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263
FXUS63 KGRR 210704
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
304 AM EDT Wed Aug 21 2019

LATEST UPDATE...
Synopsis/Discussion/Marine

.SYNOPSIS...
Issued at 300 AM EDT Wed Aug 21 2019

- Scattered showers and a few storms this afternoon

- Dry weather tonight through the weekend

- Cooler and much less humid Thursday through Saturday

&&

.DISCUSSION...(Today through next Tuesday)
Issued at 300 AM EDT Wed Aug 21 2019

Primary fcst concerns involve determining convective potential
later today. In addition to scattered showers the cold front will
bring potential for a few thunderstorms this afternoon.

It is noted that trends in the latest CAMs and 00Z HREF members
have backed off on convective potential somewhat as compared to
earlier guidance runs. This since instability particularly over
our se fcst area does not look as it will be quite as strong as
guidance indicated in previous model runs. In fact the latest
ecmwf only has around 1000 j/kg of SB Cape later today which is
significantly less than it indicated yesterday.

Nevertheless at least a few thunderstorms are expected this aftn
mainly over our se/e fcst area where instability will be
relatively stronger just prior to fropa. Svr wx is unlikely given
lack of stronger instability.

Otherwise areas of fog will continue to develop early this morning
and will gradually dissipate during the mid morning hours. Fair wx
is forecast tonight through the rest of the week and weekend as a
high pressure ridge will take hold of our wx pattern. Temps will
be seasonably cooler late this week through the weekend with high
temps in the 70`s and low temps in the 40`s up north to the 50`s
near to south of the I-96 corridor.

&&

.AVIATION...(For the 06Z TAFS through 06Z Thursday)
Issued at 1140 PM EDT Tue Aug 20 2019

Conditions will deteriorate to MVFR/IFR overnight due to
development of low clouds and patchy fog. Conditions will improve
to VFR by late morning and a cold front will bring scattered
showers.

A thunderstorm is also possible late in the morning to early
afternoon mainly at KJXN where greater instability will develop.
This could cause brief reductions to MVFR/IFR there. Northwest
winds will gust to around 20 kts at times in the afternoon with
subsiding winds and VFR conditions Wednesday night.

&&

.MARINE...
Issued at 300 AM EDT Wed Aug 21 2019

Winds and waves will ramp up later today after cold frontal
passage with highest waves of around 3 to 4 feet forecast this
afternoon and evening. Strongly considered a small craft
advisory/beach hazards statemetn but based on a consensus of
latest guidance it was felt conditions will likely remain just
below sca criteria. Relatively minimal wind speeds and wave
heights are forecast late this week into the weekend with fair
wx.

&&

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

$$

SYNOPSIS...Laurens
DISCUSSION...Laurens
AVIATION...Laurens
MARINE...Laurens