744
FXUS63 KAPX 241740
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
140 PM EDT Tue Sep 24 2024

.KEY MESSAGES...

- A bit dreary and damp today/tonight

- Quieter weather for the rest of the week into the weekend

&&

.UPDATE...
Issued at 1047 AM EDT Tue Sep 24 2024

Broad troughing overtaking the central US and Upper Midwest
today...as ridging moves into the PacNW. 120+kt upper jet feeding
into sharp shortwave troughing digging into the central
Plains...with a swirly spinning up over western MN/eastern Nebraska.
Attendant surface occluded system with this stretches from western
MN back into the central Plains. Meanwhile...on the downstream side
of this sharp shortwave trough...niblet within the flow lifting NNE-
ward through central WI into northern MI...with subtle ridging aloft
between this and the next bit of energy over IL...where surface low
is located; cold front with this stretches down into TX along
deformation axis, and warm front stretches eastward through the OH
Valley into the Carolinas. Anomalous moisture focused along this
boundary...with some northward moisture advection into the Upper
Great Lakes on SSW flow aloft. Broad easterly low-level flow over
the region this morning; some subtle hints of departing surface
troughing over Lake Huron between this and incoming surface low and
inverted trough stretching up along the WI coast...with a couple
more distinct areas of precip/convective precip over Saginaw Bay and
west central MI, respectively. Drizzle and low stratus/fog present
over interior northern Lower thanks to easterly upslope flow and
moisture advection; ceilings less than 1000ft in most cases with
visibilities less than 1SM over interior northern Lower and also
along the Lake Huron coast due to subtle lake influences. A little
bit of subtle clearing/breaking up of the stratus deck over NW Lower
into parts of the EUP with the weak upper ridge oozing in. Expecting
rain to continue to track NE/NNE-ward through the region
today...though have some concerns the best moisture and forcing
could remain to our southeast...so will keep an eye on this going
forward.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 333 AM EDT Tue Sep 24 2024

Pattern/synopsis: Weak low pressure is near STL. This low will
deepen somewhat as it lifts slowly ne, reaching central lower MI
tonight. The low is forced in part by a shortwave trof moving
east across Superior late tonight, and in part by a closed 500mb
low crossing MO. The dominant big-picture trend is for a
somewhat deeper, and somewhat slower, system.

Forecast: Easterly flow off of Lk Huron is generating lake
effect clouds (MVFR) into ne lower MI. OSC briefly reported
precip (DZ) earlier in the morning. Area radars are showing an
area of bubbly mid-level returns from w central lower MI to ne
WI. Most of this is likely not reaching ground, but a few spots
could be. As the surface low moves toward AZO by dusk, and a
warm front also lifts into far southern lower MI. Though the
deepest moisture/best forcing remains just downstate, plenty
leaks into northern MI as the day proceeds. And that further
interacts with overlake instability, with 850mb temps around
10-11C over Lake Huron. There is more of a southerly component
to the 1000-850mb winds, and the longest fetch from Lk Huron
into eastern upper MI for much of the day. MlCape values are
quite limited, but values of 100-200j/kg are possible in ne
lower MI.

Pops will tend to increase from se to nw with time today. Pops
are higher downwind of Lk Huron, including eastern upper MI,
even though that is further north than better moisture fields.
Sct to numerous showers are progged for much of today and
tonight in ne lower/eastern upper MI, starting to diminish very
late tonight. Precip could and probably will switch nature,
from showery to drizzly and back again. There is also a slight
chance for thunder in ne lower MI. Further, 850-700mb
deformation/stretching on the north side of the approaching
surface low is certainly present. That could contribute to
localized healthy rainfall rates. This is particularly the case
this evening, with localized QPF in excess of 0.25" in se
portions of the forecast area.

Max temps today in the 60s to around 70f. Lows tonight in the
50s.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
Issued at 333 AM EDT Tue Sep 24 2024

Pattern Synopsis and Forecast:

Midlevel split flow pattern continues to occupy North America.
Southern stream flow currently influencing the Great Lakes region
will continue to push warmer than average temperatures for the long
term period.

Current troughing over the Mid-Mississippi Valley pass through the
Great Lakes region. Shortwave ridging builds this Wednesday and
beyond. This pattern supports surface high pressure to occupy
the CWA for the majority of the long term, resulting in quiet
weather and above average temperatures for late September.

Primary Forecast Concerns/Key Messages:

No impactful weather expected throughout the entirety of the
long term forecast period: Conditions are expected to remain
quiet and dry for the majority of the period. After a few
lingering showers finally diminish, surface high pressure will
begin to build this Wednesday. This patten supports clearing
skies with highs in the low to mid 70s for the next several days
and lasting through the remainder of the forecast period. Only
chances of precipitation is later next week as ensembles hint at
an additional trough moving into the Ohio Valley around the
Sunday/Monday timeframe. Guidance continues to struggle with a
solution next week most likely due to discrepancies in the exact
track of the ruminants of what will be Hurricane Helene.
Confidence along with messaging will remain low at this time
until future ensembles have a more detailed solution. Until
then, little if any precip is expected to persist though the
entirety of the long term.

&&

.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 139 PM EDT Tue Sep 24 2024

N-S oriented trough axis over Lake MI this afternoon...with
developing surface low over IL...to track northeastward into the
Thumb of MI and Lake Huron overnight. Expecting a moisture axis to
linger over NW Lower (TVC/MBL...PLN?) this evening into the
overnight (through about 8-10z), and expect IFR to LIFR
cigs/visbys...though not impossible this axis hangs up a little
further east. Elsewhere...TS possible for APN between 0-9z with any
rain. Generally, IFR to LIFR cigs expected through the night, with
slow improvement from west to east after daybreak Wednesday. Surface
winds generally at or below 10kts with an easterly component,
ultimately becoming northwesterly by morning (quickest at TVC, MBL).
Not impossible to get some gusts around 15kts at times this
afternoon where some breaks in the clouds form.

&&

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

&&

$$

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