940
FXUS63 KMQT 051058
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
658 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-based 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.
- Gusty wind producing showers and thunderstorms this evening
  west half.
- Showery weather and much cooler conditions Thursday through
  the weekend under the influence of low pressure.

&&

.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 /TONIGHT THROUGH TUESDAY/...
Issued at 515 AM EDT Wed Jun 5 2024

Flow over and around N America thru early next week will feature
pronounced high latitude blockiness. Through the remainder of this
week and into the weekend, building mid-level ridging/positive
height anomalies, first from ne thru n central Canada and across the
Arctic Ocean, and then over western N America will force troffing to
develop from s central Canada across the Great Lakes/eastern U.S.
The last 24hrs of medium range model guidance has trended toward the
western ridge deamplifying/progressing downstream a little quicker
next week, resulting in quicker weakening/eastward progression of
the troffing affecting the Great Lakes. For Upper MI, this pattern
evolution will lead to a period of blo normal temps (seasonably
cool) thru early next week. However, the large scale pattern does
suggest the potential of unseasonably cool days in the mix,
particularly on Thu. The aforementioned model trends for next week
suggest a little more aggressive warming that would bring temps back
to around normal early in the week and then above normal late week.
Farther down the road, the end of the ensemble guidance and the 00z
June 4 ECMWF weeklies suggest we`re probably heading toward an
overall warm last half of June as heights build across the central
and eastern U.S. The CFSv2 counters that idea to some degree with
coolness lingering a little longer thru mid month. As for pcpn over
the next 7 days, the development of the mid-level troffing from s
central Canada thru the Great Lakes region will support showery
weather at times Thu thru the weekend. Models have lacked run-to-run
consistency and have been and continue to be quite varied on the
details of the flow affecting Upper MI. So, pcpn fcst has much more
uncertainty than normal. Overall, expect many areas to be dry much
of the time as shra are likely to be sct in coverage on most days.
Thu is likely to be the day with the most nmrs shra. With mid-level
trof weakening and drifting e early next week, dry weather is more
likely to prevail.

Beginning tonight, secondary cold front will sweep across the area
in association with another shortwave quickly following today`s
wave. Shra/tsra arriving over the w late aftn will continue eastward
thru the evening with the risk of strong/gusty winds diminishing
with loss of daytime heating and stabilization. Overnight,
broadening mid-level low centered nw of Lake Superior will increase
its influence over Upper MI. Within the circulation, another
shortwave will approach from northern MN. As a result, some shra
will linger thru the night.

On Thu, Upper MI will be situated firmly under mid-level low
circulation with center over or very near to Upper MI. Shortwave
tracking se from ne MN combined with the start of daytime heating
will support a rapid development/expansion of shra during the
morning. The shra should diminish in coverage over the w in the aftn
in the wake of the wave. Considerable cloud cover will limit daytime
heating/instability, so thunder potential is overall minimal. Fcst
will only include a mention of thunder over the e and se fcst area
due to a little more instability potential before clouding over and
development of widespread shra. Under considerable cloudiness,
passing shra, rather stiff wnw winds and 850mb thermal trof driving
se into the area, it will be unseasonably cool for much of the area.
Highs in the 50s F will likely be the rule across the w thru n
central ranging up to the low/mid 60s F s central/se. Lakeside
locations exposed to wnw winds across Lake Superior may not see max
temps above 50F. W side of the Keweenaw likely to be coolest.
Showers will diminish Thu night in the wake of shortwave, but won`t
end, particularly over the e where there is actually some isentropic
ascent as warmer air to the n and ne weakly advects toward the
thermal troffing over the area.

On Fri, center of mid-level low drifts e toward southern Ontario.
Weak shortwave ridging develops into western Upper MI btwn that low
and another mid-level low over s central Canada. This is suggestive
of fewer shra over western Upper MI on Fri compared to Thu, more
areas likely to be dry thru the day. To the e, closer to the mid-
level low, there will be a greater chc of shra. High temps on Fri
will be coolest over the e where more clouds/shra are expected. Mid
50s to around 60F expected there. Low/mid 60s expected to the w,
except closer to Lake Superior where temps will be in the 50s.

Over the weekend, the lack of run-to-run consistency and model
disagreement on the details of the flow from s central Canada thru
the Great Lakes region leads to decreasing confidence in pcpn
chc/coverage, and that plays a role in temps as well. As a result,
fcst is generally broad brushed with 30-50pct chc of shra, targeting
the aftn hrs when a little instability will aid shra development.
Expect high temps in the 50s near Lake Superior in areas exposed to
nw winds across the lake and 60s F inland.

With medium range models trending toward troffing easing and
shifting e early next week, expect a trend to dry weather across the
board. For the moment, there`s not really any support for including
a specific shra chc Mon or Tue. There`s some indication of a
shortwave trof to affect the Upper Lakes on Wed, and that would
offer the next mention of chc shra. Temps will head back to around
normal.

&&

.AVIATION /06Z TAFS THROUGH 06Z THURSDAY/...
Issued at 658 AM EDT Wed Jun 5 2024

A cold front bringing showers and thunderstorms across the area
continues east throughout the rest of the day as conditions at KCMX
and KSAW quickly drop down to IFR this morning, possibly dropping
down to LIFR for an hour or two late this morning (I`d give it about
a 60 to 70% chance for it to occur before returning to IFR
conditions fairly quickly; it will be dependent on heavier rainfall
rates). Meanwhile, KIWD should progressively improve to VFR this
morning, with the other TAF sites joining in on the improving
conditions by early to mid afternoon. VFR conditions continue
through this evening as high base showers and thunderstorms form in
the western U.P. late this afternoon and travel eastward through
this evening. Some gusty and erratic winds, as well as some hail,
could be seen with these high base showers and thunderstorms late
this afternoon and evening across the area. We could see cigs
deteriorate down to MVFR Thursday morning as another low pressure
approaches.

&&

.MARINE...
Issued at 515 AM EDT Wed Jun 5 2024

Low pres trof currently over western Lake Superior will continue
eastward, exiting the eastern lake mid to late aftn. While wind
gusts to around 20kt are expected today, showers and thunderstorms
along/ahead of the trof may result in locally enhanced winds just
ahead of and just behind the trof. A secondary trof will lead to
more thunderstorms developing over MN and moving out across western
Lake Superior this aftn/evening, posing a risk of locally strong
wind gusts. During tonight and Thu, steady w to wnw winds generally
at around 20kt with occasional gusts to 30kt will set in from w to
e. These winds will remain unchanged thru Fri. A slight diminishing
of winds will occur over the weekend with sustained speeds falling
back to around 15kt.

Also of note, there will likely be some fog present thru this
evening, mainly across the e half of Lake Superior. Passage of
second trof should clear the fog off of the lake during tonight.

&&

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

&&

$$

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