSIS...04
SHORT TERM...04
LONG TERM...Hoving
AVIATION...Duke
HYDROLOGY...63
MARINE...04



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