669
FXUS63 KAPX 111809
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
209 PM EDT Sat May 11 2024

.KEY MESSAGES...

- Showers today, gradually diminishing w to e. Clouds somewhat
  slower to clear late today/tonight.

- Patchy frost possible late tonight.

- Rain chances increase later Sunday/Sunday night.

- Some frost potential Tuesday morning?

&&

.UPDATE...
Issued at 925 AM EDT Sat May 11 2024

Current forecast remains on track with no notable changes as rain
begins to diminish from west to east this morning and afternoon. For
details, see the short term discussion below.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 317 AM EDT Sat May 11 2024

Synopsis/pattern: A digging shortwave will close off over
northern lower MI this morning. Surface cyclogenesis is
underway, with a 1004mb low over nw lower MI. This system will
somewhat slowly work across northern lower MI and Lk Huron into
this evening.

Forecast: Wet weather is expected across northern MI early
today, but with slow but gradual improvement from w to e during
the day and evening.

Showers are gradually progressing eastward across the forecast
area early this morning. Somewhat surprisingly, a few embedded
t-storms developed since midnight, from the ACB-GLR area down to
Rose City and Gladwin. Cold mid-level temps and reasonable
forcing are able to take advantage of meager MuCape values of
around 100j/kg. A few additional t-storms are possible thru
midday, mainly in ne lower MI.

As the mid-level low center closes off, deformation around the
north flank of the low will increase. This process is resulting
in the banded precip seen over the east half of upper MI. This
will progress se-ward into far n central lower MI and then ne
lower MI today. Sneakily healthy QPF will result; total rainfall
will exceed 0.50" across a good chunk of ne lower MI, and
especially near APN.

Back edge of precip will make gradual eastward progress. MBL is
done by mid-morning; TVC and Naubinway by early afternoon.
Things slow after that; the I-75 corridor isn`t done until
almost evening, and the ne lower MI coast waits until almost
midnight.

Highs today will be cool as a result...near 50f to the mid 50s.

Clouds will also be slower to clear heading into tonight;
something of considerable interest for potential aurora viewers,
but also for agricultural interests. Skies may not clear in TVC
until mid-late evening, and along I-75 until around or shortly
after midnight. Our window for radiational cooling is thus
somewhat small, as clouds will increase again into nw lower MI
toward morning. In fact, a few showers could return toward dawn
near Lake MI.

Min temps remain progged down into the mid 30s to lower 40s.
Frost (and fog) potential continues across a broad portion of
the interior.

&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...
Issued at 317 AM EDT Sat May 11 2024

Pattern Forecast: Mean long wave trough across eastern North America
with a train of short waves lining up back across the northern
Pacific...and split flow over the western U.S. with an upper low
over the Great Basin.  As one short wave trough moves through the
upper Great Lakes tonight/Saturday...a second currently over western
Canada will propagate east as it wraps up into a small closed
circulation near James Bay on Monday. By Tuesday the Great Lakes
will likely be in between the northern branch upper low which will
take its time passing James Bay...and the southern branch wave which
as of now is expected to remain well south of Michigan. More short
wave troughing may be on the way by Thursday.

Northern branch short wave trough heading across Canada this
weekend...while most of the main dynamics/height falls will remain
well to the north...will push a cold front into the upper Midwest
early Sunday and across northern Michigan Sunday night/early Monday.
This front may become stationary over Lower Michigan Monday as it
loses its upper level impetus (becoming the warm front for southern
branch surface cyclone eventually?).  High pressure expected to
ridge in from the north for Tuesday/Wednesday.

Primary Forecast Concerns:

Rain chances increase later Sunday/Sunday night: Strong low/mid
level warm advection/isentropic ascent spreads into northern
Michigan Sunday morning...though accompanied by short wave ridging
aloft so wondering about the vertical motion profile (is it "bottom
heavy").  Strength of isentropic upglide suggests that negative PV
advection and "sinking" isentropic surfaces won`t offset the upward
motion much if any.  The only thing this impacts is precipitation
timing during the first half of the day...will nudge PoPs up a bit
Sunday morning in line with the SREF guidance which bring measurable
precip chances to the I-75 corridor by midday.  Later Sunday
afternoon/night stability weakens with arrival of low level theta-e
ridge and cold front so precipitation chances expected to be more
prevalent (along with thunderstorm chances).  Rain may come to an
end across eastern Upper after midnight.

Shower chances lingering near Saginaw Bay Monday?: This all hinges
on where the cold front ends up as it stalls at least in the
vicinity of the US-10 corridor.  Simply from a probabilistic/
uncertainty standpoint should keep some low PoPs around Gladwin/
Arenac counties (at least) as convection should bubble up along the
boundary during the afternoon and could sneak into there.  In
addition...deformation precipitation band along the confluent
northern side of the southern branch wave moving into the mid
Mississippi Valley may get a little close for comfort as well again
to areas adjacent to Saginaw Bay.

Some frost potential Tuesday morning?  Minimal probabilities for
now: Just going to leave this here for now as something to consider
later...cooler air settles in behind the cold front but questions
about wind and extent of cloud cover across Lower Michigan.
Frost probabilities right now based on temperature probability of
exceedance is less than 25 percent.

Dry into midweek: As long as northern edge of above mentioned
precipitation shield remains south of the forecast area...high
pressure ridging in from the north and resultant north/northeast
boundary layer flow should result in dry weather for Tuesday and
Wednesday (and temperatures generally near normal).  Rain chances
for Thursday and Friday.

&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 200 PM EDT Sat May 11 2024

IFR/MVFR CIGs are anticipated at times over the next few hours at
APN as rain showers linger across northeast lower Michigan.
Otherwise, VFR conditions are expected to continue into tonight
across the area. Calm winds and clear skies will allow for efficient
radiational cooling tonight and, with recent rainfall, may lead to
BR/FG development later tonight into early Sunday morning. Highest
confidence currently lies at CIU for BR/FG development, with
potential also at MBL, APN, and PLN. Otherwise, additional showers
may move across the area Sunday morning.

&&

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

&&

$$

UPDATE...DJC
SHORT TERM...JZ
LONG TERM...JPB
AVIATION...DJC