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000
FXUS63 KAPX 201810
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
210 PM EDT Tue Jul 20 2021

.NEAR TERM...(Through Tonight)
Issued at 202 PM EDT Tue Jul 20 2021

...Turning a bit cooler tonight...

High impact weather potential: Minimal. A few non-severe
thunderstorms the remainder of this afternoon.

Pattern synopsis and forecast:

Amplified (at least for summer) mid and upper level pattern continues
across NOAM, with northern Michigan centered under northwest flow
between sharp Intermountain West ridge and northeast NOAM centered
troughing. Embedded shortwave trough working its way southeast
across the area early this afternoon, with its attendant cold front
also pushing southeast across lower Michigan. Detachment of best
mid and upper level support to our northeast has resulted in
mainly a dry frontal passage for most, with just some isolated
showers and storms across the northeast parts of our area as
cooler air aloft overtops a marginally unstable lower level
environment.

Mid and upper level flow regime described above continues tonight,
with prevailing northwest flow driving shortwave trough into New
England by sunrise Wednesday. Large area of Canadian high pressure
builds into the region in its wake, forcing cold front to drop into
the lower Ohio Valley by morning.

Primary forecast concerns/challenges:

Addressing lingering shower/storm potential this afternoon and
overnight temperature trends.

Details:

Still can`t rule out a few more showers and thunderstorms into very
early this evening, especially across northeast lower Michigan where
low level convergence will be maximized. Minimal 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
small hail and marginally gusty winds. High pressure builds into
the area from north to south overnight, bringing with it clearing
skies and cooler temperatures. Expect widespread lows in the
lower and middle 50s, with some of our traditional ice box
locations likely making a run into the upper 40s. Great sleeping
weather indeed.

&&

.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 18Z TAFS through 18Z Wednesday afternoon)
Issued at 202 PM EDT Tue Jul 20 2021

MVFR to IFR producing low clouds expected to mix out later this
afternoon and early evening, with skies trending clear overnight
into Wednesday morning. Gusty winds will also subside tonight. No
vis restrictions anticipated.

&&

.MARINE...
Issued at 202 PM EDT Tue Jul 20 2021

Gusty north to northeast winds will gradually subside tonight,
with sub-advisory winds and waves expected through Wednesday night
as high pressure builds into the region. May see a few gusty
thunderstorms into early this evening across Lake Huron.
Otherwise, dry weather is expected.

&&

.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...MB
SHORT TERM...FEF
LONG TERM...FEF
AVIATION...MB
MARINE...MB