Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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294
FXUS63 KGRR 280526
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
126 AM EDT SUN AUG 28 2016

LATEST UPDATE...
Aviation

.SYNOPSIS...
Issued at 320 PM EDT Sat Aug 27 2016

Showers are moving out of Michigan late this afternoon and a weak
cold front will wash out across southern Lower Michigan tonight.
Humid weather will continue into the middle of next week and
temperatures will remain above normal. Chances for additional
showers and thunderstorms are low through mid week.

&&

.UPDATE...
Issued at 911 PM EDT Sat Aug 27 2016

I updated our forecast grids to show likely pops for showers and
thunderstorms crossing the area from mid evening into the early
morning hours of Sunday. Most areas will see at least a little
more rainfall overnight.

The latest radar mosaic loops show an area of showers and
thunderstorms developing on a weak cold front heading east from
near central Lake Michigan back into central Illinois south of
Rockford. Nearly all of the high resolution models show this line
continuing to develop as it moves east southeast this evening.
Since the latest RAP model shows a 20 to 30 knot low level jet
west to east across the CWA this evening and there is around 1000
j/kg of MU cape well past midnight with this feature, I have
increased the pop to likely across the area tonight. In the grids
I tried to time the storms northwest to southeast across the CWA.
The cape is narrow on the model soundings so I see little threat
of severe storms, just locally heavy rain for a short time in most
location. The storms should be done by sunrise.

&&

.SHORT TERM...(This evening through Monday night)
Issued at 320 PM EDT Sat Aug 27 2016

Forecast concerns deal with pcpn chances tonight and potential for
fog.

Latest radar loop continues to show pcpn moving away from the cwa as
a wave of low pressure moves over Lake Michigan enroute toward
northern Lower. The upper trough driving the low will remain north
of Lake Superior and not have much if any influence on the weather
across the cwa. The upper flow from the southwest will continue to
push minor short waves across the cwa and so we`ll have low chance
pops to account for them. The trailing cold front, if you want to
call it a front, will wash out over the southern cwa tonight leaving
high dewpoints in the mid 60s across the cwa. The humid weather will
continue into next week. Given the copious rainfall earlier today
across much of the cwa, any clearing tonight could lead to some fog
so we added patchy fog to the grids tonight and Sunday night. Other
than a slight chance of a shower tonight, mainly dry weather is
expected through Monday night. Highs Sunday and Monday will be in
the lower to mid 80s.

.LONG TERM...(Tuesday through Saturday)
Issued at 320 PM EDT Sat Aug 27 2016

Tuesday will have a chance of showers and thunderstorms as a
shortwave trough amplifies with a closed low and sfc cyclone moving
across central Canada and trailing cold front traversing the Great
Lakes. The trough axis shifts east with sfc and upper ridging
bringing generally fair weather Wednesday through Saturday.

&&

.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 126 AM EDT Sun Aug 28 2016

I reduced the expected impacts from the overnight fog. It appears
there will be enough wind in the boundary layer that the fog
should not get too dense. Some patchy IFR is still possible, but
overall, believe vsbys will largely just dip down into the MVFR
category. Some MVFR ceilings will be around too.

Any MVFR vsbys and ceilings will improve shortly after sunrise.
The reminder of the day will remain VFR along with light winds.

Fog may begin to redevelop toward 06Z Sunday night, but have left
this out of the TAFs for now.

&&

.MARINE...
Issued at 320 PM EDT Sat Aug 27 2016

High pressure moving over the lake will result in winds aob 10 knots
and waves less than 2 feet through Sunday.


&&

.HYDROLOGY...
Issued at 207 PM EDT Sat Aug 27 2016

The Portage River at Vicksburg fell to just below flood stage this
morning. However with locally over an inch of rain possible through
tonight, the river level is expected to rebound to just above flood
stage this weekend and then slowly fall. No other locations are
currently near flood stage.

&&

.GRR Watches/Warnings/Advisories...
MI...None.
LM...None.
&&

$$

UPDATE...WDM
SYNOPSIS...04
SHORT TERM...04
LONG TERM...Ostuno
AVIATION...JK
HYDROLOGY...63
MARINE...04



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