Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 310730

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

Synopsis/Short Term/Long Term/Marine

Issued at 330 AM EDT Wed Aug 31 2016

A cold front will move 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

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 06Z TAFS through 06Z Wednesday night)
Issued at 1203 AM EDT Wed Aug 31 2016

Primarily Vfr conditions will gradually deteriorate to mvfr
overnight due to low clouds and patchy fog. Pockets of ifr
are also possible particularly at KMKG where conditions have
just dipped to ifr due to fog. Isolated rain showers will continue
to develop overnight. The threat for a storm is now too low to
warrant inclusion in any of the terminal forecasts overnight.

Conditions will improve to vfr early to mid morning and then stay
vfr through Wednesday afternoon and evening as fair weather
returns and a drier airmass moves in.


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.


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 from 10 AM EDT this morning through
     Thursday evening for MIZ037-043-050-056-064-071.

LM...Small Craft Advisory from 10 AM this morning to 11 PM EDT
     Thursday for LMZ844>849.



LONG TERM...Laurens
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