Area Forecast Discussion
Issued by NWS Gaylord, MI

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FXUS63 KAPX 171719
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
1219 PM EST Sun Dec 17 2017

.UPDATE...
Issued at 1024 AM EST Sun Dec 17 2017

Expansive low cloud deck across northern Michigan this morning
with increasing mid cloud moisture spreading into the area from west.
We may see some flurries or even a touch of freezing drizzle this
afternoon (especially northern half of the area) with some
weakish seeder-feeder processes with forecast soundings largely
warmer than -10c. Later this afternoon and evening, 12z models
continue to advertise a brief period of enhanced mid level f-gen
ramping up from the Tip of the Mitt into parts of eastern upper
this evening as an area of low pressure slides south of the area.
This will likely bring a period of light snow to this area, with
some light accumulations possible. Much weaker forcing to the
south with just a few snow flakes or sprinkles.

&&

.NEAR TERM...(Today through Tonight)
Issued at 308 AM EST Sun Dec 17 2017

...A touch of snow in eastern upper MI tonight...

High impact weather potential...minimal.

A relatively uneventful early morning in northern MI. High pressure
is sliding between Lake Huron and James Bay, while a strung-out
stationary front was just south of MI. As the high continues east,
southerly return flow will ramp up, and the front will creep
northward into southern lower MI, resulting in milder wx here. A
sheared-out shortwave will induce a weak wave along the boundary,
moving from northern MO to southern Lake MI by this evening. Neither
forcing nor moisture are particularly impressive, but some small
precip chances may emerge.

In the meantime, earlier weak returns on radar have faded out. Low
clouds are generally pretty extensive across northern lower MI (some
breaks near Lake MI), and are creeping into eastern upper MI from
the se. Low clouds are not extensive to our south (many breaks
along/south of I-96), but a mid-cloud deck is expanding to our west
over WI, and cirrus in encroaching from the sw. Thus, opportunities
for sunshine today look to be few and far between. The low-level
moisture now present is less than 3k ft deep, which is pretty
shallow for flurry/drizzle production. However, moisture will
deepen from s to n as we move thru the afternoon (up to 5-6k ft).
This looks like a better chance of getting some flurries or
freezing drizzle (given entirely moist layer is warmer than -10C),
noting that some weak seeder-feeder processes may occur from mid
clouds aloft.

Max temps today 20 to 30f.

F-gen forcing will have an opportunity to briefly ramp up this
evening, with a weak surface wave passing to our south. Nam/Rap are
both inclined to focus a band of light precip over the Straits area
and eastern upper MI this evening, then waning. This would fall as
snow, and could see a half-inch get laid down in parts of eastern
upper. To the south, forcing is lesser and dry air between 10k and
3k ft will be more difficult to overcome. Still, a few flakes could
get down form time to time. Generally will be cloudy, though late in
the overnight eastern upper MI gets on the downglide side of the
fgen couplet, and thinning clouds could be seen in western Chip/Mack
Cos.

Temps will not drop off much with the cloud cover and low-level warm
advection. Mins will be in the upper teens to mid 20s, and those
will be seen relatively early in the night.

&&

.SHORT TERM...(Monday through Tuesday)
Issued at 308 AM EST Sun Dec 17 2017

...Milder with some snow or mixed precip followed by lake effect...

High Impact Weather Potential: Possible icy roads Monday night and
early Tuesday in some spots.

Primary Forecast Concerns/Challenges: Precipitation type Monday
night.

A much milder southwest flow Monday leads to highs of well into the
30s to the lower 40s. An Alberta Clipper moving by to the north
along with an associated cold front will then bring some light
precipitation to the region overnight Monday. It looks marginally
cold enough for mainly snow north with perhaps a mix of rain and
snow or all rain south especially near the lake shores of Lake Huron
and Lake Michigan. Any rain that falls on frozen road surfaces would
likely lead to icy conditions so will add that wording into the
hazardous weather outlook. Snow accumulations generally an inch or
less. Brisk winds and colder air moves steadily into the region
Tuesday into Tuesday night. It should be cold enough by Tuesday
afternoon to start up the lake effect machine. Moisture is fairly
shallow with inversion heights under 5,000 feet so snow
accumulations are not expected to get out of hand (maybe an inch or
two). Falling temperatures through the day with brisk northwest
winds.

.LONG TERM...(Tuesday night through Saturday)
Issued at 308 AM EST Sun Dec 17 2017

...Lake effect then all eyes will be on the track of low pressure...

Lake effect should generally remain light Tuesday night into early
Wednesday as inversion heights are a mere 4,000 feet or so and deep
moisture is lacking. High pressure nosing in from the northwest
along with warm air advection at lower levels and lighter winds
should limit lake effect activity Wednesday. Attention will then
turn to a developing area of low pressure in the central Plains.
This system should increase warm air advection/isentropic ascent
Wednesday night leading to mainly light snow development. The GFS
has joined the previous ECMWF solutions with a weaker and more drawn
out system (affects through at least Friday). The 17/00z ECMWF
tracks the low much farther north into far northern lower while
deepening it. Either way, a tight thermal gradient will make the
precipitation type a tough call. Expect a long duration
precipitation event but it`s way to early to determine the details.
At this point the best chance of an all snow event is across eastern
upper and far northern lower while a mix with or a change over to
all rain is across central and southern counties. Another shot of
much colder air and lake effect are likely to follow for Friday
night into next weekend (could be significant). Looking farther
out...the chances for brutally cold arctic air to invade the region
is increasing for Christmas week. This is due to a possible
abnormally strong western ridge which could open up the floodgates
for the cold air.

&&

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 1215 PM EST Sun Dec 17 2017

Widespread MVFR cigs through the TAF period with periods of IFR
cigs possible tonight. Weak weather system may bring a few
flurries or some patchy light freezing drizzle tonight, but
chances are so low that they were not included in the terminals.
Areas of fog likely developing tonight, generally MVFR vsbys with
localized IFR vsbys possible. Fog dissipates on Monday and cigs
gradually improve.

&&

.MARINE...
Issued at 308 AM EST Sun Dec 17 2017

Southeast winds today, as high pressure moves from Ontario to
Quebec. Winds will veer sw tonight, and increase considerably
during the day Monday. Relatively favorable marine conditions
thru tonight, but gales may emerge on Monday and Monday night on
some waters.


&&

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

$$

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



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