461
FXUS63 KGRR 062359
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
759 PM EDT Sat Jul 6 2024

.KEY MESSAGES...

- A chance for a few showers yet this evening

- Small chances for showers Sunday night

- A very summer-like week ahead with warmth and thunderstorm
  chances

&&

.DISCUSSION...
Issued at 351 PM EDT Sat Jul 6 2024

- A chance for a few showers yet this evening

A shortwave trough swinging east through the state this afternoon
has kicked off some isolated showers over interior portions of the
state. Residual moisture at the surface where dew points are still
around 60F combined with cool mid levels has surface based CAPE
values at 1,000 j,kg this afternoon. So, expect scattered showers
and given the instability isolated storms to continue to percolate
through around 900pm. The activity should diurnally fade after
sunset. Some patchy stratus and fog is possible tonight, but
nothing like last night.

A dry Sunday is expected as surface ridging will be working
through the area. We are looking for a partly to mostly sunny day
on Sunday.

- Small chances for showers Sunday night

Small chance for rain showers and isolated thunderstorms exist
Sunday night ahead of our next weak trough of low pressure. We
have low pops in the forecast at this point in the 20-40 pct
range. Highest pops are in the northwest CWA up towards Ludington.
Instability is on the low side and the precipitation will likely
be affected by the diurnal minimum. CAPE is generally less than
500 j/kg.

- A very summer-like week ahead with warmth and thunderstorm chances

A broad, slow moving 500 mb trough will be over the western Great
Lakes region to start the work week. An associated surface trough,
also relatively weak, will slowly cross the region late Monday and
Tuesday. Overall forcing for ascent will not be strong, and surface
wind fields will be light/negligible. However, with strong July sun,
weak convergence in vicinity of the diffuse surface boundary, and
lake breezes, expect a chance of showers/storms Monday (20-30%) and
Tuesday (30-50%).

The upper trough weakens and starts to drift east of the region
Wednesday and Thursday, as surface high pressure slows becomes
established over the northern Great Lakes. This will result in
minimal shower/storm chances (10-20%) mid week, and as 500 mb
heights build further to above 588 dm, summer heat should continue
to build. The Friday-Saturday timeframe currently looks dry and
warm, and the summer heat looks poised to continue into next weekend
and beyond.

Highs will generally be in the low to mid 80s during the early to
middle part of the week, before inching into the upper 80s Saturday.
Lows through the period will be in the upper 50s to middle 60s.
Summertime in Michigan. Enjoy the warmth.

&&

.AVIATION /00Z TAFS THROUGH 00Z MONDAY/...
Issued at 759 PM EDT Sat Jul 6 2024

Skies are mainly clear at 00z across the TAF sites. We expect VFR
weather to continue through roughly 06Z. Some scattered stratus
and fog is expected overnight. We have brought IFR conditions into
MKG and GRR after 08Z, but have kept things VFR at the other
sites. The 06Z TAFs may be able to refine this threat as satellite
imagery should have a signal as to where the low clouds are
forming by then.

The stratus and fog should lift quickly after daybreak with VFR
conditions returning by 14Z. We expect a diurnal cumulus field
fill in at most sites by midday Sunday with bases around 4,000
feet.

Winds will be light and variable tonight becoming southwest on
Sunday at 5 to 10 knots.

&&

.MARINE...
Issued at 345 PM EDT Sat Jul 6 2024

Winds and waves are below Small Craft Advisory and Beach Hazards
Criteria this afternoon with buoys showing 2 feet or less wave
heights. This will remain the case tonight as a ridge of high
pressure moves through the area. Southerly winds develop on Sunday
on the backside of the high and ahead of a surface trough that is
approaching from Minnesota. Sunday winds will be on the lighter
side, 5 to 15 knots, but increase a bit further Sunday night.
Winds of 10 to 20 knots will be possible Sunday night. The
WaveWatch3 keeps conditions on the calmer side indicating only 1-2
footers. Beyond Sunday night into Monday morning, conditions look
even more benign with light winds and less than 2 foot waves.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...None.

&&

$$

DISCUSSION...Duke/Smith
AVIATION...Duke
MARINE...Duke