Area Forecast Discussion
Issued by NWS Gaylord, MI

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FXUS63 KAPX 221615
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
1115 AM EST Wed Nov 22 2017

.UPDATE...
Issued at 1018 AM EST Wed Nov 22 2017

Overlake instability remains large this morning and lake effect
snows, not surprisingly, continue in weaker NW flow. This despite
shallowing out moisture and increasingly anticyclonic low level
flow with higher pressure moving in. Winds will back more westerly
through the day and eventually more SW heading into tonight.
Overlake instability remains more than sufficient over this time,
and see no reason why there won`t at least be flurries where winds
come off the Great Lakes. WAA increasing through the night out
ahead of weak low pressure and a warm front will not completely
eliminate the instability. Thus, any light ongoing lake effect
snows will likely get a little boost overnight. Maybe up to an
inch in WSW flow snowbelts tonight into Thanksgiving morning.

&&

.NEAR TERM...(Today through Tonight)
Issued at 231 AM EST Wed Nov 22 2017

...Diminishing lake effect snow showers today...

High Impact Weather Potential...Minor additional accumulations of
lake effect snow today.

Pattern Synopsis/Forecast...NW flow lake effect snow showers
continue to impact much of our CWA early this morning as low level
CAA continues in the wake of the departing cold front. Lake
aggregate troughing is lending some enhanced low level convergence
to ongoing lake precip production...as is the last vestiges of upper
level troughing as the axis of this feature slides east of Michigan.
Large area of strong high pressure remains parked over the Plains
States...with some low level ridging trying to poke into Michigan
ahead of this feature.

As we head into today...low level winds will gradually back to a
more westerly component by midday/early afternoon as the surface
ridge axis builds into the Great Lakes region. This will redirect
our ongoing lake snow bands northward into far Northern Lower
Michigan along and north of M-32. Overall coverage and intensity of
the snow showers will gradually wane as subsidence and drier low
level air begin to build into the region via the approaching
upstream ridge axis. Locations targeted by NW flow will see an
additional inch or two of lake snow thru the morning hours...with
westerly flow areas receiving well under an inch of additional snow
accumulation this afternoon.

Low level winds will then shift to the SW this evening on the back
side of the ridge axis and ahead of our next fast-moving low
pressure system scheduled to slide thru Michigan late tonight into
Thursday. This system will steadily weaken as is pushes eastward
thru the Great Lakes...and with little in the way of synoptic
moisture to work with...precip chances will be small from this
system. Remaining lake effect precip from today will end this
evening...but will experience a minor revival late tonight as that
weakening moisture-starved low pressure system reaches Michigan. By
this time...low level SW flow combined with weak lift/moisture from
the system will produce some scattered snow showers for the Straits
area and portions of NW Lower Michigan. Any snow accumulations will
be very minor (well under an inch).

High temps today will only warm into the upper 20s and lower 30s.
Low temps tonight will cool back into the low to mid 20s.

&&

.SHORT TERM...(Thursday through Friday)
Issued at 231 AM EST Wed Nov 22 2017

...A few light snow showers possible Thanksgiving Day...

High Impact Weather Potential: Minimal.

Pattern Forecast: By late Wednesday night into early Thursday
morning, weak shortwave energy is expected to be meandering overhead
through longwave troughing anchored across the eastern half of the
CONUS. A weak cold front will be situated over southern Ontario,
tied to low pressure over Hudson Bay. As a result, a few light snow
showers may dot the map early on Thanksgiving Day; otherwise, warm
air advection ramps up in earnest Thursday night through Friday
ahead of a potent clipper system set to track across southern Canada
late this weekend into the upcoming weekend.

Primary Forecast Concerns/Challenges: PoPs Thursday morning and
again through the day Friday.

Latest trends over the past 24 hours yield increased confidence in a
few snow showers roaming parts of northern Michigan (primarily north
of M-72) early Thursday morning in conjunction with the
aforementioned mid level perturbation moving eastward across the
forecast area and well out ahead of the cold front situated over
southern Ontario. Limited deep layer moisture should limit the
overall coverage and intensity of any snow showers, and at this
point have continued to exclude the overly moist NAM (though that
thought warrants keeping an eye on merely due to busy holiday
travel).

Warm air advection then ramps up Thursday night into Friday as a
deepening area of low pressure tracks across southern Canada. Could
be a window late Thursday night into early Friday for a wintry mix
across far northern locales as isentropically driven precip blossoms
to our north, but by far, better chances for more widespread
precipitation arrive later Friday afternoon into Friday
evening...likely to fall in the form of rain.

High temps in the 30s on Thursday warm to above normal under warm
air advection for Friday...ranging from hte low 40s across the far
north to the upper 40s near the M-55 corridor.

.LONG TERM...(Friday night through Tuesday)
Issued at 231 AM EST Wed Nov 22 2017

High impact weather potential: Accumulating lake effect snow chances
increase Saturday through early Sunday.

Much cooler air is expected to wrap into northern Michigan behind
Friday night`s departing system. However, guidance is much less
bullish with the respect to the degree of cold and attendant lake
effect snow chances. Still believe there is a window, albeit brief,
Saturday morning into Saturday night for a period of accumulating
lake effect snow before over-lake instability diminishes as low
level temps begin to warm and high pressure noses in from the south
aiding to scour out any lingering moisture.

Tranquil weather is then anticipated Sunday through the start of
next week with precip chances gradually increasing once again toward
the middle of next week as another system spins up across the
central/northern plains.

&&

.AVIATION...(For the 12Z TAFS through 12Z Thursday morning)
Issued at 631 AM EST Wed Nov 22 2017

Residual NW flow lake effect snow showers will gradually diminish
throughout the day as high pressure begins to build into Michigan.
Focus of highest POPs will shift northward to far Northern Lower
Michigan along and north of M-32 as low level flow backs to the
west today and eventually to the SW tonight on the back side of
the ridge axis. Overall conditions will remain VFR...but will drop
to MVFR/possibly IFR within some snow showers. NW surface winds
around 10 kts will shift to the west this afternoon and then to
the SW tonight.


&&

.MARINE...
Issued at 1115 AM EST Wed Nov 22 2017

Wind speeds have diminished over the Great Lakes as a ridge of
sfc high pressure extended from north Texas into the western Great
Lakes. This ridge will slide southeast tonight, allowing for weak
low pressure and a cold front to approach tonight. Winds will
increase to lower end advisory levels over Lakes Michigan and
Huron into Thursday. Winds really ramp up Late Thursday night and
especially into Friday ahead of stronger low pressure developing
in central Canada. Gales are looking likely on at least Lake
Michigan.

&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LH...SMALL CRAFT ADVISORY from 6 PM this evening to 5 PM EST Thursday
     for LHZ347>349.
     SMALL CRAFT ADVISORY from 6 PM this evening to 6 AM EST Thursday
     for LHZ345-346.
LM...SMALL CRAFT ADVISORY from 6 PM this evening to 5 AM EST Friday
     for LMZ323-342-344>346.
     SMALL CRAFT ADVISORY from 6 PM this evening to 6 AM EST Thursday
     for LMZ341.
LS...NONE.
&&

$$

UPDATE...SMD
NEAR TERM...MR
SHORT TERM...MG
LONG TERM...MG
AVIATION...MR
MARINE...SMD



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