Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 161133

Area Forecast Discussion
National Weather Service Marquette MI
633 AM EST Thu Nov 16 2017

.SHORT TERM...(Today and tonight)
Issued at 437 AM EST THU NOV 16 2017

Early this morning, low pressure continued to track north of Lake
Huron while high pressure began to drop south across the Upper
Mississippi Valley. This resulted in a strong pressure gradient and
resulting pressure rises spreading over the region, fostering the
development of strong and gusty north-northwest winds. The strongest
winds were confined to along the shore of Lake Superior. Lake effect
snow also impacted areas across the northwest to north wind snow
belts overnight and early this morning, but has begun to diminish in
intensity and coverage.

Through the rest of morning hours, expect the lake effect snow
showers to diminish from west to east. Even though the majority of
the expected accumulating snow has already fallen, roads may be snow
covered and slick this morning. Therefore, did issue an SPS to
highlight any potential impacts. Strong and gusty northerly winds
will continue to impact the shore of Lake Superior, especially
across Marquette and Alger Counties. With resulting large waves
due to the strong onshore flow, especially east of Marquette,
beach erosion and lakeshore flooding remain possible through the
mid-morning hours. Otherwise, things will quiet down through the
afternoon hours. Expect cloud cover to linger today, even as snow
showers dissipate. The combination of reduced insolation and
lingering cold air aloft should keep temperatures down today, in
fact little diurnal trend in temperatures are expected today,
especially across the east. The south central will see the larges
diurnal trends given the downslope northerly winds.

Tonight, return flow/warm air advection will work in concert with
developing southeasterly upslope surface winds to bring back chances
for widespread precipitation late tonight. With forecast soundings
show ample dry mid-level air, would not be surprised if the timing
of precipitation is delayed a bit further than currently reflected.
Once precipitation does start, looks like around or after midnight,
the primary precipitation type should be snow. Across the south
central and east, temperatures will gradually warm above freezing
through the early morning hours as the air mass becomes modified off
of Lake Michigan. This will allow precipitation to transition over
to rain. Before this transition takes place, there could be a period
of freezing rain. Overall, precipitation amounts are expected to
remain light.

.LONG TERM...(Friday through Wednesday)
Issued at 426 AM EST THU NOV 16 2017

Models suggest that a progressive pattern will prevail over the
northern CONUS from late this week into the middle of next week with
a mid level trough and associated storm system moving through the
Great Lakes on Saturday and another significant clipper shortwave
trough moving through next Tue with an accompanying blast of cold
air and nw flow LES into Wed.

Friday-Sunday, The models have converged toward the more consistent
ECMWF but remains slower than the GEFS mean solution. So, overall
confidence in the pcpn/winds forecasts has improved.

Following closer to the 00Z/12Z ECMWF, expect widespread pcpn mainly
as rain to spread across Upper Michigan Friday into Friday evening
with fairly strong WAA and moisture advection (PWAT above 0.75 inch)
as the sfc trough moves through the Upper MS valley into the western
Great Lakes. The WAA pcpn should diminish from west to east Fri
evening as the sfc trough moves through much of the cwa.

There may be some fzra mixed with snow west and central early Fri
with an elevated warm layer developing. Any fzra/fzdz should change
over to rain midday as temps climb into the mid 30s. Fzra or ice
potential will be limited by initial dry 900-700 mb layer as noted
on fcst soundings. Dryness through DGZ could also lead to more fzdz
than fzra mixing with the snow tonight/early Fri.

CAA and nw flow LES will develop Saturday afternoon behind the
deepening low with periods of LES possible into Sat night. Some
additional enhancement to les could be provided by mid-level
trough axis rotating through the area. 850 mb temps drop down to
-8C to -10C by late Saturday and drop to near -15C Sunday morning.

Big question on Sat is with best CAA delayed until at least late
in the day and Sat night, model soundings suggest convective
layer may be too shallow and not cold enough to get much in the
way of LES during the day on Saturday over the west half. Better
chcs for accumulating les will likely be Sat night into Sun for
the nw wind snowbelts, however shallowness of convective moist
layer and increasingly anticyclonic sfc-850 mb flow from the west
will likely keep amounts on the light side.

Any lingering LES should generally diminish Sun into Sun evening as
sfc and mid level ridging builds into the area.

Monday-Wednesday, model confidence in strength/timing of a clipper
shortwave moving in Mon night/Tue is low but CAA associated with
this feature should bring LES back into the area Tue into Wed for
the nw wind snowbelts as 850 mb temps fall around -15C by Wed.

.AVIATION...(For the 12Z TAFS through 12Z Friday morning)
Issued at 633 AM EST THU NOV 16 2017

Lingering lake effect snow will dissipate through the morning hours,
but expect at least MVFR ceilings to remain in place through much of
the day. Across the western terminals, conditions should improve to
VFR late today into the overnight hours. There is the potential for
light snow towards the very end of this TAF period. However, given
the stout dry mid-level air progged to be in place opted to hold off
on mentions at this time as the timing of this snow may be pushed
back even further. KSAW may see lower ceilings as upslope flow
continues with winds veering northerly to southeasterly. Otherwise,
winds will become south-southeasterly tonight and gusty towards
the latter half of this TAF period.


.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 437 AM EST THU NOV 16 2017

North-northwest gales of 35 to 40 knots continue this morning across
the central and eastern half of Lake Superior, but they are expected
to gradually diminish from west to east through the mid-morning
hours. As high pressure moves across the lake later today, winds
will continue to diminish to around or less than 20 knots briefly
tonight, before ramping back up during the overnight hours to 20 to
30 knots. By Friday morning, winds are expected to further increase
across the central and east to gales of 35 to 40 knots. Therefore, a
gale watch has been issued for Friday morning through much of the
day. Friday night into Saturday, winds will briefly subside to
around or less than 20 knots, but will veer northerly and increased
to 20 to 30 knots by Saturday morning. Another round of gales looks
possible late Saturday through Sunday morning across the central and
east. Sunday night into Monday, winds will relax to around or less
than 20 knots, but by Monday evening expect the winds to ramp up to
around 20 to 30 knots. Another round of gales looks possible Tuesday
into Wednesday.

Upper Michigan...
  Lakeshore Flood Advisory until 10 AM EST this morning for MIZ005-

Lake Superior...
  Gale Watch from late tonight through Friday afternoon for LSZ244-

  Gale Warning until 10 AM EST this morning for LSZ248>251-266-267.

  Gale Warning until 8 AM EST this morning for LSZ243>245-264-265.

Lake Michigan...
  Gale Warning until 10 AM EST this morning for LMZ221-248-250.

  Gale Watch from Friday morning through Friday evening for LMZ221-



SHORT TERM...Ritzman
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