Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 271930

Area Forecast Discussion
National Weather Service Grand Rapids MI
330 PM EDT WED JUL 27 2016

Synopsis/Short Term/Long Term/Hydro/Marine

Issued at 330 PM EDT Wed Jul 27 2016

A cool front will gradually sag south through the state of Michigan
tonight with showers and a few thunderstorms occurring along it. The
highest concentration will likely be this afternoon and evening
north of Interstate 96. An area of low pressure will move along the
front Thursday and Thursday night across Illinois and Indiana.
Showers and a few thunderstorms will remain possible, especially
across Southern Lower Michigan Thursday and Thursday night. Friday
looks to be dry with high pressure building in.


.SHORT TERM...(This evening through Friday night)
Issued at 330 PM EDT Wed Jul 27 2016

The upper flow through the short term will remain out of the west-
northwest, with shortwave troughs gradually aiding in developing a
low amplitude upper trough. What this means is we are probably
looking at low chances for precipitation as the shortwaves move
through with a general slight cooling trend.

The first shortwave aloft moves through the area tonight, so cannot
rule out a chance for a shower or storm overnight. The highest
concentration of showers and storms will be this evening, in the
heating of the day. The storms are of the pulse type variety with
the overall threat for anything severe being quite low. Feel we will
see a gradual south push to the activity before it tends to
diurnally fade overnight. Some activity will try to push in from the
west as well out of Wisconsin.

On Thursday, another shortwave looks to move through the region
aloft, likely touching off additional scattered showers and storms.
As we move from Thursday night into Friday high pressure should
gradually take more control as the boundary pushes towards the Ohio
River. A low will be moving along the front so best chances for any
precip in our area will be in the southern half of the cwa. Thinking
Friday night will be fairly dry following the GFS which has seemed a
bit more stable in its solutions in regard to the Fri/Sat time frame
of late.

.LONG TERM...(Saturday through Wednesday)
Issued at 330 PM EDT Wed Jul 27 2016

Various model/ensemble solutions over the past few days have been
hinting at the possibility of a wave impacting the area on Saturday,
leading to a chance of showers and psbl tstms. Today it`s the GEM
doing it and a couple days ago it was the ECMWF (although with
earlier timing). It`s difficult to completely discount this idea
given the troughing at 500 mb that has been consistently advertised
for the first half of the weekend.

The complicating/limiting factor however is that the guidance has
also been showing a sfc high impacting the nrn grtlks region over
the weekend, leading to relatively dry conditions. Will need to
carry at least low chance pops on Saturday to account for the
possibility of a shortwave and possible sfc reflection on Saturday
into Saturday evening.

Better confidence exists for dry weather on Sunday since if a wave
does come through on Saturday there should be subsidence/drying in
it`s wake. Upper ridge builds over the region Monday so dry looks
good then too. Shower and tstm potential is expected to return
Tuesday and Wednesday as warmer and more humid air mass arrives on
the back side of departing high.


.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 203 PM EDT Wed Jul 27 2016

The bulk of the tstm activity this afternoon/evening is expected
to be north of I-96 and east of Hwy 131... so left the thunder
threat out of the TAFs with the exception of LAN between 20Z and
00Z where decent sfc convergence will exist at pk heating. A few
isolated cells cannot be ruled out at the other terminals but feel
the chance is too low to include elsewhere. Any tstm could
produce brief IFR or lower conditions due to heavy rain.

A general decrease in coverage and intensity of convection is
expected after sunset although a few showers could linger through
the night mainly north of I-96. Some areas of fog could form late
tonight, especially where it rains today and at AZO/BTL/JXn where
dew pts are a bit higher and where skies should be clear enough to
form radiation fog with calm winds. Fog will mix out Thursday
morning by 13-14Z.

Scattered tstms are expected to redevelop area-wide after 16-18z


Issued at 330 PM EDT Wed Jul 27 2016

Winds and waves are expected to remain below advisory criteria the
next couple days as high pressure settles into the Great Lakes
region. North to northeast flow does increase Thursday afternoon and
Thursday night, but the high wind/waves should remain well off shore
of our area. The flow over the weekend turns easterly and will be
fairly light. So, no advisories look necessary through the weekend.


Issued at 330 PM EDT Wed Jul 27 2016

Thunderstorms in Central Michigan this afternoon have produced
locally heavy rainfall, including radar estimated amounts over 2
inches in a portion of Clare County. Other than ponding of water on
roadways, flooding is not anticipated. The storms Wednesday
afternoon will mainly affect Central Michigan, then the most likely
region for rainfall on Thursday will be in Southwest Michigan.
Rainfall amounts Thursday will likely not be substantial enough for


.GRR Watches/Warnings/Advisories...


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