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FXUS63 KGRR 090007
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
807 PM EDT Wed Jul 8 2020

LATEST UPDATE...
Aviation

.SYNOPSIS...
Issued at 248 PM EDT Wed Jul 8 2020

- Hot Temperatures Today into Thursday

- Showers and Storms Today and Thursday into Friday

- Slightly Cooler For the Weekend

&&

.DISCUSSION...(This evening through next Wednesday)
Issued at 248 PM EDT Wed Jul 8 2020

- Hot Temperatures Today into Thursday -

Surface high pressure persists today and into Thursday, resulting in
hot temperatures continuing. With dewpoints up into the mid to upper
60s today and tomorrow, heat indices will reach just shy of 100
during the afternoon. Will continue the previous forecast mentality
and hold off on headlines given the short duration of indices just
shy of 100, and the expected isolated showers both afternoons.

- Showers and Storms Today and Thursday into Friday -

Similar to what we saw yesterday, isolated showers and storms have
initiated this afternoon focused along and east of the lake breeze
convergence zone orientated along/east of US-131. One of these cells
happened to form directly over our office resulting in 0.71" of
rain within 30 minutes, so needless to say, these cells can
produce heavy showers. This type of activity is expected to carry
on into the rest of the afternoon and early evening, with the
main type of showers/storms being the hit-or-miss pulse variety.
Some lightning will be possible along with locally heavy rainfall.

Additional scattered afternoon convection can be expected for
Thursday ahead of an upper level trough. These scattered showers and
storms will persist into the overnight hours as the trough slowly
moves through the region. Severe weather is not expected, but some
locally heavy downpours can be expected thanks to precipitable water
in the 1.5-2.0" range, as well as some lightning.

- Slightly Cooler For the Weekend -

Broad troughing will move back into place this weekend allowing for
northwest flow and some relief from the 90 degree temperatures, with
temperatures in the 80s expected. This relief may be short lived,
however, as heat returns mid to late next week.

&&

.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 807 PM EDT Wed Jul 8 2020

An isolated shower or storm is still possible for another hour or
two as the lake breeze front and outflow boundaries from earlier
storms collide. One such shower is occurring just east of AZO at
00z. These showers should fade completely by 02z to 03z. VFR
conditions will then take over as we head into the overnight.

Late tonight however, some of the high resolution models are
indicating some scattered showers and storms developing,
especially down towards AZO. Did not include this is the TAFs at
this point given the low probability.

A much better chance for showers and storms exists on Thursday
afternoon. Scattered to potentially numerous showers and storms
will fire in the heat of the day after 19z or so. All TAF sites
could be affected, but the further east the better the chance.

Winds will be light and variable tonight picking up out of the
south-southwest on Thursday at 5-15 knots.

&&

.MARINE...
Issued at 248 PM EDT Wed Jul 8 2020

Winds and waves continue to stay light and low this week, resulting
in few marine concerns to note. The main potential for hazards will
be with possible scattered showers and storms Thursday night into
Friday with the passage of a front. Locally heavy rain may reduce
visibilities, and lightning will be possible in some storms.


&&

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

$$

SYNOPSIS...Thielke
DISCUSSION...Thielke
AVIATION...Duke
MARINE...Thielke
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