747
FXUS63 KGRR 142244
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
644 PM EDT Fri Jun 14 2024

.KEY MESSAGES...

- High confidence for oppressive heat/humidity next week

- Low Confidence on heavy rain next week

&&

.DISCUSSION...
Issued at 328 PM EDT Fri Jun 14 2024

- High confidence for oppressive heat/humidity next week

Fine weather will continue through Saturday. There were a few
renegade showers earlier this afternoon but those have dissipated
and the diurnal cu field does not look capable of producing
showers given the dry atmospheric profiles. So showers were not
included in the forecast through the evening.

After a stellar Saturday, the sfc high will move east and a deep
southerly flow regime will be established for Sunday and into the
middle of next week. The operational models continue to show an
unusually strong upper high centered southeast of Lower Michigan.
This creates what has been colloquially called the "ring of fire"
with occasional, and in this case persistent, MCS activity to the
west and north. The operational Canadian and GFS remain in line
with one another on the main features with the operational EC
being an outlier with stronger upper ridging. However, when
looking at the NAEFS and ECMWF ensemble means and standardized
anomalies, the differences of the models become smaller.

So while there is some spaitio temporal differences in position
of the ridge and moisture advection, the pattern remains
consistent. So there is high confidence in that maximum
temperatures in the 90s could continue through the middle of the
week.

Monday and Tuesday continues to look to be the hottest days with
850mb temps ranging from +18C to +22C, depending on the model you
look at. The concern along with these hot temperatures will be the
dewpoints in the upper 60s to low 70s. That could bring apparent
temperatures to advisory criteria, especially considering this
heat could linger for days. The trend for warm overnight
temperatures remains consistent as well with lows only dropping
into the low 70s. This lack of recovery will be another factor
along with the daytime maxes and the humidity.

- Low Confidence on heavy rain next week

So while there is good confidence in the upcoming heat the
biggest question is whether or not there will be any precipitation
to go along with it. The strength of the upper ridging and
capping inversion could reduce any instability needed for
showers, so while humidity may be present, there may not be enough
vertical motion for showers/storms. There are constant changes
run to run in the models and the best moisture to allow for rain
remains north of southern Michigan. There is some potential for
weak shortwave troughs and MCS/MCV effects on the western
periphery of the upper high bringing more favorable conditions for
showers and storms on any day next week. Confidence in the details
of location and timing for those features remains low.

&&

.AVIATION /00Z TAFS THROUGH 00Z SUNDAY/...
Issued at 644 PM EDT Fri Jun 14 2024

Very high confidence in VFR through the TAF period as scattered
cumulus around 7-8kft diminish quickly after sunset. Dry low-
level easterly flow and high pressure keep conditions P6SM visbys
and SKC through mid- day Saturday. Saturday and afternoon will see
the arrival of clouds above 15kft ahead of our next weather
system. Muskegon has west winds due to the lake breeze which will
quickly match the prevailing northeasterly flow in the next few
hours. East to southeasterly winds are expected tomorrow with
winds at or below 10 knots.

&&

.MARINE...
Issued at 328 PM EDT Fri Jun 14 2024

Winds are gradually turning onshore this afternoon but are rather
weak with gusts below 15 knots at the buoys. Coastal webcams show
flat waves still although there may be a slight increase late
this afternoon before winds go offshore again.

Winds and waves should be light for Saturday then increasing south
to southwest winds Saturday night with building waves for Sunday
and a Small Craft Advisory will be needed.

&&

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

&&

$$

DISCUSSION...Ostuno/Ceru
AVIATION...Thomas
MARINE...Ostuno