Area Forecast Discussion
Issued by NWS Gaylord, MI

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FXUS63 KAPX 271741

Area Forecast Discussion
National Weather Service Gaylord MI
141 PM EDT Tue Oct 27 2020

Issued at 1039 AM EDT Tue Oct 27 2020

Morning composite analysis reveals elongated surface high pressure
across the Great Lakes and back into the central Plains but with
some subtle lake induced troughiness along the NW Lower Lake
Michigan shoreline. Aloft, low amplitude short-wave trough axis
is pressing into the western Great Lakes this morning with 140+
knot upper jet axis stretching from Missouri northeastward through
southern Lower Michigan. Associated upper jet forcing is
producing a corridor of higher level radar returns through central
Lower Michigan and into northern Lower. Mostly virga,
particularly this far north, but a few locations have reported
some light precip. Meanwhile, spotty lake convection lingers on
northern lakes Michigan and Huron, drifting into parts of NW Lower
Michigan on a presently light low level flow.

Background upper jet induced radar returns continue across Lower
Michigan into the afternoon before diminishing...with little
fanfare. Meanwhile, as discussed by overnight forecaster below,
surface high pressure gets shunted into the lower lakes region
through today while lowering surface pressures develop across the
northern lakes...resulting in an increasing southwesterly flow
across the region. This will eventually draw lingering lake
convection back through the region as we go through the afternoon,
possibly bolstered some by daytime heating and a touch of low
level instability. So, some spotty showers anticipated, snow or
mixed snow->rain as temperatures warm to the high 30s to lower

Southwesterly winds gradually increase this afternoon and particularly
tonight as low level flow increases to 30 to 40 knots off the
surface and underneath an increasing/lowering inversion. Gale
warnings currently in place look fine and we may have a need for
some lakeshore flood headlines. Will coordinate that with
surrounding offices.


.NEAR TERM...(Today through Tonight)
Issued at 343 AM EDT Tue Oct 27 2020

...Still some lake effect today, becoming breezy tonight...

High impact weather potential: lakeshore flooding possible
along Lake Mich coastline overnight into Wed morning.

High pressure is centered over the NE/IA border area, with ridging
extending into the northern Great Lakes. This high will gradually
get shunted southward into the northern OH Valley by late tonight.
Meanwhile, various shortwaves will be digging into s central Canada,
lowering pressures in the southern prairie provinces and into
northern Ontario. Lake effect precip will linger into today, but we
start to shunt the colder air out of the region tonight as sw winds

Presently, mixed lake effect rain/snow showers hug the coastlines
of Lakes Mich/Huron/Superior. Our 1000-850mb winds are weakening
in the pre-dawn hours, as the surface high shifts southward over
the region (and as a separate, weaker blue H forms just east of
the Great Lakes). Light winds and land breezes will contribute to
mesolow development, something we have seen with some frequency
since yesterday. After 12Z, we finally see a real synoptic fetch
established, with wsw 1000-850mb winds increasing to 10kt by 15Z,
and 15-20kt by 18Z. This will fairly quickly carry ongoing Lakes
Huron/Superior activity out of our area. However, residual lake
effect rain/snow showers will gradually get pushed into the Lake
MI coastal counties of nw lower MI, as well as central Mackinac
Co. This will be most prevalent from 10am to 2pm. After that,
expect maybe some sct showers to linger thru the afternoon in the
Straits area, where the wsw fetch is longest. Hard to see more
than isolated showers further south from mid-afternoon on.

Far western Chip/Mack Cos should be the first to break into partial
sunshine, by midday or very early afternoon. That will be slow to
push eastward, but nw lower MI at least will see clouds decrease by
late afternoon.

Tonight, the pressure gradient continues to tighten between the high
to our south, and lowering pressure to our north. Sw to wsw winds
continue to strengthen somewhat. 850mb temps will recover to 0C or
better in southern and western sections by morning. That shallows
out lake effect instability, and with drier air in place at low
levels, expect places near and south M-72 to be partly cloudy to
mostly clear all night. The north, though, will see a mid cloud deck
make inroads during the night, as a shortwave goes glancing by
Superior and adjoining parts of Ontario. Precip chances look pretty
meager, but there is perhaps a slight chance of rain/snow north of M-
28 in Chippewa Co overnight.

It will get increasingly windy tonight, especially over and just
downwind of Lake MI. Wind headlines should not be needed over land,
but wind/wave action will open the door to some lakeshore flooding
potential overnight along the Lake MI coastline in both peninsulas.
Will add this to the Haz Wx Outlook, but leave later shifts to
issue advisories (or worse) as needed.

Max temps today upper 30s to mid 40s, pretty much just like the last
few days. Min temps will briefly dip into the upper 20s to lower 30s
early tonight, but rise overnight.


.SHORT TERM...(Wednesday through Thursday)
Issued at 343 AM EDT Tue Oct 27 2020

High Impact Weather Potential: Low

Pattern Synopsis:

A strong zonal jet will continue to spread across the Great Lakes
Wednesday as a cut-off upper-level low shifts into the southern
Great Plains. This low will get reabsorbed back into the main flow
and quickly traverse the SE CONUS Thursday. At the surface, a
cyclone should trek across Hudson Bay into Quebec Wednesday while
what is currently Hurricane Zeta is expected to to make landfall
along the Gulf coast Wednesday evening per the latest NHC forecast.
The aforementioned cut-off low will provide strong support aloft for
the remnants of Zeta, which will progress into the Mid-Atlantic late
Thursday as high pressure builds into the center of the country.


A weak front associated with the cyclone over Hudson Bay looks to
swing down through the area Wednesday morning which, in tandem with
the strong jet streak aloft, should provide sufficient forcing for
some rain/snow showers across eastern Upper and Tip of the Mitt
Wednesday. Forecast soundings show favorable low-level moisture in
place across this area that decreases with southward extent. Enough
near-surface could remain after the frontal passage to support some
additional lake effect showers, mainly across eastern upper, with NW
winds behind the front Wednesday night. Somewhat enhanced northerly
winds are expected Thursday with a tightening pressure gradient due
to Zeta passing to our south. More light rain/snow showers are
possible Thursday, mainly along and west of US-31/M-37 due to these
northerly winds and some shallow moisture near the surface.
Otherwise, some warmer temperatures arrive on Wednesday with
afternoon highs in the upper 40s and low 50s. A chilly day is
expected on Thursday due to the frontal passage as highs only get
near 40 in the afternoon, feeling even cooler with north winds.

.LONG TERM...(Thursday night through Monday)
Issued at 343 AM EDT Tue Oct 27 2020

High Impact Weather Potential: Monitoring strong wind/snow potential
late this upcoming weekend.

A formerly cut-off low should fully merge with the primary upper-
level flow and depart into the Atlantic Friday as ridging looks to
move over the Great Lakes Saturday. Guidance consistently brings an
impressive trough through the region late this weekend with an
associated strong cyclone across Hudson/James Bay. Confidence is
beginning to increase that strong NW flow behind an attendant cold
front could bring our first shot for accumulating lake effect snow
to the area. While forecast temps look to waver near the freezing
mark, sufficient moisture appears to be in place to support lake
effect precip chances of some kind. As alluded to above, strong wind
gusts are also becoming a concern late this weekend as this system
approaches. Plenty of time still exists between now and then,
however, and details will become more clear as the weekend nears. On
a brighter note, it is looking like northern Michigan will have a
pleasant Halloween weather-wise. With ridging moving in, no precip
is in the forecast until late Saturday night, which is somewhat
rare. Most of our major observation sites have had precip 9 of the
past 10 Halloweens. If northern Michigan is particularly lucky, we
could even get a good glimpse of the full moon Halloween night
before cloud cover creeps in ahead of the system.


.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 140 PM EDT Tue Oct 27 2020

Last bit of lake induced clouds and showers are spreading through
parts of northern Lower michigan, primarily north of M-72 and
producing MVFR conditions at PLN/TVC. APN will likely turn MVFR in
the next few hours as cloud cover continues to spread inland.

Increasing SW flow will draw in warmer air into the region tonight
and should bring an end to lake effect. However, another upper
level wave will be sliding across the northern lakes later tonight
into Wednesday bringing some additional mid and high cloud cover.

Increasing winds tonight will lead to LLWS across parts of
northern Lower Michigan and gustier surface winds on Wednesday.


Issued at 343 AM EDT Tue Oct 27 2020

Sw to wsw winds ramp up today and especially tonight, as broad
high pressure settles to our south. Anticipate the ongoing gale
warning being expanded south to Manistee, and small craft
advisories being issued for all of our other waters.


LH...SMALL CRAFT ADVISORY from 6 PM this evening to 8 PM EDT
     Wednesday for LHZ346>349.
     GALE WARNING from 11 PM this evening to 11 AM EDT Wednesday for
LM...GALE WARNING from 11 PM this evening to 11 AM EDT Wednesday for
LS...SMALL CRAFT ADVISORY from 6 PM this evening to 8 PM EDT
     Wednesday for LSZ321-322.


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