Area Forecast Discussion
Issued by NWS Gaylord, MI

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FXUS63 KAPX 151419
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
1019 AM EDT Sun Oct 15 2017

.UPDATE...
Issued at 1018 AM EDT Sun Oct 15 2017

Unseasonably warm/humid warm sector airmass getting abruptly
shoved aside, as 997mb surface low ejects across northern Huron,
and a trailing cold front accelerates across northern MI. The warm
air is only hanging on in ne lower MI, and the front will exit
there over the next 2 hours. OSC/APN are trying to take a run at
70f before fropa. Meanwhile, MBL is down to 53, PLN 48, and
Newberry 42.

Plenty of showers along the front. Dry slot behind the front is
resulting in a period of post-frontal light rain/drizzle. More
widespread wraparound rain is impacting parts of central upper MI
and Superior. This will graze eastern upper MI over the next 3-4
hours before exiting. Expect lake instability to generate some
rain showers downwind of Lakes MI/Superior/Huron in NNW 1000-850mb
flow this afternoon, though moisture availability becomes more
questionable as time goes by.

Tight pressure gradient w of the departing low is contributing to
windy conditions in the cold advection zone of this system. This
has been especially noticeable in upper MI and on Superior, and is
now progressing se-ward, including a recent 41kt gust at the
northern Lake MI buoy. Windier conditions will expand across
northern MI thru this afternoon. 45 mph gusts should be seen in
well-exposed locations, especially along the coastlines.
Otherwise, expect most gusts to be below that level. Still, it
will be quite windy, and we still have plenty of leaves on the
trees (making us more prone to taking down branches). So the wind
advisory will be maintained.

&&

.NEAR TERM...(Today through Tonight)
Issued at 239 AM EDT Sun Oct 15 2017

High impact weather potential: Brisk and cooler NW winds developing.

Pattern synopsis and forecast:

Early this morning, deepening low pressure was working through srn
Wisconsin, out ahead of well-defined mid level trough working into
the Mississippi valley. Forcing was fairly impressive with this
system. A handful of minor shortwaves were working through nrn
Michigan out ahead of the main trough, ushering in pockets of
increased WAA and DPVA. The back edge of the forcing, which was also
aided by nice upper divergence in right entrance region of a 130+ kt
jet across eastern WI, was just ahead of the leading edge of a dry
slot. Pockets of rain were within these regions of forcing,
expanding over the last few hours. The greatest coverage of rain was
within the strongest WAA, which was wrapping east of lower Michigan,
into nrn Lake Huron, across eastern upper and back into the
deformation which was into MN and NW Wisconsin. Although weak, there
was a few hundred j/kg of MUCAPE with meager lapse rates aloft of
6c/km. This has resulted in some thunder in eastern Wisconsin. As
what tends to happen a lot, stronger convection resulting in much
higher rainfall amounts from nrn Il to srn lower Michigan, has
prevented the deeper moisture from getting into nrn Michigan. The
max rainfall seen thus far was where it was expected, across the SE
CWA nearer Saginaw Bay, but only a half inch to maybe 0.75" has
fallen thus far.

Heading through sunrise, the stronger forcing shifts east of nrn
lower, while deformation and low level convergence remain active
across eastern upper. While rains are likely to continue there, the
dry slow will turn the precip in much of nrn lower to more of a
light rain/drizzle. The sfc low will be pushing east of nrn Michigan
after sunrise, with a stronger pressure gradient in cold advection
starting to work into eastern upper and NW lower, spreading through
NE lower by early afternoon. A wind advisory has already been issued
for NW winds gusting to 45 mph, but trends do suggest speeds may
very well be more in the 35 to 40 mph range. Maybe the immediate
downwind counties of NW lower can get there, coming in off quite the
amount of instability over Lake Michigan. Best shot appears to be
Leelanau county south through Manistee. Temperatures get relatively
cold with h* readings falling to 0c to -2C through the afternoon.
The deeper moisture from the deformation that wraps across the area
could lead to some lake enhanced rains into eastern upper and a good
chunk of NW lower. Couple that with the stronger winds, and we will
have quite the "raw" day. Again, moisture will have a hard time
reaching -10C in nrn lower, so maybe this is gonna be more like a
blowing light rain/drizzle. Moisture gradually depletes heading
through later this afternoon but there could still be some lesser
coverage light rains. Fcst soundings into tonight show that moisture
remains rather minimal for the generation of lake effect, but as we
know, lake effect tends to create it`s own environment. The
tremendous overlake instability (approaching 20C delta T`s) will
probably keep isolated lake effect rains going. This may be more
true as the parent mid level trough axis arrives late this evening
and into the overnight. High pressure moves in late tonight.

Highs today will be early, before cold advection ceases warming and
likely sends temperatures down a little through the day. Lows
tonight will fall into the mid to upper 30s over much of the region.

&&

.SHORT TERM...(Monday through Tuesday)
Issued at 239 AM EDT Sun Oct 15 2017

...Cool initially, but temperatures gradually moderating...

High Impact Weather Potential...None.

Pattern Synopsis/Forecast...Main surface ridge axis will extend into
northern Michigan on Monday morning, with warm air advection quickly
developing as heights rise behind the departing upper trough. This
will lead to some erosion of the low level clouds. However,
isentropic lift interacting with slightly better moisture just
upstream will lead to increasing mid/high level clouds through the
day into Monday night, especially the northern part of the forecast
area. Despite the warm advection aloft, a shallow layer of cooler
air at the surface will keep Monday`s temperatures on the cool side
with most guidance in agreement with highs in the low to mid 50s.

Warm advection continues in earnest Monday night into Tuesday,
leading to more moderate lows Monday night in the upper 30s to mid
40s. It will turn breezy over the lakes Monday night as a surface
low tracks across southern Hudson Bay, tightening the pressure
gradient over the Upper Great Lakes. Heights aloft will continue
their gradual rise on Tuesday as a subtle upper ridge eventually
approaches. Subsidence from anticyclonic vorticity advection
overhead will lead to mostly sunny skies on Tuesday with highs
largely in the low to mid 60s. Still somewhat breezy, though.

.LONG TERM...(Tuesday night through Saturday)
Issued at 239 AM EDT Sun Oct 15 2017

High Impact Weather Potential...None.

Expansive area of surface high pressure over the eastern CONUS will
lead to a rather quiet stretch of weather over northern Michigan
through the period with warming temperatures. A shortwave will pass
north of the region with a weak cold front crossing the Upper Great
Lakes midweek. This will lead to breezy conditions again on
Wednesday. By the end of the week, an amplifying upper ridge will
lead to a pronounced warmup with many areas climbing into the low
70s Friday and Saturday.

&&

.AVIATION...(For the 12Z TAFS through 12Z Monday morning)
Issued at 604 AM EDT Sun Oct 15 2017

Strong low pressure over nrn Lake Michigan will cross the region
quickly this morning, dragging a cold front through during the
morning and early afternoon. The pressure gradient will tighten up
and bring quite gusty NW winds aided by deepening overlake
instability. Until then, a few more hours of LLWS at APN.
Expecting a few periods of reduced VSBYS due to light rain and
drizzle before the NW winds gradually result in no restrictions.
Winds start to wind down to some degree late this afternoon, and
more so through tonight as higher pressure settles into the
region. CIGS will go from IFR to VFR through the day.


&&

.MARINE...
Issued at 239 AM EDT Sun Oct 15 2017

Strong low pressure crosses nrn Michigan early this morning,
dragging a cold front through the region. The pressure gradient
tightens up quickly through the morning/early afternoon with
strong cold advection ensuing. Overlake instability becomes large
and results in widespread gale force winds. More confidence now in
not reaching storm force. Rains will taper off to more of a
blowing drizzle/light rain across nrn lower nearshores. Some of
this rain may become enhanced due to lake effect but nothing
heavy. Winds start tapering off later this afternoon and
especially into the evening when an axis of higher pressure
settles in. This high pressure and lighter gradient will hang
around through Monday, before winds ramp up out of the SW ahead of
the next cold front slated for Tuesday. There is a good chance for
advisory level winds Monday night into Tuesday morning.


&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...WIND ADVISORY until 8 PM EDT this evening for MIZ008-015>036-041-
     042.
LH...GALE WARNING until 8 PM EDT this evening for LHZ345-346.
     GALE WARNING until 11 PM EDT this evening for LHZ347>349.
LM...GALE WARNING until 8 PM EDT this evening for LMZ323-341-342-
     344>346.
LS...GALE WARNING until 8 PM EDT this evening for LSZ321-322.
&&

$$

UPDATE...JZ
NEAR TERM...SMD
SHORT TERM...MK
LONG TERM...MK
AVIATION...SMD
MARINE...SMD


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