Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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586
FXUS63 KGRR 190001
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
801 PM EDT Mon Sep 18 2017

LATEST UPDATE...
Aviation

.SYNOPSIS...
Issued at 330 PM EDT Mon Sep 18 2017

Rain showers will slowly move north out of Indiana late tonight,
reaching to about I-96 by daybreak Tuesday.  This rain is expected
to continue to drift north on Tuesday, but gradually dry by the time
it reach Central Lower.  The steadiest rains can be expected toward
the Lansing and Jackson areas.  Another period of scattered showers
and possible thunderstorms will move in Wednesday night.  This rain
is largely expected to fall over Central Lower.  Much of the
remainder of the week appears fairly dry.

After a cooler day on Tuesday with highs in the low to mid 70s, we
will see temperatures mainly 80 to 85 for the rest of the week.

&&

.SHORT TERM...(This evening through Wednesday night)
Issued at 330 PM EDT Mon Sep 18 2017

A period of showers with embedded thunderstorms is expected late
tonight but mostly into Tuesday.  Another chance comes Wednesday
night.

Isentropic lift will gradually arrive overnight from the south,
crossing the front over Indiana.  Will confine the higher POPs to
areas south of I-96.  This lift moves north on Tuesday, but the
deeper moisture stays over the eastern CWA.  So expect the bulk of
the rain will fall east of a Clare to Kalamazoo line.  Some areas in
the East could see upwards of a half inch of rain, while the
northwest CWA will likely stay dry.

A weakening front pushes in by Wednesday night and some showers and
storms will be possible mainly late at night.

.LONG TERM...(Thursday through Monday)
Issued at 330 PM EDT Mon Sep 18 2017

Mainly dry and warm conditions are expected through the Thursday
through Monday time frame. A cold front that is forecast to wash out
across the area on Thursday may be the only chance of rain through
the long term. Surface dew points in the upper 60s combined with the
weak front may be just enough to touch off a shower or storm on
Thursday. Only have 20 pops in the forecast for Thursday.

Otherwise, building 500mb heights and surface high pressure situated
in the Eastern Great Lakes should provide dry and warm weather
Friday through Monday. 850mb temperatures are forecast to be in the
upper teens C through the period, so we should be looking at high
temperatures well into the 80s each day. Normal highs are in the low
70s, so we are looking at 10 to 20 degrees above normal

&&

.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 801 PM EDT Mon Sep 18 2017

Complicated aviation forecast tonight and Tuesday. First, it
appears we are going to be dealing with some IFR/LIFR stratus and
fog tonight into early Tuesday, particularly for the TAF sites
along the I-94 corridor. The idea is that the stratus currently
around Monroe MI will expand westward this evening with the low
level moist east flow off of Lake Erie, and possibly expand more
northward toward the I-96 corridor overnight as the low level flow
turns more southeasterly.

The other issue is that an area of showers with embedded tstms
will be spreading into the region from the southwest toward
daybreak - possibly earlier. The arrival of the shortwave
responsible for the rain should help mix out/lift the IFR/LIFR
cigs and vsbys to MVFR by mid morning. Most of the shower and
tstm activity is expected to impact areas south and east of GRR on
Tuesday.

&&

.MARINE...
Issued at 330 PM EDT Mon Sep 18 2017

Other than the risk of a few thunderstorms late tonight and early
Tuesday it appears quiet on the lake.


&&

.HYDROLOGY...
Issued at 330 PM EDT Mon Sep 18 2017

Abnormally dry conditions continue especially in areas south and
east of Grand Rapids. Portions of central Kalamazoo and Calhoun
counties saw relief with over an inch of rain on Sunday. Scattered
showers and storms on Tuesday will provide some additional spotty
relief to the dry conditions in southern Michigan, but a large part
of the area will again see little to no rainfall. Showers or storms
are also possible over parts of the area Wednesday night, but
widespread heavy rainfall is not expected with this batch either.

&&

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

$$

SYNOPSIS...JK
SHORT TERM...JK
LONG TERM...Duke
AVIATION...Meade
HYDROLOGY...CAS
MARINE...JK



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