Area Forecast Discussion
Issued by NWS Gaylord, MI

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FXUS63 KAPX 120351
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
1051 PM EST Wed Jan 11 2017

.UPDATE...
Issued at 824 PM EST Wed Jan 11 2017

Tight thermal gradient stretches from the midwest up through
central and northern lower Michigan this evening. Compact surface
low is riding along that gradient, located over central Illinois
with a front stretching northeast through the Saginaw Bay area.
Strong thermal packing/deformation forcing along the northern side
of this wave has produced a few hours of light to moderate
snowfall up through parts of NW lower Michigan thus far. But
strongest deformation forcing will be sliding right up across northern
lower Michigan over the next 3 to 5 hours or so, and expect some
beefier precip rates at times.

Meanwhile, warm nose aloft bisects northern lower Michigan roughly
from Cadillac to near GLR and over to APN and will only slowly
edge S/E through the course of the evening and early overnight
hours. Precip south of this line will remain mixy and convective
through the course of the evening with snow/sleet/rain or freezing
rain (dependent on surface temps). But thus far, icing has not
been an issue that I can tell from ASOS icing remarks, and I have
refrained from issuing any winter weather headlines. But, I have
and will continue to issue special weather statements talking
about wintry mixed precip and light icing possibilities.

North of the line, precip has been all snow with the heaviest
snowfall thus far occurring where we have advisories already
in place. Heavier snowfall will slowly shift southward over the
next several hours pushing some better accumulating snowfall into
areas around Gaylord, Traverse City, etc. But I think accumulations
for those areas will run in the 2 to 3 inch range at best.
Snowfall in eastern upper Michigan is pretty much over (save for
some minor lake effect) and will be canceling advisory there
shortly.

&&

.NEAR TERM...(Tonight and Thursday)
Issued at 337 PM EST Wed Jan 11 2017

...More accumulating snow tonight...with some mixed precip south...

High Impact Weather Potential...Advisory criteria snowfall in the
north...some mixed precip in the far south especially near Saginaw
Bay.

Pattern Synopsis/Forecast...Frontal boundary extends from Eastern
Upper Michigan thru Northern Lake Michigan to the Kansas/Missouri
border this afternoon. Areas of snow continues to develop along and
north of this front...the most intense of which continues to impact
Upper Michigan attm. Additional patchy areas of light snow are
developing south of that main area across Eastern Iowa...Southern
Wisconsin and portions of Lower Michigan ahead of low pressure
developing along this boundary. This low center will push NE into SE
Lower Michigan by midnight and then thru far SE Ontario overnight.
Focus for strongest lift...deepest moisture and thus highest pops
will shift from our northern CWA this afternoon/early evening to the
SE half of our CWA just ahead of the approaching low. Low level WAA
just ahead of the low will push an elevated warm nose into our SE
counties...which will likely produce an area of mixed precip
especially near Saginaw Bay. Enhanced area of lift and moisture
quickly peels away overnight with the departing low...leaving much
of Northern Lower Michigan in a general chance of light snow with
little in the way of additional snow accumulation overnight. One
more weak wave moves thru our CWA Thursday morning just ahead of the
500 mb trough axis...with generally an inch or less of additional
snow accumulation expected.

Primary Forecast Concerns...Main forecast issues are additional snow
amounts expected across our entire CWA late this afternoon and
evening...and the potential for ice accumulation in our far SE CWA
as a result of mixed precip this evening. As focus for precip
production will shifts from our northern CWA to our southern CWA as
we head into the evening...widespread snow will develop across much
of Northern Lower Michigan. Expect enough additional snowfall for
our advisory counties to maintain that headline into the evening...
expecting another 2 to 4 inches in these locations. The rest of
Northern Lower Michigan (outside of the advisory) will receive a
general 1 to 3 inches of new snow...with lessor amounts near Saginaw
Bay where mixed precip and temps just above freezing will diminish
the ability to accumulate snow. In coordination with GRR and DTX...
expect our far SE CWA will likely stay just above freezing thru most
of the evening hours...and thus thru most of this precip event. This
should limit ability for ice to accumulate on surfaces...and thus
limit the threat of developing hazardous conditions. Have opted to
hold off on issuance of any headlines for now in light of this
expected scenario...but will certainly keep a close eye on surface
temps and precip type as we ahead thru the evening hours. Once the
low passes to our SE...CAA in its wake will cool temps into the
teens for Eastern Upper...far Northern and interior sections of
Northern Lower Michigan...and into the low to mid 20s near the Lakes
Michigan and Huron shorelines. High temps on Thursday will be mainly
in the 20s.

&&

.SHORT TERM...(Thursday night through Saturday)
Issued at 337 PM EST Wed Jan 11 2017

...After a little LES into Friday, a Break for the Weekend...

High Impact Weather Potential...None.

Pattern Synopsis/Forecast...As a clipper system moves north of the
region, the cold front ushers in another chilly air mass as the 850
mb temperatures fall to colder than -20C in Lake Superior. Winds
Thursday night remain WNW to NW through 12z, but the 850-700 mb
layer RH over N Lower is less then 10%, and by 12z that same air is
pushing into Lake Superior and E Upper. This will squash any snow,
save for a possible flurry in N Lower, and allow some NW snow bands
to form and then diminish through the day on Friday. Then high
pressure and dry air take over keeping the forecast area virtually
precipitation free. A sfc trough moves through on Saturday
afternoon, with the GFS showing some snow, but the ECMWF and NAM
don`t show much, and it is down closer to the US-10 corridor. So
will continue a dry day for Saturday as well.

Primary Forecast Concerns...The only concern would be if the
moisture in the 850-700 mb layer would be a little more and hang in
there a little longer than progged in E Upper. This could produce
some moderate amounts for Thursday night into Friday. However,
considering the models showing the same basic idea, will figure that
snow amounts will be minor to light in E Upper, and worse case in N
lower would be light amounts, although Flurries is more likely(so
zero to minor amounts).

.LONG TERM...(Saturday night through Wednesday)
Issued at 337 PM EST Wed Jan 11 2017

High Impact Weather Potential...

...Warming trend next week with rain or snow possible...

High pressure in control Saturday night into Sunday night yielding
precipitation free conditions. Moderating temperatures aloft will
make it too warm for lake effect processes. Extended models are then
in general agreement that low pressure moves up to our west during
the Monday night into Tuesday night time frame. This will lead to
chances for rain or snow (my bet would be mainly rain), possibly
even some freezing rain as well. The system will be slow to move out
so there will be lingering chances for mainly rain Wednesday. Highs
moderating from the middle and upper 20s Sunday to well into the 30s
for the first half of next week (maybe even a few 40s Tuesday).

&&

.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1051 PM EST Wed Jan 11 2017

Low pressure sliding through SE lower Michigan will continue to
bring heavier snow to northern lower Michigan into the early
overnight hours, winding down overnight into Thursday morning.
IFR conditions with periods of moderate to briefly heavy snow can
be expected at various times at the terminal sites.

Improvement late overnight into Thursday morning and there will be
window of MVFR and possible VFR conditions Thursday morning. But
another round of lighter snow rolls through the region later in
the morning through Thursday afternoon bringing a return of MVFR
and possible IFR conditions through the afternoon. Improvement
Thursday night.

&&

.MARINE...
Issued at 337 PM EST Wed Jan 11 2017

Low pressure lifting NE through Southern Lower Michigan will keep
winds south of the Bridge at or just below SCA criteria thru
tonight. Widespread snow will continue to develop north of this
system across all of our nearshore areas this evening...with some
mixed precip expected near Saginaw Bay. Winds will weaken Thursday
morning before ramping back up to SCA criteria again Thursday
afternoon and night in response to a tightening pressure gradient
south of a clipper system tracking north of Lake Superior.


&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...WINTER WEATHER ADVISORY until midnight EST tonight for MIZ016-
     017-019>021.
LH...SMALL CRAFT ADVISORY until 5 AM EST Thursday for LHZ347>349.
LM...SMALL CRAFT ADVISORY until 5 AM EST Thursday for LMZ323-342-
     344>346.
LS...NONE.
&&

$$

UPDATE...TBA
NEAR TERM...MLR
SHORT TERM...JSL
LONG TERM...AJS
AVIATION...TBA
MARINE...MLR



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