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000
FXUS63 KGRR 261734
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
134 PM EDT MON SEP 26 2016

LATEST UPDATE...
Aviation

.SYNOPSIS...
Issued at 330 AM EDT Mon Sep 26 2016

Fall like weather will prevail through much of this week with
considerable cloudiness, scattered showers, and highs in the 60s.

&&

.SHORT TERM...(Today through Wednesday)
Issued at 330 AM EDT Mon Sep 26 2016

High probabilities for showers early this morning as cold front
presses east through the state. Then showers ending from west to
east 12z-15z with arrival of dry slot. Expect breezy/gusty
conditions to develop later this morning into the afternoon as deep
mixing in the dry slot taps 30-35 kt winds shown at 5k ft.

Arrival of colder H8 air should lead to development of lake strato
cu and a few light showers this afternoon, mainly north of I-96.
Lake induced instability of a few hundred joules/steep lapse rates
could lead to some gusty showers in the nrn cwfa late
afternoon/early evening.

Upper low and deep moisture are progged to gradually sink southward
Tuesday afternoon and Tuesday night. Will have sct/chc pops
increasing to likely from north to south as this occurs. Best
coverage of showers, and possibly a few tstms, will be Tuesday night
when the upper low is overhead and lake effect component is still
present.

Lake component is lost on Wednesday as low level flow goes
offshore with sfc low settling south of the state. However
scattered to numerous showers will continue to rotate around the
upper low and temps could struggle to get out of the 50s.

.LONG TERM...(Wednesday night through Sunday)
Issued at 330 AM EDT Mon Sep 26 2016

The long term portion of the forecast is looking more and more
unsettled with cool conditions expected and occasional chances of
showers possibly everyday.

The latest trend for the long term is that the upper low does not
ever move far away from the area. It could remain close enough to
keep a chance of rain showers in each day, especially as it looks
more likely to rotate back closer to the area. The unfortunate thing
is that upper lows are tough to forecast the movement for, so we do
not have a great deal of confidence in the details of the forecast.

We have tried to lower temps some anticipating more cloud cover and
some rain showers. We have broad-brushed low rain chances in the
forecast for each day from Thu through Sun. It will not rain the
entire time, and there could be some drier periods depending on how
the upper low and how it`s waves wobble with regard to the CWFA.

&&

.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 130 PM EDT Mon Sep 26 2016

The prevailing conditions are forecasted to remain VFR. A few
showers will move in this evening...and persist into tonight. A
small chance for MVFR exists. The gusts over 25 knots will
gradually diminish this evening and overnight as the diurnal
mixing decreases. Cold air advection will persist though...so
gusts will be possible tonight...mainly along the lakeshore which
includes KMKG.

Deeper moisture will arrive from the north on Tuesday...but not
likely until after 18z Tue. Thus any precipitation should remain
in the form of localized showers. Gusts will once again increase
on Tuesday as the temperature starts to warm up leading to
increased mixing.

&&

.MARINE...
Issued at 330 AM EDT Mon Sep 26 2016

West winds to 30 knots and cold advection across the unseasonably
warm waters of lake michigan will cause waves to build as high as 10
feet today - continuing through Tuesday night. Waterspouts and a few
tstms will become possible Tuesday and Tuesday night as an upper low
moves overhead.


&&

.HYDROLOGY...
Issued at 102 PM EDT Sun Sep 25 2016

River levels are around normal for this time of year. Showers and
thunderstorms are expected tonight and lake effect rain showers are
possible Monday into Wednesday. Through Wednesday, over an inch of
rain is possible to the north and west of Grand Rapids with less
than a half inch to the south and east. Rivers and streams should
remain below bankfull through the week.

&&

.GRR Watches/Warnings/Advisories...
MI...None.
LM...Small Craft Advisory until 8 AM EDT Wednesday for LMZ844>849.

&&

$$

SYNOPSIS...Meade
SHORT TERM...Meade
LONG TERM...NJJ
AVIATION...MJS
HYDROLOGY...63
MARINE...Meade