220
FXUS63 KAPX 120729
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
229 AM EST Thu Dec 12 2019

.NEAR TERM...(Today through Tonight)
Issued at 226 AM EST Thu Dec 12 2019

...More significant snow for parts of the area today...

High impact weather potential: Widespread accumulating snow
producing significant travel impacts, especially across the Tip of
the Mitt and eastern upper Michigan.

Pattern synopsis/forecast: Progressive northern stream flow
continues, with steady height rises taking place overhead as deep
trough responsible for shot of Arctic air is rapidly moving east
into Quebec and New England. Off the deck thermal profiles have
warmed considerably since this time yesterday, as evident by H8
level temperatures almost increasing by 10C. Per the usual with
these dense cold airmasses, surface response to this warming is
delayed, with current temperatures once again in the single digits
and teens. Combination of those warming temperatures aloft and
increasingly shallow convective depths has definitely disrupted the
lake processes, with just shallow clouds and a few lingering
flurries found across the area.

Break in our active weather sure won`t last long, with water vapor
imagery displaying sharp shortwave trough digging rapidly southeast
across the Dakota`s, with an expanding area of light to moderate
snow along and just ahead of this wave. This "clipper" system will
race east into and through the area later this afternoon and
evening, bringing that widespread snow along with it.

Primary forecast concerns/challenges: Snow amounts and attendant
headlines into this evening.

Details: Expect snow to rapidly spread into the area this morning,
with the juxtaposition of deeper moisture and forcing from the
approaching wave favoring the steadiest snows across the Tip of the
Mitt counties and across eastern upper Michigan by later this
morning through the afternoon. Overspreading of this deeper moisture
across a still favorable over-water thermal gradient will likely
ignite at least some lake response across northern Lake Michigan
this morning. Hi-res guidance concurs, showing hints of at least
some lake snows spreading north into the Straits and eastern upper
Michigan. Not expecting this to be too big a deal given transient
nature of any banding and shallow convective depths. Strong
indication that a dry wedge centered just off the deck will spread
northeast quickly this morning, ending the widespread snow threat
across a portion of northern lower Michigan (especially south of M-
72), with chances for snow once again increasing later this
afternoon as dry slot is lost (perhaps with a bit of a lake
component into northwest lower Michigan). As for snowfall totals,
good deep moisture and strong omega centered in an elevated/deep
dendritic growth layer both support some decent totals across the
north half of the area, likely ranging from 4 to 8 inches, with the
greatest amounts along and north of the M-68 corridor....warranting
a winter weather advisory for that area. Given that expected dry
slot, expect snow totals to drop off fairly rapidly as one goes
south, with likely just trace amounts down near Saginaw Bay. As for
temperatures, development of south and southeast winds will
definitely usher in a milder airmass, with much of the area ranging
from the middle 20s to lower 30s by later this afternoon, with even
slightly warmer readings in our far southwest and southeast counties.

Kinda an interesting and challenging forecast heading through
tonight as forcing departs and moisture thins from top to bottom in
the column. May see light snow/flurries transition freezing drizzle
as ice nucleation is lost. To complicate matters, while inversion
level temperatures become too warm for ice nucleation, they may be
just cold enough to entice some lake moisture contribution into
northwest lower Michigan...further moistening the low level
environment in support for drizzle.  Definitely something to monitor
as we head into the evening hours. Otherwise, a downright mild night
when compared to recent conditions, with temperatures remaining
steady-state or even slowly rising into the 20s and lower 30s.

&&

.SHORT TERM...(Friday through Saturday)
Issued at 226 AM EST Thu Dec 12 2019

High Impact Weather Potential: Minimal

...Fairly Quiet Friday, more light Lake Effect late Saturday...

Synopsis/Forecast: Friday morning the weak clipper from Thursday
will be filling in and weakening over northern Michigan. The
decaying low will still influence our wind field though, as we hang
on to light southerly winds. Also through the morning a subtle wave
traversing the Rockies will spin up yet another weak compact low
through the Central Plains before moving into the Ohio Valley.
Overall, relatively little sensible weather over the area through
mid-day thanks to a lack of forcing or moisture. As the fetch
increases across the big lakes maybe some light flurries and/or
freezing drizzle will get pushed into ern upper. Forecast soundings
show little to no ice nucleation. A lot of these slight chance pops
also depends on the exact position of the decaying surface low.
Better snow chances slowly return Friday night as profiles saturate
top down, allowing seeder-feeder processes to take over, especially
in ern upper. Friday`s highs are expected to be a couple degrees
above normal.

Northwest flow kicks in Saturday with cold low-mid level air pouring
into the region. The low pressure system crossing the Ohio Valley
gets absorbed into an intensifying nor`easter. Increasing overlake
instability late Saturday will bring more chances for lake effect as
the day wears on. Slightly milder temperatures will continue
Saturday before a return to colder conditions comes later in the
weekend. Between the nor`easter and incoming high pressure, our
winds will get increasingly breezy late Saturday evening and
overnight.

&&

.LONG TERM...(Saturday night through Wednesday)
Issued at 226 AM EST Thu Dec 12 2019

High Impact Weather: Minimal

Sunday into the beginning of the week bring multiple waves passing
by, mainly to our north, that will each bring increased chances for
lake effect. This mainly targets northwest flow belts on Sunday,
then fans out some with a general decrease in likelihood as surface
high pressure moves in Monday. There remains potential for a strong
system to ride up through the Ohio Valley late Monday night into
Tuesday. this could bring gusty winds and another round of synoptic
snow, but confidence in this is very low at this point. The general
pattern heading into midweek is more of the same as on the weekend:
northwest flow with rounds of light lake effect possible. The
extended period will run a couple degrees below normal.

&&

.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1140 PM EST Wed Dec 11 2019

Westerly flow light lake effect snow continues in the snowbelts of
northern Lower Michigan, although they have weakened substantially
this evening and will continue to do so overnight. MVFR lake
cloud cover is still impacting the NW Lower Michigan coast but
will also thin out overnight as winds back to south by morning.

But after a brief respite, more snowfall is on the way for
Thursday. Low pressure over the front range of the Rockies will
eject into the Midwest tonight and slide up through northern Lower
Michigan Thursday. This system will spread another round of
snowfall across northern Michigan with the heaviest snow
anticipated north of M-32 into the U.P. Conditions will gradually
trend to MVFR and possibly IFR through the day...with the worst
conditions at PLN.

&&

.MARINE...
Issued at 226 AM EST Thu Dec 12 2019

Another round of gusty winds, this time from the south and
southeast, will bring small craft advisory conditions for many of
our nearshore waters today into this evening. Well deserved break in
the recent gusty winds looks to begin later tonight, lasting into
the first half of the weekend.

&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...WINTER WEATHER ADVISORY from 6 AM this morning to 1 AM EST
     Friday for MIZ016>018-086>088-095>099.
LH...SMALL CRAFT ADVISORY until 6 AM EST Friday for LHZ348-349.
     SMALL CRAFT ADVISORY until midnight EST tonight for LHZ345>347.
LM...SMALL CRAFT ADVISORY until 7 PM EST this evening for LMZ341-342.
     SMALL CRAFT ADVISORY until 6 AM EST Friday for LMZ323-344>346.
LS...SMALL CRAFT ADVISORY until 7 PM EST this evening for LSZ321-322.
&&

$$

NEAR TERM...MB
SHORT TERM...STJ
LONG TERM...STJ
AVIATION...BA
MARINE...MB

NWS APX Office Area Forecast Discussion