Area Forecast Discussion
Issued by NWS Gaylord, MI

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FXUS63 KAPX 170016

Area Forecast Discussion
National Weather Service Gaylord MI
816 PM EDT Mon Apr 16 2018

Issued at 758 PM EDT Mon Apr 16 2018

Didn`t quite feel comfortable letting the winter weather advisory
for Mackinac and Chippewa Counties expire at 8 pm with snow
showers and vsbys in the 1-2sm range ongoing. Therefore, have
extended the advisory through 11 pm. Activity should actually
diminish in the next couple of hours but just want to be on the
safe side. Meanwhile across northern lower, lake enhancement is
picking up so another 2 to 4 inches looks on track. Advisory
ending time of 5 am Tuesday looks okay for now but the midnight
shift will evaluate to see if it will need to be extended.


.NEAR TERM...(Tonight through Tuesday)
Issued at 333 PM EDT Mon Apr 16 2018

...More accumulating snow tonight...

High impact weather potential: Additional snow accumulation
expected, especially in the traditional snow belts of northwest
lower Michigan.

Pattern synopsis/forecast: Widespread light to moderate snow
continues to pinwheel back northwest as deep upper level low
pressure works its way slowly across northern Ohio. Strong vort lobe
rotating along the east periphery of this low will entice the
development of a secondary upper level center over the northern
Lakes this evening, which will slowly drift southeast through our
region tonight and early Tuesday. Combination of attendant forcing
and some marginal lake contribution will result in more accumulating
snow, especially across portions of northwest lower Michigan.

Primary forecast concerns/challenges: Additional snow amounts and
attendant headline concerns.

Details: Main area of snow expected to pivot further northwest with
time early this evening as vort lobe begins to close off the
secondary center over Lake Superior. Snow expected to become a lot
more scattered across northeast lower Michigan, with best forcing
and some increasing lake contribution forcing better snow coverage
into the eastern upper and northwest lower Michigan. That should
pretty much continue right through early Tuesday morning, although
coldest temperature anomalies rotating into central Lake Superior
should focus better snow showers west of eastern upper Michigan
quickly this evening. Persistent northwest flow remains across Lake
Michigan, with 5kt inversion temperatures around -12c/-13c just cold
enough to continue some lake moisture contribution. Plenty of deep
moisture extending well above this shallow convective layer should
support good seeder-feeder processes through the overnight. With
that said, given marginal nature of instability and really no good
omega within the dendritic growth layer, snowfall intensity should
be muted some. Simple persistence of activity and strong signs of
upslope enhancement (very moist low levels favor this idea) should
result in a least a couple more inches in those favored areas.
Scattered lighter snows elsewhere, with minimal additional
accumulations expected. Northwest winds expected to become gusty as
departing surface low helps strengthening overhead pressure
gradient. Wind gusts will be nothing like what was recently
experienced, but just enough to result in some blowing and drifting
snow in those open areas. Snow showers slowly wind down Tuesday as
temperatures modify and deeper moisture begins to strip out. Just a
bit "milder" tomorrow, with highs in the middle and upper 30s.

Headlines: All warnings will be dropped. Given expected lake
enhancement, will follow overnight forecaster and extend winter
weather advisories to more of those traditional northwest flow areas
of northwest lower Michigan. Not expecting a ton of snow, but given
ongoing hazardous travel conditions and additional snow expected,
felt an advisory was more than warranted.


.SHORT TERM...(Tuesday night through Thursday)
Issued at 333 PM EDT Mon Apr 16 2018

...Some more snow Wednesday night...

High Impact Weather Potential...Some more snow expected late
Wednesday through Wednesday night, mainly along and south of M-72.

Pattern Synopsis/Forecast...Another cyclone developing out over the
Central Plains Tuesday night is progged to lift east-northeast
towards the Lower Great Lakes on Wednesday. The system itself is
expected to move across the Mich-In-Oh border, but its associated
precip should extend into northern Lower from late Wednesday into
Wednesday night as strong upper level divergence overspreads the
area. Available moisture with this system will be respectable with
PWATs climbing above a half inch, but the better moisture does
appear to stay to our south. Thereafter, high pressure begins to
build in from the west.

Primary Forecast Concerns...Snowfall extent and amounts late
Wednesday into Wednesday night. Potential for some patchy lingering
drizzle Thursday?

Models have been wavering a little on how far south the system will
pass Wednesday night, which will impact the northward extent of any
snowfall. Heavier QPF is generally placed along and south of M-72,
which is where forecast soundings are most supportive for snow.
Warmer temperatures at precipitation onset will lead to some rain
initially late Wednesday. Snow ratios also look to start out around
10:1, so it doesn`t look like any significant accumulations are
likely. Perhaps a slushy inch or two south of M-72.

It looks like some very light precip may extend northward to the
Straits area with this system. One forecast complication will be
drier northeast flow encroaching from the north. This will limit the
chances for ice nucleation on the northern periphery of
precipitation, and the very shallow moist surface layer on forecast
soundings suggests there could be some patchy freezing drizzle
(perhaps mixed with snow at times) north of M-32 Wednesday night.
Some drizzle may linger into Thursday morning across our southern
counties given some residual shallow low level moisture.

We`ll start to see an uptick in temperatures Wednesday and Thursday
with highs pushing the low 40s. There may also be a little sun both

.LONG TERM...(Thursday night through Monday)
Issued at 333 PM EDT Mon Apr 16 2018

High Impact Weather Potential...

It has been a while since I`ve been able to say this, but things
look rather quiet through the extended period. High pressure will
begin building into the region Friday and remain in control into the
beginning of next week. Aside from precipitation free conditions,
temperatures will begin to moderate to near normal by the start of
next week.


.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 731 PM EDT Mon Apr 16 2018

More of the same with snow showers leading to IFR to MVFR vsbys
and MVFR cigs through tonight. A couple of additional inches of
new snow are expected, especially at KPLN and KTVC. Gusty
northwest winds through Tuesday morning. Snow showers will
diminish Tuesday morning then end Tuesday afternoon but MVFR cigs
are likely to continue.


Issued at 333 PM EDT Mon Apr 16 2018

Tightening pressure gradient behind departing low pressure will
result in small craft advisory producing gusty northwest winds
through Tuesday on all nearshore waters. Winds subside later Tuesday
and Tuesday night.


MI...WINTER WEATHER ADVISORY until 5 AM EDT Tuesday for MIZ019>022-
     WINTER WEATHER ADVISORY until 11 PM EDT this evening for MIZ008-
LH...SMALL CRAFT ADVISORY until 5 PM EDT Tuesday for LHZ345>349.
LM...SMALL CRAFT ADVISORY until 5 PM EDT Tuesday for LMZ323-341-342-
LS...SMALL CRAFT ADVISORY until 5 PM EDT Tuesday for LSZ321-322.


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