367
FXUS63 KMQT 061830
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
230 PM EDT Thu Jun 6 2024

.KEY MESSAGES...

- Non-severe thunderstorm chances continue in the east through
  this evening.
- Showery weather and much cooler conditions through the
  weekend under the influence of low pressure, then warming and
  drying early next week.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 229 PM EDT Thu Jun 6 2024

RAP analysis shows a vertically stacked trough over much of northern
Ontario that continues to send shortwave impulses through the Upper
Midwest and Upper Great Lakes region. This is the forcing for the
showers and occasional thunderstorms evident on radar returns. Most
of these storms have gone up and come back down in just a handful of
radar scans, but a few of them have had vigorous enough updrafts to
produce gusty winds (peak so far as of 18Z is a gust of 32 kt at
KESC) and pea sized hail. The outlook for these storms is fairly low
as peak SBCAPE in the 12Z HREF is only around 500 J/kg and not much
shear to work with. Precipitation rates are also not expected to be
extreme as HREF mean total precip by 12Z Friday is only around a
tenth to a half of inch.

With cool, northwesterly flow aloft, temperatures are once again
cooler day-over-day, with highs only in the 60s and upper 50s today
and lows in the 40s to low 50s. Mixing is allowing a 30-35 kt jet at
950mb to mix towards the surface, leading to gusty W and NW winds at
the surface through tonight. As troughing weakens and shift
northeast, expect a drying trend overnight with regards to
precipitation, though broken to overcast skies will prevail through
at least 12Z Friday.

&&

.LONG TERM /TONIGHT THROUGH WEDNESDAY/...
Issued at 426 AM EDT Thu Jun 6 2024

Building high latitude blockiness will peak this weekend as building
mid-level ridging/positive height anomalies from eastern Canada thru
n central Canada and across the Arctic Ocean, where the anomalies
peak, merge with a building ridge over western N America. This has
already forced trof development from s central Canada into the Great
Lakes. This trof will persist into the weekend before evolving into
a more general eastern N America trof as western N America ridge
begins to shift e. The ridge will then deamplify and continue
eastward under a temporary change to more progressive flow next
week. This progression will bring the next shortwave trof to the
Great Lakes in the midweek period. For Upper MI, this pattern
evolution will support blo normal temps/cool conditions thru early
next week. Then, the return of a more progressive flow regime will
send temps up to around normal for Tue/Wed. Farther down the road,
the last 24hrs of medium range ensemble guidance remains consistent
in the flow evolution toward the end of the model runs. The signal
is for building heights across the central and eastern U.S. in the
June 15-20th period. This ties into the 00z June 5 ECWMF weeklies.
So, we`re probably heading toward an overall warm/humid last half of
June. As for pcpn over the next 7 days, the mid-level troffing thru
the Great Lakes region will support showery weather at times thru
the weekend. Overall, expect many areas to be dry much of the time
as shra are likely to be mostly sct in coverage. With mid-level trof
weakening and drifting e early next week, dry weather will return.
Shortwave trof arriving midweek will bring the next chc of shra
late Tue/Wed.

Beginning tonight, shra will diminish in the wake of shortwave that
passes across Upper MI this aftn/evening, but the shra won`t end.
Best chc of shra lingering thru the night will be over the eastern
fcst area. That area will actually be under some isentropic ascent
as warmer air to the n advects toward the 850mb thermal troffing
that will be set up from nw to se across Upper MI tonight.

On Fri, center of mid-level low that is over the area today will be
moving to southern Ontario. Weak shortwave ridging develops into
western Upper MI between that low and another mid-level low over s
central Canada. This suggests a drier day over western Upper MI.
In fact, with models also showing a drier air mass advecting into
the area, it may end up as a dry day. Will carry 20pct chc of shra
early over nw Upper MI before moisture thins out. Otherwise, expect
dry weather across the w on Fri. To the e, model trends are drier as
well, but given closer proximity to the mid-level low with deeper
moisture lingering, will continue a mention of shra, but mainly just
for Luce County. High temps on Fri will be coolest over the e where
more clouds and some shra are expected. Mid 50s to around 60F
expected there. Low/mid 60s F expected to the w where there will be
increasing breaks in the clouds. Closer to Lake Superior, temps will
be in the 50s F under wnw flow off of the lake.

Models have moved toward decent agreement in taking a shortwave that
reaches British Columbia on Thu and driving it ese to the western
Great Lakes during Sat. It will also pull some shortwave energy from
the mid-level low over s central Canada to Lake Superior/Upper MI.
This will work to expand the circulation/cyclonic flow of mid-level
low to the e back to Lake Superior/Upper MI as well. While a more
organized area of shra associated with the shortwave from British
Columbia will mostly pass s of fcst area, daytime heating and
cooling mid-levels (500mb temps fall from around -14C Fri evening to
around -21C Sat aftn) will result in 100-500j/kg of MLCAPE building
across across Upper MI, likely supporting sct/nmrs shra development
for Sat aftn. Given the MLCAPE and cold pool aloft moving over the
area, some thunder will be possible as well, particularly across the
s half of Upper MI. With lower wetbulb zero heights of 5-7kft, there
could be some small hail, especially if the higher end MLCAPE
develops. Expect high temps generally in the 60s F, except for 50s F
near Lake Superior in continued w to nw flow.

On Sun, although model consistency isn`t great on exact details,
most of the models hint at a shortwave/mid-level trough axis moving
across the area in the Sat night/Sun time frame. Would expect at
least isold shra from this feature, perhaps aided by weak isentropic
ascent from the north as winds shifting from nw to n advect a pocket
of warmer 850mb air into the area. North flow off Lake Superior will
result in another day of 50s F temps near the lake while 60s F will
be more common inland. 850mb temps fall back at least a couple of
degrees from Sat, so Sun highs will be a little lower than Sat.

On Mon, mid-level troffing shifts e with upstream ridge building
toward the western Great Lakes. Thus, expect drier and warmer
conditions on Mon with highs in the 60s to lwr 70s F, warmest toward
the MI/WI stateline. Some lakeside locations along Lake Superior
will not get out of the 50s F. As discussed earlier, next shortwave
trof progresses e to the western Great Lakes midweek, bringing the
next chc of shra late Tue into Wed. Shra may reach western Upper MI
as early as Tue aftn. Dry weather will follow later Wed/Thu.

&&

.AVIATION /18Z TAFS THROUGH 18Z FRIDAY/...
Issued at 131 PM EDT Thu Jun 6 2024

MVFR conditions are present at CMX and IWD while VFR prevails at SAW
this afternoon. -SHRA will be present in the VC of IWD and SAW this
afternoon but should cease by 23Z. All 3 TAF sites will be likely
(50+%) to be MVFR for much of the overnight hours, but improvement
to VFR is expected by at least the late morning to early afternoon
of tomorrow. Gusty W to WNW winds are expected throughout the TAF
period at all 3 TAF sites.

&&

.MARINE...
Issued at 426 AM EDT Thu Jun 6 2024

Across Lake Superior, steady W to WNW winds, generally at around
20kt with occasional gusts to 30kt, will set in from w to e
today/tonight and then continue thru Fri. Highest gusts will be
around and w of the Keweenaw today and then across the e half of
Lake Superior tonight/Fri. A slight diminishing of winds will occur
over the weekend with sustained speeds falling back to mostly around
15kt. However, passage of a sfc trof will bring a little uptick in
winds for Sun across the e half of Lake Superior where NNW winds
will be back closer to 20kt again. Sfc high pres ridge arrives on
Mon, leading to winds falling to under 15kt.

&&

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

&&

$$

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