Area Forecast Discussion
Issued by NWS Gaylord, MI

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FXUS63 KAPX 191927

Area Forecast Discussion
National Weather Service Gaylord MI
327 PM EDT Tue Sep 19 2017

.NEAR TERM...(Tonight through Wednesday)
Issued at 325 PM EDT Tue Sep 19 2017

...Clouds increase overnight with some fog potential...

High Impact Weather Potential...None.

Pattern Synopsis/Forecast...Surface high pressure remains over
eastern Canada, extending into far northern Michigan this afternoon.
Meanwhile a pronounced shortwave was rotating over northern Indiana
with a subtle surface trough extending northeast into the Thumb.
Aside from some stratocu patches streaming off Lake Huron in the
easterly low level flow, a gradual clearing was working in from the
northwest this afternoon. This clearing will be counteracted once
the shortwave lifts northeast this evening, bringing an increase in
low level moisture and stratocu overnight. Late tonight into
Wednesday, an amplifying mid level ridge will briefly build into the
region with a warm front eventually lifting north of the Great
Lakes. This ridge will begin to shear out overhead Wednesday
afternoon as a deep cutoff low over the Canadian Prairies pushes a
cold front into the Upper Midwest.

Primary Forecast Concerns...Increase in low clouds and potential for
fog and isolated showers tonight.

Models are in strong agreement with a substantial increase in low
level moisture off Lake Huron this evening into the overnight as the
shortwave lifts northeast. This will lead to widespread low clouds,
especially away from Lake Michigan. Despite the clouds, this
increase in low moisture combined with temperatures falling into the
mid 50s to low 60s and light winds may allow for some areas of fog.
Fog chances would especially increase if we decouple enough to allow
winds to become calm, but currently don`t expect this to be the case
for most of our area given decent pressure gradient.

There is a slight chance a few light showers could develop overnight
as warm air advection develops out ahead of an approaching warm
front. The likelihood of this is low, however, and they would be
very spotty...perhaps more in the form of patchy drizzle given the
depth of moisture will only be about 1km or so above the surface.

Clouds will gradually diminish late Wednesday morning from west to
east as a narrow ribbon of drier air builds in with the mid level
ridge. Winds will veer more southerly ever so slightly during the
afternoon as the warm front lifts through and will be on the breezy
side as the pressure gradient increases ahead of an approaching cold
front. This will push temperatures into the upper 70s to low 80s
across northern Lower and mid 70s for eastern Upper.


.SHORT TERM...(Wednesday night through Friday)
Issued at 325 PM EDT Tue Sep 19 2017

...Summer-like for the first day of Fall...

High impact weather potential...Thunderstorms possible at
times Wednesday night through Friday.

Area will be under a strengthening upper ridge through the rest of
the week.

Warm front crosses the region Thursday and weakens as it does. CAPE
values increase from around 500-1000J/kg in the morning to 2500+j/kg
in the afternoon as the front moves slowly through. Little surprised
that we are not in a better chance of severe category. 25 to 30kt
LLJ just to our SW in the morning hours. However, the LLJ weakens
during the day and 0-6km Bulk Shear values are marginal (~20kts) at
best. Better instability and shear is farther south. So front will
cross Thursday morning with decaying area of convection, then expect
some showers and thunderstorms to develop later in the day as well.

Steamy days expected as well as warmer and more moist air comes
pouring into the area after the warm front moves through. Dewpoints
in the 60s to near 70F expected with near record/record temps
Thursday and Friday (first day of Fall). It would be kind of ironic
to see the region`s first 90F degree day of 2017 on the first day of
Fall. MUCAPE values approach 3000J/kg in the SE parts of the CWA on
Friday with the high dewpoints in place. Just need a kicker to get
convection going with somewhat better shear expected, although winds
throughout the column remain on the lighter side.


.LONG TERM...(Friday night through Tuesday)
Issued at 325 PM EDT Tue Sep 19 2017

Under strong upper ridge, not much in the way of sensible weather
expected early on in the extended period. Temperatures will remain
10F to 20F degrees above normal through early next week. Ridge
eventually breaks down early next week and as it does, a cold front
will approach from the west bringing the chance for showers and
thunderstorms. Right now, that looks like it will not happen until


.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 203 PM EDT Tue Sep 19 2017

As daytime heating gets into full swing, starting to see a general
decrease in cloud cover across northern MI early this afternoon
with pockets of MVFR stratocu lingering at APN. Low pressure
currently over NW Indiana will slowly lift northeast this evening,
bringing an increase in clouds tonight. Low stratocu looking
pretty likely overnight given strong model agreement and IFR to
LIFR cigs observed downstate this morning. Good chance for some
IFR fog, especially if we decouple enough for winds to become
calm. Slight chance for an isolated light shower overnight at APN,
but dry otherwise. Visibilities would improve shortly after
daybreak Wednesday, but low cigs will likely improve only slowly
through late morning. Winds stay light out of the southeast
through the period.


Issued at 325 PM EDT Tue Sep 19 2017

Winds will shift to the southeast tonight, becoming more southerly
by Wednesday night as high pressure pushes farther to the northeast
and a cold front slowly approaches from the west. Winds will become
a tad gusty Wednesday afternoon but should remain below small craft
advisory criteria along with waves. Areas of fog may develop
overnight tonight, dissipating shortly after daybreak Wednesday.




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