949
FXUS63 KMQT 050621
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
221 AM EDT Wed Jun 5 2024

.KEY MESSAGES...

- A cold front moves through the U.P. today. Expect some
  occasional downpours from the associated showers and
  thunderstorms. No flash flooding is expected.
- Some high-base showers and thunderstorms look to develop over
  the western half of the U.P. late this afternoon. A strong
  thunderstorm or two with gusty winds and hail is possible.
- Showery through at least this weekend with a trend toward much
  cooler temperatures as a closed low sets up shop over the Great
  Lakes.


&&

.SHORT TERM /THROUGH THIS AFTERNOON/...
Issued at 220 AM EDT Wed Jun 5 2024

A strong cold front is beginning to make its way into the far west
early this morning, bringing showers and thunderstorms along and
ahead of the frontal boundary across our area. With limited CAPE
relegated to the mid levels of the atmosphere and weak shearing, no
severe weather is expected this morning through early this afternoon
in association with the cold front. That being said, with the RAP
reanalysis on the SPC mesoanalysis page showing PWATs around 1.50
inches moving into the U.P. (which is above the 90th percentile of
modeled climatology), heavy rainfall is a threat within the
stronger convective cells as the cold front crawls its way eastwards
today. With WFO Duluth already having Local Storm Reports in the 1
to 3 inch range already, I wouldn`t be surprised if quite a few
spots across the U.P. got an inch or more of rainfall today, even as
the convection continues to weaken with time. That being said, with
drier conditions to moderate drought conditions in the far west
still remaining over the U.P. ahead of showers and thunderstorms, no
flash flooding is expected at this time. That being said, the plants
will certainly enjoy the rainfall, and hopefully it will relieve the
last of the drought conditions over the far west.

Behind the cold front, expect skies to clear out as cooler and much
drier air moves into the western half of the U.P. this afternoon. As
a secondary shortwave moves towards the Upper Great Lakes this
afternoon, expect its cold front to move into the western U.P. by
the mid to late afternoon hours. The forcing along the front appears
strong enough to create some high-base showers and thunderstorms
over the western U.P. late today. With strong lapse rates in the
lower levels of the atmosphere, skinny but surface-based CAPE up to
500 J/kg, and plenty of dry air in the upper levels of the
atmosphere, we could see a strong elevated thunderstorm or two
develop late this afternoon over the western half of the U.P.. While
rainfall amounts from these showers and storms look to be fairly
light (around 0.10 inch of liquid or possibly less) given the strong
dewpoint depressions near the surface before convective initiation,
they may produce some gusty winds and hail at times. These showers
and storms head towards the eastern half of the U.P. as we head into
the evening hours.

&&

.LONG TERM /THURSDAY THROUGH TUESDAY/...
Issued at 447 PM EDT Tue Jun 4 2024

Models and ensembles trending toward a blocky pattern in the high
latitudes of North America from the middle of this week into at
least the early part of next week. Models indicate mid-level
ridging/positive height anomalies, first from ne Canada across the
Arctic Ocean, and then over western N America will force mid-
level troughing to develop from s central Canada across the
Great Lakes/eastern U.S. The western ridging deamplifies next
week, but the EPS is slower to deamplify that ridge and is less
progressive with it than the GEFS/GEPS. The positive height
anomalies will remain across the Arctic Ocean thru ne
Canada/Labrador Sea next week. For Upper MI, this pattern will
lead to above normal temps through Wed trending down to an
extended period of blo normal temps (seasonably cool) most days
thru next week. However, the large scale pattern does suggest
the potential of unseasonably cool days in the mix, particularly
Thu thru the weekend. Would not be surprised to see a day or
two with highs widespread in the 50s F w and n. The less
progressive EPS solution would allow the cool weather to persist
longer thru next week than the GEFS/GEPS. As for pcpn, the
development of the mid-level troughing will support
showers/t-storms late tonight/Wed as the lead cold front passes
across the area. Models advertise a mid-level low closing off
over the Great Lakes region by Thu, leading to showery weather.
Generally, the pattern of mid-level troughing or a mid-level low
near the area through at least the first half of next week will
support frequent opportunities of showers. Model details will
be muddied on the timing/track of shortwave impulses circulating
around mid-level low into Upper MI, so pcpn fcst will have much
more uncertainty than normal. At this time, widespread, all day
rains appear unlikely unless a well organized wave develops
within this pattern. Many areas will be dry much of the time as
showers are likely to be scattered in coverage on most days.

Beginning Wednesday, a vigorous shortwave now moving out across the
Northern Plains today will take on a negative tilt as it swings into
the western Great Lakes Wed morning. With the arrival of the
negative tilt shortwave there will be uptick in forcing/upper
diffluence along the associated cold front as it moves w-e across
the area. Precipitable water increasing to around 200pct of normal
will support locally heavy downpours. HREF 90th percentile has
streaks of 1.5 inch or higher pcpn amounts, indicating the heavier
rainfall potential with some of the convection. Elevated cape of
several hundred j/kg along and ahead of the cold front will also
support isolated t-storms. In the wake of the fropa showers/t-storms
will abruptly end, followed by clearing from w to e early Wed
morning thru early to mid aftn on Wed. Attention then turns to
secondary cold front arriving late Wed afternoon/evening in
association with another shortwave. Aloft, height falls continue
thru the day with Upper MI becoming situated under expanding mid-
level low and cooling mid-levels. With fcst soundings showing
potentially several hundred j/kg of MLCAPE building, deep layer
shear 25-35kt, and a drier profile blo cloud layer, there is a
potential for gusty wind producing storms late Wed aftn/evening
across the west half of Upper MI. While winds probably won`t reach
severe criteria, it will definitely be something to monitor late Wed
afternoon, especially if instability ends up on the higher end of
current guidance which would raise the potential of isolated
severe wind gusts. Showers/t-storms will spread into the eastern
fcst area during Wed evening with the gusty wind risk
diminishing as instability wanes.

On Thu, Upper MI will be situated firmly under mid-level low
circulation with recent guidance now showing the center over or very
near to Upper MI. Some shower activity will be ongoing to start the
day. Under cold pool aloft combined with any shortwaves swinging
around the circulation and the building of weak sfc based
instability, showers will take on a diurnal component and expand in
coverage away from the stabilizing influence of Lake Superior under
nw winds. Would expect s central and se Upper MI to see most
numerous shower coverage. Will be a cooler day with highs in the 50s
near Lake Superior for areas where nw winds are directly onshore
ranging up to the mid/upper 60s F s central. If showers/clouds are
more widespread than currently expected, highs will be lower.
Showers should diminish Thu night with the loss of diurnal
instability.

Friday into Saturday will likely be very similar to Thursday, but
with the mid-level low shifting slightly e, though diurnal shower
coverage will likely decrease a bit each day from Thursday`s
coverage. As with Thursday, if clouds/shower coverage are more
widespread, highs Fri and Sat will be lower than the current
forecast of upper 50s to mid 60s F.

Over the late weekend thru early next week, details of the structure
of the mid-level flow from s central Canada thru the Great Lakes
region is very uncertain. Models have shown little agreement or run-
to-run consistency on the expansiveness, location, movement of mid-
level low and shortwave timing/amplitude in the flow. Pattern is
certainly suggestive of daily shower potential and the ensembles
also support this by indicating persistent mid-level troughing into
early next week. Similar to the previous days, if showers and clouds
are more widespread or persistent on Sunday, high temps will only be
in the 50s across the w and n and 60s s central. Overall, it appears
the influence of the mid-level low should diminish during the early
part of next week, so would expect showers to become more
isolated at that time.

&&

.AVIATION /06Z TAFS THROUGH 06Z THURSDAY/...
Issued at 104 AM EDT Wed Jun 5 2024

Overnight, SAW and CMX will remain VFR and dry and CMX will have
some LLWS. A cold front will move west to east across the TAF sites,
and the showers and thunderstorms from that front will usher in
lower ceilings and potentially low visibility. IWD will fall to IFR
by late tonight before going back to VFR Wed morning. SAW and CMX
will fall to IFR by Wed morning and then go to VFR Wed afternoon.

&&

.MARINE...
Issued at 447 PM EDT Tue Jun 4 2024

Other than some 20-25 kt ne wind gusts over western Lake Superior
and se winds over eastern Lake Superior, winds tonight will
generally be less than 20 kts. Thunderstorms moving out over western
Lake Superior this evening ahead of an approaching trough will pose
a risk of strong wind gusts. This trough will then sweep across Lake
Superior late this evening thru early Wed aftn with more storms
possible. While wind gusts to around 20kt will continue, the showers
and thunderstorms along/ahead of the front may result in locally
enhanced winds ahead of and just behind the trough. More
thunderstorms developing over MN and moving out across western Lake
Superior Wed afternoon/evening will also pose a risk of locally
strong wind gusts. Thereafter from Wed night thru Fri, fairly steady
w to nw winds of mostly 20-25kt are anticipated with occasional
gusts to 30kt. Winds may die down slightly by Sat.

Also of note, fog will be dense at times on western and central Lake
Superior into this evening. This fog should depart with passage of
the trough late this evening through early Wed afternoon.

&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.

&&

$$

SHORT TERM...TAP
LONG TERM...Voss
AVIATION...07
MARINE...Voss