Area Forecast Discussion
Issued by NWS Gaylord, MI

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654
FXUS63 KAPX 220250
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
1050 PM EDT Thu Sep 21 2017

.UPDATE...
Issued at 1050 PM EDT Thu Sep 21 2017

Elongated ridge axis stretches from the mid Mississippi River
Valley up through the central and eastern Great Lakes region with
broad surface high pressure over much of the eastern CONUS.
Unseasonably warm and a somewhat humid airmass has spread into
the Great Lakes in the last day or so. Evening SPC mesoanalysis
page/00Z soundings reveal a fair amount of MLCAPE/MUCAPE across
the western Great Lakes back into the plains even at this later
hour...although mostly elevated conditional instability and somewhat
capped. Earlier daytime convection over NE lower Michigan has
fizzled...as expected...but there is one lone cell over northern
Lake Huron indicative of the elevated instability out there.

Tough call on the overnight forecast. Guidance solutions continue
to suggest we see another push of low-mid level theta-E air cycle
from the Midwest up through the far western Great Lakes and
across northern Michigan. Increased theta-e convergence combined
with the elevated instability might be enough to re-kindle some
showers and possibly thunderstorms later overnight into Friday
morning...particularly in the U.P. and areas westward where the
strongest part of the low level jet/moisture surge will reside.
Thus...plan on leaving low end pops in the forecast at this point
and we will see how things unfold.

Otherwise...a mild and humid night for the last day of summer
2017 along with patchy-areas of fog.

&&

.NEAR TERM...(Tonight through Friday)
Issued at 353 PM EDT Thu Sep 21 2017

...Record high temperatures likely again Friday...

The unseasonable heat and high humidity is expected to continue over
the next several days. This is due in large part to a large and
blossoming upper level ridge which will park itself over the central
and eastern states.

Have only been able to pop a couple showers or storms near and over
Lake Huron thus far this afternoon due to a lack of a definitive
trigger in combination with dry mid/upper levels. So with that in
mind don`t expect too much more activity to form for the remainder
of the afternoon and evening. Have backed off pops into the low
chance/slight chance category, mainly only across northeast lower.
Could be a few showers or storms across the northern quarter of the
forecast area overnight as a surface warm front moves across the
region but overall not a whole lot of activity is expected.
Remaining warm and muggy overnight with patchy fog. Lows only in the
middle 60s to near 70. Hot and humid conditions again Friday as
ridging aloft dominates. More record high temperatures are expected.
Model soundings show a moderate cap in place which should stave off
convective development. Highs ranging from the middle 80s to lower
90s as 850 mb temperatures push 20C with good mixing.

&&

.SHORT TERM...(Friday night through Sunday)
Issued at 353 PM EDT Thu Sep 21 2017

...Warm and humid air mass to occupy northern Michigan this
weekend...

High Impact Weather Potential: Minimal.

Pattern Forecast: Deep positively-tilted trough dominating the
western half of North America this afternoon...with broad but
"dirty" long wave ridging over eastern North America.  This ridge
being sullied by a broad weakness in the pattern over the mid-
Atlantic and southeastern U.S...and of course the continued
adventures of tropical cyclones "Jose" and "Maria" in the western
Atlantic.  This basic upper air configuration persists into the
weekend...with a closed upper high building northeast from the
southern Plains across the Great Lakes (500mb heights near 590DM).
Weakening cold front is pressing across Michigan...main
baroclinicity over the next several days will be west and north of
Michigan...curving around the upper ridge.  Weak height falls Sunday
will nudge a southwest-northeast orient front into Lake Superior and
western Upper.

Primary Forecast Concerns: Warm and humid weather heading into the
weekend...with a rather moist air mass in place resulting in mild
overnight lows (in the 60s versus normals in the mid-upper 40s).
Highs Saturday and Sunday are going to threaten records at most
climate stations.  Records for this weekend include (Sat/Sun):

ANJ: 84(1936)/88(1892)
GLR: 83(2004)/86(2007)
HTL: 88(1937)/86(2007)
TVC: 90(1937)/89(2007)
APN: 89(1937)/89(2007)
PLN: 86(2004)/87(2007)

Dew points are expected to remain in the 60s through the weekend...
so will definitely have a mid-summer feel to the first official
weekend of autumn.  Little rain threat is anticipated through the
weekend...with best rain chances expected to remain north of Lake
Superior.

.LONG TERM...(Sunday night through Thursday)
Issued at 353 PM EDT Thu Sep 21 2017

High Impact Weather Potential...

The persistent upper level ridging holds firm for the start of the
extended period, through Tuesday anyhow...keeping precipitation and
unseasonably warm readings locked in over the Great Lakes.  On
Wednesday...the log jam begins to break, and the troughing that had
been present over the central conus shifts east.  This will result
in quite the drastic pattern flip, bringing widespread rain chances
for Wednesday and much cooler temperatures by Thursday....as the H8
zero degree isotherm drops as far south as the Northern Lower.
Precip chances on day seven are up in the air yet...however, I think
it`s reasonable to think we could be looking at some lake effect
rain. But that`s a long way off yet and we`ll keep an eye on it.

&&

.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 737 PM EDT Thu Sep 21 2017

A few lingering showers remain across NE lower Michigan this
evening in the VCNTY of APN...but will fade over the next hour or
two. Otherwise...VFR conditions undissipated across northern
lower Michigan this evening. Some fog development possible later
this evening and overnight...most likely at PLN and APN. VFR
weather again on Friday with some afternoon CU development around
4-5K feet.


&&

.MARINE...
Issued at 353 PM EDT Thu Sep 21 2017

Continued light winds through tonight. Southerly winds will ramp
up Friday into Friday night as the surface pressure gradient
tightens up. Some choppy conditions will develop on Lake MI,
especially toward the far north end of the Lake. Advisory-level
waves are a possibility.


&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LH...NONE.
LM...NONE.
LS...NONE.
&&

$$

UPDATE...BA
NEAR TERM...AS
SHORT TERM...JPB
LONG TERM...KB
AVIATION...BA
MARINE...AS



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