Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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237
FXUS63 KGRR 311148
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
748 AM EDT WED AUG 31 2016

LATEST UPDATE...
Aviation

.SYNOPSIS...
Issued at 330 AM EDT Wed Aug 31 2016

A cold front will move south of the state this afternoon, taking
the high humidity and scattered showers with it. North winds
behind the front will usher in much lower humidity for the rest of
the week.

A secondary cold front and upper low will probably result in
considerable cloudiness and scattered light rain showers on
Thursday, particularly east of Highway 131.

Confidence is high that most of the upcoming holiday weekend will be
dry and pleasant with sunny, warm days and cool nights. However a
low chance of storms could arrive on Labor Day as warmer and more
humid air arrives.

&&

.SHORT TERM...(Today through Friday)
Issued at 330 AM EDT Wed Aug 31 2016

Two areas of showers and isolated tstms are impacting the area this
morning. The first is southeast of GRR and is associated with the
actual cold front. The second is north of GRR along the dew point
boundary. While areas north of I-96 should dry out early today, will
maintain pops through at least 18Z south of I-96 until the
trailing dew point front/gradient has cleared the area.

Have trended the forecast for Thursday a bit more on the pessimistic
side, featuring more in the way of cloud cover as well as some
scattered light rain showers - mainly east of highway 131. We will
be on the wrn periphery of upper trough digging into the ern grtlks
region, with a couple shortwaves/vorticiy maxima swinging south
through the state and a secondary/back door sfc cold front/trough.
Cold advection/thermal troughing at h8 and a moist low level nne
flow off lake huron should lead to considerable stratocumulus clouds
and sprinkles or light showers, especially before 18z.

We could still have some lower cloud issues even into Friday morning
south and east of GRR since the sfc high does not fully build in
until later Friday. Continued moist low level northeast flow/thermal
toughing from the thumb area toward south central lwr MI on the srn
periphery of the incoming sfc high may lead to some lingering
stratus or stratocumulus clouds for at least the LAN/JXN areas.

.LONG TERM...(Friday night through Tuesday)
Issued at 330 AM EDT Wed Aug 31 2016

High pressure will remain in control of the wx pattern Friday night
through Sunday and produce fair weather. Temperatures will average
near normal early in the weekend but will undergo a gradual
moderating trend Sunday into early next week. High temperatures
should reach the lower 80`s by Sunday and the middle 80`s by Labor
Day.

Persistent southerly flow on the back side of the departing ridge
will also result in increasing moisture for Labor Day. There is a
small chance for a shower or thunderstorm as early as Labor Day.
However the better chance for scattered showers and storms will come
Tuesday through midweek as the next system moves in from the west.

&&

.AVIATION...(For the 12Z TAFS through 12Z Thursday morning)
Issued at 747 AM EDT Wed Aug 31 2016

Widespread IFR cigs early this morning south of a line from MKG to
LAN will gradually lift to VFR levels by 18z. Still can`t rule
out a few showers developing along the I-94 corridor including
AZO/BTL/JXN through 18z. Winds will be out of the north at around
10 kts today. VFR weather is likely tonight although some MVFR
cigs may approach from the north toward 12z Thursday.

&&

.MARINE...
Issued at 330 AM EDT Wed Aug 31 2016

No change of marine headlines. Prolonged period of moderate to
strong north flow Today and Thursday will lead to hazards for
boaters and swimmers. Considering how warm the lake currently is (70-
75F), and the strength of the cold advection, we could easily see
some waves over 6 feet south of Holland.

At night however the winds should tend to take on more of an
offshore component, leading to lower wave heights.

Will have to monitor waterspout potential on Thursday as the upr
trough drops in. It is also worth noting that upwelling of colder
water is highly likely due to lengthy period of decent north flow.
This should lead to markedly colder water temps at the beaches by
the end of the week.


&&

.HYDROLOGY...
Issued at 105 PM EDT Tue Aug 30 2016

Scattered slow-moving thunderstorms Tue afternoon are capable of
producing local rainfall amounts over a half inch in a short
amount of time. Deeper atmospheric humidity and correspondingly
higher PW values are in southern Michigan but greater instability
and storm coverage will be in central Michigan Tue afternoon.
Small basins will likely be able to handle any locally heavy
rainfall, but minor ponding of water on roadways is possible.
After the cold front clears on Wed, the next chance for
appreciable rainfall will hold off until next week.

&&

.GRR Watches/Warnings/Advisories...
MI...Beach Hazards Statement through Thursday evening for MIZ037-043-
     050-056-064-071.

LM...Small Craft Advisory until 11 PM EDT Thursday for LMZ844>849.

&&

$$

SYNOPSIS...Meade
SHORT TERM...Meade
LONG TERM...Laurens
AVIATION...Meade
HYDROLOGY...CAS
MARINE...Meade



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