Area Forecast Discussion
Issued by NWS Gaylord, MI

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FXUS63 KAPX 261731
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
131 PM EDT Fri May 26 2017

.UPDATE...
Issued at 847 AM EDT Fri May 26 2017

Updates to the sky cover forecast to reflect morning trends.
Erosion of low clouds/fog is already well underway, with
considerable breaks developing along the M-66 corridor and at the
tip of northern lower. Eastern upper MI enjoying a very sunny
start to the day. Low levels remain moist, and diurnal heating
will sprout a cu/stratocu field relatively quickly. But in
general, have updated to reduce cloud cover and/or accelerate the
clearing trend. Locally dense fog along the Lake MI coast of nw
lower will also erode with time.

&&

.NEAR TERM...(Today through Tonight)
Issued at 353 AM EDT Fri May 26 2017

...Probably more clouds than sun many areas today...

High Impact Weather Potential: Minimal outside of reduced
visibilities in fog this morning.

Pattern Synopsis/Forecast: Midnight surface/composite analysis shows
upper Great Lakes sandwiched in the col region between a couple of
weather systems...one area of low pressure over western NY/PA with
an inverted trough extending back into Lake Huron.  A 994mb low was
located over Manitoba with a cold front extending south into the
eastern Dakotas.  Weak high pressure ridge noses into Upper MI/
eastern WI from northeast Ontario.  00Z APX sounding was moist below
750mb and at above freezing temperatures...which was supporting
mostly drizzle across parts of north central/northeast Lower and
eastern Upper...while drier air across western Upper/eastern WI per
GRB sounding.  7.4 micron WV imagery also shows drier air pressing
into the western side of a mid/upper level deformation axis oriented
generally north/south from the eastern shore of Lake Superior south
across Lake Huron and into eastern Lake Erie/western PA.  Deeper
moisture lies to the east of this axis across Ontario (along with
colder cloud tops).  Meanwhile...narrow band of high-based showers
moving into western WI along what appears to be a small scale
vorticity center tracking into far northwest WI.  So far skies are
mainly clear west of the US-131 corridor...as moisture tries to wrap
in from the northeast but fairly strong low level divergence and
weak isentropic downslope motion (290K surface) depicted across
northwest lower seems to be keeping cloud cover at bay for the time
being.  Temperature/dew point spreads are small in areas where skies
have clear and winds have decoupled...so will have to watch for some
fog/low stratus trying to form around TVC/CAD and points west during
the pre-dawn hours.

Primary forecast concerns: Mostly centered around cloud cover
today...and fog this morning.

Clouds should persist across a good chunk of eastern Upper/northern
Lower east of the US-131 corridor through this morning...starting to
see some fog developing around MBL/LDM/FKS so plan on carrying that
into the daylight hours over northwest Lower.  Still some pockets of
drizzle this morning across north central/northeast Lower...though
these should thin later this morning.  Lower cloud deck should begin
to mix into a shallow convective deck heading into this afternoon...
while some upstream altocumulus across WI spreads into Lower MI.
Temperatures should climb into the 60s away from the lakes this
afternoon with anticipated lake breeze development with weak
pressure gradient in place.

Flat upper level ridging builds into the state for tonight...there
is a convectively induced vorticity center coming out of KS early
this morning that will need to be monitored...but right now looks
like any precip threat is pretty minimal with better instability
expected to be well south of the forecast area.

&&

.SHORT TERM...(Saturday through Sunday)
Issued at 353 AM EDT Fri May 26 2017

...Mostly dry Saturday with increasing rain chances Sunday...

High impact weather potential: Chance of thunderstorms Sunday
through early Sunday evening.

Pattern forecast: Weak upper level ridge axis overhead Friday/Friday
night continues to flatten as it progress east of the area Saturday
morning with a weak shortwave rippling through the flow across
northern Michigan and attendant surface low skirting portions of
southern Lower. Mid-upper level flow pattern becomes more amplified
Saturday night through the remainder of the weekend as a deep upper
level low centered over southern Manitoba gradually progresses
southeastward into the Upper Midwest. This will allow a couple of
lobes of energy to pinwheel around the southern periphery bringing
increased shower chances at times over the upcoming holiday weekend,
most numerous on Sunday.

Primary forecast challenges/concerns: Shower chances and temperature
trends through the weekend.

The main story to kick of the weekend will be increasing
temperatures on Saturday with high temperatures climbing to above
normal readings...ranging from near 70 north of the bridge and
spanning to the 70s to near 80 degrees south. Light flow should
allow for a classic lake breeze day on both coasts of northern
Lower. This may provide just enough support to kick off a few
showers (mainly across the higher terrain), but with low
probabilities and any showers being short lived, the bulk of the day
is expected to feature little in the way of sensible weather.

Rain chances begin to increase late Saturday night, but more so on
Sunday as aforementioned energy rotates around upper level low
pressure progressing toward the Upper Midwest. As was mentioned by
the prior shift, the highest shower coverage still looks to be
during the afternoon. No evidence to remove inherited thunder
chances with pockets of MLCAPE upwards of 500 J/kg anticipated, but
likely will hinge on the amount of sunshine realized throughout the
day. Worth at least mentioning some pieces of guidance suggesting
greater instability (>1,000 J/kg) nosing into southeastern sections
of the CWA. If that instability were to come to fruition (which I
have doubts about due to dew points often being modeled too
aggressively, and the aforementioned concern about cloud cover) when
combined with a corridor of 40-45 kt deep layer bulk shear and low
level lapse rates approaching 7 C/km...a rogue strong storm can`t be
completely ruled out. Worth checking back in future outlooks as the
"kick off to summer" will be in full force.

.LONG TERM...(Sunday night through Thursday)
Issued at 353 AM EDT Fri May 26 2017

High impact weather potential: Slight chance of thunderstorms Monday.

Well advertised upper level cutoff low pressure continues to spin
across the Upper Great Lakes/southern Canada through the remainder
of the forecast period providing unsettled weather and a return of
below normal temperatures to northern Michigan. Waves of scattered
showers are possible each day (timing dependent on individual pieces
of upper level energy expected to cross the area), which is evident
by low end PoPs continuing to litter the forecast Monday through
Thursday. High temps falling back to several degrees below
normal...ranging from the upper 50s to middle 60s area-wide.

&&

.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 131 PM EDT Fri May 26 2017

Some potential for brief MVFR conditions tonight and Sat morning,
but mostly VFR.

Narrow ridge of high pressure will cross MI today, while an
incoming front makes only slow progress across MN/Iowa/MO. Main
area of shower/tsra activity with the incoming system will pass to
our south tonight. Low levels remain moist, and with the Great
Lakes still chilly, marine fog/stratus may start to expand out
again tonight. For now, localized MVFR conditions (mainly cigs)
are the main concern.

Light winds.

&&

.MARINE...
Issued at 353 AM EDT Fri May 26 2017

Fairly weak gradient in place for much of the forecast period...
should see some lake breeze development dominate local wind
directions today. Reduced visibilities in fog may be more of an
issue today through Saturday...otherwise not anticipating marine
headlines at least in the first part of the weekend.


&&

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

$$

UPDATE...JZ
NEAR TERM...JPB
SHORT TERM...MJG
LONG TERM...MJG
AVIATION...JZ
MARINE...JPB


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