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000
FXUS63 KAPX 231051
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
651 AM EDT Tue Apr 23 2024

.KEY MESSAGES...

- Showers and a few thunderstorms into this evening. Marginal
  risk for a severe wind gust in southern areas.

- Cool tonight and Wednesday, turning warmer Friday into the
  weekend.

- Active weather this weekend with a chance for thunderstorms.

&&

.SHORT TERM /THROUGH WEDNESDAY/...
996mb surface low is diving toward the north shore of Lk Superior.
An initial cold front is crossing western upper MI and central
WI. Warm advection ahead of the front is contributing to a band
of rain showers, now over the center of this forecast area.
These will progress east out of the area this morning, though a
few trailing showers could form a bit behind the primary band.
Then, mid-level moisture departs for a time, at least up until
more substantial height falls arrive late today.

Low clouds are tending to expand in the region. The south half
of the forecast area will stay somewhat cloudier, but will still
warm thru thin spots with late April sun angle. The north half
will likely go partly sunny at times, especially in the 1st half
of the day. That will contribute to them redeveloping showers
sooner, by late morning/midday in eastern upper MI and the
Straits. A few hundred J/kg of MlCape may allow for a few
thunderstorms up there, but shear up there is far less than
further south (0-6km bulk shear circa 25kt). That meager
instability is unlikely to result in stronger t-storms.

Eventually, forcing and instability migrate south into northern
lower MI this afternoon/evening. Instability will have a hard
time exceeding 200J/kg, but wind fields are far stronger, and
0-6km shear values are some 50-60kt. Perhaps there`s a chance
for a strong/severe wind gust...aided by strong wind fields of
course, but also by the relatively dry sub-cloud layer. (That`s
assisting us in getting gusty winds early this morning, as the
showers move in). SPC has suppressed the marginal svr risk a bit
southward, along and south of an MBL-Harrisville line, which
seems fine.

Max temps today 55-60f eastern upper MI, in the 60s in most of
northern lower.

Chillier and much drier air pours in tonight. Precip chances
will get carried off to the south and east with time. Maybe a
few snowflakes are seen toward the tail end. Dawn temps will
range from near 20f in eastern upper MI, to near 30f in the far
south.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/...
Pattern Synopsis and Forecast:

Cool northwest flow aloft on Wednesday behind a departing trough
axis with below average daytime temperatures. Rapid moderation
expected thereafter for the end of the week as ridging aloft builds
overhead in response to a deep upper low in the Central Plains.
Upper low and attendant sfc cyclone then move northeast into the
Upper Midwest resulting in warm, moist advection across northern
Michigan. Consequently, rain showers, and thunderstorms, are likely
this weekend.

Primary Forecast Concerns:

System departs to the east Wednesday with cooler, below average
temperatures expected (especially during the morning hours when wind
chills will be in the 10s and 20s). Atmosphere will quickly rebound,
however, as heights rise and ridging builds into the area late week.
Temperatures will rise into the 50s and 60s once more during this
time. Warm temperatures will remain through the weekend due to
breezy southerly sfc winds and continued above normal height
anomalies aloft.

A series of potent, compact upper lows will advect from the C Plains
to the Upper Midwest Friday into this weekend. Consequently, warm,
moist advection is anticipated with a mix of showers and
thunderstorms possible Friday night through the weekend (in addition
to breezy winds). Current guidance suggests the best period for
thunderstorm activity will be Saturday as dewpoints surge into the
50s and perhaps low 60s fostering instability values ~500-1000j/kg
(GFS/CMC ENS guidance shows 50%+ chance for 500j/kg). As the upper
level features move to the west of the region, robust southwest flow
overspreads northern Michgian. Progged GFS/CMC soundings are quiet
impressive through the lower to middle troposphere with 40-50kts
around 850 mb and vicinity. It does appear there will be showers
earlier in the day on Saturday and so the degree of afternoon
instability will potentially be in question (which is usually an
issue for northern Michigan) but the potential for robust
thunderstorms is at least hinted at given the current progged
pattern. As a reference, CSU-MLP (Colorado State University Machine
Learning Probabilities) do(es) suggest the potential for severe
weather across northern Michigan on Saturday with a 5-15%
probability (albeit this run was from Sunday evening, latest data is
blank for some reason). That being said, we`ll take our time and
monitor this in the coming days, the finer details will certainly
change.

&&

.AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/...

Low pressure moves se across the Great Lakes today. Occasional
showers will be seen thru this evening. Most of these will be
from a VFR cloud deck. However, restrictions are briefly
possible with any heavier showers or possible isolated TSRA.
More widespread lower cigs (MVFR) are expected to invade for
part of tonight, and much colder air returns.

Somewhat gusty sw winds today, becoming n to ne by late
tonight.

&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...Small Craft Advisory from 11 PM this evening to 2 PM EDT
     Wednesday for LHZ345>348.
     Small Craft Advisory until 2 PM EDT Wednesday for LHZ349.
     Small Craft Advisory until 2 PM EDT Wednesday for LMZ323-341-
     342-344>346.
     Small Craft Advisory from 8 PM this evening to 6 AM EDT
     Wednesday for LSZ321.

&&

$$

SHORT TERM...JZ
LONG TERM...JLD
AVIATION...JZ