National Weather Service - Area Forecast Discussion

000
FXUS63 KAPX 200453
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
1153 PM EST Mon Nov 19 2018

.UPDATE...
Issued at 939 PM EST Mon Nov 19 2018

Gradual departure of synoptic precip has not been anywhere near
as clean as was theorized. Surface low is near the south end of
Georgian Bay, and mid-level moisture has emphatically been
stripped out. But cyclonic low-level flow continues, and
entrainment of dry air from the north has been a slow process.
Light precip remains reasonably widespread in northern lower,
with the Straits region and parts of ne lower MI exceptions. And,
with the departure of that mid-level moisture, precip did not
stay all snow. A period of light freezing rain marched north to
south across a significant portion of nw and n central lower MI.
An SPS remains up thru midnight addressing this.

Colder air is making inroads nonetheless, with GLR down to 21f and
CIU 19. That, in and of itself, will gradually turn leftover
precip over to snow again. Cloud-top temps will also be cooling,
from the lower to mid minus teens per Nam Bufr soundings, also
supporting a changeover back to snow. Have increased pops
tonight, and of course added a mention of mixed precip thru
midnight-ish.

&&

.NEAR TERM...(Through Tonight)
Issued at 330 PM EST Mon Nov 19 2018

...Colder Drier Air Arrives Tonight...

High Impact Weather Potential: Minimal. Transition to northerly
flow lake effect snow showers behind arctic cold front.

Pattern Synopsis/Forecast: Short-wave impulse and associated upper
divergence bullseye is now sliding across northern Michigan with
a broad area of light snowfall working through the eastern half of
the CWA. Attending surface low is over the Tip of the Mitt/NE
lower Michigan with a wavy front through the M-68 corridor and
arcing back down through Lake Michigan. Some very cold although
very dry air is poised north of the front across Ontario which
will overspread the region overnight into Tuesday.

Meanwhile, along the arctic front, better lake enhancement has
finally materialized and is now wrapping back down through Emmet,
Cheboygan and Charlevoix counties, some of the best snows of the
day. Also of note, a nice mesoscale low has formed over northern
Lake Michigan within the sharp low level trough and is now making
it`s way onshore into the Grand Traverse Bay region...likely
aiding the enhancement.

Primary Forecast Concerns: Ongoing headlines and transition to
northerly flow lake effect snows.

Short-wave and attending surface low will advance out of northern
lower Michigan over the next several hours while attending cold
front gets pulled down through northern lower Michigan by early-
mid evening. We may yet get a final push of transient heavier
snowfall that drops down through northern lower MI with the front
bringing some "last minute" accumulating snow.

For the advisory area itself, I was all set to cancel it ahead of
schedule given the lackluster snow/accumulations thus far. But as
mentioned some of the best enhancement of the day is now ongoing,
and just in time for the beginning of the afternoon commute. So
I`ll probably just let it ride until the heavier snows drop down
on through.

Quick transition to northerly flow lake snow showers takes shape
this evening with colder but much drier air overspreading the
region through the night. There will be a window of time through
this evening where better larger scale moisture/weak or neutral
QG-forcing for ascent will lead to some decent lake effect snow
showers in and around the Grand Traverse Bay region before
diminishing overnight as strong subsidence and much drier air work
into the region. With that in mind, I have beefed up snow
accumulations a bit in and around the Grand Traverse Bay region.

&&

.SHORT TERM...(Tuesday through Thursday)
Issued at 330 PM EST Mon Nov 19 2018

High Impact Weather Potential: Mainly light accumulations of snow
expected Tuesday afternoon through Tuesday night across eastern
upper and northwest lower.

Pattern Synopsis/Forecast: Broad troughing continues aloft across
the Great Lakes through the middle of the week before heights begin
to rise Thanksgiving Day. Weak surface ridging overhead during the
day Tuesday will quickly get ushered by a developing clipper system
set to drop southeast across the northern Great Lakes Tuesday night.
A strong area of Canadian high pressure will then settle atop the
region by Wednesday afternoon through the end of the forecast period
on Thursday.

Primary Forecast Concerns/Challenges: PoPs and snow amounts through
the forecast period.

Cold H8 temperatures aloft (~ -16 C) to start the day Tuesday will
promote north-northwesterly flow lake induced snow showers downwind
of Lake Superior and Lake Michigan; however, as the aforementioned
surface ridge slides overhead, low-level winds will gradually back
more westerly and eventually west-southwesterly Tuesday afternoon.
This will shift any lingering light snow showers to the typical west
flow lake belts near the M-32 corridor, although any accumulation
through the day is expected to be minimal. Deeper moisture begins to
arrive from the northwest by early evening in advance of an
approaching clipper system, set to trek from northern Lake Superior
Tuesday evening to eastern Lake Huron by Wednesday morning. Lake
enhanced snowfall will be the primary concern with this system given
a sufficient delta T environment, although a cold front crossing the
region will certainly bring synoptic support with it as well. As was
alluded to be the prior forecaster, lake aggregate troughing off of
Superior is expected to result in a more impressive area of low-
level convergence across portions of eastern upper than along the
northwest lower shoreline. Model forecast soundings suggest initial
inversion heights in the 9-10 kft range gradually fall throughout
Tuesday night, along with moisture stripping away to the east behind
the departing wave aloft. Expected snow accumulation from this event
across eastern upper and northwest lower continue to look on the
order of 1-3 inches, highest across the Tip of the Mitt...lesser
amounts under an inch east of I-75/south of M-32.

Strong cold air advection behind the departing system during the day
Wednesday will likely be sufficient enough to continue light
northerly flow lake effect snow showers; however, minimal
accumulation and associated impacts are expected at this time.

During the day Thursday, warm air advection will gradually take over
aiding to gradually boost temperatures aloft and putting an end to
any lingering light lake induced snow showers/flurries.

Temperatures remaining below normal through the forecast period with
highs ranging from the low-upper 20s across the forecast
area...coldest on Wednesday as many areas struggle to reach the mid
20s. Overnight lows certainly chilly as well with the coldest temps
expected Wednesday night...ranging from single digits across many
areas to the mid-teens nearest the Great Lakes shorelines.

.LONG TERM...(Thursday night through Monday)
Issued at 330 PM EST Mon Nov 19 2018

High Impact Weather Potential: Minimal.

Brief mid-level ridging will drift overhead giving a boost to
temperatures late this week. However, troughing redeveloping
upstream will aid in bringing another system across the region
Friday night into Saturday. Given the moderating thermal profile
through this time, rain looks to be the predominant precip-type
before cooler temperatures and more snow chances return for the
following week.

&&

.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 1152 PM EST Mon Nov 19 2018

Light lake effect snow at times.

Low pressure is moving east of Lake Huron. Lingering snow is
diminishing to spotty lake effect snow. Brief restrictions are
possible overnight, mainly at APN and TVC, but for the most part
VFR conditions are expected. A relative lull will settle in
Tuesday morning, before a clipper low approaches from the nw. This
will expand snow back into some areas late Tuesday, along with
potential MVFR conditions.

Northerly winds will be a touch brisk overnight. Winds will back
westerly Tuesday, initially lighter, becoming gusty again in the
afternoon and evening.

&&

.MARINE...
Issued at 330 PM EST Mon Nov 19 2018

Behind departing low pressure, gustier northerly winds develop
tonight leading to small craft advisory conditions on Lake
Michigan and Huron. Winds will decrease late tonight through a
good part of Tuesday. But, stronger winds arrive once again later
Tuesday afternoon and into Wednesday. Expect marine headlines to
continue.


&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LH...SMALL CRAFT ADVISORY until 5 AM EST Tuesday for LHZ347>349.
     GALE WATCH from late Tuesday night through Wednesday morning for
     LHZ347-348.
LM...SMALL CRAFT ADVISORY until 6 PM EST Wednesday for LMZ323-342-
     344>346.
     SMALL CRAFT ADVISORY from 5 AM Tuesday to 6 PM EST Wednesday for
     LMZ341.
LS...NONE.
&&

$$

UPDATE...JZ
NEAR TERM...BA
SHORT TERM...MG
LONG TERM...MG
AVIATION...JZ
MARINE...BA

NWS APX Office Area Forecast Discussion