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000
FXUS63 KGRR 231137
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
737 AM EDT Tue Apr 23 2024

.KEY MESSAGES...

- Showers Early this Morning; Marginal Severe Risk Expanded

- Frost/Freeze Risk Wednesday Night/Thursday Morning

- Warmer and unsettled weather moves in for the weekend

&&

.DISCUSSION...
Issued at 357 AM EDT Tue Apr 23 2024

- Showers Early this Morning; Marginal Severe Risk Expanded

 Showers out ahead of the incoming short wave will continue to
spread over the region early this morning. The dry air at the
surface delayed the onset of precipitation, however scattered
showers continue to spread over the region and will continue
through the first half of the morning. Coinciding with this short
wave will be a strong low level jet. Winds upwards of 35 mph will
be possible through the early morning hours. The 925 mb winds
should become more amplified with more directional shear from the
850 and 700 mb layers. Looking at BUFKIT soundings CAMS have a
weak capping inversion from 2,500 to 4KFT this afternoon. If this
is breached, the steep low to mid level lapse rates of 7 to 9 C/KM
should greatly aid in convection.

 Couple those lapse rates, the strong shear from the LLJ and the
cold air aloft and there is a decent chance for severe hail.
Latest mesoscale analysis has decent DCAPE moving into the region.
Given that, SPC has expanded the marginal risk for severe storms
for across the region this afternoon. Timing wise, latest CAMS
brings the best opportunity for strongest convection will be late
in the day associated with the cold front, around 00Z. A
secondary LLJ is associated with that boundary as well, though it
is weaker then the one moving through this morning.



- Frost/Freeze Risk Wednesday Night/Thursday Morning

Clearing skies under surface high pressure and very dry air at the
lower levels will create favorable conditions for radiational
cooling Wednesday night into Thursday morning. Temperatures will
likely drop into the upper 20s across a wide swath of southern Lower
Michigan. The coldest temperatures will probably in the northeast
counties where mid 20s can`t be ruled out. The good news is that the
trend of a slightly warmer airmass at 850 mb continues with recent
model runs.

- Warmer and unsettled weather moves in for the weekend

As this final blast of cold air departs the area, a reorientation of
the longwave pattern will move into the central CONUS, setting
Michigan up initially on the "sunny" side of a building upper ridge,
but by Friday afternoon the ridge axis will have passed us and we`ll
fall into several days of deep southwesterly flow.

This pattern will allow much warmer and more humid air to stream
into our state, along with fairly plentiful cloudiness. At least 2
major disturbances/shortwaves will move through this southwest flow,
and bring rounds of rain and possibly storms beginning Friday night
and continuing all weekend. It`s unlikely the whole weekend will be
a washout, but the exact timing and placement of these shortwaves
are still pretty uncertain at this time, so some of the more
pertinent forecast details remain elusive. Instability and the risk
of possible severe weather will be monitored over the coming days,
as breaks of sunshine during the day followed by one of these
shortwaves coming through near peak heating could easily result in a
severe threat.

&&

.AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/...
Issued at 729 AM EDT Tue Apr 23 2024

Initial batch of showers has underwhelmed as it came through, due
in part to the dry air at the lower levels that had to be
overcome. Rain has been minimal and ceilings have stayed well into
VFR category overnight and this morning. We should see a break in
the showers over most of the area for a good chunk of the morning
and early afternoon - and may even see a few breaks of sun.
Exception is Jackson, where clouds and showers might hang on
throughout much of the day without much break. Elsewhere, showers
and a few storms are expected to develop mid afternoon and move
through the area until mid evening, at which point the winds start
to switch to more of a northwesterly direction as a cold front
passes. Model guidance is suggesting development of an MVFR
ceiling overnight into Wednesday morning, but cold air advection
should limit the potential for things to get much worse/lower than
that.


&&

.MARINE...
Issued at 403 AM EDT Tue Apr 23 2024

An active/hazardous period on Lake Michigan will continue through
Wednesday. Gusty winds will continue with southerly flow this
morning. Winds will briefly slacken over the lake this afternoon.
However winds will shift to the north to 30 kts behind the front
tonight into Wednesday. Though the small craft remains, there is
still a chance for brief periods of gales. Hazardous winds and
waves should subside Wednesday night into Thursday as a sfc
ridge builds overhead

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...Small Craft Advisory until 8 PM EDT Wednesday for LMZ844>849.

&&

$$

DISCUSSION...Ceru/AMD
AVIATION...AMD
MARINE...Ceru