FXUS63 KMQT 081732

Area Forecast Discussion
National Weather Service Marquette MI
1232 PM EST Fri Dec 8 2023

.SHORT TERM...(Early this morning and today)
Issued at 148 AM EST FRI DEC 8 2023

Key Messages:
-Morning fog may be dense in spots across Central Upper Michigan.
-Pockets of drizzle this morning central and west this morning.
-Another warm day with highs in the 40s. Breezy winds possible near
the lakeshores.

Mid-upper level ridge overhead with a moist and warm airmass at the
surface under southerly upslope flow has supported a low cloud deck
with pockets of fog across the central portions of Upper Michigan.
So far, dense fog hasn't been observed, but I suspect some isolated
pockets are out there. This has largely kept temperatures mild, with
all obs under the cloud canopy in the mid-upper 30s. Outside of this
area, higher and scattered clouds have supported some cooler
conditions, but those have only been able to fall into the low to
mid 30s so far. Some gusty winds have been observed over Lake
Superior thanks to a stronger pressure gradient ahead of a system
lifting into Ontario today. Some surface obs near the lakeshores
have been in the 20-30 mph range this morning. I suspect there may
be a localized terrain enhancement to some of these, particularly in
the Keweenaw and near Munising.

As we progress through the early morning hours, the winds will
remain out of the south or southeast through early afternoon.
Expecting the ongoing gusty winds to continue until then, when they
shift to southwesterly. Before this, a wave of weak isentropic
ascent, coupled with the upslope moist flow may support drizzle
across mostly the central portions of Upper Michigan. Model
soundings also show a saturated near surface layer across the
Keweenaw as well, which would also support pockets of drizzle there
as well. Its not out of the realm of possibility for some freezing
drizzle to develop, particularly in areas that are in the low 30s
right now; however, accumulation or impacts are not expected. Temps
should begin warming as the sunrises and mix out any lingering fog.
Expecting another warm day with highs in the low to mid 40s.

.LONG TERM...(Tonight through Thursday)
Issued at 536 AM EST FRI DEC 8 2023

Key messages:

- No widespread, significant system snowfalls across Upper MI thru
next week.
- Quick-moving low pressure brings rain and some snow Saturday. Snow
potential greatest in a narrow swath over a portion of the west and
central U.P., but probability of more than 2 inches of snow for
now is less than 10 percent.
- 2 to 5 inches of lake enhanced and lake effect snow is likely (at
least 60% chance) for areas favored by nw winds Saturday night into
- Above normal temps to prevail on most days through next week with
warmth peaking again late next week.

The slow start to establishing typical winter snow cover in Upper MI
will continue. At this point in the season so far, most of Upper MI
is currently running at only 25-50pct of the mean snowfall based on
a Sept 1st to Dec 7th 1991-2020 mean per the Midwest Regional
Climate Center. Only far eastern Upper MI is near the mean. Medium
range model guidance is in good agreement in showing western N
America ridging and eastern N America troffing into early next week,
followed by deamplification of the flow thru late week. With the
western ridge broad, a build up of arctic air will not occur in
Canada. As the flow deamplifies and ridging/positive height
anomalies shift downstream mid and late next week, Pacific
air/anomalous warmth will spread e across southern Canada, sending
temps 15-30F degrees above the long term avg during the last half of
the week. With the Dec warmth to the n, above normal temps will
prevail overall for Upper MI thru next week, but eastern troffing
will allow for temps to fall back to at least around the early to
mid Dec normals thru early next week (Sun and Tue coolest days). A
notable stronger push of warming alluded to above, similar to what
is currently being experienced across Upper MI, will occur a week
from now. Looking beyond next week at the week before Christmas,
ensembles, EPS in particular, show positive height anomalies and
widespread above normal temps spread across southern Canada, the
Northern Plains into the Great Lakes. The latest CFSv2 points to a
similar above normal temp regime, and it continues that warm pattern
right thru the end of the month. However, the 00z 12/7 run of the
ECMWF weeklies points toward a cooling trend late month. As for
pcpn, a shortwave lifting into the Great Lakes on Sat, followed by
another wave arriving from the w, will bring the only notable pcpn
event from now thru all of next week. Initially, pcpn will be mostly
rain with a change to snow from w to e thru Sat night as a
transition to nw flow lake effect occurs. A few inches of snow will
be possible across the w and n. Lingering nw flow LES will wind down
Sun/Sun night. Thereafter, no significant pcpn events are expected,
and thus no widespread, significant snowfalls either. In fact,
pcpn/snowfall will be well below normal with very little pcpn/snow
outside of the lake effect areas, and even there, snowfall thru next
week will be well blo normal. A second push of colder air Mon night
into Tue will bring the only other round of LES, but it will be

Beginning tonight, mid-level troffing will extend from
Manitoba/northern Ontario to the Rockies with unphased shortwaves
within in it. One wave will support sfc low pres just n of
International Falls, and that low will drift ne during the night. A
couple of more waves will be moving into and thru the base of the
trof with one then heading ne toward the western Great Lakes by Sat
morning. For Upper MI, end result will be a mostly dry night with
unseasonably warm conditions for Dec. After the mild day today,
cloud cover will hold temps up tonight. Min temps will be around
some of the record high mins for the date across Upper MI. Here at
NWS Marquette in Negaunee Township the record high min temp for Dec
9 is 32F, but temps will likely fall blo that before midnight Sat
night. Rain associated with the wave lifting toward the western
Great Lakes will begin to spread into the s central fcst area around

Although just 24-36hr time frame from initialization, models still
show quite a bit of disagreement on the relatively compact pcpn
shield developing with the wave lifting thru western Great Lakes on
Sat. The regional CMC is most bullish with pcpn spreading across all
of w and central Upper MI while the FV3 and ARW barely brush
Schoolcraft and Luce counties. Based on consensus of recent and
latest model runs, including the previous fcst, will paint 60-90pct
chc of pcpn over the central and eastern fcst area with a sharp drop
to no pcpn mention over far western Upper MI. Given the antecedent
warmth over the area, unphased waves and positive tilt of the mid-
level trof, expect most of the pcpn with this first wave to be in
the form of rain on Sat, and this is shown by the downward trend in
snow accumulation probabilities from the NBM. If snow occurs, it
would be over central portions of Upper MI
(Baraga/Marquette/Iron/Dickinson counties). Expect little
accumulation (less than 1 inch with no travel impacts due to above
freezing temps). That said, the recently arrived 06z HRRR/NAM paint
a more concerning outcome with the sfc low tracking farther w,
including a narrow mdt/hvy pcpn band developing just w of the
center, basically in the aforementioned counties. Stronger
forcing/dynamic cooling would also likely favor a shift to hvy/wet
snow. We'll see if the upcoming 12z model runs support the 06z
HRRR/NAM trend. If so, a stripe of 2-5 inches of sloppy/wet snow
accumulation would certainly be possible on Sat, occurring over just
a 3-5hr period. Travel impacts would also be expected. To the w,
another shortwave will support a sharpening sfc trof that will sweep
into western Upper MI late aftn/early evening. 850mb temps falling
blo -4C will support lake enhancement. Wetbulb zero heights above
700ft AGL suggest some rain initially at low elevations near the
lake as this next batch of pcpn initially arrives/develops. Snow
will become steadier during the evening as the trof/wind shift
passes. Fcst soundings don't show much of a favorable overlap of the
upward motion with the DGZ, and that combined with temps around
freezing will hold snow accumulations down during the best period of
forcing. By Sun aftn, NBM 50th percentile snow accumulations are
only 1.5-2 inches, which seems underdone given the period of lake
enhancement. The 90th percentile is 4-5 inches in the usual highest
terrain areas, and that seems like a better fit for this situation.
The trof will shift e thru Sat night, bringing lake enhanced
rain/snow changing to snow. Accumulations e will be lower than over
the w.

Deeper moisture departs from w to e late Sat night thru Sun morning,
marking a transition to pure nw flow LES under 850mb temps of -10 to
-12C. DGZ will be near the top of the convective layer and largely
above the best upward motion, so SLRs will be held down a bit. With
inversions at around 4kft w, LES will be light. To the e, inversions
upwards of 6-7kft will support better LES and 1-3 inch snow
accumulations on Sun. The lingering LES will end w to e Sun night
into early Mon morning.

Next shortwave will dive se into northern Ontario and Upper MI Mon
night. WAA/isentropic ascent ahead of this wave should lead to some
-sn developing across the n and e Mon night, followed by nw flow LES
for Tue as 850mb temps dive toward -16C. Drier air mass flowing into
the area with the CAA will limit LES intensity as will the quick
passage of the 850mb thermal trof, but snow accumulations in the 1-3
inch range are certainly a possibility. It will be a blustery day on
Tue with gusts 20-30mph as well.

A warming and dry period will set in Wed thru the end of the week as
westerlies retreat n. Warmth should peak on Thu with high temps back
into the low/mid 40s F.

.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 1232 PM EST FRI DEC 8 2023

Satellite imagery shows a break in the cloud cover over KIWD as of
1220PM EST. This break will bring VFR conditions for about an hour
before heading off eastward and hitting KCMX around 3PM EST,
bringing VFR conditions over there for about an hour too before
heading off into Lake Superior. Otherwise, expect the general
improvement from IFR/MVFR to MVFR/low-end VFR by this evening across
the TAF sites. A compact low pressure moving through Lake Michigan
tonight looks to bring lower cigs by very late tonight/Saturday
morning across the TAF sites, with KCMX and KSAW seeing RA initially
before transitioning to SN by late Saturday morning. There is a high
chance (~80%) that the RA/SN will bring visby reductions as well
Saturday. I'm expecting (~70% chance) KSAW to drop down to LIFR
again by Saturday morning as models show the deformation band of the
low close to the TAF site. KIWD and KCMX drop to MVFR/IFR,
respectively, by Saturday morning.

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 536 AM EST FRI DEC 8 2023

With low pres tracking thru far nw MN into northern Ontario, expect
se to s winds 20-30kt becoming s to sw today across Lake Superior.
Strongest winds will occur this morning with the southeasterlies.
Some gale force gusts are expected from around Whitefish Pt to
Passage Island, including around the tip of the Keweenaw. SW winds
will settle back to blo 20kt after midnight tonight thru Sat
morning. A cold front will then sweep across Lake Superior late Sat
aftn and night, bringing a wind shift to the nw 20-30kt. There is a
40-60pct chance of low end 35-40kt gales, with the greatest chc near
the MN n shore and in a swath from n of the Keweenaw down to btwn
Marquette and Grand Marais. The probability of gales over 40kt is
about 10pct. Winds will slowly subside on Sun with the risk of gales
over by sunrise on Sun. Expect winds under 25kt on Sun aftn and
mostly under 20kt Sun night. Another cold front approaching on Mon
will cause sw winds to ramp up to 20-30kt by late aftn, strongest w
half. With passage of the front, there is a high probability (at
least 90pct) of w gales 35-40kt shifting to the nw Mon night and

Issued at 536 AM EST FRI DEC 8 2023

For WFO Marquette in Negaunee Township:

Record high max temp
Dec 8: 44F (1984)

Record high min temp
Dec 8: 33F (2015)
Dec 9: 32F (2015)

Upper Michigan...
Lake Superior...
Lake Michigan...


LONG TERM...Rolfson