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000
FXUS63 KAPX 201437
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
1037 AM EDT Tue Jul 20 2021

.UPDATE...
Issued at 1028 AM EDT Tue Jul 20 2021

Shortwave trough in the process of working its way southeast
across the northeast Great Lake this morning, with its attendant
cold front doing the same...currently bisecting northern lower
Michigan. Most of the area remains dry, with just a few showers
and storms across northern Lake Huron as colder air aloft
undercuts a marginally unstable lower level environment. Expect
front to continue to push southeast, exiting our area this
afternoon. Still, arrival of those cooler temperatures aloft and
expected enhanced low level convergence across northeast lower
Michigan may yet spark a few showers and thunderstorms, especially
east of I-75. Limited projected mixed layer cape (less than 1K
joules/kg) and less than impressive mid level lapse rates should
preclude much of a severe concern, although can`t rule out some
gusty winds given marginally dry sub-cloud environment. Wide
range of temperatures this afternoon, with readings ranging from
the lower to middle 70s across northwest lower and eastern upper
Michigan, to the middle 80s on the south side of the sunrise side.

&&

.NEAR TERM...(Today through Tonight)
Issued at 338 AM EDT Tue Jul 20 2021

...Increasing chances of showers and storms today into early
evening...

High Impact Weather Potential...Slight chance of non-severe
thunderstorms...mainly across Eastern Upper and NE Lower Michigan.

Pattern Synopsis/Forecast...Large area of strong high pressure
remains centered from the Plains thru the Mid Mississippi Valley
into the southern Great Lakes region early this morning. Low
pressure and the associated cold front has reached Lake Superior and
is slowly dropping south toward Michigan. Latest satellite images
shows vast majority of resulting cloud cover and precip is post-
frontal...with little in the way of clouds and no precip south of
the front attm.

Surface low and cold front will continue to slowly drop south to
near the Straits early this morning and then continue thru Northern
Lower Michigan as we head thru the rest of the morning and into the
afternoon. Narrow band of weak instability and limited moisture
along the front combined with diurnal heating/instability should
kick off some scattered showers and possibly a few thunderstorms
today...especially across Eastern Upper and NE Lower Michigan where
lake breeze boundaries will enhance low level convergence. Cold
front should clear our CWA by around mid afternoon...with
instability quickly dropping off behind the front. Shear is rather
weak...and given weak/limited nature of other convective parameters
(mentioned above)...strong/severe storms are not expected. CAA in
the wake of the front will greatly limit our daytime heating
potential. High temps will range from the lower 70s across Eastern
Upper and far Northern Lower michigan to the mid 80s near Saginaw
Bay.

Residual post-frontal clouds will diminish from NW to SE tonight as
high pressure builds back into our region. Ongoing northerly flow
and CAA will drop our overnight lows into the low to mid 50s tonight.

&&

.SHORT TERM...(Wednesday through Thursday)
Issued at 338 AM EDT Tue Jul 20 2021

High Impact Weather Potential: Minimal attm...

Pattern Synopsis/Forecast:

As we enter the short term period of the forecast...Tuesday`s
shortwave energy will be to our SE...with ridging briefly returning
to the Great Lakes state for the daylight hours of Wednesday. By
Wednesday evening...will be looking for the persistent troughing
along the West Coast of North America to finally move inland...while
shortwave energy to our northeast begins to drop southward through
the flow. This should approach and impact us going into
Thursday...bringing the next chance for showers and/or a rumble of
thunder...departing to our southeast by Thursday night.

Primary Forecast Concerns: Rain/storm chances Thursday...

As has been mentioned the last few nights...models are having a
tough time initializing the mid-level moisture...or perhaps, a lack
thereof...to our north. Pondering the idea of this having something
to do with the smoke from those Canadian wildfires...?? Not entirely
sure, but it`s the first thing that comes to mind. Anyway, this
should not be a problem for Wednesday`s forecast...which is right
full of mid-level subsidence, thanks to surface high pressure and
subtle ridging aloft moving into the region...but will likely play
some part in the precipitation forecast for Wednesday
night/Thursday. It might be better to say Thursday, as guidance
suggests it may not be until very late Wednesday night, if not
daybreak Thursday, when precipitation chances should move in. There
is still some uncertainty in exact timing and positioning...
particularly with regard to how long the drier air aloft is able to
hold on over the area...how deep the departing trough from Tuesday
will be...and how sharp/well-defined the incoming shortwave energy
will be Thursday morning. The solution with the more-well-defined
shortwave energy has better dynamics for our area...with better
synoptic lift co-located with a plume of mid-level moisture moving
into the area (which would typically lend to a better chance for
precipitation)...as well as perhaps slightly warmer 850mb temps,
which could lend to increased instability chances as the cooler air
attempts to move in aloft. However...given that the antecedent air
mass from Wednesday will be a touch on the anomalously dry side of
things (pwats likely in the 0.5 inch range, which is on the dry side
of climo)...suspect it will be a little more difficult for
precipitation to move in initially Wednesday night.
Additionally...if surface high pressure is able to hold on over the
area a bit longer...this could result in little to no instability
over the area Thursday, further undermining precipitation chances.
Do note that models seem to be trending a little slower with the
precipitation, even into Thursday...so suspect there is some
credence to the idea of the surface high holding on, with lowered
precipitation chances for the day Thursday. Taking a quick gander at
some of the smoke forecast guidance that is out there...looks like
it should begin to advect back in perhaps as early as Wednesday
afternoon...which could further complicate precipitation chances
across the area (as has been posited earlier, regarding current
model derived moisture guidance).

.LONG TERM...(Thursday night through Monday)
Issued at 338 AM EDT Tue Jul 20 2021

High Impact Weather Potential: Minimal attm...

As shortwave energy from Thursday departs...and upstream
troughing plows the top of the ridge eastward across central
Canada...will look for ridging to return to the Great Lakes for
Friday. There is some concern that Friday may not be completely
sunshine and kittens, given some instability and likely a lingering
boundary and/or warm front in the area, associated with that
ridge and return flow from high pressure to our southeast...though
it may hold off until Saturday...as more direct influence of the
troughing passing well to our north in northern Canada looks to
arrive, perhaps with some fanfare. Would look for it to be
increasingly warm and humid going into the end of the week and
weekend nevertheless, though...depending on how quickly high
pressure is able to depart to our east...and how quickly upstream
troughing moves in. A lot of uncertainty in the exact details...but
the general idea is still there, for perhaps an unsettled end to the
week. Additionally...with the ridging in the vicinity, in
association with southwesterly flow aloft (for a change)...looks
like it could be warm again for next weekend.

&&

.AVIATION...(For the 12Z TAFS through 12Z Wednesday morning)
Issued at 645 AM EDT Tue Jul 20 2021

A weak moisture-starved cold front will drop south thru Northern
Lower Michigan today...providing a chance of showers and possibly
a thunderstorm across far Northern and NE Lower Michigan (PLN and
APN). VFR conditions will deteriorate to MVFR as low clouds settle
into our region behind the cold front. Surface winds will shift to
the NW and eventually north behind the front and strengthen to 10
to 20 kts with some higher gusts possible today.


&&

.MARINE...
Issued at 338 AM EDT Tue Jul 20 2021

Winds and waves will reach SCA criteria across our nearshore waters
of Lakes Michigan and Huron south of the Mackinac Bridge today into
tonight as winds strengthen behind a cold front that will pass thru
our area. Chances of showers and thunderstorms will increase today
as well as a result of the passage of this frontal boundary.


&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LH...SMALL CRAFT ADVISORY until 11 PM EDT this evening for LHZ347>349.
LM...SMALL CRAFT ADVISORY until 4 AM EDT Wednesday for LMZ323-342-
     344>346.
LS...NONE.
&&

$$

UPDATE...MB
NEAR TERM...MR
SHORT TERM...FEF
LONG TERM...FEF
AVIATION...MR
MARINE...MR