Area Forecast Discussion
Issued by NWS Gaylord, MI

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FXUS63 KAPX 240241

Area Forecast Discussion
National Weather Service Gaylord MI
1041 PM EDT Thu Mar 23 2017

Issued at 1039 PM EDT Thu Mar 23 2017

Deep moist advection continues across the area, finally starting to
do a number on what had been a hard to dislodge surface rooted dry
layer. Southeast flow continues to largely offset initial
evaporational cooling across northern lower, keeping showers mostly
liquid at the surface (although have noted some icing on elevated
surfaces here at the office despite mid 30 degree temperatures). A
touch cooler conditions north of the big bridge, and do suspect some
light freezing rain is occurring on those secondary road surfaces.

Overall trends really change little tonight, with this initial round
of rain pinwheeling east, with development of even more focused deep
layer moisture convergence likely leading to more shower
organization across at least parts of the area through the overnight
into Friday. Still some uncertainty exactly where that relatively
narrow max moisture convergence axis will reside, but would expect
to see some halfway decent rain amounts wherever it does eventually
line up. May even hear a rumble of thunder or two, although per
instability and radar trends, it does appear best opportunity for
thunder will remain to our south. Maintenance of deep south and
southeast flow should continue to largely offset any evap cooling,
so expecting much of the precipitation to remain just rain over
northern lower (some isolated icy spots do remain possible). Thermal
progs change little over eastern upper, so expect at least pockets
of light freezing rain to continue with some minor ice accumulations
by morning. Inherited advisory has this well covered.


.NEAR TERM...(Tonight through Friday)
Issued at 321 PM EDT Thu Mar 23 2017

...Increasing chances of precip...including freezing rain...

High Impact Weather Potential...Areas of freezing rain developing
tonight into early Friday leading to some travel problems...
especially across Eastern Upper Michigan.

Pattern Synopsis/Forecast...Large area of strong high pressure
continues to push east away from Michigan...while low pressure
develops to the lee of the Rockies. Southerly flow/WAA in between
these two systems continues to strengthen across the Plains...
Mississippi Valley and the Western Great Lakes region. Moist return
flow within these areas produced an area of scattered light precip
across Wisconsin...which tried and failed to make it across Lake
Michigan into our CWA thanks to very dry air still entrenched across
much of Michigan. Another large area of convection is developing
over Minnesota and Iowa...with additional convection extending thru
Illinois...all of which is developing along and north of the
approaching warm front. This front will lift into Lower Michigan
tonight and will likely stall around the Straits area on Friday. Low
level dry air will eventually give way to moist air surging
northward into the Western Great Lakes region tonight...leading to
increasing chances of precip across our entire CWA.

Model soundings still show the likelihood of mixed precip across our
northern CWA... especially across Eastern Upper Michigan which will
likely see a light mix of precip types...including light freezing
rain... beginning after 03z and continuing into Friday morning
(around 15Z or so). In coordination with MQT...will issue a Winter
Wx Advisory for Chippewa and Mackinac counties for this timeframe
for mixed precip with the potential for ice accumulations of around
a tenth of an inch or so...combined with some light snow and sleet
as well. WAA across the Northern Lower Michigan should keep the
potential window of mixed precip relatively small...only a few hours
during late evening and into the overnight hours. Will refrain from
issuing a headline for far Northern and NE Lower Michigan for now
but will certainly keep a close eye on precip type trends thru
tonight. By 15Z on Friday...all precip should have switched over to
plain rain as temps warm into the upper 30s and 40s.


.SHORT TERM...(Friday night through Sunday)
Issued at 321 PM EDT Thu Mar 23 2017

...Unsettled weather through the weekend, freezing rain for some...

High impact weather potential: Freezing rain possibilities,
particularly for northeast lower and eastern upper, through the

Pattern Forecast:  High pressure currently over the region will
continue to move off the Atlantic coast as low pressure moves out of
the central Plains and towards the Great Lakes. This will be a slow
moving, occluding low pressure system as the cutoff upper wave
weakens and begins to open. Strong return flow behind the departing
high and ahead of the approaching low will advect Gulf Moisture up
through the Ohio Valley and into northern Michigan. Currently
progged PWAT values in the range of .8 to 1" are impressive for this
time of year, well above 90th percentile. Meanwhile, high pressure
moving through northern Ontario will be advecting cold air south,
with sub zero H8 temps pushing possibly as far south as the Straits.
This should serve to stall the northern progression of the warm
front attendant to the approaching low, which looks to be just to
our south across central Michigan.

Primary Forecast Concerns: Where to start? That precipitation will
fall through the period seems a good bet as the slow moving system
takes it`s time getting out of the area. The big issue will be the
low level temperatures, and the effect that will have on p-types.
The primary concern right now is the potential for freezing rain.
With the warm front setup to our south, and high pressure to our
north sustaining cold advection, the likelihood of freezing rain
somewhere is pretty high. The problem is with just how far north the
warm front can get, and how far south the low level cold air will
get. Given the location of the warm front, I think the southern
portions of the CWA are likely to stay all rain. But as you get
north of M-72, low level temperatures start to drop below freezing
with deep, mid-level warm layers as warm as 6C. And while low level
temperatures will fall as you go further north, the warm layer will
become less pronounced. Right now, favored areas for freezing rain
look to be in NE lower and eastern upper. While there will be a
general idea for freezing rain placement in the grids, it should be
considered just that at this juncture as just small changes in
temperatures will greatly impact the freezing potential. Saturday
looks like it could be a little more prolonged freezing rain
potential north of M-32, as the cold air makes it furthest push
south. This will just have to be nailed down more as it gets into
the near term.

.LONG TERM...(Sunday night through Thursday)
Issued at 321 PM EDT Thu Mar 23 2017

High Impact Weather Potential...

A surface low passes south of the region and spreads a broad area of
precipitation across the area for Monday...with wrap around moisture
keeping pops in the forecast into Tuesday. Temperatures will be
running real close to climo, which should keep precip all rain. The
fly in the ointment could be as the night time diurnal swing brings
us close to the freezing mark, combined with CAA on the backside of
the low.  That said...confidence is higher toward a wetter solution
than whiter, as significantly drier air accompanies the cooler
air...which comes in late Tuesday, along with high pressure at the
surface and lasts through Thursday.  Based on what the ECMWF and GFS
are showing...I think temperatures could be cooler on Wednesday and
Thursday than what blended solutions are showing for the grids, but
that`s a long way off yet.


.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 725 PM EDT Thu Mar 23 2017

Conditions expected to deteriorate heading through tonight and
Friday as the atmospheric column continues to saturate. Widespread
light to moderate rain will develop overnight, with cigs expected
to quickly lower as saturation in realized. May see a brief period
of freezing rain, especially at KAPN, when precipitation initially
arrives. This should be short-lived as surface temperatures slowly
creep back above freezing. Low cigs, rain, and mist expected
through Friday as a warm front stalls out overhead, only to return
slowly south as a cold front during the afternoon and evening.

Brief period of wind shear expected at KMBL tonight in an
otherwise fairly light wind regime through this taf period.


Issued at 321 PM EDT Thu Mar 23 2017

Winds and waves will remain at SCA criteria for portions of Northern
Lakes Huron thru much of tonight...and then diminish below
criteria by Friday. Chances of precip will increase tonight for
all nearshore areas...with some mixed precip possible across the
far north. Wx will remain rather unsettled thru the weekend...with
good chances of precip possibly mixed during the night.


MI...WINTER WEATHER ADVISORY until 11 AM EDT Friday for MIZ008-015.
LH...SMALL CRAFT ADVISORY until 5 AM EDT Friday for LHZ348-349.


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