Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 261122
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
722 AM EDT Tue Mar 26 2024

.KEY MESSAGES...

- Strong/severe storms today

- Dry to End The Workweek

- Multiple Chances For Precipitation As March Ends

&&

.DISCUSSION...
Issued at 318 AM EDT Tue Mar 26 2024

- Strong/severe storms today

As expected, rain developed over the cwa within the past few
hours. Radar shows the showers moving quickly north. At this time,
no thunder has been detected. Farther southwest, the dry slot is
beginning to develop over Illinois and this will be a key to our
weather today.

A surface low was over central Iowa with a trough trailing south
and a cold front behind it. The low is progd to continue to
deepen as it tracks toward the western UP.

Today`s scenario involves the rain moving north and the drier air
of the dry slot moving over the cwa later this morning/early
afternoon. Coincident with this will be the trough/cold front
moving east across Lake Michigan. Soundings and forecast upper air
progs shows a lot of wind aloft. As this occurs, mid level lapse
rates near 7C/km will nose northward from Ohio. MUCAPE isn`t all
that impressive; a few hundred joules/kg. But if we get enough dry
air to move in following the rain, the degree of destabilization
may overperform a bit. Moisture isn`t great, but probably enough
for some storms to develop. Helping the cause for storms will be
the additional lift from the associated short wave that also
arrives around 18z.

CAMS show a broken line of convection developing along/ahead of
the front by early afternoon over the western cwa and moving
east. Given a LLJ around 50 knots and a mid level jet around 110
kts, any storm that develops could generate severe wind gusts.

0-3km SRH values top out in the 300-400ms range on the HRRR, which
is probably enough to generate some rotating supercells.

There appears to be more than enough ingredients coming together
to generate some severe wind gusts and/or an isolated tornado. SPC
has placed the cwa south of M-57 and east of the lakeshore in a
Slight Risk for severe storms today with the rest of the cwa in a
Marginal Risk. The threat window looks to be 2PM - 7PM.

Cooler air will move back into the cwa behind the front tonight.
Dry weather is expected Wednesday.

- Dry to End The Workweek

No impactful weather is expected Thursday or Friday as surface and
upper-level ridging, in tandem with a overall dry atmosphere, drives
conditions across the Central Great Lakes. The dry air in place
means plenty of sunshine is expected. Highs in the 40s are expected
Thursday as longwave troughing exits, with temperatures climbing
into the 50s for Friday under increasing mid-level heights and a
brief thermal ridge.

- Multiple Chances For Precipitation As March Ends

The weekend into the first part of next week will feature a mainly
zonal 500mb pattern with a mid-level baroclinic zone not far to the
north. Ensemble guidance suggests a few chances of precipitation
centered around the Saturday Morning, and Sunday Night - Tuesday
timeframes as surface lows move through the Central Great Lakes.
However, as is not uncommon in the extended range and especially in
a zonal flow pattern, exact details remain uncertain as to timing
and amounts. A high pressure system in the Hudson Bay region and
associated northerly component to the flow pattern brings the
potential of snow showers mixing in across Central Michigan near
peak overnight cooling. The zonal pattern also keeps temperatures
generally consistent in the upper 40s to near 50s through the
weekend and into Monday.

&&

.AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/...
Issued at 716 AM EDT Tue Mar 26 2024

Widespread showers have generally ended this morning, however
scattered showers remain possible through the morning given the
moist environment so have kept VCSH in the TAFs. MVFR cigs persist
at generally sub-fuel alternate levels. LLWS also persists through
the morning as a low-level jet provides 45-55kts of LLWS. The
primary aviation concern will be this afternoon when a line of
low-topped thunderstorms generates ahead of a cold front and
sweeps east across Michigan. Given low instability have used VCTS
to highlight the main thunder window. Regardless, it will be windy
today with south winds gusting to near 30 knots. Any showers or
thunderstorms have the potential to bring areas of 40-50 knot
gusts to the surface but this is low confidence at this time. A
few hours of VFR are expected around the cold frontal passage
before MVFR conditions and west-southwesterly winds take hold for
the overnight hours.

&&

.MARINE...
Issued at 318 AM EDT Tue Mar 26 2024

Strong south winds ahead of a cold front today will likely reach
gale force through this afternoon before falling below 35 knots
later this evening; a Small Craft Advisory will likely be needed
tonight.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...Gale Warning until 2 AM EDT Wednesday for LMZ844>849.

&&

$$

DISCUSSION...04/Thomas
AVIATION...Thomas
MARINE...04


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