Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 291149
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
749 AM EDT Thu Jun 29 2017

LATEST UPDATE...
Update/Aviation

.SYNOPSIS...
Issued at 330 AM EDT Thu Jun 29 2017

A meandering frontal boundary will remain draped across the Great
Lakes Region through Friday night. Warm and humid air interacting
with this front will bring periods of showers and thunderstorms,
with a risk of locally heavy rainfall and possibly a few strong
or severe storms.

&&

.UPDATE...
Issued at 741 AM EDT Thu Jun 29 2017

Will be updating the fcst shortly to remove or lower pops for
today and to have at least partly sunny skies. Latest trends
suggest a relatively quiet day with most new convection probably
holding off until very late today or more likely tonight.


&&

.SHORT TERM...(Today through Saturday)
Issued at 330 AM EDT Thu Jun 29 2017

Showers and tstms continue to develop and track east through the
area early this morning with a 50-60 knot swly low level jet and
axis of higher pwat air near 1.75 inches overhead. The main
concern with these storms is locally heavy rainfall where storms
repeat, although can`t rule out some gusty winds.

As the low level jet weakens later this morning with the main core
shifting toward the eastern Great Lakes Region, models indicate
that the coverage of convection will decrease, with only isolated
coverage of storms expected this afternoon. The best chance for
diurnal storms to redevelop will be near and south of I-94 in
area of better sfc convergence. SB Capes are progged to rise to
near 3000 J/KG since a warm/humid air mass will be in place, so
svr storms cannot be ruled out.

Confidence is low tonight on the behavior of a new low level jet,
but guidance indicates that showers and storms will become more
widespread along the frontal boundary across nrn IL/IN into sw
Lwr MI. This could turn into a flood threat south of I-96 late
tonight into early Friday, but again confidence is low at this
time.

New guidance has the position of the frontal boundary, and sfc
low moving along it, a bit farther southeast on Friday than
previous runs. Thus the Svr threat is mainly from GRR to the south
and east and that threat is contingent upon developing some
breaks in the clouds/heating and sfc based instability, which is
questionable if nocturnal convection becomes widespread tonight
and persists much of the morning.

The main frontal boundary finally edges away to the southeast
Friday night. However continued troughiness over the region on
Saturday and lingering moist air mass will probably lead to some
sct`d diurnal showers or storms, mainly near and east of highway
131 away from the stable lake influence.

.LONG TERM...(Saturday night through Wednesday)
Issued at 330 AM EDT Thu Jun 29 2017

Fair wx is anticipated for Saturday night into Sunday with near
normal temperatures for this time of year. The next system will move
in from the northwest late Sunday through Sunday night and bring a
chance for showers and perhaps a few thunderstorms.

Increasing elevated instability to the north of a warm front will
result in potential for some showers and thunderstorms by Tuesday.
The relatively best chance for showers and thunderstorms will come
Tuesday night and Wednesday as a mid level disturbance slowly moves
in from the west.

Temperatures for early to mid next week will average near to
slightly above normal but with a gradual increase in humidity.

&&

.AVIATION...(For the 12Z TAFS through 12Z Friday morning)
Issued at 748 AM EDT Thu Jun 29 2017

The chance of tstms has decreased substantially and will have VFR
conditions today with southwest winds gusting to 25 kts. There
will probably be a BKN deck of diurnal cumulus clouds developing
inland from Lake MI by mid morning.

Next chance of thunder returns toward/after 00Z, especially south
of I-96. Coverage is expected to increase along I-94 corridor by
06z tonight so will carry predominate thunder at AZO/BTL/JXN overnight
with VCTS farther north at MKG/GRR/LAN. Sfc winds will diminish
below 10 kts tonight.


&&

.MARINE...
Issued at 330 AM EDT Thu Jun 29 2017

No changes to the going marine headlines at this time with strong
swly low level jet overhead.


&&

.HYDROLOGY...
Issued at 223 PM EDT Wed Jun 28 2017

River levels continue to fall and should continue falling into
tonight. There could be some minor rises by Thursday as a quarter
to three quarters of an inch of rain is expected tonight into
Thursday morning. Another half inch to an inch of rain is expected
on Friday, causing more moderate rises by Saturday.

During both these periods of expected rainfall there will be the
chance for thunderstorms with heavier amounts of rain. This could
cause sharp rises, especially where soils are still saturated such
as along the Muskegon, Chippewa and Pine Rivers.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Beach Hazards Statement until 5 PM EDT this afternoon for MIZ037-
     043-050-056-064-071.

LM...Small Craft Advisory until 5 PM EDT this afternoon for
     LMZ844>849.

&&

$$

UPDATE...Meade
SYNOPSIS...Meade
SHORT TERM...Meade
LONG TERM...Laurens
AVIATION...Meade
HYDROLOGY...Ostuno
MARINE...Meade



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