Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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085
FXUS63 KGRR 281154
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
754 AM EDT Wed Jun 28 2017

LATEST UPDATE...
Aviation

.SYNOPSIS...
Issued at 330 AM EDT Wed Jun 28 2017

Periodic showers and thunderstorms are expected today through
Friday as an active frontal boundary and warmer and more humid
air impacts the area. Severe weather is possible on Friday.

&&

.SHORT TERM...(Today through Friday)
Issued at 330 AM EDT Wed Jun 28 2017

A lot of weather going on in the short term, but the best chance
of svr wx and heavy rainfall appears to be on Friday.

Incoming 40-60 kt swly low level jet will send higher
pwat/theta-e air into the area today. The result will be numerous
to widespread showers moving into the area, arriving along the
lakeshore later this morning/toward noon, and probably impacting
most areas north of I-94 this afternoon. Rainfall amounts expected
to range from only a few hundredths south of I-96 to a quarter to
half inch around Ludington.

Little to no instability is progged today as the rain comes in
over top of a dry/stable low level air mass with sfc dew points
currently in the 40s. So while likely pops are warranted
near/north of I-96 today it looks like the thunder risk is quite
low. Main threat of thunder is toward evening around Ludington per
latest RAP13 MUCape progs. With all the clouds and showers moving
in today, and the rain falling into the drier low levels, suspect
high temps will be held down - in the low to mid 70s.

There`s a good chance that tonight will be relatively quiet since
the models have been consistently showing the 50-60 kt low level
jet pointed at northern Lake Huron. With the sfc low and warm
front well to our north tonight, this suggests only scattered
showers/tstms at best, with best coverage still in the NW CWFA
closer to the apchg sfc cold front. Instability tonight is still
shown to be rather limited, with MUCapes under 1000 J/KG. That
said we will have 50-60 kts at H8 and any convection could mix
down some gusty winds if the sfc based inversion is shallow
enough.

The sfc cold front stalls over the srn CWFA on Thursday and could
be a focus for strong diurnal sfc based storms Thursday afternoon
and evening along I-94. Storms could persist in the srn cwfa on
Thursday night as the front lifts back north as a warm front.

Best risk of severe weather and heavy rainfall is Friday as sfc
low tracks ne just west of us, and helps pull in sfc dew pts near
70. If we get any sfc heating and develop sfc based convection, it
could be a very active day since the warm front will be in the
vcnty and deep layer shear is progged to be 30-50 kts with Capes
over 2000 J/KG.

.LONG TERM...(Friday night through Tuesday)
Issued at 330 AM EDT Wed Jun 28 2017

Moderate to potentially strong instability will linger Friday
evening so showers and thunderstorms are likely to continue through
Friday evening before gradually tapering off as instability
diminishes overnight.

A drier airmass will move in behind this system for the weekend with
near normal temperatures for this time of year. However a northward
moving warm front will bring potential for more showers and
thunderstorms Monday night into Tuesday as elevated instability
ramps up north of the front. The relatively best chance for pcpn
will be over our southern fcst area in closer proximity to the sfc
low/warm front.

Temperatures for early to mid next week will continue to average
close to normal but with increasing humidity. A high pressure ridge
will then gradually build in from the north and bring fair wx for
midweek.

&&

.AVIATION...(For the 12Z TAFS through 12Z Thursday morning)
Issued at 750 AM EDT Wed Jun 28 2017

The winds will be the main aviation impact over the next 24
hours. South winds will increase to 10 to 20 knots by noon, with
frequent sfc gusts to 30 knots this afternoon into tonight.
Stronger gusts to 35-40 knots are possible at MKG. The winds
tonight at 2000 ft AGL are shown to increase to 50-60 kts,
especially after midnight, leading to possible LLWS.

Showers will move in this afternoon from the west but VFR
cigs/vsbys should still prevail. A brief period or two of MVFR or
lower vsbys could develop if heavier showers make it in. A risk
of thunder will develop tonight, mainly west of JXN/LAN, although
only sct`d coverage is expected with generally VFR weather still
prevailing. Again, the gusty south-southwest winds will be the
main impact tonight.

&&

.MARINE...
Issued at 330 AM EDT Wed Jun 28 2017

Strong south winds today, shifting more swly tonight into
Thursday, will create hazardous waves of up to 8 feet on Lake
Michigan. The going Small Craft Advisory and Beach Hazard Headline
through Thursday look good.


&&

.HYDROLOGY...
Issued at 324 PM EDT Tue Jun 27 2017

The Chippewa and Pine River warnings have been downgraded to
advisories with continued improvement. The Pine River levels are
dropping at a rate such that the advisory could potentially be
dropped by this time tomorrow. The Chippewa River will experience a
more gradual fall. The majority of river in a stretch from Ludington
eastward remain elevated, as well.

Additional rainfall is slated for late Wednesday into Thursday. This
midweek precipitation has the potential to delay improvement,
keeping rivers elevated. Additional rainfall could affect the area
again by Friday. Details in the exact placement of the heaviest rain
is still not certain, but the potential exists for more than 3
inches of rain to fall in some places over the next 5-7 days.

Further south, rivers are slightly above to near normal. Given
recent rainfall totals, river levels are almost certain to rise if
forecast precipitation amounts are achieved through the next week.
Those living near rivers should pay close attention to forecast
updates and monitor river trends closely.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Beach Hazards Statement through Thursday afternoon for MIZ037-
     043-050-056-064-071.

LM...Small Craft Advisory until 2 PM EDT Thursday for LMZ844>849.

&&

$$

SYNOPSIS...Meade
SHORT TERM...Meade
LONG TERM...Laurens
AVIATION...Meade
HYDROLOGY...JAM
MARINE...Meade



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