Area Forecast Discussion
Issued by NWS Gaylord, MI

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FXUS63 KAPX 230232
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
932 PM EST Mon Jan 22 2018

.UPDATE...
Issued at 931 PM EST Mon Jan 22 2018

Another round of moderate to heavy precip is lifting across
northern lower MI presently. This is moving into areas that have
had the highest (known) amounts of freezing rain thus far, with
our co-op observer in Petoskey at 0.22 of ice as of 8 pm. Surface
temps are slowly falling, now at 28/29f in much of Cheboygan/Emmet
Cos. And Bufr soundings very much emphasize that FZRA will be the
primary p-type over the tip of northern lower MI until after
2/3am.

So confidence is high that this next batch of precip will push at
least those two counties past warning criteria for ice accums
(0.25"). It is very much debatable as to whether a headline
upgrade is actually worth it; they`ve had wintry precip up there
since noon, and in a few more hours, this event is largely over.
On the other hand, it is slowly getting colder at the surface, and
with even a brief burst of heavy precip incoming, that has to
have an impact. Freezing rain is a very different animal at 28f
(Cheboygan) than it is at 32f (GLR).

So did indeed upgrade those two counties to a warning. Note that
an `ice storm warning` headline would be by-the-book the most
appropriate. But feel that would be overkill from a public-
perception standpoint, and a winter storm warning should get the
point across sufficiently.

There is one more round of moderate precip rates potentially
ahead. That is a few hours either side of daybreak, as central and
nw lower MI get clipped by deformation-forced precip on the north
edge of the 500mb/700mb closed lows that pass to our south. We
should be wiping out the warm nose right about then, so this is
primarily a less impactful rain-snow issue.

&&

.NEAR TERM...(Tonight through Tuesday)
Issued at 337 PM EST Mon Jan 22 2018

Stacked low pressure now in Iowa this afternoon with the warm
front still making some progress north from srn lower Michigan.
The deepest moisture and strongest forcing, driven primarily by
WAA and upper divergence, was pressing through far nrn lower
Michigan and into eastern upper. Moderate to heavy snows were
ongoing in this area while freezing rain/sleet were falling just
to the south of there underneath the elevated above freezing
layer. In areas further south of there, the influx of warmer air
was changing things over to rain with precipitation intensity
lessening as deeper moisture is starting to strip due to the onset
of dry-slotting.

The low pressure will continue a track to the ENE and cross nrn
Michigan into Tuesday morning, with the deeper moisture in
deformation on the backside of the system wrapping into the region
while cold advection ensues. The strong forcing currently pushing
through far nrn lower and eastern upper will likely shift north of
these areas, but some moderate precipitation rates are likely to
continue at times across eastern upper as they will be closer to
the better forcing and deeper moisture. In nrn lower, moisture
remains more stripped out aloft and periods of drizzle and
freezing drizzle (across the far nrn lower and far NW lower) will
be more common as the depth of the low level moisture is all under
-10C for much of the night. As the low pressure crosses late
tonight into tomorrow morning, the winds turn more northerly and
begin drawing colder air into nrn Michigan and shoves the elevated
warm nose off to the east. This process will gradually change
precipitation to a period of just snow, which will bring some
light accumulations of snow, maybe 1 or 2 inches across mainly nrn
lower. Tuesday afternoon things will start to dry out enough to
where precipitation ends from west to east, with the exception of
N/NNW flow regimes, as instability grows over Lakes Superior and
Michigan. Only a small/slight chance as the depth of the
instability and moisture is very shallow.

Lows tonight in cold advection, falling into the teens in eastern
upper, while areas closer to Saginaw Bay ("warmest" air) will hold
in the lower and middle 30s. Temperatures keep falling through
Tuesday, into the 10 to 15F range in eastern upper to the lower
20s near Saginaw Bay.

&&

.SHORT TERM...(Tuesday night through Thursday)
Issued at 337 PM EST Mon Jan 22 2018

...Short LES Period, then Quiet Through Thursday...

High Impact Weather Potential...Minimal

Pattern Synopsis/Forecast...The sfc low moves into southern Quebec
by 00z/Wed, and continues to move to the NE into the Canadian
Maritimes. This leaves the Upper Great Lakes in a north flow pattern
for the evening of Tuesday (00z/Wed-06z/Wed). 850 mb temperatures
fall to around -10c with the water temperatures in Lakes  Superior
and Michigan around +2c to +3c We will be marginal for lake snow but
it is possible, so have some pops in for the early part of evening,
but dry things out as the winds continue to move and the
temperatures warm a degree or two, and the 850-700 mb layer RH
remains below 40%. So will expect that the snow will taper off, to
at most flurries, and keep Wednesday dry. Wednesday evening, only
the GFS has any chance of snow, with all of the other models
considerably warmer at 850 mb  with the WNW flow. If anything fell
it would be minor, but will leave Wednesday night dry. Subsidence
fights the warm front, and 850 mb moisture. The models skew toward
the low to mid-level moisture being clouds keeping the region dry.
So will keep the day dry.

Primary Forecast concerns...Issues are the LES, not that it could be
more, but that it will be less. It seems that the pattern is not
cold enough, for a lot of instability over the lakes for LES.
Otherwise, as the "Warm front" moves through, the enhancement may
actually get something going, but with the consensus of the models
(GFS/ECMWF/NAM/SREF) going dry as the front moves through, will keep
it dry as well.

.LONG TERM...(Thursday night through Monday)
Issued at 337 PM EST Mon Jan 22 2018

As high pressure moves to our east, a brief period of warm advection
will bring above normal temperatures over the weekend. A cold front
attendant to low pressure passing to our north could bring some
precipitation over the weekend, with temperatures supporting rain or
a wintry mix during warmer afternoon hours. Cold air filtering in
behind that front will bring some lake effect chances as we begin
next week.

&&

.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 700 PM EST Mon Jan 22 2018

Wintry mix to diminish and eventually end on Tuesday.

Mature surface low is in ne IL this evening, and will cross lower
MI tonight. Widespread IFR to at times LIFR conditions this
evening, with fzra/sn at PLN and rain elsewhere. Precip will mix
with and turn back over to fzra/sn at all the TAF sites
overnight. Those will diminish to shsn on Tuesday, and eventually
end, with MVFR cigs lingering.

Gusty east winds will back to the north late tonight thru Tuesday.


&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...WINTER WEATHER ADVISORY until 5 AM EST Tuesday for MIZ008-015-
018-019-021>024.

WINTER STORM WARNING until 5 AM EST Tuesday for MIZ016-017.

&&

$$

UPDATE...JZ
NEAR TERM...SMD
SHORT TERM...JL
LONG TERM...AM
AVIATION...JZ



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