Area Forecast Discussion
Issued by NWS Gaylord, MI

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FXUS63 KAPX 150247
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
1047 PM EDT Sat Apr 14 2018

.UPDATE...
Issued at 842 PM EDT Sat Apr 14 2018

...Significant wintry mix precipitation event later tonight through
Sunday night...

Impressive mid level low pressure continues to slowly spin east
along the Missouri/Iowa state line. Split warm conveyor belt out
ahead of this system, with one branch tied to deep tropical moisture
plume rotating into the Gulf Coast states, with the second branch
wrapping back northwest from Illinois into the northern Mississippi
Valley. Northern Michigan currently split between these branches,
with just a few light mixed showers in weak elevated warm air
advection regime. Trends through the overnight is for a gradual
congealing of the moisture axis/warm conveyor belt as it rotates
further north as low pressure pivots to our southwest. This should
increase southern Great Lakes precip coverage, which is expected to
rotate north into our area later tonight and Sunday. While that is
pretty much a given, what exact type that precip takes is a decidedly
more difficult forecast challenge. Hi-res guidance continues to
support a deep elevated warm nose rotating north nearly in lock-step
with the deeper moisture advection. Low levels remain very cold,
with an ever increasing depth to the surface based below freezing
layer as one goes north. Really starting to look like a rare
prolonged mixed sleet/freezing rain event for much of northern lower
Michigan right through Sunday, with more of a snow/sleet mixture for
eastern upper Michigan. Freezing rain amounts could be substantial,
at or above a quarter of an inch, by early Sunday afternoon, with
perhaps an inch or two of sleet. Still appears snow/sleet totals on
the order of several inches will occur for areas north of the big
bridge by Sunday evening. Biggest concern for this whole event,
especially for northern lower, is for a shallower than advertised
surface based sub-freezing layer, which would support even more
freezing rain potential. Will definitely continue to monitor
upstream surface observation trends. Very gusty east to northeast
winds will continue, only exacerbating the very hazardous
conditions. Combination of freezing rain/sleet and those gusty winds
will also likely result in some additional power outages. Of course
winter storm warning remains.

&&

.NEAR TERM...(Tonight through Sunday)
Issued at 356 PM EDT Sat Apr 14 2018

...Round of a wintry mix once again...

High Impact Weather Potential...Accumulating snowfall over eastern
upper and the tip of the mitt, sleet and freezing rain over much of
northern lower.

Primary Forecast Concerns...Amounts and type of precipitation.

Pattern Synopsis/Forecast...Models are still in consensus on the
track of a developing low pressure system over the Mississippi River
Valley and tracking through the southern Great Lakes region. Deeper
moisture ahead of a stationary front associated with aforementioned
system is located just to the south of southern Michigan/Indiana
border. High pressure over Ontario is building into northern
Michigan...along with accompanying dry air and
subsidence...diminishing the lingering snow over northern lower. As
the low pressure system moves eastward another push of deep moisture
arrives in earnest. This system has been a struggle with p-type and
continues to be so with this next batch of precip. Model soundings
show a great warm nose, but very cold below that to the
surface...thinking sleet with be more apt to develop in a such a
sounding...although confidence is not very high as some models are
showing an even more prominent warm nose over the southern CWA and
then up the spine of northern lower Michigan. With about 1.00" of
QPF forecast, hoping for a more sleet scenario than freezing rain.
We will definitely be monitoring the situation and will change the
forecast as necessary.

&&

.SHORT TERM...(Sunday night through Tuesday)
Issued at 356 PM EDT Sat Apr 14 2018

...Winter storm FINALLY departs...

High Impact Weather Potential...Continued heavy wintry precip into
Sunday night, gradually diminishing heading into Monday. Additional
accumulations of snow and ice will continue to impact travel.

Pattern Synopsis/Forecast...The intense winter storm will continue
to slowly make its way through the eastern Great Lakes region.
Heading into Sunday night and Monday, the departing occluded system
will develop two distinct low pressure centers...the main core of
the system just east of Lower Michigan and a secondary surface low
rotating around it through the eastern Great Lakes. By Monday night
into Tuesday, the system will be weakening as it slowly departs and
wobbles into eastern Canada. Slightly colder air (H8 temperatures
getting down to around -10C) wrapping in around the back side of
this system may allow for a period of lake enhancement Monday night
into Tuesday as the system slowly departs.

Primary Forecast Concerns...Precip types Sunday into Monday until
colder air filters in with a changeover to snow. Also snow and ice
amounts through the period.

By Sunday night, it looks like the system`s dry conveyor belt will
begin to wrap up into northern Michigan. The more widespread,
heavier precip will start to slowly diminish in intensity and
coverage from south to north Sunday night into Monday morning,
lingering longest over eastern Upper. However, additional energy
rotating around the storm will warrant holding onto likely PoPs
through Monday evening. Thereafter, as the system gradually departs,
expecting precip to become scattered Monday night into early
Tuesday, mostly diminishing by Tuesday afternoon.

In terms of ptype, it looks like the warm nose will hang on across
northern Michigan through early Monday (though cooling with time),
then it gradually retreats off to the east and completely exits our
area by Monday evening. This will allow for a continued wintry mix
through Monday morning across mainly northern Lower, with forecast
soundings showing the potential for at least partial melting aloft.
Mainly snow expected across the eastern UP. Another 4 to 8 inches of
snow looks possible across eastern Upper through Monday, perhaps a
little higher near Paradise and Whitefish Point. Less snow south of
the Bridge, but still another 2 to 4 possible across the Tip of the
Mitt Sunday night through Monday. Thermal profiles are still very
tricky across northern Lower, but there is potential for perhaps
another tenth of an inch or so of ice mainly along and west of I-75,
less than a tenth to the east. Winds look to diminish pretty quickly
Sunday night as the center of the low passes nearby. They`ll remain
somewhat brisk Monday into Tuesday, but not nearly as strong as over
the weekend.

Mainly scattered light snow showers heading into Monday night and
Tuesday morning with minimal additional impact (up to an inch or 2
of additional snow in the snowbelts), but drier air will arrive by
Tuesday afternoon.

.LONG TERM...(Tuesday night through Saturday)
Issued at 356 PM EDT Sat Apr 14 2018

High impact major winter storm will be a thing of the past Tuesday
night as deep mid level trough and attendant surface low exit into
the northeast states. Pattern remains progressive and aggressive
thereafter, with next strong shortwave arriving during mid-week.
While dynamics continue to look impressive, its predecessor (current
storm) will have largely scoured out Gulf of Mexico moisture. Strong
dynamics will do their best to overcome lack of deeper moisture, and
with a still marginally cold thermal regime, could definitely be
looking at more wintry precipitation. Something to keep an eye on in
the coming days. Through simple forced modification, airmass will
warm a bit heading through the end of next week, although little
doubt readings will still remain below normal.

&&

.AVIATION...(For the 06Z TAFS through 06Z Sunday evening)
Issued at 1044 PM EDT Sat Apr 14 2018

...IFR conditions return today...

Next round of significant mixed precip beginning to organize off
to our south, with this area of wintry weather expected to rotate
north across northern Michigan today. Expect primarily a mixture
of sleet and freezing rain, with enough warming at KMBL to perhaps
change everything over to just plain rain this afternoon. Both
sleet and freezing rain amounts will be significant. Much lower
cigs and visibility will accompany this expanding area of wintry
weather. Very gusty east/northeast winds to continue.

&&

.MARINE...
Issued at 356 PM EDT Sat Apr 14 2018

Gales over Lakes Michigan and Huron continue through Sunday
night...while small craft advisories remain for Whitefish Bay and
the Sault Ste. Marie river. Persistent northeasterly winds tonight
through at least Monday morning...sometimes gusting to 40-45kts.
Winds will begin to diminish Monday morning. Wintry mix of weather
will develop once again tonight and last through at least Monday as
well.


&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...WINTER STORM WARNING until 5 PM EDT Sunday for MIZ020>036-041-
     042.
     WINTER STORM WARNING from 2 AM Sunday to 2 AM EDT Monday for
     MIZ008-015.
     WINTER STORM WARNING until 2 AM EDT Monday for MIZ016>019.
LH...GALE WARNING until 8 PM EDT Sunday for LHZ345>349.
LM...GALE WARNING until 8 PM EDT Sunday for LMZ323-341-342-344>346.
LS...GALE WARNING until 8 PM EDT Sunday for LSZ321-322.
&&

$$

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



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