737
FXUS63 KMQT 161118
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
718 AM EDT Mon Sep 16 2024

.KEY MESSAGES...

- Isolated to scattered coverage of showers and non-severe
  thunderstorms today over western Upper MI eastward to
  Marquette County.

- Extended stretch of well above normal temperatures continues
  through at least Saturday with highs mainly in the upper 70s
  and 80s.

&&

.SHORT TERM /THROUGH THIS AFTERNOON/...
Issued at 322 AM EDT Mon Sep 16 2024

Water vapor imagery and RAP analysis show mid-level troffing along
the W Coast and a broad mid-level high encompassing the Great Lakes
to New England. A shortwave moving over Hudson Bay is aiding a 25-
30kt low-level jet from northern MN ne to James Bay. This also
coincides with 850mb theta-e ridging and 1000+j/kg of CAPE for
parcels lifted from around 850mb. As a result, radar imagery has
shown development of elevated isold shra/tsra across ne MN in the
last hr or so. Closer to home, it`s an incredibly warm night for mid
Sept across western to n central Upper MI in the s wind downslope
areas. Temps are in the lwr 70s F as of 07z, and that`s higher than
normal high temps at this time of year. Big Bay is the warm spot at
76F. Across the s central and eastern fcst area, largely decoupled
winds and nothing more than sct thin ci clouds have allowed temps to
fall mostly into the mid 50s to lwr 60s F range. Patchy fog has
formed in that area as well.

Developing shra/tsra in ne MN will likely further develop/push out
across western Lake Superior and may sneak into western Upper MI
this morning before low-level jet weakens. Models also indicate a
subtle 850mb wind shift that will further aid the convection. For
now, kept pops only in the 15-25pct range, but will be monitoring
radar trends over the next several hrs to determine if any increase
is needed based on how coverage of shra/tsra changes. This aftn,
attention turns to sfc-based convection potential. Models show quite
a range of potential MLCAPE this aftn with highest values over
western to n central Upper MI, ranging from around 700j/kg at the
low end to 2500j/kg from the NAM at the high end. Consensus seems to
run in the 1000 to ~1500j/kg range. With instability maximizing over
nw Upper MI eastward to Marquette County, which is in the same area
where lake breeze is likely to develop to provide a focusing
mechanism, will paint that area for aftn shra/tsra with pops in the
20-50pct range. With deep layer shear under 15kt, svr storms are not
expected. The lack of shear will lead to generally short-lived
convection with new development occurring along outflows of the
initial cells. With precipitable water upwards of around 175pct of
normal, very brief hvy rainfall will be possible. Otherwise, expect
another unseasonably warm day today with highs ranging thru the 80s
F with some locations reaching the upper 80s. Southerly winds will
hold temps to the 70s F lakeside of Lake MI.

&&

.LONG TERM /TONIGHT THROUGH SUNDAY/...
Issued at 247 AM EDT Mon Sep 16 2024

A rex block over the eastern U.S. allows us to receive warm
southerly air for most of this week, before the troughing over the
western U.S. finally is able to fight its way into the Upper Great
Lakes and bring some much needed rainfall to the U.P. this weekend
and early next week. While the strength of the ridging from the rex
block to our east will decay with time this week, the anomalously
warm air could allow us to bring the high max temperature record on
Tuesday and possibly the high min temperature record a few evenings
late this week into early next week as cloud cover increases. We may
also finally see some much needed rainfall re-enter Upper Michigan
late this week into early next week.

The last of the showers and thunderstorms associated with the
shortwave activity early this week leave the western half of the
U.P. tonight as the last of the shortwaves lifts away. As this
occurs, the clear skies overnight will allow the low temperatures to
sink into the mid to possibly even lower 50s across the interior
areas, especially over the central. Overall, expect any rainfall we
do receive over the west half to be pretty light (a tenth of an inch
or less), with the east half pretty much slated to receive nothing.
There may be some patchy fog that develops over the south central
late tonight. Should it form, low temperatures may be warmer than
what is currently predicted.

Expect sunny skies from Tuesday to around Thursday as ridging over
us slowly decays while a vertically-stacked low lifts from the
Intermountain West into the Canadian Prairies. With warm southerly
air continuing to flow into our area Tuesday, we could see a few of
the high daily max temperature records broken across the area,
particularly in the downslope areas near Lake Superior. While
Wednesday and Thursday aren`t looking to be as warm, we can still
expect high temperatures in the upper 70s to lower 80s across the
area, which means some spots could flirt with tying or breaking the
max high temperature record even on those days. As for fire weather
concerns, it does look like we could flirt with some limited
concerns on Tuesday as the min RH in the interior south central
could get into the lower 30 percents. However, with winds being
light, not much concern is warranted at this time. Min RHs are
expected to be a little higher Wednesday and Thursday, although the
continued drying of fuels may be something that still needs to be
monitored.

While model spread increases from this weekend into early next week,
the differing suites do agree that cloud cover and possibly even
rainfall look to move over us late in the extended period. As the
cloud cover increases Thursday night onwards, the European ensemble
highlights min temperatures being anomalously warm for this time of
year. Thus, we may see some high min temperature records broken from
Thursday night onwards as the cloud cover could provide extra
insolation and cause low temperatures to struggle to make it down
into the mid to upper 50s. As the aforementioned low over the
Canadian Prairies continues to lift towards Hudson Bay Thursday
night into Friday, a cold front weakening with time looks to move
into our neck-of-the-woods around that same time. This cold front
could bring our first rainfall back across the area since
today/tonight. Additional chances for rainfall look possible this
weekend into early next week as another low lifts from the Desert
Southwest towards the Upper Midwest.

&&

.AVIATION /12Z TAFS THROUGH 12Z TUESDAY/...
Issued at 717 AM EDT Mon Sep 16 2024

VFR will continue thru this fcst period at IWD/CMX/SAW. However,
there will be isold to sct shra/tsra across western Upper MI today.
While CMX has a better chc of being affected than IWD, confidence in
the terminal being impacted is still too low to include mention in
fcst. Mostly southerly winds are expected today though winds at CMX
will shift with lake breeze passage, becoming w late morning/early
aftn, then easterly early this evening.

&&

.MARINE...
Issued at 247 AM EDT Mon Sep 16 2024

Light winds of 20 knots or less continue over Lake Superior this
week as high pressure ridging over the eastern U.S. influences our
weather pattern for the next several days. Nevertheless, some
showers and thunderstorms are possible today and tonight as a
shortwave low rides along the ridging overtop us.

&&

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

&&

$$

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