Area Forecast Discussion
Issued by NWS Gaylord, MI

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993
FXUS63 KAPX 181101
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
601 AM EST Sun Feb 18 2018

.NEAR TERM...(Today through Tonight)
Issued at 353 AM EST Sun Feb 18 2018

...Light precip through tonight...

High Impact Weather Potential...Minor. Some light snow and light
icing possible in eastern upper Michigan tonight.

Pattern Synopsis/Forecast...Composite surface/upper air analysis
reveals a progressive westerly flow pattern across the CONUS with
strong short wave energy dipping down through the PAC NW. Low
amplitude short wave impulse that brought some light snow to the
region last night is now progressing quickly through the eastern
lakes into New England. Parent surface low is over the eastern
Hudson Bay region with a trailing cold front the arcs down through
the northern lakes region and back into the central/northern
plains to low pressure across the front range of the Rockies.

Upstream short wave energy will further dig into the western CONUS
through tonight...forcing downstream SW flow through the plains
and Great Lakes while impressive upper level ridging builds across
Florida and the far SE states. This will force a rather impressive
thermal/moisture gradient through the northern Great Lakes/upper
Midwest region...with an inverted surface trough nosing up into
northern Michigan along the gradient.

Primary Forecast Concerns...Initial precip chances (and type)
through tonight as warm advection and F-gen processes begin to
unfold across the northern lakes. Early on...cold front still
looking to sag into northern Michigan this morning with colder
air skirting the region early before the flow quickly turns back
around and begins to shove the front back northward as a warm
front. With that colder air...we do have some minor lake effect
snow showers/flurries ongoing this morning and I`ve had to add
some PoPs to the forecast early.

Meanwhile...upstream warm advection forcing is already developing
within the southerly return flow across the northern plains with
a little bit of light returns evident on the national radar
mosaic. This initial warm advection forcing will develop eastward into
northern Michigan this afternoon along the developing/tightening
thermal gradient and may bring a little light snow/flurries across
upper Michigan and parts of northern lower Michigan. I inherited
some higher PoPs this afternoon particularly across eastern upper
Michigan. But...per forecast soundings that reveal a wedge of dry
air in the lower-mid levels that hangs on through the afternoon
yielding not much more than a brief period of very light snow/
flurries. Thus...have trimmed PoPs back into just the chancy
category.

Tonight...tightening thermal gradient and inverted surface
trough/quasi-stationary front continues to develop and nose
across the U.P. and into the Straits area as we go through the
night...aided by a weaker piece of short wave energy that advances
up through the northern lakes region. Better forcing/deeper
moisture/higher QPF potential sets up into the cold air...N/W of
the trough axis and largely just outside of this CWA across Lake
Superior. Across eastern upper Michigan...forecast soundings
largely support some light snow this evening transitioning more
into freezing drizzle later tonight...as moisture aloft thins out
temporarily heading into Monday. No plans as of yet to issue any
winter weather headlines...but suspect we will need something for
later tonight and especially the beginning of the work week as
freezing drizzle/freezing rain concerns increase.

&&

.SHORT TERM...(Monday through Tuesday)
Issued at 353 AM EST Sun Feb 18 2018

...Messy Weather Upcoming the Middle of the Week...

High Impact Weather Potential...Freezing drizzle/rain will impact
areas along and north of M-32 Monday through Tuesday.

Pattern Synopsis/Forecast...The models are beginning to come
together with a track consensus as the sfc low/inverted trough at
12z/Mon is roughly along the same axis on both the GFS and ECMWF.
The initial precipitation type looks to be a mix of drizzle/freezing
drizzle/snow as the sfc temperatures and the soundings are right on
the edge of freezing and a dry air layer above 850 mb and below
-10c. However, by the afternoon, the moisture in the column has
filled in a bit, and things become a transition to RA/FZRA/and a bit
of snow. Although, looking at the 850 mb temperatures warm air is
pushing into the Straits keeping things mainly snow in the UP.

That changes in the evening with the ECMWF pushing a fair amount of
warm air (above 0c) air into E Upper by 12z/Tues. The GFS puts some
warm air into E Upper, by 12z/Tues, but keeps Whitefish Point
solidly in the cold air and snow. The warmer air doesn`t get into E
Upper on the GFS until 18z/Tues. This is when the two models
disagree with the evolution sfc low with the GFS maintaining an
inverted sfc trough across lower Michigan, while the ECMWF spins up
a decent sfc low that tracks into E Upper, probably putting the
region into a fair bit of rain. Consensus model blends have the
temperatures below freezing in portions of E and C Upper, and above
freezing everywhere else to the south. which stays that way until
overnight when the cold front moves through the region.

Primary Forecast concerns...The ice amounts agrees with WPC`s idea
of 0.10" in the 12-24 hour time frame, mainly Monday night. The
problem become the placement of the ice. WPC places most of the ice
right over N Lower. While the blends, which don`t include the ECMWF
seem to have the ice a little farther to the north. Needless to say
that there isn`t a lot of confidence in where the ice is the best.

One thing that seems certain, is that when the cold front moves
through, thinking that there isn`t much in the way of freezing rain.
the models seem to be cooling things off but have residual pops in
the forecast so that it turns out FZRA instead of RA or SN.

.LONG TERM...(Tuesday night through Saturday)
Issued at 353 AM EST Sun Feb 18 2018

...A Brief Cool off, then Gradually Warming for the Weekend...

Extended (Wednesday through Saturday)...High pressure builds into
the Upper Great Lakes Wednesday following the storm on Tuesday.
Models builds the 500 mb heights through the end of the week. ECMWF
keeps things dry from Wednesday through thursday night, while  the
GFS is dry Wednesday through Friday night. The ECMWF and GFS are
then 12-18 hours out of Phase with each other, with one model
bringing something in, as the other model is pushing a storm out. so
low confidence on the forecasts past Thursday night.

&&

.AVIATION...(For the 12Z TAFS through 12Z Monday morning)
Issued at 601 AM EST Sun Feb 18 2018

Lingering band of MVFR cloud cover remains across portions of
northern lower Michigan...tied to Lake Michigan as some slightly
colder air spreads into the region. TVC most likely impacted with
westerly flow off the open parts of the lake. MVFR cloud cover
will thin out later this morning and this afternoon as winds turn
into the SW/S and pulls some warmer air back into the region. But
there will be thicker mid and high cloud cover aloft as that
warmer air returns.

Tonight...VFR conditions anticipated. But further increasing
southerly flow will ultimately pull more moisture and low cloud
cover into the region heading into Monday (after the current TAF
period). Increasing southerly flow also leads to LLWS conditions
at the terminal sites tonight.




&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
&&

$$

NEAR TERM...BA
SHORT TERM...JL
LONG TERM...JL
AVIATION...BA



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