742
FXUS63 KGRR 150110
AFDGRR
Area Forecast Discussion
National Weather Service Grand Rapids MI
910 PM EDT Fri Mar 14 2025
.KEY MESSAGES...
- Storms after midnight with gusty winds developing into Saturday
- Much cooler and showery on Sunday
- Another potent system expected around Wednesday through Thursday
&&
.UPDATE...
Issued at 900 PM EDT Fri Mar 14 2025
An overall consensus blend of latest CAMs corroborated with rgnl
radar trends still suggests that showers and storms will not move
into our area until 06Z Sat at the earliest and mainly around to
after 07Z Sat. This will be a weakening line of showers and storms
given unfavorable timing and weak instability. The llj and
kinematics are favorable though so we do expect some gusty showers
and storms (but most if not all of the winds will be sub severe).
Our going forecast and headlines for the synoptic wind event
overnight/Saturday look excellent with no changes needed this
evening.
&&
.DISCUSSION...
Issued at 331 PM EDT Fri Mar 14 2025
- Storms after midnight with gusty winds developing into Saturday
We are issuing a Wind Advisory for the land areas beginning at 06z/
2 am EDT to account for the wind with the showers and storms that
will be coming through later tonight, and for the synoptic winds
expected for much of Saturday.
Visible satellite imagery this afternoon shows some impressive
signatures already with the incoming system, as a large area of dust
can be seen in the dry slot lifting NE. It is ahead of this where
vigorous convection will fire this afternoon and lift ENE through
tonight.
We will see a quiet, windy, and warm evening for SW Lower Michigan,
before showers and some storms move in after 06z tonight. The line
of storms are expected to lose quite a bit of their punch by the
time they make it here during the overnight hours with a cooler
atmosphere. Forecast model soundings indicate that MU CAPEs will
only be a few hundred J/kg just ahead of the line. In addition, most
of the CAPE is slightly elevated, but with only a weakly stable sfc
layer.
Our expectation regarding storm intensity remains the same as
mentioned in the previous discussion. The low level jet will be
strong with 40-50 knots of wind only 1-2k ft agl. It will not take
much to mix these winds down, especially with some initially drier
low levels helping to produce some dry microbursts. However, with
the storms weakening, most of the winds will be sub-severe and a
hybrid synoptic/convective scenario. Given we will have strong
synoptic winds Saturday and the winds behind the line tonight will
be close to Advisory criteria, it seemed the best and simple way to
just add later tonight into the advisory.
Once the convection moves through, we will be in the dry slot of the
system, likely cutting rain chances off through most of the day on
Saturday. The stronger core of winds, combined with the strong
subsidence and good mixing due to the sunshine expected, winds of 45
to 55 mph will be quite common over the entire area during the
daylight hours. Not out of the realm of possibilities to see gusts
approach Warning criteria along the northern lakeshore where some
mesoscale effects could occur.
Very late in the day on Saturday and Saturday night, we will see
additional jet energy lift rapidly NNE toward western Lake Erie and
Lake Huron. What this will do is bring another healthy slug of
moisture along the front that will have slowed down, and bring
another round of showers with a few storms, especially toward U.S.-
127.
The bulk of any stronger to severe storms should stay mainly near
and east of the low track, east of our area. However, there is some
weak lingering instability of a couple hundred J/kg of CAPE from the
heating of the day that this system could act on. In addition, very
strong mid-level flow will help to produce 50+ knots of deep layer
shear. The lack of good instability will keep the threat limited,
but non-zero with the strong shear present.
- Much cooler and showery on Sunday
The secondary energy, associated sfc low, and showers/storms will
all move out by Sunday morning. However, the upper trough axis is
still west of the area, and will have enough moisture and
instability with the cold pool aloft coming in to keep showers over
the area through much of the day. The showers will initially be
rain, but will change over to a bit of snow before ending as 850 mb
temperatures drop to around -9C by Sunday evening.
- Another potent system expected around Wednesday through Thursday
We will see at least two, and possibly three drier days for the
area, with moderating temperatures. The sfc ridge axis moves
overhead Sunday night, and shifts east by Monday. This is associated
with a broad ridge over the Plains that will gradually build east.
The low level flow will transition to a southerly flow by Monday,
helping temperatures start warming back up. This will really be
noticeable Tuesday and Wednesday as 850 mb temps warm to around +9C
again.
Precipitation chances could make a return here as early as
Wednesday, but it starting to look like it will be more so late
Wednesday and Thursday. Another strong upper trough will come in off
of the Pacific and lead to strong leeside low development over the
Central Plains.
Confidence in the system is high, while the timing and exact track
is still a little uncertain. It is more likely that we will see the
warmth ahead of it, with eventually some showers and storms
developing as the low approaches. As the low passes, it will likely
have cold enough air to change some of the pcpn on the back end of
it to snow.
&&
.AVIATION /00Z TAFS THROUGH 00Z SUNDAY/...
Issued at 735 PM EDT Fri Mar 14 2025
Overall forecast remains on track. VFR conditions are expected for
the next six hours. A line of showers and thunderstorms arrives
after 06z impacting all terminals with IFR visibilities for around
2-3 hours. In addition, a period of prolonged non-thunderstorm LLWS develops
after 00z as winds of 50-60 knots at and above 2000 ft develops. There
is a low chance of gusts exceeding 40 knots within any
thunderstorms in addition to normal hazards, and gusts exceeding
30 knots are likely. Gusts increase to 40 knots or greater late
Saturday morning into the late afternoon from the south-southwest
before subsiding in the evening. There is a low chance that
afternoon thunderstorms develop near LAN, JXN, and BTL. Where
chances are slightly better at LAN and JXN have included a PROB30
for thunderstorms after 20z Saturday.
South-southeast winds around 15-25 knots are expected ahead of the
storms.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Wind Advisory from 2 AM to 8 PM EDT Saturday for MIZ037>040-
043>046-050>052-056>059-064>067-071>074.
MARINE...Small Craft Advisory until 8 AM EDT Saturday for LMZ844>849.
Gale Warning from 8 AM to 8 PM EDT Saturday for LMZ844>849.
&&
$$
UPDATE...Laurens
DISCUSSION...NJJ
AVIATION...Thomas
NWS GRR Office Area Forecast Discussion
