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000
FXUS63 KMQT 221828
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
228 PM EDT Mon Apr 22 2024

.KEY MESSAGES...

- Elevated fire weather conditions this afternoon give way to a
quick round of showers and perhaps a few rumbles of thunder
this evening.
- Rain quickly moves out the second half of the night with clearing
skies.


-A Clipper Low system brings two rounds of precipitation. The first
is a west-to-east moving line of showers with ~15% chance of
thunderstorms tonight.
-The second round of precipitation comes Tuesday with rain changing
to snow with a few rumbles of thunder possible (~15%) in the south
and generally less than an inch of snow in the north.
-Dry weather in the midweek under high pressure.
-Active weather pattern continues with above normal precipitation
and temperatures favored for the weekend and beyond (40-50%)

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 226 PM EDT Mon Apr 22 2024

Upper ridging over the central US is beginning to slide eastward
with a compact shortwave moving into the Northern Plains. At the
surface, an associated surface low is moving into Manitoba, leaving
the Great Lakes under a tight pressure gradient as a surface high
remains sprawled out over the eastern CONUS.

SW winds continue to gust up to 20-30mph across much of the UP, and
though high clouds continue to stream across the area, lower to
midlevels remain dry and well-mixed (per early afternoon NUCAPS
soundings). This is sending dewpoints into the teens and lower 20s
across much of the western half of the UP, while to hte east, these
are coming in a couple degrees higher in the lower to mid 20s. With
temperatures already in the lower 60s across most of the area,
widespread RH values near (or even below!) 20% are observed in the
western half of the UP. This is all to say that elevated fire
weather conditions continue to be the rule this afternoon. Don`t
burn! As we head into the late afternoon, dewpoints should slowly
climb as more lower level moisture works in ahead of our next
approaching rain-maker.

A shortwave currently rippling through IA and MN this afternoon
moves into the UP this evening, eventually phasing with the Manitoba
low later tonight. This will bring a narrow swath of rainfall to the
area tonight, with most of the area expected to see some rainfall
for a 1-2hr window. As a dry slot works in behind it, skies quickly
clear from west to east the second half of the night. Most guidance
brings showers into the western UP between 00-02Z, then rain moves
out of the eastern UP between 06-08Z. Given such dry antecedent
conditions, this may be a bit ambitious for an onset timing. Thus,
unsurprisingly, rainfall amounts are lighter across the western half
of the UP compared to areas more eastward that will have more time
to moisten up. Still, totals remain fairly light, generally at or
below a tenth of an inch. Will note that the HRRR favors some
stronger embedded convection, indicated by simulated reflectivity up
to 40dbz. That, too, is a little suspect; this solution remains the
outlier, and soundings show little to no elevated instability. Thus,
have allowed thunder to fall off with this forecast update, but
wouldn`t be totally surprised to hear of a rumble or two overnight
with the HREF showing some CAPE sneaking in overnight (but mainly
following our shortwave).

Otherwise, though winds fall back into the early evening, they
should pick up again with the passing wave before decreasing again
behind it. Temperatures stay mild overnight, generally falling into
the lower 40s with a few spots in the upper 30s throughout the
western UP.

&&

.LONG TERM /TONIGHT THROUGH SUNDAY/...
Issued at 511 AM EDT Mon Apr 22 2024

An active weather pattern will be over Upper Michigan for this
forecast period beginning with the approach of a Clipper trough and
subsequent low pressure tonight and Tuesday. Ridging aloft will
induce high pressure and calm, dry conditions in the midweek period
ahead of the next low pressure ejecting out of the Plains Friday
into the weekend. Broadly speaking, late April and early May show no
signs of stopping this active pattern, though the details become
largely uncertain beyond this weekend.

Beginning with tonight, the initial wave of showers encroaches on
the western UP beginning at around 00Z Tuesday. Model guidance has
continued to slow down the onset of showers with each run. While
these rain showers will not be a hydro threat, the thunderstorm
potential with these showers is intriguing. Among the HREF ensemble
suite, the HRRR is the most aggressive with convection, showing
multiple zones of simulated 40+ dBZ with MUCAPE values near 500
J/kg. HRRR soundings show that this MUCAPE is entirely limited above
750mb, so strong forcing may be the limiting factor. However, should
an energetic storm initiate, there will be shear present, as HREF
mean SRH is up to 400 m2/s2, though there is some spread in the
guidance as to whether the shear and instability line up properly.
Even if parcels are not super buoyant, low-CAPE/high shear storms
tend to overperform expectations, so if a storm can get going, an
isolated severe wind threat is not out of the question along with
some small hail. However, given the failure modes, chances of
thunderstorms are broadly about 15% for the first line of showers in
this forecast package.

Following the passage of the first line of showers by 12Z Tuesday, a
brief break in precipitation is expected before the low drops
through the eastern portions of Upper Michigan during the day
Tuesday. This will bring a surge of cooler air, sufficient
wraparound moisture, and lift from convergence and orographic lift
to cause showers. The north half of the UP will face rain showers
turning to snow while the south half will be dealing with another
round of thunderstorm potential. The HREF indicates that for much of
the UP, chances are below 10% of exceeding an inch of snow, however,
the high terrain of Baraga and Marquette counties as well as the
entire sine of the Keweenaw could see 1-2 inches of snowfall.
However, the springlike conditions lately have warmed the ground
notably, making the likelihood of accumulation less than the same
amount of QPF in a typical winter setup, so even in the heavier
areas of snowfall, impactful accumulations are not expected. Further
south, clearing skies in the dry slot of the low will allow
temperatures to climb into the 60s in the southern reaches of the
UP, which the HREF suggests could allow SBCAPE to build above 250
J/kg. Despite more surface-based storms being possible, a much less
favorable shear environment should keep the strength of any
thunderstorms limited.

Once showers end Tuesday evening across all of the UP (whether snow
showers in the north or thundershowers in the south), ridging aloft
will quickly build in behind the departing shortwave trough. This
will ultimately result in high pressure building over the lake, with
the 00Z GEFS suggesting 1030mb high pressure centered directly
over Lake Superior by Wednesday afternoon. This will keep
Wednesday and Thursday dry, not only in lack of precipitation
and clouds, but also in RH. The LREF shows about 5-15% chances
of RHS falling into the teens in the interior west, which given
how medium range guidance often usually misses low-RH signals in
high pressure scenarios, the actual forecast likelihood of RHs
falling into the teens is more like 50%. While this is not good
news for fire weather, the silver lining is that winds should be
light, with even the 90th percentile of LREF winds showing
around 10 mph.

The tranquil weather will be interrupted by the arrival of the next
trough and resultant low pressure Friday. Ensembles have trended
slower with precipitation and the ensemble spread on timing is still
somewhat high, but the GEFS is surprisingly consistent with the
track of the low passing through Lake Superior, the UP, or northern
Lake Michigan. Showers become likely (70+%) by Saturday, with
thunder at least 15% likely, though impacts are tough to say given
the current spread in intensity and timing. Ridging building back
over northern Ontario will bring an eventual end to showers,
but with each passing feature, the chaos in the system grows and
uncertainty continues to build in the details. Looking forward,
the pattern continues to be quite active with multiple trough
and ridge passages expected to come. Despite the details
disagreeing, there is good agreement in above normal
precipitation and temperatures, with the CPC outlooks reflecting
this with up to 50% chances of above normal conditions in the
8-14 day outlook.

&&

.AVIATION /18Z TAFS THROUGH 18Z TUESDAY/...
Issued at 121 PM EDT Mon Apr 22 2024

Dry air will remain in control into this evening before a narrow
band of rain moves through. When the rain moves through conditions
may drop down to MVFR this evening for an hour or so, most likely at
CMX...otherwise VFR conditions will prevail through the rest of the
night at all TAF sites. Another round of rain showers and lowering
ceilings will bring in restrictions late in the forecast period,
with MVFR and possibly IFR ceilings settling in. SW winds gusts to
around 25kts continue through the afternoon and evening, briefly
tapering off this evening before picking up again with the passing
disturbance overnight. Winds turn over the N/NW into Tuesday while
coming in slightly lighter.

&&

.MARINE...
Issued at 511 AM EDT Mon Apr 22 2024

Southwesterly winds will gust today from just below 20 kt to 25 kt
throughout today. A line of showers with a slight (~15%) chance of
thunderstorms will pass over the lake from west to east tonight,
which may also be accompanied by gusty winds above 20 kt. A brief
respite behind the showers will not last long as winds turn
northerly and northeasterly Tuesday as an Alberta Clipper low passes
from northern Ontario across the eastern reaches of Lake Superior.
This low will force gales to 35-39 kt across much of the lake along
with 8-10 foot waves. The low will depart quickly though and waves
will fall below gales Tuesday night and below 20 kt early Wednesday.
Winds remain light and somewhat variable under high pressure
Wednesday and Thursday before a system approaching Lake Superior
Friday will bring gale potential, though uncertainty is high in
regards to timing.

&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
  Gale Warning from 8 AM to 2 PM EDT Tuesday for LSZ243>245-
     263>266.

  Gale Warning from 2 PM Tuesday to 2 AM EDT Wednesday for
     LSZ267.

Lake Michigan...
  Small Craft Advisory until 8 AM EDT Wednesday for LMZ248-250.

&&

$$

SHORT TERM...LC
LONG TERM...GS
AVIATION...LC
MARINE...GS