Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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351
FXUS63 KGRR 191804
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
204 PM EDT Tue Sep 19 2017

LATEST UPDATE...
Aviation

.SYNOPSIS...
Issued at 305 AM EDT Tue Sep 19 2017

A weakening area of low pressure will track through southern parts
of Lower Michigan today. Thus some showers and even a few
thunderstorms will be possible. An area of high pressure shows up
for Wednesday resulting in mainly dry conditions. A weakening cold
front dissipates over the region as it moves in Wednesday night
and Thursday. A few showers and thunderstorms may occur. The well
above normal temperatures will continue.

&&

.UPDATE...
Issued at 1100 AM EDT Tue Sep 19 2017

I tweaked temps downward a bit over the cloudier/rainy SE, while
rising temps over the sunnier/drier NW. Expect temps to range from
the lower 70s SE to around 80 over the NW.

Also extended POPs into this evening mainly SE of a Alma to
Kalamazoo line. The deeper moisture that was over NW OH/SE MI
will continue to drift almost due north, continuing to give areas
such as LAN and JXN showers through the day and into the evening.

&&

.SHORT TERM...(Today through Thursday)
Issued at 305 AM EDT Tue Sep 19 2017

The main challenge in the short term deals with the potential for
rain over the next couple of days.

The right entrance region of an upper level jet moves in for this
morning. This feature was helping to trigger the showers and
thunderstorms currently lifting in our direction across Illinois
and Indiana. With increasing PWAT values for my southern zones to
over 1.5 inches this morning it looks like the momentum of the
current area of rain will continue. Thus I bumped up POPs mainly
across the south for this morning. Instability shows up as well
over the south...so a few storms could occur. The precipitation
will diminish later today into tonight as the lift moves out.

The main axis of mid to upper level lift stays west of MI Wed into
Thu. There will be a low level front pressing in from the
northwest Wed night. This feature dissipates over the area on Thu.
It may pool up the moisture somewhat so that a few showers and
storms may still occur. Will hold onto the low POPs for now.

With deep layer warm air advection occurring Wed into Thu...we
will jump back into the 80s for high temperatures.

.LONG TERM...(Thursday night through Monday)
Issued at 305 AM EDT Tue Sep 19 2017

There may be isolated showers/storms Thursday night and Friday, but
coverage will be spotty at best. After that, dry through the
weekend. Abnormally dry conditions exist south of I-96 and those
locations will see no relief through the weekend.

A large area of high pressure will develop over the eastern portion
of the U.S. during the long term and any system trying to move east
from the west will be forced north into Canada long before they ever
get to Michigan. As heights rise, so too will sfc temperatures. We`ll
be looking at mid summer conditons with highs in the mid 80s and
dewpoints well into the 60s.

Summer like conditions will continue into the middle of next week at
which point the models have been consistent in showing a cool
down.

&&

.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 204 PM EDT Tue Sep 19 2017

Stratus and fog has been slow to lift today, which is normally
the case as we move through September. This is due to a lowering
sun angle which is not as effective in low cloud erosion.

The consensus of high resolution short term models shows the
clouds lifting some this afternoon and early evening, to VFR
towards KMKG and MVFR at KJXN. This evening and overnight the low
clouds and fog will become more widespread than last night. We
are expecting at least IFR in all areas with LIFR and VLIFR
likely. The fog and stratus will lift through the course of
Wednesday morning.

&&

.MARINE...
Issued at 305 AM EDT Tue Sep 19 2017

With a relatively weak pressure gradient in place along with an
offshore component of the wind...wave heights will remain under
small craft advisory criteria through tonight. Some building of
the waves is possible on Wednesday as the direction veers with
time and the wind increases somewhat. It still looks like values
at this time will be too low for any marine headlines.


&&

.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.
&&

$$

UPDATE...JK
SYNOPSIS...MJS
SHORT TERM...MJS
LONG TERM...04
AVIATION...Duke
HYDROLOGY...CAS
MARINE...MJS



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