Marginal Risk for Storms

Our week of sunny skies and summer-like temperatures will come to an end today which may come as a shock to many when temperatures drop into the 50s this afternoon.  We have a marginal risk for severe weather today with the chances of rain and storms increasing throughout the day.  Tomorrow we could see an inch or two of snowfall.

This hazardous weather outlook is for portions of southwest Lower
Michigan.

.DAY ONE...Today and Tonight

Showers and thunderstorms are likely starting late this morning
and continuing through the middle of the afternoon. Local wind
gusts to 45 mph are possible as the line of storms moves through.

---

There are winter storm warnings to our west in Wisconsin for 5 to 10 inches of snow.  Any flowers they have like we do here in Michigan are going to be smashed.

---

Grand Rapids Forecast

[pdf-embedder url=”https://michigan-weather-center.org/wp-content/uploads/2023/04/4-16-grr.pdf” title=”4 16 grr”]

---

Forecast Discussion

- Spring-like storms today -

The morning weather map features a negatively tilted upper trough
over the plains that is in the process of catching up to a surface
low loitering in southern Wisconsin. This system will become
vertically stacked later today and then slowly drift toward the
Straits of Mackinac by midday Monday. Ahead of this storm, Lower
Michigan is waking up in a warm and increasingly unstable airmass
this morning. An attendant cold front from the Wisconsin low is
currently in central Illinois and will be driving northeastward
through Lower Michigan during the day today.

There is not much doubt that a line of showers and storms will
develop ahead of this cold front and affect most of our area today,
but the big question remains how much diurnal heating and
destabilization can occur ahead of the cold front. Model timing
remains pretty locked in with a midday and early afternoon fropa
across most of our counties, so this means the eastern and
northeastern sections (east of US-127) will have the best chance for
some stronger storms today. We remain in an SPC Marginal risk, and
overall the main threat would be strong winds associated with the
line of organized convection itself, and perhaps an isolated hail
threat if any discrete convective cells can form ahead of the main
line. 00z HREF helicity swaths support the idea that a few of these
discrete cells are possible early this afternoon.

- Cold front and snow for Monday -

Temperatures plunge behind the cold front tonight as wrap-around
rain showers start to mix with and change to snow after midnight
tonight. Snow showers continue on Monday as cold air continues to
pour across Lake Michigan. In shocking contrast to the last few days
of temperatures in the 80s, high temperatures on Monday will
struggle to reach 40 degrees, and the cold wind will be biting.
Several model cycles in a row support an inch or two of wet snow
accumulation Sunday night and Monday morning - probably mostly on
grassy and elevated surfaces. What this means is that no one should
be shocked to wake up Monday morning to see some of the white stuff
covering the lawn. As the low finally pulls away to the east on
Monday afternoon, shower activity will be on the decline. However,
with 850 mb temps approaching -10C by Monday night, and with lake
tempeatures around +5C, the delta-T will be marginally enough to get
the lake-effect process going, which will probably prolong the snow
showers a bit longer. Thankfully, fairly warm ground should limit
impacts from this late-season winter weathermaker.

- Rain chances return by midweek -

Upper ridging moves in for midweek, with a warm front lifting
northward at the same time and stalling near northern Lower
Michigan. This will allow temperatures to rebound closer to normal
temperatures for this time of year. Unfortunately, the upper ridging
quickly gives way to southwest flow and active shortwave activity
once again. This will result in pretty much daily chances for rounds
of rain across Michigan for the end of the week and into the start
of the weekend. Overall, another 1-1.5 inches of rain are possible
late this week, so it looks like we`re heading right back into a wet
pattern again.