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000
FXUS63 KMQT 131917
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
317 PM EDT Sat Apr 13 2024

.KEY MESSAGES...

- Scattered showers developing late afternoon into tonight with
  maybe a few thunderstorms possible along WI border and south
  central. Overall rain amounts 0.05 to 0.20 inch, highest
  central and east.
- Mostly dry weather through Tuesday morning. RHs fall to
  around 30% in the interior west Sunday and Monday, causing
  some fire weather concern.
- A low pressure tracks through the Upper Great Lakes during
  the midweek, causing widespread rain showers.
- Chances of precipitation remain likely (~50%) into the late-
  week, though uncertainty exists on timing, intensity, and
  precipitation type.

&&

.UPDATE...
Issued at 848 AM EDT Sat Apr 13 2024

Temperatures early this morning bottomed out in the lower to mid 30s
across most of the area, but some spots particularly in the western
half of the UP dropped further into the 20s. Still, as of sunrise,
we are already recovering nicely in the the lower to mid 30s in the
west, and the upper 30s in the east. Temperatures have been adjusted
downward slightly over the next couple of hours to account for those
slightly lower values.

Otherwise, spotty shower activity is evident on DLH radar closer to
the international border. Whether any of this is actually reaching
the ground is the real question - but will still keep in that slight
chance for showers to move into the UP this afternoon ahead of the
main round of rain showers overnight.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 317 PM EDT Sat Apr 13 2024

Afternoon RAP analysis shows the weak ridge axis shifting east of
the area, ahead of a weak shortwave moving along hte Ontario/MN
border. Rather dry midlevel air is apparent on water vapor over the
Great Lakes , but deeper moisture is present with the approaching
shortwave. WAA out ahead of this, with a tight theta-e gradient
draped from the UP northwest through the Arrowhead of MN, has
touched off some weak convection that is finally moving across Lake
Superior and the western and north-central UP UP. That said, with
steep surface dewpoint depressions on the order of 20 degrees, and
very dry afternoon NUCAPS soundings, weak radar returns do not
appear to actually be reaching the ground. Apart from the broken
cloud cover streaming in, would expect no more than some sprinkles
or a stray light rain shower the rest of the afternoon.

Otherwise, temperatures are climbing well into the 50s so far across
the western half of the UP, while northerly flow off of Superior is
keeping the eastern UP comparatively cooler, in the lower to mid
50s. The Keweenaw, Meanwhile, is struggling even to get out of the
40s. Across the western half of the UP, we should see many spots
peaking in the 60s while elsewhere temperatures aren`t expected to
budge much more.

Showers continue to stream into the area this evening ahead of the
approaching shortwave, generally along and north of the theta-e
gradient analyzed over the area. This track would largely keep
showers limited to the northern half of the UP before the shortwave
drops through from 03Z onward. Coverage of showers expands ahead of
the associated cold front, with some dynamical support as the right-
exit region of the upper jet streak becomes directed over the area.
However, showers quickly wrap up from 06Z onward as the front moves
out. Weak, elevated instability apparent in soundings will lead to a
chance for some rumbles of thunder across the south-central UP, with
some heavier embedded rainfall amounts possible in storms.
Otherwise, would expect the highest rainfall totals overnight to be
across the Keweenaw, through the north-central and eastern UP. heavy
rainfall is not expected, with amounts topping out below a quarter-
inch.

Skies clear out behind the passing front, but temperatures stay
fairly mild overnight with most of the area bottoming out in the
mid and upper 30s.



&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...
Issued at 416 AM EDT Sat Apr 13 2024

With the departure of troughing aloft, Sunday looks to be fairly dry
under northwesterly flow. In spite of the 00Z HREF showing lingering
low cloud cover especially near Lake Superior, extremely dry
midlevels could cause dew points (and thus RHs) to tank, especially
in the interior west. HREF minimum RH values in the afternoon fall
into the 30% range, and with northwest wind gusts up to 15-20 mph,
fire weather partners should monitor the forecast, especially along
the MI/WI state line. Otherwise, bias-corrected model guidance shows
highs near 70 in the south-central UP, with 60s across much of the
rest of the southern half of the UP with 50s near the Lake Superior
lakeshores as flow off of the ~38 degree lake will moderate the
temperatures there. If breaks in the low level cloud cover occur
sooner than later, the 70 degree isotherm may come as far north as
Gwinn and Amasa.

Monday, as upper 1010s mb surface high pressure remains over much of
the Great Lakes, the day will begin dry. However, PoPs creep up
throughout the day in the west as the UP becomes underneath the
right entrance region of a 100kt 250mb jet along with slight
850mb WAA and subtle shortwave energy embedded in northwesterly
flow at 500mb. The LREF only shows a couple of hundredths of
precipitation throughout the day Monday, so impacts should be
minimal of whatever showers do form on Monday. If showers end up
not materializing, fire weather could yet again be another
concern as RHs could fall into the 30s in the interior west once
again with wind gusts of 10-20 mph. It will be worth watching
as this time frame enters the domain of higher resolution model
guidance in the next 12-24 hours.

Upstream, a deep cutoff low at 500mb over the Desert Southwest will
be kicked east as a trough transiting through British Columbia
compresses the ridging over the West Coast. As the Desert Southwest
trough kicks east, it will initiate a lee cyclone, peaking in
strength in the 980s mb range Tuesday in the Central Plains. The low
will then lift into the Upper Great Lakes region by late Wednesday,
weakening slightly into the 990s mb of central surface pressure.
Widespread showers are near-certain, with the transport of Gulf of
Mexico moisture above in the 97.5th percentile of the NAEFS
climatology resulting in PWATs climbing to near an inch. Despite
this, there is still considerable spread in the ensembles regarding
precipitation totals, as the 90th percentile of guidance shows
around 2 inches of QPF possible by the end of the week, but the 10th
percentile is around a half inch. Wind gusts will also be worth
watching as the NBM shows wind gusts in the 25-35 mph range by
Tuesday night. NBM PoPs show that widespread showers will taper off
somewhat Thursday, but as the GFS 500mb plots show multiple 500mb
shortwaves following the passage of the low, precipitation may
linger into the weekend, especially as LREF mean accumulated precip
climbs steadily (a pattern common in wet patterns with
significant ensemble spread). One thing to watch with the late
week precipitation relative to the mid-week system will be
precip type, as the LREF shows some members with snow as soon as
Thursday morning. Uncertainty is high at this time, but given
the assortment of ensemble accumulated snowfall solutions,
winter lovers may be getting one more shot at some accumulation
by the end of next weekend.

&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 115 PM EDT Sat Apr 13 2024

VFR conditions prevail the rest of today while midlevel clouds begin
to fill in ahead of our next disturbance. This may bring some low-
impact showers to CMX by late afternoon, then to IWD and SAW later
tonight. Showers end by 06Z, but with lower-level moisture behind
rain showers and onshore flow, patchy fog and low stratus will lead
to MVFR and possibly IFR ceilings at CMX later tonight. Ceilings may
also lower to MVFR at SAW, but confidence is low. Expect
restrictions to linger at CMX the rest of the forecast period.

&&

.MARINE...
Issued at 416 AM EDT Sat Apr 13 2024

Gales have now ended across Lake Superior this morning, with wind
gusts falling below 25 kt by the mid-afternoon hours. A few gusts of
20-25 kt are possible as a weaker low pressure passes south of Lake
Superior today, primarily during the period of northeasterlies
funneling into Duluth. Through Monday evening, ridging will
keep wind gusts below 20 kt. As a strong low begins to eject out
of the Rockies Monday night, the enhanced pressure gradient
will cause northeasterly and easterly wind gusts up to 30 kt
through Tuesday morning. As the low approaches Lake Superior
Wednesday, gales are likely (50+%), though the direction will
rapidly shift as the most likely path of the low brings it
directly across Lake Superior. Northwesterly winds remain high
behind the low as between the departing low, high pressure over
the Plains, and any trailing low pressures into the weekend,
gradient flow will be strong, though uncertainty is high in
timing the strongest winds. Once wave heights fall below 4 feet
tonight, expect waves below 4 feet until Monday night, when 4-8
foot waves begin to overspread the lake by late Tuesday, with
the highest being 8-10 ft waves north of the Keweenaw
Peninsula Tuesday night.

&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
  Small Craft Advisory until 8 PM EDT this evening for LSZ251.

Lake Michigan...
None.

&&

$$

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