Area Forecast Discussion
Issued by NWS Gaylord, MI

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FXUS63 KAPX 170413
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
1113 PM EST Sun Feb 16 2020

.UPDATE...
Issued at 1013 PM EST Sun Feb 16 2020

Strong high pressure remains centered over the Western Great Lakes
region late this evening. Light westerly flow with plenty of cold
air in place continue to produce some lake clouds and light snow
showers across some of our snowbelt areas. Rest of our CWA is
clear. In the meantime...low pressure continues to organize to the
lee of the Rockies. Leading edge of increasing low and mid clouds
is making its way thru Wisconsin...with little indication of any
precip actually reaching the ground despite some spotty radar
echoes.

Expect an overall diminish in lake cloudiness overnight as low
level WAA begins as the high center shifts east of Lower Michigan.
We will see some increase in clouds across our far SW late
tonight...but majority of increasing clouds should happen during
the day on Monday. Will make some adjustments to clouds and POPs
for the balance of the night...but overall expect a quiet and cold
night with low temps mainly in the single digits above and below
zero.

&&

.NEAR TERM...(Through Monday)
Issued at 252 PM EST Sun Feb 16 2020

...A Cold Night Upcoming...

High impact weather potential: None.

Pattern synopsis: Broad mid and upper level troughing centered
across much of the northern CONUS early this afternoon, the center
of which is a piece of the polar vortex rotating just north of
Hudson Bay. Several low amplitude shortwaves embedded within this
larger trough axis...with lead shortwave (responsible for
yesterday`s quick hitting shot of light snow and gusty winds) now
well to our east, with secondary wave and attendant cold front
passing through our area today. Further west, third wave of the
bunch seen diving southeast across southwest Canada (this will be
the one responsible for our next round of widespread accumulating
snow Monday night). Surface features dominated by large area of high
pressure building into the western Great Lakes...with this ridging
extending down through the lower Ohio Valley. Brief shot of cold air
advection on the front-side of this high responsible for the
production of some lake clouds and light snow showers today,
especially so off Lake Superior where the coldest air resides.

As mentioned the last several days, flow regime is a progressive
one, and shows no signs of slowing down as we head through the
beginning of this week. This forces a steady east retreat of western
Great Lakes high pressure, all-the-while that Canadian wave digs
into the upper Mississippi Valley by later Monday afternoon.

Primary forecast concerns/challenges: Addressing diminishing lake
snows this evening, overnight cloud and temperature trends, and the
beginning stages of that system to arrive Monday night.

Details: High pressure builds quickly overhead this evening, ending
any remaining light lake effect snow showers in the process. Would
expect skies to continue to scatter out this evening, with higher
level clouds potentially on the increase late. This sets the stage
for temperatures to free-fall this evening and early overnight.
Light winds will only help the temperatures plummet, and have forged
ahead with the overnight forecaster idea of cutting even the coldest
statistical guidance by at least a few degrees. Thus, expect lows to
drop below zero in our traditional ice box locations, with the
coldest readings likely centered in the Au Sable River Valley where
skies will remain clear the longest.

Those increasing high clouds later tonight signal the start of top-
down saturation tied to the next approaching wave and developing
surface low pressure. Low level environment will be awfully dry to
start, and will likely take much of Monday to saturate in persistent
warm air advection pattern. May see some light snow attempt to
develop during the afternoon, but the vast majority of the
accumulating snow will hold off until the overnight period. While
temperatures recover nicely from chilly early morning readings,
reaching the upper 20s and lower 30s during the afternoon,
increasingly gusty southeast winds will make it feel several degrees
colder.

&&

.SHORT TERM...(Monday night through Wednesday)
Issued at 252 PM EST Sun Feb 16 2020

...Winter Isn`t Done Yet...

High Impact Weather Potential...Moderate to heavy amounts of snow in
Eastern Chippewa and Mackinac Counties.

Pattern Synopsis/Forecast...As the low moves across C Lower (roughly
on a line from MKG to APN), the forecast area remains mainly in the
cold enough for all snow, except maybe near Saginaw Bay, as the sfc
temperatures may get into the mid 30s around 12z/Tue. Otherwise, it
will be snow across the region, and with the lake component from the
SSE winds off Lake Huron, in eastern Chippewa, and Mackinac counties,
the heaviest amounts are expected to be near Detour/Drummond island
(at least with the last two model runs). Amounts look to be moderate
to heavy (4-8" amounts)the last two runs for E Upper, while the
amounts in N Lower are light to moderate, with the lighter amounts
near M-55 with the possibility of rain mixing in near Lake Huron and
primarily near Saginaw Bay. The sfc low looks to get into Lake Huron
around 09z/Tue to 12z/Tues, depending on the model, but for the most
part this should be when the cold air breaks loose and begins the
cold advection for Tuesday. The GFS is a little slower than the
ECMWF with the colder air over N Lake Michigan, but by 00z/Wed, we
should be cold enough to have some prolonged lake effect snow bands,
with light amounts, in N lower and maybe some light to moderate
amounts in  E Upper. The three US models (NAM, GFS, and SREF) all
have some significant LES near Whitefish point through the day on
Wednesday.

Primary Forecast Concerns...With the models coming in with the last
2-3 runs fairly consistent, think that the amounts look good, with
the system as moves through the region. The one thing that could go
wrong with the this forecast is underestimating the amount of Lake
Huron support in E Upper, which the models seem to have. It is
possible that if the 850 mb temperatures can still remain a bit
cooler long enough before the warmer air gets into the system, then
there could be more heavier (possibly warning criteria) snow in the
eastern zones of both Chippewa and Mackinac counties. However at
this point things point to advisory level with the amounts.

.LONG TERM...(Wednesday night through Sunday)
Issued at 252 PM EST Sun Feb 16 2020

High Impact Weather Potential...minimal.

Extended (Wednesday evening through Sunday)...The LES holds on for a
few hours Wednesday night, but the winds begins to back from the
northwest to the west overnight, so that by Thursday morning the
bulk of the LES is north of CYAM, on a westerly wind. It`s then that
the rest of the extended forecast period gets very quiet as a
prolonged dry spell looks to set in with warm SW winds through the
weekend with above normal temperatures. Although Saturday, on the
GFS there is a very small chance for something, but most of that is
in Ontario. So will leave it out for the time being. Models are
going for a run at 40, in E Upper on Sunday, while a good portion of
N Lower will make it. So the general trend is for drying out and
warming temperatures through the rest of the week.

&&

.AVIATION...(For the 06Z TAFS through 06Z Monday night)
Issued at 1113 PM EST Sun Feb 16 2020

High pressure will slide east of Michigan tonight with low
pressure advancing into the Western Great Lakes region on Monday.
Aside from some lingering lake effect clouds and flurries across
far Northern Lower Michigan...VFR conditions will prevail at all
TAF sites overnight. Clouds will increase and cigs will lower on
Monday as moisture increases ahead of that approaching low
pressure system....but cigs will generally stay VFR. Still appears
increasing chances of snow and resulting deteriorating conditions
will hold off until Monday night. Winds will become
light/variable overnight and then shift to the SE and strengthen
to 10 to 20 kts with some higher gusts expected.

&&

.MARINE...
Issued at 252 PM EST Sun Feb 16 2020

Winds become light tonight as high pressure builds directly
across the big waters. Southeast winds increase Monday, and
especially Monday evening, as developing low pressure crosses the
area. Widespread small craft advisory conditions appear likely by
late Monday and Monday night. Winds become northwest and remain
gusty on Tuesday.

&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LH...NONE.
LM...NONE.
LS...NONE.
&&

$$

UPDATE...MR
NEAR TERM...MB
SHORT TERM...JL
LONG TERM...JL
AVIATION...MR
MARINE...MB



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