109
FXUS63 KAPX 210345
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
1145 PM EDT Mon May 20 2024

.KEY MESSAGES...

- Showers and storms ending overnight.

- Better chance for strong to severe storms with a potential
  squall line Tuesday night in advance of a surface cold front.

&&

.UPDATE...
Issued at 1008 PM EDT Mon May 20 2024

Compact mesoscale convective vortex (MCV) continues to make
steady progress thru Lower Michigan late this evening. Well-
defined line of strong/marginally severe convection continues to
fire ahead of it...stretching from NE Lower thru South Central
Lower Michigan. Convection has shown a downward trend over the
past couple of hours with loss of diurnal instability. Expect
this trend will continue as the MCV exits Lower Michigan
overnight...taking the resulting convection with it. Back edge
of the associated precip has moved into far NW Lower
Michigan...and will continue to slowly push eastward...bringing
an end to precip chances associated with this system. Overnight
lows will cool into the 50s to lower 60s.

&&

.SHORT TERM /THROUGH TUESDAY/...
Issued at 245 PM EDT Mon May 20 2024

Marginal instability/winds aloft in advance of a short wave
evident on water vapor imagery over southern Illinois tonight.
An area of showers and embedded thunderstorms is expected to
progress across northern Michigan through the evening and the
early overnight hours. Severe potential appears to be on the low
side from the combination of the loss of daytime heating,
limited moisture and marginal instability (just a few hundred
J/kg of mixed layer cape and 0-6 km bulk shear of 30-35 knots).
Although not expected, can not totally rule out the possibility
of an isolated severe storm or two with damaging winds and large
hail the primary threats.

A break in the action is then expected late tonight into much of
the daylight hours of Tuesday. Can not rule out an instability
driven pop up shower or storm Tuesday afternoon (mainly across
northeast lower). A bigger threat for severe storms arrives
Tuesday night (see long term forecast discussion below).

Muggy tonight with lows in the 50s to near 60. Highs Tuesday
ranging from the low and mid 70s north to the low and mid 80s
south.

&&

.LONG TERM /TUESDAY NIGHT THROUGH MONDAY/...
Issued at 245 PM EDT Mon May 20 2024

PATTERN SYNOPSIS/FORECAST:

A digging trough and its associated surface low is expected to track
into the Midwest resulting in an influx of deep moisture to the
area. This will be enough forcing to push a warm front, located in
southern Michigan, northward into the area, leading to rain showers
and possible strong to severe thunderstorms for late Tuesday/
Tuesday night. As the aforementioned surface low tracks out of the
region, cooler air will slowly wrap around the low and be pushed
into Northern Michigan. As such, temperatures will be warmer to
start off the week with daytime highs in the 70s, before more
seasonable temperatures set in for later in the week.

PRIMARY FORECAST CONCERNS:

- Tuesday Night: A digging trough and its associated surface low
will track into the western portion of Lake Superior. The
aforementioned low will deepen and strengthen as it tracks to the
Lake. Along the way, strong southerly winds will push a front north
into the APX footprint and provide enough lift to support strong to
severe thunderstorms for late Tuesday/ Tuesday night. A deep
moisture fetch is had with this setup as southerly winds draw ample
moisture in from the Gulf. One thing we will have to watch is if any
potential activity downstate materializes and cuts off the deep
moisture fetch, essentially hindering the chances of severe weather.
With atmospheric conditions being primed for this event, another
question will be if the nocturnal nature of the frontal passage will
disrupt initiation along the front. As stated by the previous
forecaster, the current thinking of linear mode storms (squall line
/ MCS) is still expected, making the main threat with this event
being strong winds. However, a strong low-level jet will take full
advantage of this event to help produce strong shear and opens the
door for some storms capable of producing hail in stronger updrafts
within the line. A quick spin-up tornado along the line as it surges
northeastward into northern Michigan will also be possible and
cannot be ruled out with ample shear, moisture, and
instability/lift? available. SPC (Storm Prediction Center) continues
to have a Slight Risk (2/5) across much of northern lower Michigan
and Marginal Risk (1/5) elsewhere. Continue to monitor the latest
forecast and be sure to have multiple ways of receiving weather
alerts to ensure you are weather aware.

&&

.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 1145 PM EDT Mon May 20 2024

Compact area of low pressure will continue to track eastward out
of Lower Michigan overnight. Residual showers will come to an
end overnight into Tuesday...before better chances of stronger
convection redevelop later Tuesday night. Prevailing conditions
will remain mostly VFR/MVFR. Light/variable winds overnight
will become SE under 10 kts on Tuesday.

&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...None.

&&

$$

UPDATE...MLR
SHORT TERM...AJS
LONG TERM...NSC
AVIATION...MLR