Area Forecast Discussion
Issued by NWS Marquette, MI

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000
FXUS63 KMQT 280914
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
514 AM EDT Thu Mar 28 2024

.KEY MESSAGES...

- Westerly lake effect snow continues through this afternoon,
  mainly across the Copper Country.

- Next chance of widespread precipitation occurs Friday night
  and Saturday. Mix of light rain/snow expected with some
  freezing rain possible late Friday night/early Saturday
  morning toward MI/WI stateline.

- Another system arrives in the Great Lakes Monday/Tuesday,
  bringing some light rain/snow.

- Temperatures around normal to below normal through the middle
  of next week.

&&

.SHORT TERM /THROUGH TODAY/...
Issued at 452 AM EDT Thu Mar 28 2024

West-southwesterly surface flow continues early this morning as
Upper Michigan remains under the influence of broad cyclonic flow.
The mid-level low in association with this pattern is currently
situated over the Hudson Bay per latest water vapor imagery/RAP
analysis. Wind gusts have, however, tapered off a bit over the last
few hours with most places only gusting up to 20 mph, highest across
Copper country.  And, as forecast soundings take on more of an
inverted-v signature later this morning, snowfall will taper off
over the Keweenaw.  As a result, the current winter headlines for
that area will be allowed to expire at Thu 12Z.  Nonetheless, HREF
guidance does trend toward an additional 2 to 4 inches along the
spine of the Keweenaw through Thu 18Z.  At that point though,
subsidence will strengthen as high pressure overspreads western
Wisconsin, resulting in a downward trend in lake effect snow showers
over the west wind snow belts through late afternoon.  Meanwhile,
the remainder of the forecast area will generally be dry, and
daytime highs will range from the upper 20s/low 30s across the
west/Keweenaw/north central to mid/upper 30s over south central and
east. Farthest south could top off near 40.

&&

.LONG TERM /TONIGHT THROUGH WEDNESDAY/...
Issued at 508 AM EDT Thu Mar 28 2024

Models remain consistent in depicting blocky high latitude flow into
next week with the AO and NAO both in the negative phases, though
the AO only weakly. Positive height anomalies of varying amplitude
across northern and eastern Canada are still expected to consolidate
into a strong anomaly over the Labrador Sea/Davis Strait region
early next week. Meanwhile, a building ridge over the N Pacific is
still expected to shift e and tilt ne into sw Canada early next
week. For Upper MI, these changes in the flow with the
shifting/evolving anomalies will result in temps around normal to
slightly blo normal thru the middle of next week. Trof that has been
affecting Upper MI in recent days will shift to se Canada and the E
Coast by Fri, allowing its influence on our weather to fade
today/tonight. Dry weather will follow on Fri under sfc high pres
ridging. Out w, a trof will be amplifying down the W Coast over the
next few days in response to the building upstream ridge over the N
Pacific. A couple of shortwaves ejecting from the amplifying trof
will track to the Great Lakes region by Sat, bringing the next chc
of widespread pcpn during late Fri night/Sat. Pcpn likely to be on
the light side. Early next week, the combination of ridging into
western Canada and consolidating/strengthening positive height
anomaly over the Labrador Sea/Davis Strait will force troffing into
s central and se Canada. Meanwhile, the trof over the w will begin
to shift downstream. This brings some potential for interaction of
that trof progressing out of the western U.S. with shortwaves forced
s and se due to the western Canada ridge and Labrador Sea anomaly.
For many days, there have been some EPS/GEFS/GEPS ensemble members
showing sufficient interaction for a significant pcpn event for
Upper MI during Mon/Tue, including accumulating snow. The overall
number of ensembles indicating such an event remains small and
appears to have trended slightly fewer over the last 24hrs. So,
what has always been a very low probability of occurrence has
diminished a little more. Some pcpn is still expected Mon/Tue.

Beginning tonight, any lingering flurries over nw Upper MI will end
during the evening. To the e, with 850mb temps hovering around
-11/-12C thru the night, light LES/flurries will linger. Winds veer
a bit during the night as a weak sfc trof drops across the lake, and
the convergence should support a little increase in -shsn coverage
for a time as the trof passes. The light LES/flurries will occur
from around Munising eastward. Elsewhere, expect a quiet night with
winds becoming light as sfc high pres ridge approaches. With low-
level winds veering more nw during the night, there may be some
increase in lake stratocu, complicating temp fcst over the interior
w. For now, expect min temps in the mid teens to mid 20s F, but if
clouds are limited, temps could easily fall into the single digits
at traditional cold spots across the w half.

Sfc high pres ridge drifts across Upper MI on Fri, leading to quiet
day. Lingering lake stratocu will clear out, but high clouds will be
on the increase, at least across the west in the aftn. High temps
will range from the 30s near Lake Superior to mid 40s F interior w
half.

Pair of shortwaves moving across the Plains and vcnty of the
International Border will reach the Great Lakes region Sat morning.
Reflection at the sfc will be a weak sfc low pres tracking from the
central Plains to the Lwr Great Lakes with an inverted trof
extending nw from the low in response to shortwave moving along the
vcnty of the International Border. WAA/isentropic ascent will aid
-sn development, likely not beginning until after midnight Fri night
over the w, then spreading e thru Sat morning. There is some
potential of -fzra, but models don`t agree on whether waa will push
temps above freezing somewhere in the 2-5kft agl layer. The last few
runs of guidance support keeping a mention -fzra closer the MI/WI
stateline, generally btwn Iron Mtn and Watersmeet. Otherwise, the
-sn will mix with -ra on Sat before ending w to e during the
aftn/early evening. An inch or two of wet snow accumulation is
possible. Ensemble probabilities indicate western Upper MI has the
best chc of some accumulating snow as inverted trof does weaken as
it moves across the area.

Dry weather follows Sat night thru Sun with seasonable temps for the
end of Mar. Then, as previously mentioned, fcst early next week will
hinge on potential interaction of a progressing western trof with
shortwaves dropping around a western Canada ridge. There are still a
relatively small number of EPS/GEFS/GEPS ensemble members that bring
a significant snow event to portions of Upper MI with some of the
low pressures still dropping into the 980s mb even a few 970s mb.
The deeper ensemble members from the GFS are closer to Upper MI than
those from the GEPS/EPS. Overall, it appears that the number of
ensemble members indicating a significant snowfall for Upper MI has
decreased a little, though the 00z GEFS shows a few more than the
previous run. The positive tilt of the trof progressing downstream
from the western U.S. is not a favorable setup for phasing of
shortwaves or for a significant system to spin up unless a strong
northern stream wave can drop sharply southward. So, don`t
anticipate to see such a system affect Upper MI early next. However,
since the ensembles have not given up on the potential, it`s still
worth monitoring. Fcst will reflect a 30-50pct chc of -sn/-ra
Mon/Tue. Drying will follow Wed/Thu.

&&

.AVIATION /06Z TAFS THROUGH 06Z FRIDAY/...
Issued at 111 AM EDT Thu Mar 28 2024

The lake-effect snowfall will gradually dwindle throughout the TAF
period over the west snow belts as ridging builds in from our west.
While KIWD hangs on to MVFR cigs early this morning, expect it to
improve to VFR before dawn this morning as the cloud cigs lift due
to the departing low. That being said, we could (50% chance) see
MVFR cigs return again for a few hours over KIWD late this morning
before settling into VFR conditions for the rest of the TAF period.
As for KCMX, IFR conditions are expected to continue early this
morning due to the continuing lake-effect snow. With most of the
CAMs showing the snowfall rates lightening up after 8 AM EDT, I`m
thinking we will see an improvement to MVFR conditions by late this
morning over the Keweenaw; we could even see VFR conditions return
this evening as the peak of the incoming ridging moves into the far
western U.P. As for KSAW, expect VFR conditions across the TAF
period. While some blustery westerly winds could be seen early this
morning, winds look to weaken by this evening as the ridging moves
in.

&&

.MARINE...
Issued at 508 AM EDT Thu Mar 28 2024

With low pres to the n weakening and a high pres ridge approaching
from the w, westerly winds across Lake Superior will be settling
back, especially tonight. A few gale gusts to 35kt will linger early
this morning over eastern Lake Superior. Otherwise, winds up to 30kt
for much of today will fall back to under 20kt from w to e late
tonight thru Fri morning as the sfc high pres ridge arrives. An
approaching sfc trof will bring an increase in E to NE winds over
western Lake Superior Fri night. Gusts up to 25kt will be possible
at that time. Otherwise, with no significant systems in the area
thru the weekend, expect winds mostly under 20kt thru Sun.

&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
  Winter Weather Advisory until 8 AM EDT this morning for MIZ001-
     002.

  Winter Storm Warning until 8 AM EDT this morning for MIZ003.

Lake Superior...
  Small Craft Advisory until 8 PM EDT /7 PM CDT/ this evening
     for LSZ240>244.

  Small Craft Advisory until 8 AM EDT this morning for LSZ249.

  Small Craft Advisory until 2 AM EDT Friday for LSZ250-251.

Lake Michigan...
None.

&&

$$

SHORT TERM...TDUD
LONG TERM...Rolfson
AVIATION...TAP
MARINE...Rolfson


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