347
FXUS63 KGRR 191858
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
258 PM EDT Sat Oct 19 2024

.KEY MESSAGES...

- Roller Coaster Temps and Mostly Dry For The Next Week

&&

.DISCUSSION...
Issued at 257 PM EDT Sat Oct 19 2024

Dry ground and dry air will result in large diurnal temperature
ranges the next few days and we will continue to forecast min
temps lower and max temps higher than guidance. Lows this morning
in the 30s and highs in the lower 70s are evidence of this.

A warming trend persists into Monday as southwest flow dominates.
Monday, temperatures peak with 850mb temps around +16C which
according to SPC sounding climatology is near maximum recorded
values. A bit of uncertainty in the temperature forecast exists
dependent on how strong mixing is, with the GFS on the higher end
of the envelope in the low 80s, and the ECMWF on the lower end in
the mid 70s. Most likely, temperatures will split the difference
with highs in the mid-upper 70s.

Significant troughing behind a cold front arrives Wednesday into
Thursday as 850mb temps crash to below 0C. Cluster analysis shows
a bit of uncertainty on frontal timing dependent on the speed and
depth of the trough. The ECMWF and related solutions favor a more
progressive trough/faster front, pushing highs down to the low
60s. The GFS and its related solutions favor a deeper and slower
trough/slower front putting highs near 70 on the table.
Regardless, temperatures undergo a drastic change with highs only
in the low 50s Thursday with upper 40s on the table near US10.
Temperatures rebound towards 60 by the weekend as ridging returns
to the region.

As for precipitation, the dominance of dry air and high pressure
leaves Tuesday night into Wednesday as our main chance for rain in
the forecast period. This will be driven by a trough pushing a cold
frontal boundary across the state. With the lack of deep moisture,
rain will be light. WPC forecasts propose under 0.25 inches of rain
for much of the area. High pressure returns behind the front with
dry weather continuing into the weekend.

Confidence remains above average in the overall forecast. Strong
correlation among ensembles brings increased confidence in the large
scale pattern. Other than the aforementioned uncertainty in frontal
timing Wednesday, little variability in temperature and
precipitation exist based on grand ensemble cluster analysis.

&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 1226 PM EDT Sat Oct 19 2024

High confidence in VFR conditions over the next 24 hours with SKC
most of the period, with a brief period of a few cirrus possible
tonight. Winds will generally be south to southwest at 5-10 knots
throughout the TAF window.

&&

.MARINE...
Issued at 257 PM EDT Sat Oct 19 2024

South to southwest winds will continue through early next week.
Winds and waves may build high enough for a SCA to be needed north
of Holland by late Sunday or Sunday night.

&&

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

&&

$$

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