Area Forecast Discussion
Issued by NWS Gaylord, MI

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FXUS63 KAPX 190333
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
1033 PM EST Tue Dec 18 2018

.UPDATE...
Issued at 907 PM EST Tue Dec 18 2018

Surface high pressure stretches from the far eastern lakes region
down through the Appalachians. Broad low pressure is across
central Canada. In between, pressure gradient has tightened
considerably across eastern upper and northern lower Michigan with
the last several hours, now leading to some rather gusty winds in
spots.

We had quite a bit of lake induced StratoCu running up Lake
Michigan into the U.P. earlier in the day. But the last bit of
lake induced cloud cover does indeed appear to be rolling up
through parts of eastern upper Michigan and largely thinning
(still OVC014 at ERY). But aside from the lake StratoCu there is
also a fair amount of high cloud cover streaming out of the
Midwest and across northern Michigan that will continue to do so
through the night into Wednesday.

Rest of tonight, no precipitation anticipated of course. But with
a good amount of high cloud cover streaming through, will call it
partly cloudy overall. Meanwhile, we will continue to see gusty
winds throughout the night in many locations. I`ve increased
winds/gusts a bit accordingly.

&&

.NEAR TERM...(Through Tonight)
Issued at 332 PM EST Tue Dec 18 2018

...Seasonably mild weather to continue...

High impact weather potential: None.

Pattern synopsis/forecast: Deep layer high pressure and attendant
strong subsidence regime centered right across the Great Lakes early
this afternoon. Southerly return flow just starting to get better
organized, with warm air advection through the lower levels helping
scatter out much of the earlier cloud cover. Surface temperatures
responding accordingly, with readings pushing up into the 30s,
warmest near and south of Grand Traverse Bay where sunshine started
earlier.

Large scale features remain quite progressive tonight, with current
overhead ridging sliding east, all-the-while next shortwave trough
and developing cold front dig into the northern Plains by morning.

Primary forecast concerns/challenges: Temperature and cloud trends.

Details: A rather uneventful night expected, as despite gradual
retreat of surface high, the overall atmospheric environment remains
rather dry. Passage of subtle mid level impulse later this afternoon
and early across Lake Superior does bring a bit better mid level
moisture across eastern upper Michigan, but not nearly deep enough
to generate precipitation. Otherwise, increasing higher level clouds
and maintenance of southwest winds/warm air advection on backside of
retreating surface high will keep temperatures steady-state or even
rise a bit during the overnight, with readings near Lake Michigan
likely remaining several degrees above freezing.

&&

.SHORT TERM...(Wednesday through Friday)
Issued at 332 PM EST Tue Dec 18 2018

...Light rain and/or snow showers at times...

High Impact Weather Potential...Minimal.

Pattern Synopsis/Forecast...High pressure will have retreated to the
East Coast by daybreak Wednesday as troughing deepens over the
nation`s midsection. Within this longwave troughing, a shortwave
crossing the Canadian Prairies will induce a clipper system that is
progged to cross Ontario Wednesday night-Thursday, dragging a cold
front through the Upper Great Lakes. Meanwhile, an intensifying
southern-stream system will eject from the Gulf States through
Appalachia by Friday, with impacts expected to largely remain east
of northern Michigan.

Primary Forecast Concerns...Precipitation potential through the
period.

Pretty impressive plume of moisture for mid-December is slated to
cross northern Michigan late Wednesday into Wednesday night with
PWATs pushing 0.75" (2-3+ standard deviations above the mean).
However, forcing looks rather unimpressive with only a weak
shortwave progged to lift northeast across northern Michigan.
Consensus now points to rain showers spreading into eastern Upper by
late afternoon, perhaps brushing the Tip of the Mitt as activity
lifts northeast Wednesday night. Temperatures will remain warm
enough to keep precip all in the form of rain overnight. Expect
shower activity to fill in farther south along the cold front as it
crosses northern Michigan during the day Thursday, still in the form
of rain during the day but mixing with snow in the evening as colder
air starts to infiltrate behind the front. Deeper moisture will
progressively strip out from top-down Thursday night, pointing to a
period of light snow showers, drizzle, and freezing drizzle. Not
anticipating anything of impact, however.

Models continue to track farther east with the system lifting
through the Appalachians Thursday night into Friday. This would keep
the bulk of associated precip to the east of northern Michigan, but
the marginally colder air wrapping in around its backside may
trigger some scattered N/NNW flow lake effect snow showers across a
portion of northwest Lower and eastern Upper. Conditions for lake
effect look marginal at best and are trending less favorable, so not
expecting any accumulation.

.LONG TERM...(Friday night through Tuesday)
Issued at 332 PM EST Tue Dec 18 2018

High Impact Weather Potential...Minimal.

Weak ridging at the surface will cross northern Michigan Friday
night into Saturday followed by an influx of colder air Saturday
night. This will kick-start the lake effect machine again heading
into the latter half of the weekend, aided by a shortwave and
clipper system passing through the region. Around an inch or two of
snow accumulation is currently expected, mainly within the W/WNW
flow snowbelts. Drier air encroaches during the day Monday, bringing
a gradual end to the lingering lake effect. Greatest uncertainty
during the extended period surrounds a potential system shown by the
ECMWF to pass by to our south on Christmas Day. Last couple runs
have trended farther south, so will wait to see how this continues
to evolve. Temperatures will trend near or slightly above seasonal
normals through the period.

&&

.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 1032 PM EST Tue Dec 18 2018

VFR conditions anticipated across northern lower Michigan tonight
and much of Wednesday. Per APX 00Z sounding, strong winds have
developed off the surface and may lead to LLWS conditions at the
terminal sites tonight into Wednesday morning.

On Wednesday, low pressure and attending cold front will develop
in the northern plains and advance into the northern/western
Great Lakes heading into Wednesday night. Model solutions suggest
that lower (MVFR) and mid level cloud cover develops upstream
ahead of this system and spreads into the region starting late
Wednesday afternoon into Wednesday night. I`m not entirely
confident that MVFR CIGS develop, or at least develop that
quickly. But erring on the side of caution for now (and for
planning purposes), I have pushed MVFR clouds back into
PLN/TVC/MBL during the afternoon timeframe.

&&

.MARINE...
Issued at 332 PM EST Tue Dec 18 2018

Small craft advisory producing gusty south to southwest winds to
continue across parts of the big waters through Wednesday night.
Winds expected to slacken a bit into Thursday. Passing cold front
and developing low pressure to our southeast looks to bring
another round of advisory conditions to end the week.


&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LH...SMALL CRAFT ADVISORY until 5 AM EST Wednesday for LHZ345>347.
     SMALL CRAFT ADVISORY until 5 AM EST Thursday for LHZ348-349.
LM...SMALL CRAFT ADVISORY until 5 AM EST Thursday for LMZ323-341-342-
     344>346.
LS...SMALL CRAFT ADVISORY until 5 AM EST Wednesday for LSZ321-322.
&&

$$

UPDATE...BA
NEAR TERM...MB
SHORT TERM...MK
LONG TERM...MK
AVIATION...BA
MARINE...MB


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