Area Forecast Discussion
Issued by NWS Gaylord, MI

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FXUS63 KAPX 200611

Area Forecast Discussion
National Weather Service Gaylord MI
211 AM EDT Sun Aug 20 2017

Issued at 1100 PM EDT Sat Aug 19 2017

Still some lingering showers over northwest Lower that should
continue to fall apart as driving instability wanes and short
wave trough evident in water vapor imagery slides out of the area.
Light winds and fairly small temperature/dew point depressions
likely to lead to some patchy fog tonight across northern
Lower...and maybe a little more widespread across eastern Upper.
Already seeing hints of visibility reductions in spots.


.NEAR TERM...(Tonight through Sunday)
Issued at 317 PM EDT Sat Aug 19 2017

High impact weather potential...none.

Fairly quiet wx in the near term. Low pressure continues to eject ne-
ward across Quebec, with trailing high pressure moving quickly east
in the WI/IL border region. Starting to see lake breezes help pop
a few showers in Luce/Alger Cos in the U.P., along with a few
non-lake breeze-induced showers east of M-33 in ne lower MI.

Ongoing convection will percolate away over the several hours, until
diurnal heating wanes. MlCape tops out near 500j/kg in the ERY area
of eastern upper, and is less elsewhere. 20-30 pops in order in
parts of eastern upper/ne lower MI. Probably don`t need a mention of
thunder in northern lower, perhaps still do for another couple of
hours in eastern upper. Activity will end fastest in eastern upper
MI, where stable marine air will overspread the entire peninsula.
Convection that develops further west will move se-ward, attempting
to cross Lake MI before fading out completely. Lake temps are warm-
ish (upper 60s), which will help slow the decay process. Still not
impossible for a stray shower to make it to Leelanau and/or the CVX
area up thru 10 pm. Convection will fade away by then at the latest.

Pressure gradient will tighten up a bit overnight as the high moves
se of Lake Erie. Probably not enough to re-couple surface winds,
except perhaps in some coastal locales. Will expand the mention
of some overnight fog.

Quiet on Sunday. A warmer day and still somewhat humid (dew points
near 60f), but the arrival of a flat 500mb shortwave ridge and
warmer temps aloft will further limit chances for convection.
Upstream cold front will work into western Superior and nw WI late
in the day. This will contribute to an increase in cloud cover
late in the day in the nw half of the forecast area. Any precip
threat should remain upstream.

Min temps tonight in the mid 50s to lower 60s. Warm max temps
Sunday, mainly low to mid 80s, 70s on some of the beaches.


.SHORT TERM...(Sunday night through Tuesday)
Issued at 317 PM EDT Sat Aug 19 2017

...Shower/storm chances return to start next week...

High Impact Weather Potential: Chance of thunderstorms at various
times late Sunday night through Tuesday.

Pattern Forecast: Low amplitude ridging across the western Great
Lakes late tonight through Sunday will gradually shift eastward by
Sunday evening as a subtle mid level shortwave and attendant surface
frontal boundary approach the region from the west. As a result,
increasingly unsettled weather conditions will become possible at
various times late Sunday night through at least Tuesday.

Primary Forecast Concerns/Challenges: Shower/storm chances late
Sunday night through Tuesday.

Continued return flow ahead of an upstream shortwave/frontal
boundary will prove to keep northern Michigan fairly mild and muggy
Sunday night, along with gradually increasing scattered shower
chances from northwest to southeast. Sunday night through sunrise
Monday, the most numerous showers/storms are expected across eastern
Upper and northwest Lower Michigan as moisture pools ahead of the
aforementioned boundary and theta-e ridge axis gradually folds
southward from the U.P. to the Straits area. Guidance continues to
suggest at least a couple hundred J/kg of MLCAPE developing ahead of
the front. Of course, not wildly impressive by any stretch, but
enough to continue the inherited mention of thunder.

Stalling frontal boundary is progged to remain draped across
northern Lower Michigan on Monday with more clouds than not, and
additional scattered showers/storms at various times. Warm and humid
conditions with highs ranging in the low-mid 80s and dew points
surging to the mid-upper 60s are expected to promote increasing
instability. Latest trends suggest more than 1,000 J/kg of MLCAPE
across sections of northern Lower Monday afternoon...and despite a
lack of impressive large scale forcing, weak boundary layer flow
should promote afternoon lake breezes to be the focus for scattered
shower/storm development. 35-40 kts of bulk shear Monday afternoon
suggests perhaps a stronger storm or two isn`t completely out of the
realm of possibilities either.

Eclipse viewing: as was mentioned by the prior shift, it still isn`t
looking great. Looks like more clouds than sun, at least across the
northern half of the state, along with a chance for additional
scattered showers/storms. Certainly still worth a look early Monday
afternoon to try to find a glimpse, but better chances for viewing
look to be across sections of the Upper Peninsula, far southeast MI
into the Ohio Valley.

Unsettled weather remains likely Monday night through Tuesday as a
much more pronounced upper level wave and attendant cold front sweep
across the Upper Midwest and Great Lakes. Periods of showers and
storms (potentially briefly heavy at times with PWs surging toward 2
inches) are becoming increasingly likely during this time frame
before cooler temps and a period of dry weather returns toward

.LONG TERM...(Tuesday night through Saturday)
Issued at 317 PM EDT Sat Aug 19 2017

Overall theme for the extended is "Much Cooler".  The challenge in
the period will come right in the beginning, with the question of
just how fast moisture will strip out after Tuesday`s FROPA.  This
run is bringing drier air in quicker than previous guidance had
indicated...and I`m not so sure I`d want to put a lot of stock in
that just yet.  There are some hints at weak secondary trough
rotating through and if you combine that with a little wrap around
moisture and even a possible lake contribution (I won`t mention any
terms such as "delta-T" just yet)...Wednesday could end up being
more like yesterday (Fri 8/18) was.

Cooler conditions will continue as the period progresses, especially
felt during the overnight hours (lows in the 40s).  Many morning
commuters will be turning the car heat on for the first time in a
while. Temperatures will begin to moderate into Friday and Saturday
(though still below climo) as high pressure continues to build.  So,
although cool...Thursday through Saturday appears to be shaping up
as a pretty nice stretch of weather.


.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 200 AM EDT Sun Aug 20 2017

Sfc high pressure will track east of the region today, while a
cold front approaches from the NW and nears PLN late in the TAF
period. S/SW winds will increase with the approach of the front,
with low end LLWS eventually being needed tonight. The atmosphere
has quite a bit of instability today, but moisture is rather
scant, with only few to scattered cumulus expected. No rainfall
until mainly after midnight when there`s a chance for showers and


Issued at 317 PM EDT Sat Aug 19 2017

High pressure will move quickly across the southern Lakes tonight,
with winds backing from nw to sw into Sunday. Winds will remain a
touch on the gusty side at times, but winds/waves should remain
below advisory levels. Winds will pick up a bit Sunday evening,
then relax again by Monday.


LH...SMALL CRAFT ADVISORY from 7 PM this evening to 5 AM EDT Monday
     for LHZ347.
LM...SMALL CRAFT ADVISORY from 7 PM this evening to 5 AM EDT Monday
     for LMZ341-342.
     SMALL CRAFT ADVISORY from 3 PM this afternoon to 5 AM EDT Monday
     for LMZ344>346.
LS...SMALL CRAFT ADVISORY from 7 PM this evening to 5 AM EDT Monday
     for LSZ321.


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