Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 171748
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
148 PM EDT Mon Jul 17 2017

LATEST UPDATE...
Hydro

.SYNOPSIS...
Issued at 330 AM EDT Mon Jul 17 2017

Fair weather is expected today through Tuesday evening with high
pressure sliding through the Great Lakes region. Highs will be near
normal both days, from around 80 today to the low to mid 80s on
Tuesday. A cold front will touch off some showers and storms Tuesday
night, that will last into Wednesday morning. Additional showers and
storms are expected during the latter half of the work week with
highs in the 80s.

&&

.UPDATE...
Issued at 1159 AM EDT Mon Jul 17 2017

A fair amount of low level moisture lingers over the region and this
lines up with the dense clouds over the far SW corner of the state.
Additional diurnal CU is forming, and many areas will go broken for
a period this afternoon. Therefore sent an update with more cloud
cover. Seems like Central Lower will experience the most sun, and
cloudier to the south.

&&

.SHORT TERM...(Today through Wednesday)
Issued at 330 AM EDT Mon Jul 17 2017

Main forecast challenge in the short term pertains to chances for
showers and thunderstorms late Tuesday night into Wednesday.
Otherwise, fair weather is expected from Today through Tuesday
evening.

High pressure will be situated across Southwest Lower Michigan
today, tonight and Tuesday. Pleasant weather is expected with dry
conditions, mainly clear conditions and comfortable dew points.
Temperatures will be near normal during this period with highs
around 80 today and in the lower to mid 80s on Tuesday.

As for the chance for showers and storms, the main time frame looks
to be overnight Tuesday night into Wednesday morning. This is when
the models forecast the low level jet to be nosing into the area.
The NAM is the most bullish on this feature, with a widespread 30-40
knots at 12z Wednesday over the forecast area. The GFS and ECMWF are
much less on the order of 15 to 20 knots. Best chances for
precipitation will be across Central Lower Michigan closer to the
front. Severe chances at this point look a bit lower given the lack
of consensus in terms of the low level jet strength, not to mention
the time of day.

On Wednesday, the showers and some embedded thunderstorms will move
through the area during the morning which will likely limit
afternoon instability. The front becomes parallel to the upper flow
and stalls across the area, so not hard to imagine it may become a
focus for additional development if we can get some sun in the
afternoon.

.LONG TERM...(Wednesday night through Sunday)
Issued at 330 AM EDT Mon Jul 17 2017

A warm front will be moving north through the cwa Wednesday night
and early Thursday and we`ll likely see scattered showers/storms
with that front ahead of a low that will move across the northern
cwa Thursday. Both the ecmwf and gfs show a short wave aloft to
support the idea of convection. High pressure briefly builds into
the state Thursday night and Friday behind the trailing cold front
which should make it as far south as northern Indiana. As it lifts
north Friday night and Saturday more showers/storms are possible.
The timeframe from Friday night through Sunday could be stormy as
the low that pushes the warm front north tracks across the cwa and
another cold front moves through Sunday.

Pretty typical summer time temperatures are expected through the
period with highs in the mid 80s and dewpoints in the 60s.

&&

.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 1251 PM EDT Mon Jul 17 2017

VFR conditions are anticipated at all the terminals through early
Tuesday afternoon. Lingering MVFR at KAZO attm should quickly
improve to VFR during the next hour or so as the small area of
lingering low clouds dissipates. Fair wx cumulus will linger this
afternoon and early evening before skies become mostly clear
tonight. Fair wx cumulus will redevelop toward midday Tuesday.


&&

.MARINE...
Issued at 330 AM EDT Mon Jul 17 2017

Will be dropping the Beach Hazards Statement and the Small Craft
Advisory with this issuance. The South Haven buoy is still at 3.9
feet, but the trend is down. Waves should be under 3.5 feet in all
areas fairly soon.

A quiet period out on the big lake is expected from this morning
through the day on Tuesday. High pressure will bring fair weather
and light winds.

Winds and waves will kick up Tuesday night into Wednesday as a cold
front drops into the area. The strongest winds look to be late
Tuesday night into Wednesday morning associated with thunderstorms.


&&

.HYDROLOGY...
Issued at 145 PM EDT Mon Jul 17 2017

Current river flow across the region is running anywhere from near
to much above normal. The Kalamazoo River basin is largely near
normal, with the Grand, Muskegon, and Saginaw River basins near to
above normal. For some locations, the upcoming pattern may lead to
above normal flows with perhaps within or above bankfull rises.

Several opportunities for thunderstorms exist beginning late
Tuesday night/early Wednesday morning right on through the
weekend due to a frontal boundary hovering around the region.
While many portions of this time frame will be dry, when it does
rain it could be quite heavy. Precipitable water values will perk
up to around 1.75" early Wednesday morning with possible storms
propagating from Wisconsin to Lower Michigan, but they could be
weakening in the process. Additional chances exist for the second
half of the week and weekend as precipitable water values
occasionally soar to 2.00" or higher, mainly Thursday and then
again this weekend. Where storms train and persist, localized
flooding is a possibility especially toward the end of the week.



&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
LM...None.
&&

$$

UPDATE...JK
SYNOPSIS...Duke
SHORT TERM...Duke
LONG TERM...04
AVIATION...Laurens
HYDROLOGY...Hoving
MARINE...Duke


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