833
FXUS63 KAPX 131749
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
149 PM EDT Mon May 13 2024

.KEY MESSAGES...

- Shower/storm chances return in southern areas today and
  tonight.

- Patchy frost possible Tue night and Wed night.

&&

.UPDATE...
Issued at 932 AM EDT Mon May 13 2024

Scattered showers and storms are expected mainly south of a line
from Frankfort to Alpena through today into this evening in the
vicinity of a boundary draped across mid-Michigan -- with initial
showers just beginning to form now along M-55. Around 500 J/kg
MLCAPE and 30 kts of deep-layer shear will be enough to support the
potential for a strong storm or two, primarily near Saginaw Bay
during peak heating this afternoon. Any strong storm that does
develop will carry the potential for gusty winds and small hail.
Severe storms are not expected this afternoon and evening.
Otherwise, skies should clear from north to south tonight with
overnight lows ranging from the mid 30s across interior eastern
upper and far northern lower to the mid/upper 40s across our far
southeast counties as more warm, moist air lingers as the
aforementioned boundary gradually sags south into Tuesday
morning.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 335 AM EDT Mon May 13 2024

Synopsis/pattern: Low pressure up toward James and Hudson Bays
is pushing a cold front into eastern upper and northern Lake MI.
Precip is well out ahead of the front, with drier mid-level air
gradually overspreading northern MI. The front will slow its
progress across lower MI today, in part thanks to a surface low
over MO. A shortwave now in northern MN will also interact with
the frontal zone later today.

Forecast: Shower coverage/intensity continues to gradually wane,
with precip generally near and south of an MBL-Harrisville line.
Partial clearing has occurred north of this. Precip is expected
to (temporarily) exit northern MI early this morning. Increasing
diurnal heating, along with continued coolish temps aloft in
low-amplitude troffing over the Great Lakes, will allow
instability to quickly regenerate near and ahead of the front.
As soon as late morning, a few hundred J/kg of MlCape will
redevelop, with forcing initially available in the form of the
front. Showers will start to get going again by late morning,
mainly east of US-131 and south of M-72. Coverage will remain
somewhat limited until deeper into the afternoon, when
instability downstate is higher, and when backing sub-850mb
winds will advect this unstable air to and across the frontal
surface. Even with the front moving downstate this afternoon,
showers become likely, with a few thunderstorms, south of an
HTL-OSC line. Coverage only slowly dwindles this evening, but
does continue a downward trend into and thru tonight as the
front continues toward far southern lower MI.

Max temps in the 60s to mid 70s. Boosted max temps over
guidance in northern sections, which will be the sunniest
today. Min temps tonight with have some mid 30s in the cold
spots (especially the eastern UP, where the growing season has
not yet begun), but range up to the mid 40s in the se.

&&

.LONG TERM /TUESDAY THROUGH SUNDAY/...
Issued at 335 AM EDT Mon May 13 2024

PATTERN SYNOPSIS/FORECAST:

Progressive and messy pattern across the CONUS...trough axis along
the West Coast...with an upper low over the southern central
Plains...and another upper low, this one in the northern stream,
centered over Ontario with an attendant 996mb surface low, but with
a lobe swiping through the Upper Great Lakes last evening. 850mb
temps ahead of this spiking up into the teens, with highs yesterday
in the mid to upper 70s over much of the area. At the
surface...front drapes across the central UP into WI, with a few
showers/storms along/ahead of this as of 4z/13...ultimately back to
a surface low in the Nebraska vicinity...at which point the
baroclinic zone turns back to the northwest along the Rockies. A bit
col region-y over eastern Nebraska/IA, though. In the southern
stream, much greater convective activity over the southern US in the
presence of a punch of PV over OK/KS, and a surface warm front
stretching along the Gulf Coast.

Looking forward...northern stream PV axis slips by...with the
southern stream disturbance to follow shortly thereafter, crossing
the OH Valley through Tuesday night...leaving Michigan along
lingering boundary/col-region between these two features in the
meantime. However...another northern stream disturbance approaching
for Wednesday night into Thursday should drive brief ridging back
into the area for midweek...which could allow for frost potential at
times. It is at this point that the outlook becomes less
clear...depending on strength of an upstream ridge over the eastern
Pacific. If this feature remains strong/blocky...would anticipate a
stronger system to approach the Great Lakes for late week into next
weekend, which would likely leave us dreary and cool, though it`s
possible we could see a brief warmup ahead of this. However...if the
upstream ridge is not as blocky, would look for nuisance unsettled
weather to perturb the Great Lakes into late week, with a greater
shot at ridging building in for next weekend (i.e., a better shot at
warmer and more pleasant conditions). Will have to keep a close eye
on this, particularly for purposes of ag interests, given that the
growing season is well underway for most of northern lower Michigan,
even up here on our little hill near Gaylord.

Primary Forecast Concerns:

Patchy Frost Potential Tuesday Night and Wednesday Night...Think we
should be mostly clear over most of the area Tuesday, particularly
as high pressure tries to seep in from the north through the
afternoon into Tuesday night. With increasing subsidence, suspect we
will be tapping into some drier air, though there are some weak
signals for lingering boundary layer moisture that could lead to a
few diurnal clouds here and there, perhaps. Setup would therefore
seem rather favorable for a chilly night Tuesday night, with frost
potential...though I do have some concerns...
a) Signals for decoupling Tuesday night aren`t as strong as I`d like
them to be for a total-tank-out situation, particularly noting the
surface high won`t be totally overhead Tuesday night...which could
keep things just mixed enough to preclude some of the frost
potential if this idea verifies. This being said, winds should be
relatively light in general (gusts likely under 15 during the day,
and probably less so at night...except for perhaps where the marine
layer may have some influence to keep things more unstable, downwind
(on largely northerly winds) of GT Bay, etc.
b) Aforementioned lingering boundary layer moisture (albeit weak)
Tuesday could throw a wrench in things...as it could keep us from
dropping overnight as much as it could if it were drier. Guidance
isn`t overly bullish attm on the drier idea, though it`s also
possible we may tap into a drier layer aloft than currently
expected, which could drop dewpoints during the afternoon further
than expected...and potentially set the stage for a much colder
night. This being said...struggling to find guidance attm that is
terribly cold for Tuesday night...and for a change, am hesitant to
drop things too dramatically.
This all being said...current forecast highs in the 60s across
northern Lower Michigan (cooler downwind of Lake Superior over the
EUP) with a typical 20-30 degree diurnal temp range would put us in
the mid 30s for lows Tuesday night. If incoming wildfire smoke is
able to keep afternoon highs cooler than anticipated...would not be
out of the question to see lows approach freezing, particularly
over the usual cold spots in the interior.

Wednesday night may actually have a shot at frost as well...given
that high pressure should still be around, and there may be some
potential for better decoupling ahead of the next system, which
should be on the horizon by Thursday morning. There will be tricky
parts to this idea, too, though...as we will likely be looking at
increasing mid/high clouds overnight that could reduce the amount of
radiational cooling we`d otherwise experience. Otherwise...frost
potential through the remainder of the period is increasingly
uncertain, given the increasing uncertainty in the pattern for the
remainder of the week.

&&

.AVIATION /18Z TAFS THROUGH 18Z TUESDAY/...
Issued at 145 PM EDT Mon May 13 2024

VFR conditions are expected across most northern Michigan TAF sites
through the issuance period. The exception may be CIU where
relatively shallow FG/BR may form late tonight/early Tuesday morning
should weak winds materialize. Otherwise, BKN/OVC clouds will
gradually work south of the area tonight, leaving clear/sunny skies
in place for Tuesday. Northwest winds around 5-10 kts this afternoon
will turn to north/north-northeast winds tonight and Tuesday. Shower
chances will continue in the vicinity of MBL into this evening
before tapering off tonight.


&&

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

&&

$$

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