Area Forecast Discussion
Issued by NWS Gaylord, MI

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922
FXUS63 KAPX 190259
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
959 PM EST Sat Nov 18 2017

.UPDATE...
Issued at 959 PM EST Sat Nov 18 2017

Forecast for overnight into Sunday morning is not without
concerns. The basic premise remains unchanged: low pressure over
eastern Lk Erie will continue to move east. Associated synoptic
precip has exited ne lower MI. Chilly nnw winds behind the low
will contribute to increased over-lake instability. Lake effect
precip has already developed off of Lakes Superior, MI, and Huron.
This activity is light, with rain in coastal areas, mixing with
and turning to snow as you enter the higher elevations.

850mb temps over the upstream lakes are around -6C now, but will
drop into the lower minus teens by daybreak. The colder air will
increase instability over the warm lakes, resulting in more
vigorous lake effect precip overnight, and will eventually turn
coastal areas to snow. Though synoptic support does not exist for
much of the night, a shortwave diving in from the nw should result
in an uptick on Superior late in the overnight, and perhaps on
northern Lake MI toward morning. Inversion heights of 6-7k ft are
unremarkable.

An not too terribly concerned with eastern upper MI. Prevailing
nnw flow should focus best banding into Luce Co, with the tail end
getting into western Mack. Will adjust accums to allow for circa
2 inches in western Mack (south of ERY), and will reduce amounts
in Chip Co.

Hi-res models offer differing solutions, and differing trends,
into nw lower MI. RAP runs have trended drier with time, keeping
liquid QPF less than 0.20 inches thru Sunday morning. HRRR has
been trending wetter, with the Luce Co band poking into the `Big
5` counties in northern lower. Max HRRR QPF is in excess of 0.40
inches along a narrow axis. This is concerning, but HRRR runs are
already producing vigorous banding into upper MI now, and those
vigorous bands are not evident...not yet. For this reason, will
not be increasing snow amounts in nw lower MI by too much. Will
push max snowfall in northern lower MI eastward tonight, to
between M-66 and I-75, with max accums thru morning of 2-3 inches.

When combined with expected snowfall Sunday morning, we`re getting
right to the edge of advisory-level accums. Am not going to jump
on this yet, but will be keeping an eye out. If banding on
Superior becomes more prominent on MQT/Montreal Rvr radars, and/or
obs out of ERY show the same, could well pop an advisory later
this evening.

&&

.NEAR TERM...(Tonight through Sunday)
Issued at 345 PM EST Sat Nov 18 2017

High impact weather potential: Slick spots on area roadways possibly
developing tonight. Snow covered and slippery roadways possible
Sunday.

...Lake effect kicking in...

Synoptic moisture peels out to the northeast through this evening as
low pressure continues to track by to our south. Progressively
colder air then advects in behind the departing system increasing
over lake instability through Sunday. This will lead to the
development of northerly flow lake effect rain and snow showers
later this afternoon which will change to snow early tonight. The
flow will back overnight into the north northwest before finally
settling into the northwest late tonight into Sunday as lake effect
snow continues. Activity may become enhanced and more widespread for
a time Sunday as a short wave drops down through the flow. Areas
roads may become slick due to falling temperatures and any rain
showers transitioning over to snow showers. Snowfall accumulations
tonight expected to range from 1 to 2 inches along and west of US
131. Accumulations Sunday of 2 to 3 inches are expected in the
normal snow belts of northwest lower and eastern upper.

&&

.SHORT TERM...(Sunday night through Tuesday)
Issued at 400 PM EST Sat Nov 18 2017

Pattern Forecast:  Active pattern continues through next week.
Background pattern remains positive PNA, with high amplitude
ridging over the western CONUS and troughing over the eastern. A
series of clippers running along the baroclinic zone, and through
the Great Lakes, will provide periodic reinforcement of the
eastern troughing with colder air helping to deepen the troughing.
The currently negative, and forecast to become more so, arctic
oscillation will certainly help the colder air push south as well.
Much of the week will see this up and down mix of brief height
rises being suppressed by a clipper before a more prolonged cold
push next weekend.


Primary Forecast Concerns/Challenges: Timing will likely be an
issue, as is often the case with these active clipper patterns.
Another rain to snow transition expected Tuesday.

Any lingering lake effect Sunday night will gradually be shut down
through the morning Monday as high pressure to our south backs the
flow to the SW and increase WAA. This will moderate temperatures a
bit, with Monday and Tuesday high temperatures near 40. Though the
Tuesday high will likely be overnight for many areas, as the next
clipper in line will arrive with colder air and precipitation by
early afternoon. Those east of I-75 may see the arrival later in the
afternoon. Precipitation will arrive mostly liquid, with a fairly
quick change over to snow through the afternoon. This should carry
into Wednesday with lake effect. Winds will begin to pickup Monday
night, remaining gusty through Tuesday night.

.LONG TERM...(Tuesday night through Saturday)
Issued at 345 PM EST Sat Nov 18 2017

Pattern remains progressive through the extended, with clippers
moving through the flow working to suppress height rises trying to
work into the region. This will bring a very familiar period of
clipper system precip, followed by some lake effect, then a brief
clearing. Signs point to a more prolonged visit of cold air starting
Sunday.

&&

.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 640 PM EST Sat Nov 18 2017

Widespread mixed precip is departing ne lower MI, as low pressure
advances across Lake Erie. Lake effect showers (mixed rain/snow)
are already developing into parts of nw lower MI. These will
become more extensive, while gradually turning to all snow as
colder air enters the region. Best snowfall amounts will occur
east of TVC. Do expect occasional vsbys restrictions at TVC,
perhaps into IFR territory at times late tonight and Sunday.
Otherwise, MVFR to VFR cigs will prevail.

NNW winds will be gusty tonight and Sunday, while gradually
backing to the WNW on Sunday.


&&

.MARINE...
Issued at 345 PM EST Sat Nov 18 2017

Lower end gale force gusts are expected for late this afternoon and
tonight for much of Lake Michigan and Huron. This is due to a
tightening pressure gradient on the backside of developing low
pressure that crosses the srn and eastern Great Lakes. Solid
advisory winds elsewhere. NW winds taper off some heading through
Sunday afternoon and night while also backing more out of the west,
but gusty conditions still expected due to deep overlake
instability. Rain and snow showers will transition over to lake
effect snow showers tonight into Sunday evening.


&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LH...SMALL CRAFT ADVISORY until 7 PM EST Sunday for LHZ345-346.
     GALE WARNING until 7 AM EST Sunday for LHZ349.
     GALE WARNING until 11 AM EST Sunday for LHZ347-348.
LM...SMALL CRAFT ADVISORY until 7 PM EST Sunday for LMZ341.
     GALE WARNING until 7 AM EST Sunday for LMZ323-342-344>346.
LS...SMALL CRAFT ADVISORY until 7 PM EST Sunday for LSZ321-322.
&&

$$

UPDATE...JZ
NEAR TERM...AS
SHORT TERM...AM
LONG TERM...AM
AVIATION...JZ
MARINE...AS



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