Area Forecast Discussion
Issued by NWS Marquette, MI
FXUS63 KMQT 240538
Area Forecast Discussion
National Weather Service Marquette MI
1238 AM EST Fri Feb 24 2017
Issued at 943 PM EST THU FEB 23 2017
Due to the very dry llvl airmass shown on local 00Z raobs as well as
general diffluent llvl flow associated with weak sfc rdg axis over
the Upr Lks, removed the potential for any lk effect pcpn near Lk
Sup. A quick look at the incoming 00Z NAM and 01Z RAP shows sn
spreading into the scentral cwa late tngt, so wl maintain the 09Z
start to the advy time for that area.
.SHORT TERM...(This evening through Friday)
Issued at 341 PM EST THU FEB 23 2017
The main forecast concern through Friday evening will be the arrival
of system snow across the area on Friday, with the potential for
upslope/lake enhancement snow in the northeast wind snow belts
Friday afternoon/evening. The initial system snow looks like it
will be on the wet and heavy side, especially across central and
eastern portions of the area. In the afternoon hours, the snow is
expected to transition over to a mixture of freezing drizzle/ice
pellets across the east.
Afternoon water vapor imagery shows a strong, deep upper-level
trough beginning to lift out of the southern Rockies with a
strengthening lee cyclone developing in far southwest
Kansas/southeast Colorado. Tonight, expect mid and upper level
clouds to stream back northward as the above mentioned system begins
to lift northeast towards the Great Lakes region. Do not expect any
precipitation tonight; however, through the early morning and
morning hours as surface to 850mb flow veers to the north-northeast
expect light lake effect snows to develop in the north and northeast
wind snow belts. 850mb temperatures do not look terribly cold and
the inversions are quite low, so not expecting much in the way of
lake effect accumulations across the north through the early morning
hours on Friday. However, further south across south central
portions of Upper Michigan were 850-700mb warm air advection begins
to lift north through the early morning hours, a fairly strong mid-
level front will strengthen and may allow for a quick 1 to 2 inches
of wet, heavy snow to fall through the early morning hours.
As we progress through the mid-late morning through the afternoon
hours, the models are fairly consistent with the warm air advection
wing to lift north across the area allowing system snow to spread
north across the remainder of Upper Michigan. Temperature profiles
are on the warmer side of things, especially across eastern and
central portions of the area, so the snow should keep wet and heavy
characteristics. As we progress through the afternoon hours, the
models are fairly consistent with a dry slot moving over at least
eastern portions of the area. Forecast soundings show cloud ice
dissipating within the dry slot; however, given the depth of the low-
level cold air would not be surprised the freezing drizzle is able
to refreeze before reaching the ground. Therefore, may see a mixture
of freezing drizzle/ice pellets. Further west across central and
western portions of the area through the afternoon hours, things
are a bit more uncertain. The GFS would favor a much drier
solution and would hold off additional precipitation chances until
the evening hours, but given the onshore flow and cooling 850mb
temperatures behind the system tend to favor the high-res models
guidance that favor higher QPF, especially across the higher
terrain in the northeast wind snow belts.
.LONG TERM...(Friday night through Thursday)
Issued at 406 PM EST THU FEB 23 2017
Beginning Fri night, 4 km NAM and CMC regional soundings still
indicate mid-level drying into at least the east half of Upper Mi
through much of Friday night which could cut off ice nucleation
until cold advection at lower-levels reintroduces ice back into the
cloud for some lake enhanced snow. For now, fcst will continue to
reflect some mix with -fzra, more likely just -fzdz, which will cut
down snow accumulations over the e half to just 1-3 inches Fri
night. If the mid level moisture does not cut out, snow
accumulations will be higher than currently fcst Fri night. To the n
central and especially w, the air mass will be cold enough to
support lake enhancement as winds back more northerly. However, the
far w will be near the edge of deep layer moisture with the system,
making for a challenging fcst. The 4km NAM and Canadian sounding
maintain deeper moisture near KIWD through much of Fri night while
the GFS sounding shows deeper moisture cutting out already by late
Fri evening. This model difference could range from 6-12hrs of heavy
snow to mainly just light snow. Will continue to lean toward the
more conservative side with fcst for the n central and w with snow
accumulations Fri night in the 3-6 inch range.
System will exit on Sat with a transition to light LES from w to e.
Finally, gusty winds up to 30mph, higher at times in exposed areas
near Lake Superior, will lead to blsn, mainly Fri night into
early Sat afternoon.
As it appears now, the potential for snowfall amounts to reach 12 or
24hr warning criteria is limited so will go with winter weather
advisories at this point, highlighting a period of wet moderate
system snow Fri morning and then the potential for moderate to
possibly heavy lake enhanced snow late Fri into Fri night. Will
continue advisories over the ne counties through Sat for combination
of light les and blsn as northwest wind gust at or above 30 mph.
Some light les could linger for the west to northwest wind snowbelts
Sat night into early Mon as h85 temps hover around -14c through much
of the period.
The only other fcst item of note occurs during the midweek period
next week. Shortwave dropping down the W Coast Sun/Mon is fcst to
shift e and ne to the Great Lakes midweek. GFS is weaker and much
farther se than the 12z run yesterday. The CMC/ECMWF remain more
amplified and stronger with sfc low that will lift into the Great
Lakes, and suggest a low track far enough n for mixed pcpn or even
just rain for a time for at least the southeast parts of the fcst
area. Majority of CMC ensembles favor a warmer look, and fcst will
continue to include mixed pcpn. Thus will definitely be a system to
monitor for next week. After this system departs late Wed, models
suggest that at a clipper system will move through the Upper Lakes
region on Thu with the potential for some more light system snow.
.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 1237 AM EST FRI FEB 24 2017
As a lo pres to the sw moves toward the area this mrng, VFR
conditions wl give way to MVFR cigs at IWD and then CMX, while the
lower clds persist at SAW with an upslope nne wind. Some sn wl then
dvlp s-n acrs Upr MI as well. In concert with incrsg nne winds and
some blsn, expect a deterioration to IFR/perhaps LIFR vsbys by late
mrng to mid aftn, earliest at SAW. Since the sn/gusty winds/blsn are
likely to impact the sites thru this evng, predominant IFR to LIFR
vsbys wl persist thru the TAF period.
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 406 PM EST THU FEB 23 2017
NE to N gales to 35-40 kts are expected over much of Lake Superior
Fri morning into Fri night and NW gales to 35-40 knots are expected
for much of central and eastern Lake Superior Sat into Sat evening.
Some heavy freezing spray is possible Fri night into Sat, but
coverage will be limited to mainly the shoreline areas along north
central Upper Mi.
Winter Weather Advisory from 7 AM EST /6 AM CST/ this morning to
7 AM EST /6 AM CST/ Saturday for MIZ001>005-009-084.
Winter Weather Advisory from 7 AM this morning to 7 PM EST
Saturday for MIZ006-007-014-085.
Winter Weather Advisory from 4 AM EST /3 AM CST/ early this
morning to 1 AM EST /midnight CST/ Saturday for MIZ010>013.
Gale Warning from noon today to 10 PM EST Saturday for
Gale Warning from 7 AM EST /6 AM CST/ this morning to 1 AM EST
/midnight CST/ Saturday for LSZ162-263.
Gale Warning from 7 AM this morning to 7 PM EST this evening for