Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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507
FXUS63 KGRR 312245
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
645 PM EDT Thu Oct 31 2024

.KEY MESSAGES...

- Winds are the main concern in the short term (Tonight-Fri
  night)

- Warm and wet Sunday through Tuesday

- Drying out Wednesday and Thursday

&&

.DISCUSSION...
Issued at 340 PM EDT Thu Oct 31 2024

- Winds are the main concern in the short term (Tonight-Fri
  night)

Earlier today we bumped up the start time of the Wind Advisory to
Noon and added South Central Lower Michigan counties into the
headline as well. Some of the peak gusts so far... 53mph at East
Grand Rapids, 51mph at Holland ASOS, 44mph and the Grand Rapids
ASOS and 44 mph at the Muskegon ASOS. Those gusts occurred with a
pre frontal trough and some associated showers. We expect some
higher gusts once again over the course of the next several hours
as cold air advection kicks in. Highest gusts will likely be found
along the lakeshore as the convection with the front itself has
almost become non existent. We should see an uptick again in
showers however as the front slides eastward into the eastern
forecast area towards LAN and JXN. Bottom line the wind gusts will
be marginal in most areas for a Wind Advisory in the 40 to 45 mph
range. Feel good with the area and the timing at this point and
will let it ride.

Otherwise, very limited weather concerns in the short term after
tonight. We will see some lake effect rain showers tonight into
Friday morning as Delta T`s over the lake increase into the upper
teens C (lake water temp around +14C and 850mb air dropping to -3C
late tonight). These showers should not be significant, but will
likely hang on into the midday hours before ending. Skies may
continue partly cloudy both on Friday and Friday night as lake
stratocumulus will hang on along with some high clouds moving in
Friday night.

- Dry and seasonable Saturday; Warm and wet Sunday through Tuesday

Saturday`s weather looks by far to be the best day of the upcoming
weekend. High pressure will start out in place Saturday morning,
providing for a crisp, but seasonable early November morning. Plenty
of sunshine should be found during the daylight hours with the ridge
only slowly moving east of the area.

The weather will deteriorate steadily through Sunday, with
widespread rainfall expected to overspread the entire forecast area
by 00z Monday. This will be the result of a large amplified trough
digging over the Four Corners region. This will establish a deep SSW
flow with plenty small and large scale lift, and a direct feed
of moisture from the Gulf of Mexico.

We will see waves of showers and some potential isolated embedded
storms from Sunday right through Tuesday. This is typically one of
our wettest patterns. The main question with this rainy period, is
the rain amounts and if there is any potential flood threat. Right
now, the most likely scenario is that we could see 1 to 3 inches of
rain over the three day period. If this was to come fruition, it
would not be a flooding concern. We are still quite dry from the
lack of rain this fall. Rivers and streams and lakes are all running
below average levels, so we have plenty of buffer to be able to
handle this amount of rain spread out. We will watch for the
potential of higher amounts.

- Drying out Wednesday and Thursday

Chances are better than not that we will dry out for Wednesday and
Thursday next week. The pattern over the 48 states does become a bit
complicated with uncertainty with how the patterns play out with the
major players. We will see the long wave trough early in the week
move out of the area by Wednesday. That would imply high pressure
moving in. Another long amplitude trough digs across the Western
U.S., and tries to bring the area back under southerly flow.

The biggest uncertainty of this feature is whether is closes off a
low over the desert SW, or if it remains intact. If it closes off,
we could see northern stream troughing move in over the area,
bringing cooler temperatures, and maybe a chance for some rain with
short wave activity. If it does not close off and stays intact, we
could get back into SW flow aloft.

We will go on the drier route for now, but could see some small rain
chances possible for later next week depending on the pattern
evolution.

&&

.AVIATION /00Z TAFS THROUGH 00Z SATURDAY/...
Issued at 645 PM EDT Thu Oct 31 2024

Windy conditions will continue at all the terminals through the
evening with southwest to west winds of 15 to 30 kts with gusts to
around 35 kts. Winds will only slowly subside overnight. A few
rain showers will redevelop at KMKG and KGRR overnight. A mix of
mainly MVFR/IFR conditions tonight due to low cigs will gradually
improve to VFR tomorrow afternoon as low clouds dissipate.

&&

.MARINE...
Issued at 340 PM EDT Thu Oct 31 2024

Concerns within the marine forecast are very much front loaded
(meaning mainly tonight). We have a Gale Warning out through 200am
tonight and that still looks very good. A few gale gusts have
already occurred, but we feel the core of the gales will happen
in the cold air advection behind the frontal passage. As of 300pm
the front has just come on shore north of Grand Haven and will
move onshore south of Grand Haven by 400pm. BUFKIT overviews via
the 3km NAM indicate that from 300pm right through the evening we
should be mixing up through levels that produce 34 knot wind gusts
(gale force).

Waves look to peak between 900pm and midnight around Grand Haven
at 14 feet. All areas should see 9 to 14 foot waves this evening.
Given much lower water levels than we had a few years ago, not
expecting any flooding or dune erosion. In the summer of 2022 we
were consistently above 582 feet in Lake Michigan water level
height. We are right around 579 feet this afternoon at Holland and
that is with a slight rise due to the strong southwest winds.
Being 3 feet down in water level allows for buffer on the beach
where the water does not reach the dune line.

Winds and waves will come down overnight and especially on Friday.
A Small Craft Advisory will be needed overnight when we end the
Gale Warning. It will need to run from 200am if that is when we
drop the Gale through 400pm or 500pm on Friday as it will likely
take all day for the waves to dampen out and fall below 4 feet.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Wind Advisory until 2 AM EDT Friday for MIZ037-043>046-050>052-
     056>059-064>067-071>074.
MARINE...Gale Warning until 2 AM EDT Friday for LMZ844>849.

&&

$$

DISCUSSION...Duke/NJJ
AVIATION...Laurens
MARINE...Duke