National Weather Service - Area Forecast Discussion

000
FXUS63 KAPX 192313
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
613 PM EST Tue Jan 19 2021

.NEAR TERM...(Through Wednesday)
Issued at 341 PM EST Tue Jan 19 2021

...Lake effect snow continues...

High impact weather potential: moderate localized accums of snow
tonight in the snow belts.

1013mb low pressure is moving into western Quebec. Trailing lake-
aggregate trof skirts far northern Lk Huron and extends into eastern
upper MI. Westerly surface winds are seen south of the trof, with nw
winds north. Resulting w to wnw Lake effect snows in northern lower
MI have focused north of APX proper and south of the Bridge today.
There are signs of some diurnal disruption of this activity. In
eastern upper MI, wnw flow has kept the best activity in central
and western Chippewa Co, near and north of M-28, including the
Sault. This has been complicated by the presence of the surface
trof, which has at times been a disruptive force to bands poking
into eastern upper MI, and at other times been a source of
convergence.

A digging 500mb shortwave will crash across the region this evening.
The mid-levels dry overnight in post-wave subsidence, and a
shortwave ridge axis eventually crosses our area on Wednesday. At
the surface, the lake-aggregate trof will be suppressed as a ridge
of high pressure builds in overnight. 1000-850mb winds will veer nw
this evening, before weakening and starting to back again overnight.
This gives way to increasing sw flow on Wednesday as the ridge
departs.

Definitely a window for better lake effect snows again tonight,
especially in the 1st half of the night. This window is on the
short side, and is complicated by the unsteady winds. Nam BUFR
soundings show inversion heights increasing, peaking at around 6k
ft mid-evening. The DGZ is skinny, but pegged right on the omega
max in the vertical. This will continue to produce classically
dry/fluffy lake effect snow, with snow liquid ratios in excess of
20:1. Have increased QPF and snow ratios in western Chippewa, and
parts of nw lower MI.

In eastern upper MI, have 2-5" progged tonight west of Brimley and
north of M-28. Currently thinking the winds veer nw quickly enough
to take the Sault out of better snow bands fairly quickly. In
northern lower, a similar 2-5" is forecast west of I-75 and east of
Gd Trav Bay, slipping down into parts of Kalkaska and Crawford Cos.

Headlines: Chippewa Co is fine. Given unusual amounts of water open
on extreme northern Lake MI for this time of year, southern
Emmet/Cheboygan Cos may remain somewhat under the gun even as winds
veer into northern lower MI. Have extended those two counties until
midnight. Tougher question: what to do with Leelanau and Gd Trav
Cos? They have not had much snow so far, and only have progged 1-2"
here tonight. These are not advisory numbers...but it`s lake effect,
and anything can happen (especially near, say, Williamsburg). Am
going to cancel the advis for Lee/Gd Trav...let`s see if I regret it.

Wednesday...the passing surface ridge axis and light winds will
quickly leave us with some seriously disrupted and weakening lake
effect, which sct pops will largely suffice to cover in the morning.
Sw flow is very firmly embedded in the afternoon, and broader warm
advection/forcing for ascent will likely carry some lake enhanced
snow showers in eastern upper MI in the afternoon. Do have afternoon
snow accums up to 1" in eastern upper.

Min temps tonight mainly in the teens, though single digits will be
seen in parts of eastern upper MI. Max temps Wed in the mid 20s to
lower 30s, though increasing sw winds in the afternoon will keep
things feeling chillier.

&&

.SHORT TERM...(Wednesday night through Friday)
Issued at 341 PM EST Tue Jan 19 2021

High Impact Weather Potential: Accumulating snow expected at times
through the period.

A potent shortwave will quickly progress across the Great Lakes
Wednesday night, providing strong support aloft for a clipper near
990mb that will trek from Ontario into Quebec by Thursday morning.
An associated cold front is expected to sweep across the area
Wednesday night ahead of a second, stronger cold front that looks to
slide from north to south across northern MI Thursday night.

Forecast/Details:

The next main round of precip for the area will arrive Wednesday
night after a short break from the lake effect snow. Favorable
forcing provided by the approaching system should produce some
accumulating snow of around 1-2", mainly along and north of M-32.
Only minor accumulations are expected elsewhere initially as forcing
and moisture become less favorable further away from the clipper.
Westerly winds behind the first front should generate at least some
lake effect precip across NW lower through Thursday. However, not
all of the precip Wednesday night through Thursday may be snow. With
some warmer temps near the lakeshores that will be close to
freezing, along with a shallow saturated profile evident in forecast
soundings, the potential for drizzle/freezing drizzle exists during
this time.

Perhaps the main focus of the short term will be the expected lake
effect snow that ramps up behind the second cold front Thursday
night through the remainder of the period. Forecast soundings show
favorable profiles to support accumulations across the typical NW
snow belts. Lake effect evolution isn`t anticipated to be too
dissimilar to what we`ve experienced in the past 24HRs currently:
saturation through the DGZ will lend towards high snow ratios,
diurnal heating and slight wind direction changes should keep lake
effect somewhat disorganized during the daytime with better
chances for organized bands after sundown, and the main impacts
will be rapid drops in visibility within any heavier snowfall and
hazardous travel conditions with quick accumulations on roadways.
Otherwise, highs near freezing on Thursday will drop about 10
degrees on Friday due to the frontal passage overnight.

.LONG TERM...(Friday night through Tuesday)
Issued at 341 PM EST Tue Jan 19 2021

High Impact Weather Potential: Continued lake effect, potential
system impacts early next week.

As discussed in more depth in the short term portion, lake effect
chances across NW lower and eastern upper look to continue into
Saturday morning. This may be the time of most intense banding given
better chances for organization after sunset. Regardless, lake
effect chances will eventually wane into the day on Saturday as high
pressure slides overhead. This should provide at least a short break
in precip for northern MI before the potential for more snow arrives
heading into the second half of the weekend. While the main system
looks to move well to our south, ascent provided by a shortwave
moving across the region could spark additional snow chances for the
area in the Saturday night/Sunday/Monday timeframe. Chilly
temperatures compared to what we`ve seen as of late are expected
over this weekend. Highs will be in the teens and low 20s with
overnight lows expected to be in the single digits for many across
interior northern MI.

&&

.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 613 PM EST Tue Jan 19 2021

Upper level wave and surface response will slide thru Lower
Michigan this evening...providing mid level moisture and synoptic
lift to enhanced ongoing westerly flow lake effect snow showers.
This feature will exit our area overnight as the upstream ridge
axis builds into Michigan into Wednesday. Prevailing conditions
will remain MVFR/low VFR...but will drop to IFR within some of the
heavier snow showers this evening. W/NW surface winds around 10
kts tonight will become SW and strengthen to 15 to 25 kts on
Wednesday.

&&

.MARINE...
Issued at 341 PM EST Tue Jan 19 2021

Nw winds will diminish greatly tonight, as a weak ridge of high
pressure builds in. Sw winds will ramp up behind this ridge on Wed
and Wed night. Gale warnings will be issued for the Lake MI waters,
and for the Straits. A gale watch is likely on some of our Lk
Huron waters (mainly south of Presque Isle Lt) Wed evening.

&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...WINTER WEATHER ADVISORY until 7 AM EST Wednesday for MIZ021-022-
     027-028-086-087-099.
     WINTER WEATHER ADVISORY until midnight EST tonight for MIZ016-
     017.
LH...SMALL CRAFT ADVISORY until midnight EST tonight for LHZ345>348.
     GALE WARNING from 3 PM Wednesday to 2 AM EST Thursday for LHZ345.
     GALE WATCH from Wednesday evening through Thursday morning for
     LHZ348-349.
LM...SMALL CRAFT ADVISORY until midnight EST tonight for LMZ323-341-
     342-344>346.
     GALE WARNING from 3 PM Wednesday to 2 AM EST Thursday for LMZ323-
     341-342-344>346.
LS...NONE.
&&

$$

NEAR TERM...JZ
SHORT TERM...DJC
LONG TERM...DJC
AVIATION...MR
MARINE...JZ

NWS APX Office Area Forecast Discussion