Area Forecast Discussion
Issued by NWS Marquette, MI

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000
FXUS63 KMQT 202021
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
421 PM EDT Thu Apr 20 2017

.SHORT TERM...(This evening through Friday)
Issued at 304 PM EDT THU APR 20 2017

The taste of early spring continues, as considerable cloudiness has
locked much of the Upper Peninsula into a very chilly and damp
environment. With the surface low lifting northeast across the Great
Lakes region, clouds have blocked the surfaces ability to warm which
held temps mainly in the middle to upper 30s. Low-level moisture
remains across the region; however, GOES-16 low-level satellite
imagery continues to indicate some drying arriving from the
southwest. This drying may held to push Td`s down a degree or two,
which should be just enough to switch the precipitation over to a
rain/snow mix or possibly all snow shortly after daylight hours. The
challenge will be with how much vertical lift remains. Atmosphere
becomes somewhat baggy with the lack of strong vertical ascent to
parcels, which could limit the ability to reach the dendritic growth
zone, thus inhibiting the ability to see stronger organization to
the snow showers tonight. This would then rely heavily upon the
topographic forcing to assist in lift. With a continued light
pressure gradient and winds turning northerly to northwesterly
tonight, still expecting some light accumulations to occur across
the Keweenaw Peninsula and possibly as far south as portions of
Marquette County. Will keep the winter wx advisory going for the
Keweenaw, but expect accumulations to range in the 2-4" category.
But rates could be intense for a few hours, when the bulk of this
could occur with reduced visiblities. Elsewhere for portions of
Marquette county accums will be closer to 1-2" at the most. By 09z
omega departs to the east with the vort axis pivoting east, and
heights beginning to rise. This could create a shallow stratus
layer, with drizzle. Temps tonight will only fall into the lower 30s
to possibly remaining in the mid 30s closer to Lake Michigan.

500mb trough becomes sluggish during the day Fri, which tries to
show a lagging trough over Lake Superior Fri aftn. On it`s heels
will be a anti-cyclonic feature progged to arrive by Fri ngt. With
less solar shielding expected during the day Fri, sfc temps shud
push into the lower 40s to perhaps middle 40s in the far southwest
CWFA. If clouds can easily depart, temps could push a degree or two
warmer. Precip will be exiting the region by mid-morning.

.LONG TERM...(Friday night through Thursday)
Issued at 418 PM EDT THU APR 20 2017

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

Friday night and Saturday, The combination of light winds and
clearing with PWAT values falling under 0.25 inch will allow temps
to fall into the mid 20s inland west near the lower end of
guidance. A good deal of sunshine and 850 mb temps rebounding to
around 4C on Saturday will allow max temps to rebound as high as
the low 60s over the western interior.

Saturday night through 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 available moisture, only chance
pops for rain showers mixed with snow were mentioned for mainly the
north before the dynamics weaken. The pcpn may mix with fzdz/dz as
the moisture becomes shallow, mainly below -10C. Even if there is a
return of at least some sunshine with trailing high pres on Sun, a
north wind off Lk Superior and 850 mb temps falling as low to around
-5C will result in below average temps ranging from the upper
30s/low 40s north to upper 40s to near 50 south central.

Mon-Thu, a developing WAA pattern ahead of the next significant
shortwave moving out of the Central Plains may bring some light snow
or possibly rain to the west as early as Sun night. The GFS was
faster in bringing in the warm air favoring mainly rain compared to
the colder ECMWF. However, any pcpn should be relatively light with
QPF less than 0.10 inch. The models were in reasonable agreement
with the timing of higher pcpn chances and amounts from Monday
night into early Tuesday as the shortwave and associated sfc low
move through the region. The track favors rain through the cwa
before colder air moves in behind a trailing cold front on
Tuesday.

Wed-Thu, there is greater uncertainty with pcpn potential and the
track/strength of the next shrtwv with larger differences between
the GFS and ECMWF and larger ensemble spread. For now, chance pops
for rain possibly changing to snow by wed night reflects model
consensus.
&&

.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 304 PM EDT THU APR 20 2017

Shallow stratus cloud deck has locked the region in IFR to LIFR
conds, and doesn`t appear to be lifting anytime soon. Will continue
with cloud bases tonight falling to around 300-600ft agl at the TAF
sites. Precip type could be a challenge tonight, but expect thru 6z
precip to be a RASN mix. Then as temperatures cool a switch over to
lgt snow to develop. VSBYs could frequently fluctuate between 1-4sm
tonight as well, but by daybreak winds should be shifting to the
northwest and drier air filtering in from west to east. This should
steadily lift CIGs back to around MVFR conds by late Fri morning and
perhaps VFR conds by early Fri afternoon.
&&

.MARINE..

East-northeast gales of 35 to 40 knots are expected through this
evening. Winds will decrease to around 20 to 30 knots as they back
to the north tonight into Friday. Winds will then stay below 25
knots until Mon night and Tue with east to northeast winds of 20-30
knots are forecast.
&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
  Winter Weather Advisory until 11 PM EDT this evening for MIZ001-
     003.

Lake Superior...
  Gale Warning until 6 PM EDT this evening for LSZ249>251-266-267.

  Gale Warning until 5 PM EDT /4 PM CDT/ this afternoon for LSZ162-
     244>248-263>265.

Lake Michigan...
None.
&&

$$

SHORT TERM...Beachler
LONG TERM...JLB
AVIATION...Beachler
MARINE...Beachler



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