Area Forecast Discussion
Issued by NWS Gaylord, MI

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FXUS63 KAPX 201144

Area Forecast Discussion
National Weather Service Gaylord MI
644 AM EST Mon Feb 20 2017

.NEAR TERM...(Today and tonight)
Issued at 333 AM EST Mon Feb 20 2017

...Rain tonight, mainly late...

High impact weather potential...a slight chance for freezing rain
tonight in the Sault and environs.

Sharp 500mb ridge axis is presently over the western lakes, and will
move overhead early afternoon today. Mid/high clouds associated with
upstream warm advection will continue to spill into the region,
thickening further as the ridge passes. Falling heights and
increasing moist advection will eventually allow rain to break out
late tonight. In general, a slowing trend is noted in the 00Z model
guidance. Precip trends are the primary concern, with max temps
today a secondary one.

Today...quiet, especially given the noted slowing trend, and warm
again. We will see thickening mid/high clouds, especially in the
afternoon as the upper ridge passes. A southeast breeze will also
increase in the afternoon, between surface high pressure in Quebec
and an incoming cold front entering MN/IA. The onshore wind from a
chilly Lake Huron will keep eastern upper/ne lower MI somewhat
cooler, while providing downslope warming into parts of nw lower MI.
In general, will steer max temps a bit above guidance, which has
worked well the last few days. Max temps will range from the upper
30s in far se Chip Co, to the mid/upper 50s in the TVC/Leland/MBL
area. TVC record high for today is 57f and will be approached; other
records appear safe.

Tonight...incoming 500mb trof will deamplify somewhat as it pushes
into the western lakes by morning. Associated cold front will reach
central upper MI and eastern WI. Narrow warm conveyor belt just
ahead of the front will move into northern MI, especially overnight.
Sharp increase in theta-e advection at low/mid levels will overcome
initially dry air, producing a band of showers that moves into at
least western and central sections of the forecast area. The vast
majority of the model suite (including the 00z ECMWF) has the
slowing trend mentioned above. Only very small chances for showers
in order before 11pm in western sections. Precip ramps up after
that, but outside of far western Mack Co, likely pops or higher are
not in order until after 2am. Those do expand across most of
northern MI overnight, but from APN to Standish pops top out at 50
percent toward dawn. No mention of thunder here; a brief, weak
instability plume develops to our west this evening, but with the
upper trof deamplifying it can`t maintain itself further east
overnight. This is in agreement with the SPC outlook.

One item of note is potential p-type issues in part of the St Marys
Valley, including the Sault. Rapid increase in warm advection aloft
(850mb temps at least 4C) will pretty definitively result in all
liquid precip. However, there will be a short window where surface
temps will hover near freezing in parts of Chip Co. This is not an
ideal set-up; getting fzra in the middle of an extended stretch of
warm wx is highly non-classical. But evap cooling may allow a few
spots to bottom out at 31f or so before coming back up. Forecast
builder-generated grids portray a slight chance of fzra in parts of
ne Chip Co, including the Sault and Sugar Isl. Will let that ride,
but will refrain from a mention in the HWO.

Qpf amounts 0.25-0.50 inches in the west and north; less than that

Min temps lower 30s to lower 40s.


.SHORT TERM...(Tuesday through Wednesday)
Issued at 333 AM EST Mon Feb 20 2017

...Still mild with rain ending Tuesday morning...

High Impact Weather Potential...Minimal, but will have to monitor
river levels following the rain Tuesday morning given all the recent
snowmelt. Expect plenty of ponding water on roads and quick rises on
small streams.

Pattern Synopsis/Forecast...Cold front will be pushing east across
northern Michigan Tuesday morning with most of the rain exiting
northeast Michigan by mid to late morning. Not much of a "cold"
front, however, as there is hardly any cooler air behind it (mostly
just a drier airmass). In fact, WAA will develop again by Tuesday
afternoon as low level flow turns southwesterly. If clouds clear out
substantially behind the front by afternoon as per the GFS and
ECMWF, this WAA will help push temperatures into the 50s across
northern Lower and low to mid 40s across eastern Upper. Some models
hinting at a weak shortwave possibly triggering a few showers over
eastern Upper Tuesday night, but forecast soundings show a pretty
dry layer above the surface that would make it difficult for much of
anything to reach the ground. A stronger shortwave associated with a
clipper type system will bring a better chance of showers Wednesday
afternoon into the evening.

Meanwhile, remaining snowpack will continue to rapidly melt through
the period with dewpoints staying above freezing and even climbing
into the 40s during the daytime hours across northern Lower. Current
snow water equivalent ranges from around 3 to 5 inches across
eastern Upper and up to about 3 inches across interior northern
Lower. Thus, expected rain on top of all this snowmelt will likely
lead to efficient runoff into area streams and rivers.

Primary Forecast Concerns...Models remain split on how quickly the
rain will push out of the area with the front Tuesday morning. There
had been agreement between the GFS/ECMWF for a speedy exit of the
rain after 12Z, but the 20.00Z ECMWF has slowed up a bit. The NAM is
the slowest solution, and the CMC lies somewhere in between. The
19.12Z hi-res ARW and NMM also had been showing a speedy exit, but
they too slowed up a bit with the 20.00Z run. All things considered,
it looks like the rain should clear our eastern counties by mid to
late morning.

Recent models runs have been trending a bit further north with
Wednesday`s clipper system. Have leaned more on GFS/ECMWF for their
good agreement and decent run-to-run consistency. In contrast, the
NAM develops quite a wound up surface low and is thus a much slower

925mb and 850mb temperatures look to be around 2 to 3 standard
deviations above the mean for this time of year on Tuesday and
Wednesday. Considering this and the expected WAA regime for the
area, on top of decent sunshine and a loss of snowpack across the
south, felt inclined to go with the warmer side of guidance for high
temps both days.

.LONG TERM...(Wednesday night through Sunday)
Issued at 333 AM EST Mon Feb 20 2017

High Impact Weather Potential...Potentially significant winter storm
with gusty winds looks to impact the region Friday into Saturday.

Chance of rain showers with the passing clipper system Wednesday
evening, perhaps briefly mixing with a bit of snow or freezing rain
across western Chip/Mack counties as temperatures fall Wednesday
night. Nothing significant. Will see a gradual cooling trend to
close out the week as a strong system developing in the Plains takes
aim at the Great Lakes region.

This far out there are still a lot of important details that remain
fuzzy with this storm, particularly its track, timing, and potential
impacts to northern Michigan. The system will be negatively tilted
as it intensifies to our west, then becomes more vertically-stacked
as it tracks into the Upper Great Lakes but still remaining very
impressive dynamically and thermodynamically. GFS and ECMWF both
showing around 200-300 J/kg of MUCAPE extending into northern Lower
Friday afternoon/evening, so some thunder even looks like a
possibility (have kept out of the forecast for now given current
uncertainties). Wind gusts will likely be an issue Friday afternoon
and especially on Saturday as the strongest pressure gradient rolls
through. Precip-wise, lots of moisture wrapped up in this system,
and with temperatures on a downward trend as the system impacts the
area, it appears this will be the next potential snow-maker for the
area. WAA-induced precip (likely snow) will overspread the area out
ahead of the system Thursday night, changing to rain from south to
north during the day Friday, then back to snow Friday night into
Saturday as strong CAA develops. Certainly could be some wintry mix
to contend with as well. GEFS plumes continue to show very wide
spread in potential snowfall totals, and it would be foolish to
propose any possible amounts this far out with so much uncertainty.
However, there has been enough model consistency to suggest the
possibility of more than a few inches for some...that is, unless the
models decide to change significantly 2 or 3 days out and northern
Michigan ends up with mainly a messy wintry mix, as has seemed to
happen too frequently the last couple months.


.AVIATION...(For the 12Z TAFS through 12Z Tuesday morning)
Issued at 643 AM EST Mon Feb 20 2017

VFR today. Becoming MVFR to IFR with LLWS tonight.

Quiet today, as high pressure near James Bay moves into Quebec. A
cold front will move into the western Great Lakes late tonight,
and showers will develop ahead of it, and move into northern lower
MI overnight. Cigs/vsbys will degrade as this happens, with MVFR
to IFR conditions developing late tonight.

Se winds will increase today, becoming more southerly tonight.
LLWS tonight, with strong se to s winds just off the surface.


Issued at 333 AM EST Mon Feb 20 2017

Southeast winds will increase today, as a cold front advances into
WI/Iowa. Small craft advisory conditions will likely be met on
many waters, and a few gale force gusts are possible on Lake MI.
Weaker sw to w winds behind the front on Tuesday.


LH...SMALL CRAFT ADVISORY until 7 AM EST Tuesday for LHZ345>349.
LM...SMALL CRAFT ADVISORY until 7 AM EST Tuesday for LMZ323-341-342-


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