Small Craft Advisory 55, NWS Grand Rapids, MI

Area Forecast Discussion
National Weather Service Grand Rapids MI
324 PM EDT Fri Aug 7 2020

LATEST UPDATE...
Synopsis/Discussion/Marine

.SYNOPSIS...
Issued at 324 PM EDT Fri Aug 7 2020

- As high moves east rain chances increase

- Warmer

&&

.DISCUSSION...(This evening through next Friday)
Issued at 324 PM EDT Fri Aug 7 2020

-- As high moves east rain chances increase --

High pressure over Michigan is producing a stellar summer day. Highs
around 80 and dewpoints in the lower 50s have created quite
comfortable conditions. That's going to change this weekend. There's
some cu out there right now, but that will dissipate with sunset
leaving mostly clear skies. We'll see one more night with lows in
the 50s then the high moves east and south flow develops. It won't
take long...Saturday night...until dewpoints climb into the mid to
upper 60s creating muggy conditions.

The upper ridge is going to flatten this weekend as a short wave
moves across the northern tier of states. This wave will push a cold
front into Wisconsin where storms are expected Saturday and Sunday.
CAMS strongly indicate that storms will be in decay mode as they
move toward eastern Wisconsin and likely won't make it across the
lake. So we have a dry forecast Saturday night. Much the same thing
for Sunday. However Sunday night and Monday the cold front gets a
bit closer and instability rises quite a bit as dewpoints climb
toward 70. ECMWF ensembles show CAPE rising significantly late
Sunday night and Monday. This is our best chance of showers and
storms. Given PWATs climbing to around 2 inches, locally heavy rain
is possible too. However shear values are progd at 20kts or less,
so strong to severe storms aren't expected.

It's worth noting the GFS is much slower moving the cold front
through compared to the ECMWF. Thus, the GFS lingers precipitation
over the cwa through Tuesday whereas the ECMWF is dry; we'll keep an
eye on that. A couple of weaker short waves were also noted moving
across southern Lower toward the end of the week, so low chance pops
will continue.

-- Warmer--

An increase in heat and humidity will occur this weekend. Highs will
be in the mid 80s Saturday and pushing 90 by Sunday. Dewpoints
around 70 will make for oppressive conditions. Highs will be in the
mid 80s and dewpoints in the 60s for the rest of the period. So,
summer conditions will be the norm.

&&

.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 106 PM EDT Fri Aug 7 2020

Some scattered cu will develop this afternoon but dissipate with
sunset. Clear skies expected overnight.

&&

.MARINE...
Issued at 324 PM EDT Fri Aug 7 2020

We have issued a Beach Hazard Statement and a Small Craft Advisory
from midday on Saturday through Saturday night from Whitehall to
Manistee. Southerly flow will increase beginning tonight and peak on
Saturday it appears in the 15 to 25 knot range. Winds will be even
stronger on the north half of the lake. Conditions will become
hazardous for smaller water craft and swimmers alike on Saturday.
South sides of south piers will be the worst places to swim.
Thankfully the more popular beaches in this stretch (Mears State
Park and Stearns Park) will be protected a bit by the pierheads.

There has been some model back and forth as to whether or not the
stronger south wind continues into Sunday and possibly Monday.
Sunday would be the better bet for it continuing as the front will
likely be pressing through on Monday. Thunderstorm complexes will
likely also affect Lake Michigan disturbing the south flow at times.
Bottom line...pay close attention to the forecast this weekend as
there is potential for dangerous waves and currents.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Beach Hazards Statement from Saturday afternoon through late
     Saturday night for MIZ037-043.

LM...Small Craft Advisory from noon Saturday to 6 AM EDT Sunday for
     LMZ848-849.

&&

SYNOPSIS...04
DISCUSSION...04
AVIATION...04
MARINE...04

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