Area Forecast Discussion
Issued by NWS Gaylord, MI

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FXUS63 KAPX 291946
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
346 PM EDT Wed Mar 29 2017

.NEAR TERM...(Tonight through Thursday)
Issued at 347 PM EDT Wed Mar 29 2017

...Wintry mix arrives tonight and Thursday...

High impact weather potential...rain/snow mix. Light snow accums
parts of northern lower MI Thu.

1002mb low pressure is near Wichita KS. This low will deepen
somewhat as it moves slowly ene, reaching central IL by Thu evening.
Associated cirrus is already invading northern MI, and there`s lots
of virga to our sw. Actual precip is in northern IL/southern MN/much
of Iowa. Increasing ascent will eventually overcome dry low level
air (see 18Z observed APX sounding, with near 40c dew pt depression
at 700mb). Precip trends are the main concern.

Model solutions are still all over the map; somewhat disturbing for
an event that will be starting shortly. Aspects of Gem/GFS are
preferred, with a more gradual northward expansion of the precip
shield into northern MI. Nam goes nuts with f-gen related precip by
late tonight. This looks much too agressive, given the impressive,
pre-existing wedge of dry air, and increasing low-level easterly
winds that will reinforce that dry air. A wide range of warm-nose
solutions exists as well for Thursday; a compromise was followed.

Tonight...upstream returns in WI/MN are showing classic banded, f-
gen signatures. Locally intense (but transient) precip rates could
overcome our dry air earlier than previously progged. Note that
these bands are migrating northward with time, which should preclude
QPF like the Nam progs tonight. But still, some spotty precip could
perhaps make it down to terra firma in sw sections as soon as around
midnight. Those chancy pops will make slow northward progress
overnight, and by late in the overnight likely pops will ease into
the CAD/MBL area. Little if any precip near/north of GLR.

P-type will depend on the surface-based melting layer. and thus will
be somewhat elevation dependent, snow in the interior and rain closer
to the lakes. As the night proceeds and the BL cools slightly, p-
type will tend to favor snow, though will still keep things mixy
thru daybreak near Saginaw Bay and along the immediate Lake MI
coast. Any snow will be wet/sloppy, with surface temps barely
dropping down to freezing. And with only light QPF progged, accums
thru daybreak will be a dusting at most.

Min temps upper 20s to lower 30s.

Thursday...steady theta-e advection will help precip expand
northward, and otherwise become more extensive. Categorical pops
will arrive in southern areas toward late morning, and chancy pops
will reach eastern upper MI late in the day. Precip rates will also
steadily ramp up as the day proceeds (18z-00z QPF nears half an inch
in the far se).

Two p-type determinants: the still-vexing BL (which should get a bit
warmer again via diurnal effects) and, in southern areas, the
arrival of a warm nose aloft. P-type will start the morning as
mostly snow, but as the morning proceeds rain will become more
prevalent. Brief window exists for snow accums in the morning,
mainly in s-central sections. Will allow for around an inch of snow
from CAD over to Gladwin and W Branch. In the afternoon, the arrival
of the warm nose aloft will turn the far south to definite plain
rain, while allowing for the development of a sleet zone that may
reach TVC and W Branch by late in the day. Meanwhile, north of there,
the BL will start to cool again, and by late afternoon snow will
again become a more dominant p-type. Afternoon snow accums will be
less than an inch. Not anticipating much fzra thru 00z, as surface
temps should be above freezing where the warm nose is present.

Max temps upper 30s.

&&

.SHORT TERM...(Thursday night through Saturday)
Issued at 347 PM EDT Wed Mar 29 2017

...Wintry mix of precipitation Thursday night...

High Impact Weather Potential: Mixed precipitation event Thursday
night could result in some tricky driving conditions.

Pattern Synopsis/Forecast: Well developed split flow regime
continues to dominate the NOAM upper air pattern. Southern stream
portion of this regime by far the most active, with most prominent
feature within it being strong shortwave trough rotating across the
southern Plains. Moisture feed out ahead of this system is rather
impressive, with 60 to 70 degree dewpoints spreading in off the Gulf
of Mexico and attendant precipitable water values in excess of one
inch. While in large part the vast majority of the dynamics
associated with this southern stream wave will pass by to our south
in the coming days, its attendant moisture plume will not as strong
upper jet dynamics and subtle northern stream wave interaction work
in tandem to bring its moisture north. Marginally cold enough air
overhead as this moisture arrives definitely sets the stage for some
interesting precipitation type concerns Thursday and Thursday night.
Pattern looks to quiet down for a time thereafter as high pressure
once again builds into the area.

Primary forecast concerns: Precipitation type and amounts Thursday
night.

Details: Forcing will be maximized early Thursday evening as area
centers under right entrance region upper jet dynamics. Best forcing
expected to remain largely south of the big bridge, and collocated
nicely with northward surging moisture plume (precipitable water
values pushing three quarters of an inch across southern areas).
Expect a large area of precipitation to be ongoing Thursday evening,
especially across northern lower Michigan. Intensity of
precipitation should wane overnight as best forcing is lost and with
strong support for a scouring out of mid level moisture. Now, what
type this precipitation takes is a much more formidable challenge.
Trends have been for a bit more aggressive push of an elevated warm
nose (centered roughly within H7-H8 layer). Evaporational cooling
potential will also be well lost by then, and feel abundant clouds
and maintenance of east flow will keep surface temperatures near or
slightly above freezing through the overnight. Loss of that mid
level moisture also complicates things, with guidance derived
soundings definitely showing the development of a drizzle scenario
heading through the overnight. Given these trends, have trended the
forecast more toward a wintry mix/light rain idea, with more snow
north and all rain south. Overall snow/sleet accumulations should
remain light given marginal surface temperatures and a waning of
precipitation intensity. Far bigger concern is for freezing
rain/drizzle as those surface temperatures hover around freezing and
solar insolation is lost. Feeling is temperatures will remain too
marginal for any significant impacts, but definitely something we
will continue to monitor.

Deformation on northern extent of southern stream wave may linger
some precipitation across parts of the area on Friday, with a
warming boundary layer switching any lingering mix over to just
plain rain heading through the morning. High pressure will bring a
return to dry weather Friday night and Saturday. First day of April
solar insolation looks to do a number on temperatures Saturday, with
widespread highs in the 40s and lower 50s.

&&

.LONG TERM...(Saturday night through Wednesday)
Issued at 347 PM EDT Wed Mar 29 2017

High Impact Weather Potential...

It appears by Sunday, we will have turned the corner temperature-
wise, and be in for at least a few days of warmer than normal
conditions.  The upper level pattern would indicate a "dirty zonal"
flow...with some disturbances passing through periodically.  Most of
this action stays suppressed to the south to keep much of the period
dry.  However, some guidance hints at moisture taking a run at the
area around Tuesday.  Much uncertainty exists though...so we`ll keep
an eye on it.  Regardless, with all the warm air being advertised,
ptype issues shouldn`t be a problem.

&&

.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 135 PM EDT Wed Mar 29 2017

VFR into early overnight, then restrictions return to MBL/PLN
toward morning.

Last bits of leftover stratus/fog burning off in the TVC area.
High pressure near Hudson Bay continues to poke into MI today,
providing coolish/dry air. That will gradually give way, as low
pressure moves ene-ward from the central plains. High clouds are
thickening, and will steadily lower tonight. Precip could push
toward MBL/TVC toward morning, in the form of mixed rain/snow, and
MVFR cigs/vsbys. This won`t reach APN/PLN until later on Thursday.

Some lake breezes this afternoon. Easterly surface winds will
become somewhat brisk on Thursday.


&&

.MARINE...
Issued at 347 PM EDT Wed Mar 29 2017

Easterly winds will increase tonight into Thursday, ahead of low
pressure moving slowly ne from se KS. Small craft advisories will
likely be reached on many waters tonight into Thu, and will be
issuing some of those shortly.

&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LH...NONE.
LM...NONE.
LS...NONE.
&&

$$

NEAR TERM...JZ
SHORT TERM...MSB
LONG TERM...KAB
AVIATION...JZ
MARINE...JZ


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