FXUS63 KAPX 180344

Area Forecast Discussion
National Weather Service Gaylord MI
1144 PM EDT Wed Oct 17 2018

Issued at 946 PM EDT Wed Oct 17 2018

Lake effect showers are cutting off rather abruptly from sw to
ne. Outside of Presque Isle/Alpena Cos, activity is largely done
in northern lower MI. Those are extensions of Superior bands that
also continue to impact eastern upper MI. Models suggest it will
still take a hefty portion of the night (til 4-5am) for snow/rain
showers to exit the St Marys Valley. Cloud cover has (as expected)
lingered longer, with healthy stratocu remaining over a good
portion of nw lower MI. However, erosion continues along the sw
edge of the cloud shield. Will generally have to slow the clearing
trend compared to model progs (as is typical), but will still go
with a decreasing cloud trend. And will tweak min temps very
slightly in response.


.NEAR TERM...(Through Tonight)
Issued at 245 PM EDT Wed Oct 17 2018

...Lake effect rain/snow showers come to an end...

High impact weather potential: None.

Pattern synopsis/forecast: Unseasonably chilly airmass draped
across the region, courtesy of one amplified mid and upper level
pattern consisting of stout western ridging and just as impressive
northeast NOAM centered troughing. Overhead deep layer northwest
flow the result, with those winds and chilly air drumming up a bit
of lake effect clouds and rain/snow showers across the area today.

Large scale features remain quite progressive heading through
tonight, with mid level height relaxing as trough axis pinwheels off
to the northeast. Expansive area of surface high pressure builds
into the Ohio Valley, the northern extent of which builds across the
northern Great Lakes quickly this evening. Attendant developing warm
air advection regime and quick loss of any synoptic moisture
contribution looks to bring a gradual end to the lake processes as we
head through the night.

Primary forecast concerns/challenges: Addressing lingering lake
effect rain and snow showers and overnight temperature trends.

Details: Favorable conditions for lake processes about set to
peak as subtle mid level wave and attendant moisture plume rotate
overhead this afternoon. Post-wave drying and larger scale
subsidence will be quite significant, with guidance derived
soundings showing a quick loss of synoptic moisture contribution
in an ever shrinking convective boundary layer. Per the usual,
expect guidance to be just a bit aggressive ending lake processes,
so gotta believe at least some scattered light lake effect rain
and snow showers will persist into this evening. Developing
overnight warm air advection will help hasten the end of the lake
effect, with a lowering subsidence inversion dropping below ice
nucleation level. So, despite still a marginally favorable low
level thermal environment, do believe conditions will trend dry
overnight, with all lake driven showers out of the area by the
early morning hours of Thursday. A chilly night, with lows mostly
in the 20s.


.SHORT TERM...(Thursday through Saturday)
Issued at 245 PM EDT Wed Oct 17 2018

...Mild with Rain Friday, colder with lake effects Saturday...

High Impact Weather Potential: Minor with continued chances of early
season snow across interior northern Lower and east Upper Michigan
through Saturday night.

Primary Forecast Concerns/Challenges: Precipitation type and
snowfall amounts into Sunday.

Pattern Synopsis/Forecast...Dry with sun for Thursday as an area of
high pressure quickly passes over the region and warming mid lvl
temperatures greatly reduce lake induced pcpn across northern
Michigan. A clipper moving over the northern Great Lakes Friday,
will lift into Quebec Saturday, while a narrow area ridge of high
pressure briefly passes over the state again for Sunday. At upper
levels, weak 500mb ridge Thursday and mild mid levels (850mb temps
around +8c) will push east while an upper trough and much colder mid
lvl temps (850mb temps dropping to -8c) settle overtop of the state

Will continue the dry forecast on Thursday over northern Michigan
with sun and afternoon temps warming into the upper 40s. Rain will
begin to overspread northern Michigan Friday in advance of an
approaching clipper. Will keep at least likely pops in across much
of the cwa through Friday evening as 850/500mb qvectors show strong
convergence over the cwa in response to the clipper and 500mb trough
pushing across the region. Model soundings keep low lvl vertical
temperature profiles warm enough (freezing levels remaining well
above 1300ft into Saturday), to mention an all rain event for
northern Michigan into Saturday morning. However, model soundings
show freezing levels dropping through Saturday afternoon (dropping
below 500 ft), as 850mb temps in the approaching upper trough fall
to around -8c between 18z Sat and 00z Sunday. Lake induced pcpn will
begin to dominate the western lakes Saturday evening and Sunday as
over water instability increases and inversion deepen to over 7k ft
(850mb dropping to -8c and nrn Great Lakes water temps linger around

.LONG TERM...(Saturday night through Wednesday)
Issued at 245 PM EDT Wed Oct 17 2018

A wet and cold pattern through the weekend, before trending toward
warmer and drier condtions. A clipper over the eastern Great Lakes
Saturday will slowly exit the region Sunday, before a second
(weaker) clipper passes over the state Tuesday. The deep upper
trough and cold pool alfot (850mb temps around -9c) centered over
the Great Lakes Saturday, will slowly push east during the weekend,
while weakening upper lvl cyclonic flow and slightly warmer mild
level temps linger into the upcoming work week. Overall will
continue the current forecast of well below normal temperatures this
weekend with continued lake induced pcpn into Sunday afternoon, with
a drier and milder period to begin the work week.


.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1144 PM EDT Wed Oct 17 2018

VFR. Becoming breezier again Thursday. LLWS Thursday evening.

Strong high pressure in se Iowa will move gradually ese across the
Ohio Valley on Thursday. Drier air is diminishing lake effect
precip, and eventually VFR stratocu deck will also erode. Solid
VFR conditions Thursday.

Somewhat brisk nw winds will back to the west and then sw late
tonight and Thursday. Winds will become gusty again Thu afternoon,
especially near Lake MI. LLWS develops Thu evening as sw winds
increase just off the surface.


Issued at 245 PM EDT Wed Oct 17 2018

Per the usual for fall, the busy marine weather continues.
Small craft advisory conditions will continue tonight as gusty
northwest winds slowly subside. Strong high pressure pushing across
the Ohio Valley will swing winds around to southwest on Thursday,
with these winds rapidly increasing in speed, especially for the
afternoon and evening. Gale force wind gusts look likely on northern
Lake Michigan during this period, with small craft advisory
conditions elsewhere. These gusty southwest winds will continue
right into Friday as the next fast moving cold front approaches the


LH...SMALL CRAFT ADVISORY until 6 AM EDT Thursday for LHZ345>349.
LM...SMALL CRAFT ADVISORY until 6 AM EDT Thursday for LMZ323-341-342-
     GALE WARNING from 2 PM Thursday to 2 AM EDT Friday for LMZ341-
LS...SMALL CRAFT ADVISORY until 6 AM EDT Thursday for LSZ321-322.



NWS APX Office Area Forecast Discussion