Area Forecast Discussion
Issued by NWS Gaylord, MI

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FXUS63 KAPX 250319
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
1019 PM EST Fri Feb 24 2017

.UPDATE...
Issued at 934 PM EST Fri Feb 24 2017

Closed mid level short wave is located over far eastern Iowa/NW
Illinois with deformation axis snowfall (tomorrow`s weather)
stretching from eastern Iowa through western Wisconsin and the
U.P. Ahead of the wave...surface low pressure is tracking up
through SE lower Michigan with a cold front stretching
southwestward into the lower Mississippi River Valley.

Very warm air and deep moisture feed ahead of the front successfully
produced several lines of showers/storms across the Ohio Valley
into lower Michigan today/this evening. Deep EML extends all the
way up into northern Michigan well ahead of the warm front and
lead to some rather beefy elevated convection this afternoon/evening...
with rain/freezing rain showers and lots of small hail and even
some severe level (quarter sized) hail. Deep warm/moist conveyor
flow is getting pinched/shoved off to the east at this juncture
with a pronounced dry slot punching into the western lakes region
ahead of the short wave.

Rest of tonight: Last bit of convection will exit out of NE lower
Michigan within the next few hours as dry slot spreads W-E across
the region. This will end the main freezing rain threat. Some
drizzle/freezing drizzle will remain a possibility through the
remainder of the night as deep moisture aloft strips out leaving a
lower level deep saturated layer largely warmer than -7C.
Deformation and lake effect snows will not arrive until later
Saturday morning into the afternoon. So...plan is to simply allow
ongoing advisories (largely issued for the FZRA/sleet/snow mess)
to expire at 06Z. Midnight shift can assess whether or not a new
set of advisories for wrap around and lake snows is warranted. My
initial look/thoughts are, they will not be needed. Some wind and
a few inches of snow...meh.

&&

.NEAR TERM...(Tonight)
Issued at 357 PM EST Fri Feb 24 2017

High impact weather potential: Accumulating snow and freezing rain
continue. Possible thunderstorms in the SE CWA.

Pattern synopsis and forecast:

Low pressure was lifting up into SW lower Michigan this afternoon
with a wide array of weather ongoing across nrn Michigan. Showers
and thunderstorms, some severe with large hail across NE lower,
back to Drizzle and freezing drizzle with intermittent snows back
to the NW. Drying aloft has ended much of the accumulating
precipitation in the NW half of the CWA, so all the action is in
NE lower attm. Amazing that the thunderstorms were occurring with
temperatures in the 30s, but instability aloft upward of 500 j/kg
is being tapped by low level convergence north of a warm front
stretched across lower Michigan, as well as upper divergence
associated with 100+ knot jet poking into srn Lake Michigan.

Heading through early evening, showers and isolated to scattered
thunderstorms will continue to impact much of NE lower, until the
aforementioned forcing and low pressure departs to the east. The
dry slot which stripped out the deeper moisture will hang around a
little longer than previously thought, keeping the weather across
the NW half of the CWA in a drizzle and freezing drizzle scenario.
Once the storms exit east, this could wind up giving us a pretty
long period of fairly quiet (drizzle) weather. Eventually, the
deeper moisture associated with the deformation zone on the back
side of the low pressure will slide back in late tonight and into
Saturday morning. Temperatures aloft continue to fall and
precipitation will turn back to snow and developing blowing snow.

Total additional snow tonight will be lower with only 1-2 inches
in western Chip/Mack counties and none elsewhere. Rather, freezing
drizzle/rain will result in an additional 0.10-0.15". Snow totals
Saturday in the traditional NW flow lake effect areas will only be
1-2". Minor amounts elsewhere.

Headlines, they will stand as is for right now. Potential changes
would be to extend current advisories through the entire night for
the longer expected period of freezing rain/drizzle. Also, will
need to watch some more minor ice accumulations across NW lower
for new advisories.

&&

.SHORT TERM...(Saturday and Sunday)
Issued at 357 PM EST Fri Feb 24 2017

...Lake effect diminishes Saturday night; Clipper arrives Sunday...

High impact weather potential: Minimal, although a wave of light
snow expected across the area Sunday.

Pattern Forecast: By Saturday night, fairly zonal flow aloft is
expected across the midsection of the country with surface high
pressure centered over the lower Mississippi Valley and associated
weak surface ridging nosing into northern Michigan. The next
shortwave progged to affect the area will be racing through central
Saskatchewan at the same time, expected to cross the northern Great
Lakes during the day Sunday. Subtle upper-level ridging returns
Sunday night-Monday out ahead of the next system ramping up across
the southern plains.

Primary Forecast Concerns: Primary forecast concerns and challenges
revolve around diminishing lake effect snow showers Saturday night
and a quick shot of synoptically driven snow on Sunday. Lingering
wrap around deep layer moisture and synoptic support associated with
today`s (Friday) low pressure system continues to depart off to the
east Saturday afternoon and evening. All while aforementioned high
pressure centered to our south aids in nosing surface ridging across
northern Michigan, resulting in a significant decrease to lake
effect coverage and intensity Saturday night. Still expect light
northwest flow lake effect snow showers to be ongoing during the
evening hours before waning completely across northern Lower - only
an additional accumulation of an inch or less. Light snow showers
may continue across far northern Chippewa County through much of the
overnight, initially of the lake effect variety followed by the
incoming weak clipper system.

Speaking of the incoming clipper system...snow is expected to
overspread the area from west to east beginning Sunday morning into
the afternoon hours. Mainly light snow is expected across the
majority of the area; however, just it`s just marginally cool enough
aloft to perhaps get a bit of west/southwest flow lake enhancement,
which may help to increase snow shower coverage and intensity across
sections of northwest Lower and southern Mackinac County. Overall,
accumulations are expected to be on the order of 1-3 inches across
northwest Lower/eastern Upper with less than an inch over the
eastern third of the CWA. Wind gusts will again increase to as high
as 30-35 mph as the pressure gradient tightens coinciding with the
system`s arrival, this causing concern for additional
blowing/drifting snow.

.LONG TERM...(Sunday night through Friday)
Issued at 357 PM EST Fri Feb 24 2017

A rather zonal pattern will begin to transition to progressive with
a train of low pressure systems impacting the forecast area
beginning Monday night/early Tuesday morning. The first storm system
will approach from the central Great Plains and begin to produce WAA
precipitation late Monday night through Tuesday night. Behind this
system northern Michigan will be in a deep upper-level trough
pattern throughout the remainder of the forecast period...bringing
periodic chances of rain and snow.

Temperatures will remain mild through Wednesday, with temperatures
reaching into the upper 30s to low 40s and then cooling off Thursday
and Friday, with highs only reaching into the mid 20s to low 30s.
Lows will be in the mid 20s to low 30s and dip into the low teens to
low 20s by Thursday morning.

&&

.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 1019 PM EST Fri Feb 24 2017

IFR conditions will be the name of the game through the rest of
the night, with drizzle/freezing drizzle at the terminal sites.
Colder air and deeper moisture will wrap back into the region late
overnight through Friday. This will bring colder temperatures and
the return of some snow to the region. But, it will also bring
improving flight conditions to MVFR as things dry out a bit.

A brief lull in the winds overnight. But winds will turn into the
west-northwest Saturday and become gusty again.

&&

.MARINE...
Issued at 357 PM EST Fri Feb 24 2017

Low pressure will cross the region tonight and into Quebec
tomorrow. E/NE quite gusty winds will gradually weaken later this
evening before picking up quite gusty out of the NW Saturday as
colder air rushes back in behind a cold front. Will stretch the
gale warning into Saturday and Saturday evening for many
nearshores. The gradient remains tight enough for advisory level
gusts through the evening.


&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...WINTER WEATHER ADVISORY until 1 AM EST Saturday for MIZ008-
     015>019-022-023.
LH...SMALL CRAFT ADVISORY until 6 AM EST Sunday for LHZ345-346-349.
     GALE WARNING until midnight EST Saturday night for LHZ347-348.
LM...SMALL CRAFT ADVISORY until 6 AM EST Sunday for LMZ323-341.
     GALE WARNING until midnight EST Saturday night for LMZ342-
     344>346.
LS...NONE.
&&

$$

UPDATE...TBA
NEAR TERM...SMD
SHORT TERM...MJG
LONG TERM...TJL
AVIATION...TBA
MARINE...SMD



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