Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 192350
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
750 PM EDT Wed Apr 19 2017

.SHORT TERM...(This evening through Thursday)
Issued at 347 PM EDT WED APR 19 2017

The main forecast concern is the arrival of rain and snow later
tonight and on Thursday as an area of low pressure tracks just south
of Upper Michigan. There is still quite a bit of uncertainty in
overall precipitation amounts given the spread among the models.
However, the Keweenaw Peninsula and the higher terrain across the
north central and west looks to have the highest chance at seeing
accumulating wet, heavy snow. Along with snow, the system will bring
gusty east-northeast winds to the whole area.

The deterministic and ensembles are in fairly good agreement with
low pressure lifting northeast across southern and central
Wisconsin, and eventually across northern portions of Lake Michigan
tonight and through the day on Thursday. Precipitation wise, there
is still some discrepancies among the models with the NAM being the
most robust with the amount of QPF expected. Considering the
moisture transport is predominately anchored across south central
and up into eastern portions of the area later tonight, thinking
that is where the highest QPF amounts will come to fruition.
Precipitation still has to make it all the way across Wisconsin, so
do not expect precipitation to reach south and western portions of
the area until roughly after 8pm EDT. Across the south central and
east, as warm air advection increases, expect precipitation to
remain all liquid. Some locations may also hear a few rumbles of
thunder as MUCAPE values upwards of 200 J/Kg lift into the area
ahead of the surface low. Further to the north across north central
and the western portions of Upper Michigan, things get quite a bit
more complicated. At first, precipitation is expected to fall as
rain, but as lift increases across the area expect rain to begin to
mix with snow, and then eventually transition over to all snow by
the morning hours on Thursday. Thermal profiles do not look terribly
impressive as we never quite reach the dendritic growth zone and in
some locations teeter on the edge of rain versus snow. However,
given the ample lift, thinking that we will see a good chance at
seeing accumulating wet and heavy snow through Thursday across the
north central and west.

Across the north central portions of the area, the highest snowfall
accumulations are expected to remain across the high terrain, where
2-4 inches looks possible. However, do expect the snow to transition
back over to rain briefly during the mid/late morning hours. Models
are fairly consistent with a dry slot moving up and across the area,
so would not be surprised if we see a break in precipitation during
the afternoon, before wrap around precipitation moves back in from
the north. As this wrap around precipitation comes back in, expect
it to mostly be snow across the central portions of the area as
colder air begins to advection further south behind the system.
Further west expect precipitation to remain mostly snow with 1-5
inches of snow possible. The higher amounts are expected to occur
across the Keweenaw where upslope flow will augment lift and overall
snowfall amounts.

.LONG TERM...(Thursday night through Wednesday)
Issued at 446 PM EDT WED APR 19 2017

Models suggest that a progressive split flow pattern will prevail
into the middle of next week with temperatures generally remaining
below average.

Thursday night, Expect the pcpn to diminish w-e as the
shortwave and dynamic support exit to the e. But clouds and some
lighter pcpn will persist thru the night especially over the
northern tier with lingering cyclonic upslope northerly flow.
additional snowfall amounts of an inch or two will be possible
mainly over the Keweenaw and Huron Mountains. So, the advy for the
Keweenaw will extend through the evening. With only marginal
moisture to -10C especially central, a mix with fzdz/dz is
possible with the potential for some minor ice accumulation in the
higher terrain.

Friday through Saturday, High pressure building into the northern
Great Lakes in the wake of the departing low will bring a drying
trend to the cwa Fri, with gradual clearing as the low level flow
becomes more anticyclonic. Expect some lingering -shsn/shra and
fzdz/dz from Marquette eastward in the morning where cyclonic nw
will persist a bit longer. Lingering clouds and nrly winds off of
Lake Superior will limit max temps to the lower 40s near the lake.
The combination of light winds and clearing with PWAT values falling
under 0.25 inch will allow temps to fall into low to mid 20s inland
west near the lower end of guidance. A good deal of sunshine and 850
mb temps rebounding to around 3C on Saturday will allow max temps to
rebound as high as the low 60s over the western interior.

Sunday, A nrn stream shortwave trough is expected to move through nw
Ontario and drag a cold front across the nrn Great Lakes from
Saturday night into Sun morning. With only moderate fgen forcing and
limited moisture available, only chance pops for rain showers mixed
with snow were mentioned for mainly the north before the dynamics
weaken. Even if there is a return of at least some sunshine with
trailing high pres on Sun, a north wind off Lk Superior and h85
temps falling to near -8C will result in below average temps.

Mon-Wed, a developing WAA pattern ahead of the next signficant
shrtwv moving out of the cntrl plains may bring some light rain to
the west as early as Monday. However, the models were in reasonable
agreement with the timing of higher pcpn chances from Monday night
into early Tuesday. Although there is still some uncertaintly with
the track, a nrly trend with the path of the system will favor
mainly rain.
&&

.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 750 PM EDT WED APR 19 2017

Approaching disturbance will spread pcpn and deteriorating
conditions into Upper MI tonight. During the evening, MVFR cigs at
KIWD/KCMX/KSAW may scatter out at times before rain arrives. In
general, expect conditions at all 3 terminals to fall to IFR late in
the night and to LIFR Thu morning. The rain may mix with or change
to snow at times overnight and Thu with snow probably more likely to
become the predominant ptype at KCMX. LLWS is possible at KIWD
overnight/early Thu morning.
&&

.MARINE..

East-northeast gales of 35 to 40 knots are expected late tonight
through the day on Thursday. Winds will decrease to around 20 to 30
knots as they back to the north Thursday night through Friday. Friday
into Saturday, winds will further decrease to around 10 to 20 knots
and back to the southwest. Sunday through Monday, winds will be
generally 15 to 25 mph with varying directions as high pressure
exits the region and a cold front pushes south across the area.
Tuesday winds will increase to 25 to 30 knots as another system
lifts out of the Plains and up across the northern Great Lakes.
&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
  Winter Weather Advisory from 6 AM to 11 PM EDT Thursday for
     MIZ001-003.

Lake Superior...
  Gale Warning from 8 AM to 6 PM EDT Thursday for LSZ249>251-266-
     267.

  Gale Warning from 6 AM EDT /5 AM CDT/ to 5 PM EDT /4 PM CDT/
     Thursday for LSZ162-263.

  Gale Warning from 8 AM to 5 PM EDT Thursday for LSZ244>248-264-
     265.

Lake Michigan...
  Gale Warning from 5 AM to 2 PM EDT Thursday for LMZ248-250.

  Gale Warning from 5 AM to 1 PM EDT Thursday for LMZ221.

&&

$$

SHORT TERM...Ritzman
LONG TERM...JLB
AVIATION...Rolfson
MARINE...Ritzman



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