Area Forecast Discussion
Issued by NWS Gaylord, MI

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FXUS63 KAPX 231104
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
704 AM EDT Wed Aug 23 2017

.NEAR TERM...(Today through Tonight)
Issued at 351 AM EDT Wed Aug 23 2017

...Unseasonably chilly with perhaps some lake enhanced rain
showers at times...

High impact weather potential...Gusty winds and attendant
significant waves will continue to result in hazardous swimming
conditions across Lake Michigan.

Pattern synopsis/forecast...One amplified long wave NOAM pattern out
there at this early hour, with northern Michigan firmly entrenched
within anomalously deep trough axis, itself downstream of one
equally impressive Intermountain West centered ridge. Deep layer
chilly northwest flow locked in overhead, with cold air advection
only intensifying with time as H8 temperatures make a run into the
mid single digits. Now, despite these cold temperatures, lake
processes have been muted via lack of any appreciable synoptic
support/moisture through the shallow convective layer.
Scattered/broken band of clouds tied to southward dropping surface
trough does signal the arrival of somewhat better moisture through
this morning. This moisture, combined with passage of subtle mid
level support and increasing over-water thermal gradient will indeed
set the stage for some shallow lake response in favored northwest
flow areas today. Arrival of next wave and moisture plume later
tonight will do the same, this time for those north favored flow
areas.

Primary forecast concerns/challenges...Cloud and shower trends
through tonight.

Details...Synoptic moisture support today is awfully thin, and what
there is remains centered in elevated layer around H8. Surface
rooted inverted-v signature noted in model derived soundings below
this layer, although rather respectable delta t`s in the mid teens
should allow some decent lake contribution to help moisten this
region. Convection will remain shallow, but deep enough warm cloud
processes to support some light lake effect showers in favored
northwest flow areas, with perhaps some isolated sprinkles
elsewhere. Would expect best shower coverage to occur this morning
as diurnal disruption helps negate the lake processes this
afternoon. Bigger story today will be those temperatures, with
afternoon readings only expected to top out in the 60s for most
(might be just low 60s for some!). These readings are a good 10 to
15 degrees below normal for this time of year. Add in some gusty
northwest winds, and definitely a taste of early fall weather across
the northwoods.

Drier air arrives this evening, with secondary surge of moisture and
renewed cold air advection kicking in very late tonight with arrival
of shortwave trough. Flow veers more northerly in the process,
perhaps bringing a few light lake induced showers to coastal areas
of Lake Huron and Lake Michigan by Thursday morning. Center of
surface high remaining well to our northwest should keep enough
pressure gradient to prevent full decoupling, keeping just enough
wind to prevent surface temperatures from really plummeting. Gonna
be a chilly one anyway, with widespread readings in the 40s by
sunrise Thursday.

&&

.SHORT TERM...(Thursday through Friday)
Issued at 351 AM EDT Wed Aug 23 2017

...Not much weather into the weekend/Some chilly mornings ahead...

High Impact Weather Potential: Minimal.

Pattern Forecast: Deepening short wave trough/closed low spinning
across northeast Ontario and the adjacent Great Lakes this
morning...with northern Michigan to the cool side of the polar jet
axis.  Broad ridging across western Canada and the Pacific northwest
with a piece of sheared energy over northern Saskatchewan.
Impressive for late August 990mb low over Quebec with cool cyclonic
flow extending back into Michigan...just a harbinger of things to
come as we slide toward meteorological fall in a week`s time.

Troughing will linger across the Great Lakes through Friday...with
northern Saskatchewan short wave trough expected to swing across the
region Thursday.  Over time...short wave ridging over western Canada
will build east into Manitoba/Ontario with split flow emanating from
a push of westerly momentum into western Canada this weekend.  Upper
Lakes region forecast to lie in the weakness of this split flow
pattern between ridging to the north and short wave troughing digging
south across the Midwest for the start of next week.  This southern
branch trough looks to tangle the reconstituted remnants of former
Tropical Cyclone "Harvey" over the Lower Mississippi Valley...
remains to be seen what may come of that.  Surface high pressure
settles into Michigan Thursday and will hang around through
Saturday.

Primary Forecast Concerns: Probably temperatures...specifically low
temperatures...for the latter half of the week.  High pressure
building in for Thursday combined with subsidence/drying in the wake
of a short wave trough passage should set the stage for good
radiational cooling potential Thursday night/Friday morning as skies
clear and winds drop off.  Interior areas will see spots drop into
the 30s early Friday morning...maybe a little frost in some of the
typical ice box locales.  Less cloud cover expected Friday...with
another night of good radiational cooling in the offing with some
spots dropping into the 30s once again.

.LONG TERM...(Friday night through Tuesday)
Issued at 351 AM EDT Wed Aug 23 2017

High Impact Weather Potential...

High Impact Weather Potential: Minimal.

Little in the way of significant weather this weekend and into early
next week.  Southern branch disturbance developing over the midwest
will need to be watched as it could push some precipitation into
Michigan in the Monday-Tuesday time frame.  A little moderation in
temperatures expected but should be close to normal for this time of
year.

&&

.AVIATION...(For the 12Z TAFS through 12Z Thursday morning)
Issued at 701 AM EDT Wed Aug 23 2017

Combination of lake and diurnal processes will bring scattered to
broken MVFR/VFR producing cu and strato cu across the taf
locations today. May see a few very light showers at times,
although with no impacts expected. Clouds expected to thin out
for a time late this afternoon and evening, with the return of
more relatively high based clouds overnight as the next surge of
moisture and colder air entices at least some lake response. Gusty
northwest winds today are expected to slowly subside tonight.

&&

.MARINE...
Issued at 351 AM EDT Wed Aug 23 2017

Passage of secondary surface trough and continued cold air
advection will continue to result in gusty northwest winds and small
craft advisory conditions across the big waters today. Increasing
over-water instability on Lake Huron does set the stage for
waterspout potential this morning, although shallow convection does
argue otherwise. Winds expected to only slowly subside tonight as
they veer more northerly with time. High pressure builds into the
Great Lakes for the end of the week, resulting in much lighter
winds.


&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...BEACH HAZARDS STATEMENT until 6 PM EDT this evening for MIZ016-
     019>021-025-031.
LH...SMALL CRAFT ADVISORY until 6 PM EDT this evening for LHZ345>349.
LM...SMALL CRAFT ADVISORY until 6 PM EDT this evening for LMZ323-341-
     342-344>346.
LS...SMALL CRAFT ADVISORY until 6 PM EDT this evening for LSZ321-322.
&&

$$

NEAR TERM...MB
SHORT TERM...JPB
LONG TERM...JPB
AVIATION...MB
MARINE...MB



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