Small Craft Advisory 9, NWS Gaylord, MI

Area Forecast Discussion
National Weather Service Gaylord MI
329 PM EST Thu Jan 26 2023

.NEAR TERM...(Through Tonight)
Issued at 323 PM EST Thu Jan 26 2023

...Diminishing Snow This Evening Cold Lows...

High Impact Weather Potential...Lowered visibility this evening near
Saginaw Bay. Single Digit Low temperatures, near zero wind chills.

Pattern Synopsis/Forecast/Concerns...A sfc trough and 500 mb
shortwave trough over the state, will continue to move east this
evening, and take the light snow with it. A sfc and 500 mb ridge
will move through the forecast area tonight, allowing for some
clearing mainly in E Upper and NE Lower. The weak gradient and sfc
high over the highlands NE of ANJ in Ontario will lead to some cold
air drainage, that the GFS shows could get to APN, PLN and ERY. In
the meantime, in NW Lower, the NW winds will shift to the SW as the
ridge moves through N Lake Michigan. With 850 mb temperatures around
-11 or -12c, the delta T ends up at 14 or 15c. However, with
diminished cloud layer moisture (850-700mb layer <35%) the LES from
SW flow into western Mackinac county or into Charlevoix or Emmet
counties looks to be minor overnight. This sets up the region for
the clipper and cold front for Friday which is discussed below.

&&

.SHORT TERM...(Friday through Sunday)
Issued at 323 PM EST Thu Jan 26 2023

High Impact Weather Potential...low for now...period of snow / snow
showers Friday afternoon and night. Watching system Saturday into
Sunday.

Pattern Synopsis: Longwave troughing will continue to encompass the
eastern two thirds of North America, with a pronounced jet streak
stretching from the Sonora Desert to the Canadian Maritimes on
Friday morning. Closer to home, a shortwave within the longwave
will be centered over the Canadian Prairies, moving SE toward the
upper Great Lakes, containing a modest amount of synoptic moisture.
As this shortwave progresses SE into the Great Lakes, the overall
trough will flatten slightly, signaling a slight weakening trend
for when the system gets to the area. Regardless of this trend, a
pronounced area of strong S to SSW flow at both 925 and 850mb will
translate to gusty surface winds Friday as the synoptic moisture
passes through. On the backside of the system, flow will turn more W
to WNW with some lake effect instability Saturday, particularly
across the eastern Yoop. Meanwhile, a wave will emerge into the
central Plains, and will drum up more synoptic moisture and lift via
frontogenesis as another jet streak builds across the Corn Belt
region. This associated wave and its synoptic moisture will progress
eastward into the Great Lakes late Saturday.

Primary Forecast Concerns...poor visibility Friday evening with
snowfall and gusty winds, subtle northward trend in Saturday system,
lake effect in the eastern Yoop

Well, it sure looks like we are teetering toward a potentially more
active period of winter weather for this weekend. The clipper system
will pass through Friday, bringing a round of snow and gusty winds.
Snow will initially begin early Friday afternoon along Lake Michigan
and into the eastern Yoop. Initial soundings show a synoptic snow
profile along the leading warm front as it passes into the region.
The passage of this front ands the steepening of low level lapse
rates will allow for strong flow just above the surface (generally
35-40kts at its peak...some models have 925mb flow as high as 45kts
over Lake Michigan and near Little Traverse Bay) to mix down to the
surface. This will lead to a potential window for 35-45mph gusts,
with the highest gusts favoring coastal areas along Lake
Michigan...particularly in Mackinac County and into spots N of Grand
Traverse Bay...generally occurring between 4-11pm Friday.

This period of gusty winds will coincide with ongoing snowfall,
which, while light, will be enough to lead to areas of blowing snow
and significantly reduced visibilities at times, all coinciding with
the evening commute. Following the passage of the cold front late in
the evening, winds will taper some, but with steep lapse rates and
lingering moisture, gusty lake effect snow showers will be possible
into the early overnight before moisture in the low levels is
depleted across northern lower. As for eastern upper, moisture looks
to linger into the overnight a bit longer, which could result in a
more prolonged period of lake effect off of Whitefish Bay. All in
all, snow accumulations for this system look to be maximized west of
I-75 in northern lower and into eastern upper, with a general 1-3"
expected (locally higher possible in western Mackinac County owing
to SSW flow enhancement potential).

For Saturday, we are looking at most spots holding dry to start,
with the exception of some lingering lake effect in the eastern
Yoop, but given a general slackening of winds and slow loss of
moisture from the low levels. The afternoon and beyond becomes very
interesting as out attention turns to the aforementioned wave
traversing the Plains and approaching from the west. An area of
frontogenetically driven snow will lead to a narrow synoptic
shield of precipitation which will pass through the Great Lakes.
Recent model trends show a more northern bump in the track as the
system moves into Michigan later Saturday into Sunday, which now
is trying to include areas along the M-55 corridor seeing the best
shot at appreciable accumulating snowfall (generally approaching
2-4"), and areas north of M-32 seeing little to none. There is
still lots of uncertainty for this system, but for now, it's
looking like this system is favoring more of a central Michigan
track, with lesser amounts further north. In the event of a
further northern trend, we may be looking at higher amounts, and
more of northern lower seeing accumulating snow.

As far as temperatures go, Friday looks like above normal temps
through the day, with highs peaking in the upper 20s to low 30s.
Colder air moves in overnight, but temps will remain above normal
for this time of year, bottoming out in the teens to near 20 along
the shores. A colder airmass will be in place in the wake of the
clipper Saturday, with highs in the upper teens to low 20s and
overnight lows in the single digits and teens, with spots in the
eastern Yoop away from the lakes reaching low single digits. This
may be subject to change with a more northerly track in the system
Saturday.

&&

.LONG TERM...(Sunday night through Thursday)
Issued at 323 PM EST Thu Jan 26 2023

High Impact Weather Potential...low for now

If any snow remains into the region from the aforementioned wave
from later Saturday, it will dissipate rather quickly as the system
progresses eastward. Beyond this, there really isn't much that would
suggest any robust lake effect snow setups, but nonetheless, the
combination of the colder airmass should lead to continued lake
effect snows through next week. Where the greatest impacts are felt
will be dependent on the dominant flow, which looks to be primarily
W to WNW. Efficiency of snows will be driven by moisture
availability, and given that models are keeping a high pressure in
the southern lakes, it's looking like activity will generally be
quite light, but that is subject to change in the event that any
more organized vort decides to make an appearance. As far as
temperatures go, this looks to be the coldest air of the season thus
far, with most spots hovering just below average. Pending on cloud
cover and wind behavior, we may be looking at some instances of
subzero lows in places.

&&

.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 1226 PM EST Thu Jan 26 2023

As noted in the update section earlier in the day, this "grungy"
trough is moving through the forecast area this afternoon and
producing light snow amounts over the region. The snow has been
varying the VSBYs between IFR and MVFR with MBL dropping into
VLIFR categories as a snow band over Lake Michigan pushes inward.
CIGS have been generally in the same ball park, with MBL being a
category lower than the rest. These conditions are expected to
remain through the afternoon, with improvement coming by the early
evening once the winds shift to the SW and the ridge has moved
through the region. Winds will drop off for a time overnight,
allowing a drainage wind to move off the Canadian hills northeast
of CYAM and possible affect CIU, PLN, and APN for a bit before the
SW winds move across the state and push the clouds back into the
region for the day.

&&

.MARINE...
Issued at 323 PM EST Thu Jan 26 2023

Tonight through Saturday...Tonight, the winds will diminish as a
bubble of high pressure moves through the region. Once the axis of
high pressure moves east, the winds in Lake Michigan will back to
the SW, which will spread to  Lake Superior and Lake Huron. Lakes
Michigan and Superior will ramp up to small craft winds by 09z/Fri.
Friday, the winds continue to increase and reaches gale gusts on
Lakes Michigan and Superior by noon and spreads to Lake Huron by
21z/Fri. Friday night, the winds on Lake Michigan and Superior
diminish to small craft criteria as the cold front approaches and
the winds veer to the NW. Lake Huron diminishes by 03z/Sat. winds
continue to diminish to less than small craft criteria by Saturday
morning. The winds continue to diminish to variable less than 10
knots over the Upper Great Lakes by 00z/Sun.

&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...Winter Weather Advisory from noon to 10 PM EST Friday for MIZ020-
     025-031-098.
     Winter Weather Advisory from 11 AM to 7 PM EST Friday for MIZ086-
     095.
LH...Gale Warning from 7 AM to 7 PM EST Friday for LHZ345.
     Gale Warning from noon to 8 PM EST Friday for LHZ346>349.
LM...Gale Warning from 7 AM to 7 PM EST Friday for LMZ323-341-342-
     344>346.
LS...Gale Warning from 7 AM to 7 PM EST Friday for LSZ321-322.
&&

NEAR TERM...JSL
SHORT TERM...HAD
LONG TERM...HAD
AVIATION...JSL
MARINE...JSL

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