597
FXUS63 KMQT 041734
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
134 PM EDT Tue Jun 4 2024

.KEY MESSAGES...

- Showers end over the east half this morning.
- Some showers and thunderstorms, a few possibly strong, could
  develop over the western U.P. late this afternoon.
- Frequent showers over the next 7 days, but particularly
  through the weekend. Thunderstorms with strong, gusty winds
  possible late Wednesday afternoon and evening over western
  Upper MI.
- Above normal temperatures through Wednesday, then turning
  cooler with an extended period of below normal temperatures
  through at least the first half of next week.

&&

.SHORT TERM /THROUGH THIS AFTERNOON/...
Issued at 321 AM EDT Tue Jun 4 2024

Low-level cloud cover continues across most of the U.P. the rest of
the pre-dawn hours this morning as the dying cold front continues to
bring scattered light rain showers along the front`s boundary.
Behind it, some areas could see some drizzle from time to time. With
light southerly flow continuing through the pre-dawn hours, fog is
not expected to form across the area, especially now that a low-
level stratus deck is in place. However, we could see an isolated
spot or two develop some patchy fog this morning, especially if some
clearing were to occur and the winds would locally lighten.

Nevertheless, expect the low-level stratus (and any fog) to burn off
by the mid morning hours as the sun rises. Likewise, the last of the
rain shower activity should be exiting our far east by late this
morning as a very weak ridge aloft moves overhead. With a stronger
cold front approaching from our west today, expect the pressure
gradient to tighten across our area, increasing southerly winds at
the surface. In addition, warm air advection sourced from the Gulf
will allow temps to reach the 80s over some of the interior areas
today, particularly over Ontonagon County where the downsloping
winds and warm air advection could bring high temperatures close to
90 in a few of the downslope areas. A few of the CAMs show some
scattered showers and thunderstorms developing ahead of the cold
front late this afternoon over the western U.P. While the convection
is expected to be surfaced-based, with CAPE values in the 1500-3000
J/kg range, severe weather is not expected during the late afternoon
hours as bulk shear values look to be too weak (well below 30
knots). However, given the abundant energy in the atmosphere, we
could see some strong winds and hail as the downdrafts `core dump`;
the chance of us seeing marginally severe winds and hail is around
5%.

&&

.LONG TERM /TONIGHT THROUGH MONDAY/...
Issued at 530 AM EDT Tue Jun 4 2024

Over the last few days, there have been some changes in how the
models depict the flow evolution over and around N America. However,
one aspect hasn`t changed, a lot of high latitude blockiness.
Through this week and into the weekend, building mid-level
ridging/positive height anomalies, first from ne Canada 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 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 thru 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 troffing will support shra/tsra tonight/Wed as lead cold front
passes across the area. Mid-level low closing off over the Great
Lakes region suggests showery weather on Thu. Generally, the pattern
of mid-level troffing or a mid-level low near the area thru at least
the first half of next week suggests frequent opportunities of shra.
Models are quite varied on the details of the flow affecting Upper
MI, so pcpn fcst will have much more uncertainty than normal. Attm,
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 shra are likely to be sct in coverage on most days.

Beginning tonight/Wed, isold/sct convection should be ongoing across
western Upper MI this evening from lingering daytime instability
within pool of elevated theta-e. Otherwise, vigorous shortwave
moving out across the Northern Plains today will take on a negative
tilt as it swings into the western Great Lakes Wed morning. CAMS are
in quite good agreement that strong convection developing across MN
today will weaken in intensity while approaching western Upper MI
mid to late evening due to a combination of diminishing sfc based
instability, a notable decrease in low-level convergence, and the
start of the advection of decreasing theta-e at 850mb. At this
point, not expecting svr storms tonight given the currently good
model agreement on the weakening trend of the storms approaching
from MN/nw WI. If any stronger storms do occur, it would be early
this evening with the isold/sct storms from late aftn still taking
advantage of late day instability. Although tsra intensity wanes,
models are in general agreement that shra/some tsra will become
increasingly organized again late in the night thru Wed
morning/early aftn as cold front sweeps across the area in
association with negative tilt shortwave and uptick in forcing/upper
diffluence. Precipitable water increasing to around 200pct of normal
will support locally hvy downpours. HREF 90th percentile has streaks
of 1-1.5 inch pcpn amounts, indicating the heavier pcpn potential
with some of the convection. As fropa occurs, shra/tsra 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 aftn/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 potentially several hundred j/kg of MLCAPE
building, deep layer shear 25-30kt (some models even higher), and
fcst soundings showing an inverted profile blo cloud layer, gusty
wind producing storms seem like a good bet late Wed aftn/evening
across the west half of Upper MI. Winds probably not svr strength,
but it will definitely be something to monitor late Wed aftn,
especially if instability ends up on the higher end of current
guidance which would raise potential of isold svr wind gusts.
Shra/tsra will spread into the eastern fcst area during Wed evening
with gusty wind risk diminishing.

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 -shra 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, shra will take on a diurnal component and expand in
coverage away from stabilizing influence of Lake Superior under nw
winds. Would expect s central Upper MI to see most nmrs shra. 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 shra/clouds are more widespread than currently
expected, highs will be lower. Shra will diminish Thu night.

Fri will be a near repeat performance of Thu, but with mid-level low
shifting e some, diurnal shra coverage will likely be less than on
Thu. As with Thu, if clouds/shra are more widespread, highs Fri will
be lower than the current fcst of upper 50s to mid 60s F.

Over the 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 shra potential. Similar to the previous days, if
shra and clouds are widespread Sat or Sun, high temps will only be
in the 50s across the w and n and 60s s central. It appears
influence of the mid-level low will diminish during the early part
of next week, so shra potential will decrease at that time.

&&

.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 134 PM EDT Tue Jun 4 2024

CMX and IWD have recovered to VFR already while SAW is still dealing
with MVFR skies for another couple hours. This afternoon, SAW and
CMX will remain VFR and dry, though some convection is expected in
the western UP, including in the vicinity of IWD. Overnight, a cold
front will spread 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 and CMX are about 40% likely to fall
to IFR in the early to midmorning hours while SAW is over 50% likely
to fall to IFR with 25% chance of LIFR by 13Z. Behind the
front, gradual improvement in flight categories is expected,
with VFR expected at IWD by 14Z, CMX by 17Z, and SAW sometime
after this TAF period.

&&

.MARINE...
Issued at 530 AM EDT Tue Jun 4 2024

A period of lighter winds, mostly under 15kt, is expected this
morning on Lake Superior. Approaching low pres trof will then lead
to increasing winds this aftn/evening. Some gusts into 20-25kt range
will be possible with the ne winds over western Lake Superior and se
winds over eastern Lake Superior. Thunderstorms moving out over
western Lake Superior this evening will pose a risk of strong wind
gusts. The trof will sweep across Lake Superior late this evening
thru early Wed aftn. While winds 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 trof. More
thunderstorms developing over MN and moving out across western Lake
Superior Wed aftn 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 settle back just a bit for Sat.

Also of note, fog will be dense at times on Lake Superior today into
this evening, especially across the w half. This fog should depart
with passage of the trof late this evening thru early Wed aftn.

&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
  Dense Fog Advisory until 11 PM EDT /10 PM CDT/ this evening
     for LSZ162-263-264.

  Dense Fog Advisory until 5 PM EDT this afternoon for
     LSZ245>247-265>267.

Lake Michigan...
None.

&&

$$

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