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National Weather Service - Area Forecast Discussion

983
FXUS63 KAPX 220012
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
812 PM EDT Sun Jul 21 2024

.KEY MESSAGES...

- Isolated to scattered shower and storm chances this afternoon,
  and again on Monday.

- Showers/storms Tuesday into Wednesday.

- Patchy Fog Potential into Midweek.

&&

.SHORT TERM /THROUGH MONDAY/...
Issued at 227 PM EDT Sun Jul 21 2024

Pattern Synopsis:

Weak troughing draped across the Great Lakes and much of the
Mississippi Valley looks to remain stationary through Monday with
amplified ridging parked over the western half of the CONUS. Lack of
any substantial temperature or vorticity advection will keep a
rather nebulous surface pattern in place across the region through
the duration of the period.

Forecast Details:

Isolated/scattered shower and storm chances -- A strip of more
favorable low-level moisture sits across mid-Michigan per latest
surface observations with dewpoints in the low/mid-60s. Expectation
still remains that isolated to scattered showers and storms will
initiate across this corridor -- mainly south of M-72 -- this
afternoon and linger into this evening. There will be a break in
rain chances late this evening through tonight before additional
chances showers/storms return on Monday. A few showers may be
possible during the late morning hours, but best chances are
expected to come in the afternoon across mid-Michigan and northeast
lower. Sufficient buoyancy will be in place to support thunder
chances, but very weak flow of 15 kts or less below 200mb will lead
to pulse-type storms that may be strong for a brief period of time.
Severe storms are not expected.

&&

.LONG TERM /MONDAY NIGHT THROUGH SUNDAY/...
Issued at 227 PM EDT Sun Jul 21 2024

Blocky pattern remains in place over North America...with longwave
ridge axis centered over the western portion of the continent...and
longwave troughing over the east...including the Great Lakes.
Leisurely PV maxima swirling over IA/MO this morning...somewhat
disconnected from the anomalous upper low over Quebec...though BCZ
stretches between these two features, with a high-bridged, washed-
out cold front and attendant PV strand draping across Michigan
today...hence the random convection earlier this morning across
central Lower. Weak warm advection to the south of this on the front
side of swirly, where some weaker stability resides aloft; cooler
and much drier air north of the boundary oozing slowly into
Michigan. Bulk of the deep moisture remains trapped across the
southern US...along and south of a boundary waving from the
Carolinas back into TX in the southern stream of the flow.
Upstream...some additional activity diving south through Manitoba
attm.

Looking ahead...surface high slowly drifts into the region into
early week, though nebulous flow hanging on could keep things from
being completely quiet...as it should allow for development of lake
breezes during the afternoons, and perhaps patchy fog at night.
Expecting longwave trough axis to sharpen to our northwest going
into Tuesday before slowly making its way southeast into the region
through midweek. This should bring increasing shower/storm chances
from Tuesday afternoon right on into Wednesday...and perhaps even
into early Thursday as the trough axis should try to hang overhead
another day. Beyond this...as upstream pattern breaks down...will
expect the ridge axis to slowly shift eastward toward the Upper
Midwest late week into the upcoming weekend. Not impossible that we
may yet be plagued by some lingering vorticity/nuisance activity
Friday...but signals point more favorably attm to potential for
warmer weather with high pressure settling in to end the week. This
being said...with ridge axis building into the central US...do have
concerns it won`t be as quiet as it seems...as pattern could be
supportive of upstream activity trekking into the Upper Great
Lakes...though will have to wait a bit to see if this general
pattern idea holds, and how far into Canada to our northwest the
ridge axis ends up getting.

Primary Forecast Concerns:

Showers/storms Tuesday into Wednesday...Think we`ll be looking
at another round of afternoon pop-up showers and storms Tuesday,
especially over interior northern Lower MI. Not a ton of
forcing to contend with, and not much wind/flow aloft...so
anything that develops would probably pop-up on mesoscale
boundaries (lake breezes and/or outflow boundaries) and not have
a well-defined storm motion. Think some could produce some
heavy downpours, despite moisture not being quite as deep as
previous events...particularly due to duration of rain over an
area.

Better forcing and moisture move in ahead of the trough axis Tuesday
night into Wednesday morning...and expect this will be our better
shot at widespread precip (though some rain/storms possible ahead of
this over the EUP Tuesday). Think this late Tuesday night/early
Wednesday morning activity could have potential to be a bit
elevated, noting some weak warm advection signals...though better
signals for destabilization appear to be Wednesday afternoon,
especially along and south of the slow-moving boundary (so...more
likely closer to Saginaw Bay). Aside from thunder potential...think
the environment appears favorable for more efficient rainfall again,
with higher freezing levels and pwats on the higher end of
climo...combined with weak flow and slower storm motions along an
already slower-moving boundary. Will have to keep an eye on this
threat going forward...but worth noting that WPC has been trying to
key in on some threat somewhere over the region of excessive
rainfall for midweek this week.

Patchy fog potential? With flow remaining nebulous through the
first couple days of the period...suspect fog potential remains
possible, though it does look like we`ll start to lose the col
region idea Monday/Monday night...as flow becomes more
southwesterly in advance of the sharpening trough for Tuesday.
We do have some reasonably dry air around...which could minimize
fog potential, particularly as high clouds drift in (moisture
should also be deepening from the top-down Tuesday into Tuesday
night ahead of the front). Think setup is still supportive of
some patchy fog, though...and this idea may kind of hang on into
the remainder of the week as high pressure drifts back into the
region again and flow remains weak overall...especially if we
get rain as advertised on Wednesday.

&&

.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...
Issued at 809 PM EDT Sun Jul 21 2024

Will need to watch for some early morning fog and stratus,
especially at KCIU and KMBL. Any fog/low clouds will mix out
quickly after sunrise. Otherwise, VFR conditions will continue
with just some passing high clouds and high based cumulus.
Expecting more scattered showers and thunderstorms to develop on
Monday, but current trends suggest they will remain between taf
locations. Light winds, with more local lake breeze development
expected on Monday.

&&

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

&&

$$

SHORT TERM...DJC
LONG TERM...FEF
AVIATION...MSB

NWS APX Office Area Forecast Discussion