Area Forecast Discussion
Issued by NWS Gaylord, MI

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678
FXUS63 KAPX 301717
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
117 PM EDT Thu Mar 30 2017

.UPDATE...
Issued at 1116 AM EDT Thu Mar 30 2017

Overview: Parent stacked/occluding low pressure system analyzed
over the Kansas/Missouri border this morning with a warm front
stretching eastward through Kentucky. Surface high pressure sits
over western Quebec down into the northern lakes. Strong upper
jet core stretches through the mid Mississippi River Valley with a
secondary core across the northern lakes...placing lower Michigan
within a favored upper divergence region of the coupled jet
structure.

Nice "warm conveyor belt" of moisture stretches from the Gulf up
into the western Great Lakes this morning. Precipitation becomes
most expansive across the lower Great Lakes well north of the
surface warm front...where a tight low-mid level thermal gradient
and strong deformation exists...coupled with the aforementioned
upper jet forcing. But northward advancement of precip thus far
this morning has "hit a wall" south of M-55...the result of dry
low level easterly flow across northern Michigan around the
Canadian high and likely part of the descending branch of the
upper jet circulation.

Rest of today: As mentioned above, regional radar plot tells the
story, at least in the near term. Northward advancement of more
widespread precip has pretty much halted south of M-55...just
getting into far Gladwin/Arenac counties. 12Z NAM forecast as well
as latest HRR trends now suggesting precip will largely remain out
of this CWA through much of the afternoon...save for parts of
Gladwin/Arenac counties. Again, radar trends certainly support
that idea. At this point, my plan is to reduce POPS/QPF/accumulations
through at least mid to late afternoon.

Late this afternoon/tonight: Guidance trends still support the
idea of another piece of upper jet forcing/enhanced precip
sliding out of Illinois and up through the SE part of the CWA late
this afternoon into the evening. One can already see this next
batch of precip blossoming over Illinois. So...will see how that
evolves and will have to play around with precip type for late
afternoon into this evening.

&&

.NEAR TERM...(Today through Tonight)
Issued at 431 AM EDT Thu Mar 30 2017

High impact weather potential: A wintry mix and possible slippery
roads tonight.

Pattern synopsis and forecast:

Early this morning, sfc high pressure continues to nose into the
Great Lakes. However, sprawling low pressure/stacked system in the
south central plains is ejecting shortwave energy along an elevated
warm front across much of srn lower Michigan. Somewhat high based
reflectivities seen on regional radars sneaking into areas south of
M-72 over the past handful of hours (mainly light snow/flurries),
within nrn extent of strongest low to mid level warm advection. The
better/heavier precipitation is still well back to the SW in nrn IL
where the strongest forcing resided, consisting of that WAA, upper
divergence in double jet structure and stronger DPVA ahead of the
stacked low.

Forecast concerns: Still some significant disagreement in location
and amounts of QPF, along with sfc temperatures due to wetbulbing
effects. This impacts where and how much snow resides, and what
precip type is expected.

From a synoptic pattern perspective, the stacked low pressure system
will track in an east-northeast manner into Indiana by Friday
daybreak. This will bring deepening moisture and stronger forcing
via the WAA, upper divergence and DPVA into the region. The location
of the strongest forcing attm looks to be in the SE CWA along and
south of a line from Cadillac to Alpena. Again, the issue here is
that there are significant differences in the data sets. The main
two issues are what the sfc temperature will be and whether or not
an FGEN band can develop this afternoon across the SE CWA. Hi-res
guidance is dead set on sfc temperatures cooling off through
afternoon via wetbulb effects. Essentially allowing for a longer
period of snow and not a mix which would limit accumulations.
However, we will likely need the stronger precipitation for enough
wetbulbing to reduce that temperature and keep it snow. This is
likely going to be relying on the FGEN to be there. Some of the hi-
res snowfall forecasts are insanely high, with double digit totals
being seen. Am certainly not going that direction to full extent, or
nowhere near it since some other data sets suggest much much lower
QPF numbers. This is a really tough scenario, and folks will
definitely want to pay attention to later forecast for updated
information, or just be ready for higher snowfall totals that the 1-
3 inches are forecast.

The stronger forcing departs after early evening, and there are
hints of periods of time where deeper moisture is stripped out enough
for less/no ice activation. This will lead to periods of light rain
and drizzle, with maybe some light freezing precip in the coolest
temperatures in the interior higher terrain of nrn lower.

This whole event doesn`t look to impact much of eastern upper, where
far SE sections of Chippewa and Mackinac counties may receive some
minor snowfall by tonight`s end.

&&

.SHORT TERM...(Friday through Saturday)
Issued at 431 AM EDT Thu Mar 30 2017

...Precip diminishes Friday followed by pleasant weekend weather...

High impact weather potential: Minimal. Brief wintry mix
transitions to all rain Friday morning.

Pattern Forecast: Area of low pressure is progged to be centered
over northern Indiana/southern Lower MI by Friday morning with
deformation precip plaguing portions of northern Michigan through
the midday hours Friday before pulling away toward the East Coast.
The patterns becomes much more quiet over the weekend, with little
in the way of sensible weather locally, as high pressure settles
atop the western Great Lakes.

Primary Forecast Concerns: The main forecast concerns revolve around
diminishing precipitation trends Friday morning into the early
afternoon. As was previously mentioned, deformation precip on the
northern periphery of low pressure/southern stream wave is expected
to linger across portions of the area Friday morning. With boundary
layer temps continuing to warm through midday, any early
lingering mixed rain/freezing rain, drizzle and snow across the
Tip of the Mitt and eastern Upper is expected to transition to
plain rain/drizzle as we head through the morning. Latest trends
suggest stubborn low-level moisture may allow for a good chunk of
northern Michigan to remain stuck under low clouds and patchy
drizzle through at least early afternoon (if not longer across
eastern areas) before a more significant shot of low-level dry air
impedes on the area from northwest to southeast. Expecting breaks
in the clouds to begin to first work their in across eastern
Upper/far northwest Lower during the mid-late afternoon and
elsewhere throughout the evening. High temperatures near 40 area-
wide...perhaps a bit warmer across eastern Upper/Tip of the Mitt
with a bit of afternoon sun.

Canadian high pressure begins to settle atop the Great Lakes Friday
night and more so Saturday-Saturday night. Despite a weak wave
zipping through fairly zonal upper-level flow during the day
Saturday, the forecast will represent little more than a bit of
increased cloud cover Saturday afternoon and night as in-place dry
air should stave off any light shower/sprinkle threat. Widespread
high temps in the mid-40s to low 50s.

.LONG TERM...(Saturday night through Wednesday)
Issued at 431 AM EDT Thu Mar 30 2017

High Impact Weather Potential...

Another fairly pleasant day is expected across northern Michigan on
Sunday with above normal temperatures, but increasing cloudiness as
the day wears on. Fairly progressive northern stream wave is
expected to be toeing the U.S./Canada border near International
Falls by Sunday evening, which may spread scattered showers across
the area Sunday night. Next week - a fairly active storm track looks
to be setting up across the CONUS with several waves diving into the
four-corners region before ejecting lee of the Rockies. Plenty of
guidance spread in the day 5-8 timeframe to warrant much in the way
of details, but worth monitoring for several wet (perhaps more
wintry late next week?) systems to work their way through the
heart of the country.

&&

.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 116 PM EDT Thu Mar 30 2017

Low pressure over the mid Mississippi River Valley will track
northeastward through the lower Great Lakes Region tonight into
Friday. Most persistent precip and lower flight categories will
remain across central and southern lower Michigan through the
afternoon...with mainly VFR across much of northern lower
Michigan. But...precip and lowering flight categories will creep
northward tonight bringing the terminal sites down to MVFR with
lower CIGS and reduced VSBYS in rain/snow.

Precip diminishes on Friday, although MVFR conditions will remain
through much of the day.


&&

.MARINE...
Issued at 431 AM EDT Thu Mar 30 2017

A low pressure system will track in an east-northeast manner into
Indiana by Friday daybreak and then into mid Atlantic by Friday
night. A mix of rain and snow will impact the nearshore waters along
with strengthening easterly winds today into Friday morning.
Advisory level winds are expected over this time for all of Lake
Huron and Michigan. Less chance across Whitefish Bay. Winds back
more out of the NE later Friday and Friday night with NE lower
nearshores seeing the continuation of advisory speeds. Winds weaken
through the latter hours of Friday night.


&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LH...SMALL CRAFT ADVISORY until 5 PM EDT Friday for LHZ345-347>349.
LM...SMALL CRAFT ADVISORY until 5 PM EDT Friday for LMZ323-342-
     344>346.
     SMALL CRAFT ADVISORY until 5 AM EDT Friday for LMZ341.
LS...NONE.
&&

$$

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



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