Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 301921
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
321 PM EDT SAT JUL 30 2016

LATEST UPDATE...
Synopsis/Short Term/Long Term/Hydro/Marine

.SYNOPSIS...
Issued at 321 PM EDT Sat Jul 30 2016

The pesky system that has lingered over the area the past few days
will linger a little while longer over the area. Showers with a
chance of a storm will remain through tonight, with only a small
chance of rain on Sunday.

The area should see a break in the rain chances then on Monday as
high pressure is able to build in over the area. Chances for
showers and storms will show up again later on Tuesday as another
system approaches the region. Temperatures will heat up through the
week.

&&

.SHORT TERM...(This evening through Monday night)
Issued at 321 PM EDT Sat Jul 30 2016

Pcpn trends for the first couple of periods are our main focus in
the short term. We continue to think that there will at least be a
chance of a few spotty showers into Sunday before we should dry out
for Sunday night through most of Monday night.

Deformation band of showers and storms from earlier that produced
heavier rains has been pushed N and E a bit this afternoon as
another short wave has pushed into far SW Lower. This short wave
has not done much in developing new showers/storms as it is moving
over an area that has had plenty of cloud cover and showers thus
far today. A few showers and isolated storm could develop just
inland from the lakeshore with a bit of convergence present along
with some diurnal instability present with morning sunshine there.

What the wave will do as it continues E/NE is wrap the showers back
a bit into Central Lower up toward Mt. Pleasant and Alma and keep
them through the mid-evening hours. A lack of instability will keep
the severe threat quite low. The heavy rain potential is dropping
as showers are not as efficient and are now more progressive with the
wave moving through.

The more organized rain showers should move east of the area by
daybreak on Sunday. Models all are trying to keep a good deal of
moisture around, and the upper flow is still somewhat cyclonic. It
is this reason that we think a few light showers could pop up
late Sunday morning and last into the afternoon. These would likely
be spotty and light.

We should dry out Sun evening, and stay dry through most of Monday
night. The upper flow finally becomes more anti-cyclonic as the
trough moves east of the area. Ridging will build in for Mon and
last through most of Mon night. We can not rule out an MCS
approaching the area late Mon night as return flow sets up, but this
looks like it would hold off until after Mon night if it does impact
the CWFA.

.LONG TERM...(Tuesday through Saturday)
Issued at 321 PM EDT Sat Jul 30 2016

Initial concern for the extended period is with precipitation
chances Tuesday and Tuesday night.  Short wave associated with upper
low in northern Manitoba Tuesday morning will move through the Great
Lakes Tuesday afternoon.  The weak nature of this wave precludes
more than low chance pops at this time.

Mid level ridging develops for for Wednesday and Thursday...allowing
temperatures to warm and moisture to return to the region. Mid level
low will move from the Pacific Northwest Tuesday to northern Ontario
by late Thursday. Associated surface front approaches late Thursday
and there is a risk of the frontal passage being delayed because of
its distance from the upper low. Increased rain chances slightly
Friday to account for a slower frontal approach/passage.

Warm temperatures are expected Tuesday and Wednesday with highs in
the middle 80s...rising to around 90 on Thursday.  Highs will be in
the middle 80s Friday...with lower 80s expected on Saturday. Another
round of muggy weather is also expected... with dewpoints rising to
around 70 ahead of the surface front.  As a result...apparent
temperatures rise into the middle 90s Thursday afternoon area
wide...and in south central Michigan on Friday. Again...a slower
frontal passage Friday could subject more of west Michigan to hot
and muggy conditions.

&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 121 PM EDT Sat Jul 30 2016

Three areas of concern for the 18z TAFs.  First and foremost is
the low cloud cover across west Michigan in the wake of morning
showers and thunderstorms. Most observations in southwest Michigan
and adjacent areas of Indiana are MVFR with occasional IFR
ceilings. While there may be breaks that develop as the initial
wave moves east...will continue ceilings for the rest of this
afternoon...but will bring ceilings up solidly into the MVFR
range.

Second forecast conundrum is precipitation chances. Plenty of
moisture is available for convection and upper level system is
approaching from the west. Even so...short range convection
allowing models do not develop widespread precipitation this
afternoon and evening...likely due to limited destabilization from
cloud cover. Will follow the HRRR/HRRREXP output...which
emphasizes development in central Michigan (KLAN/KJXN)...with a
secondary area near KMKG. Forecast confidence is low.

Final issue is low cloud and fog development overnight. Previous
forecast brought in IFR conditions...and see no reason to deviate
from that...especially given the abundance of low level moisture
from precipitation today.

&&

.MARINE...
Issued at 321 PM EDT Sat Jul 30 2016

We continue to expect that we will keep the offshore flow over the
marine area through much of Sunday. The flow should remain below
advisory conditions, and waves will be limited due to the offshore
flow. Light flow will continue likely through Monday.

&&

.HYDROLOGY...
Issued at 321 PM EDT Sat Jul 30 2016

Scattered bursts of heavy rain have occurred in the southern half of
the CWA Saturday morning. Rainfall rates between 1 to 2 inches per
hour occurred in the heaviest showers/storms. Isolated totals up to
4 inches have been reported in a couple spots. Temporary flooding of
roads several inches deep likely occurred in a number of low, urban,
and/or poor drainage spots. Not far from some heavy rain reports are
locations which have received very little the past 3 days, and in
fact still qualify for a moderate drought status, Ingham county
being a a particularly good example. There remains a threat for
isolated heavy rainfall through Saturday night.

&&

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

$$

SYNOPSIS...NJJ
SHORT TERM...NJJ
LONG TERM...MWS
AVIATION...MWS
HYDROLOGY...CAS
MARINE...NJJ


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