869
FXUS63 KMQT 052016
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
416 PM EDT Wed Jun 5 2024

.KEY MESSAGES...

- Some high-base showers and thunderstorms look to develop over the
western half of the U.P. this evening. A strong thunderstorm or two
with gusty winds and hail is possible.

- Showery weather and much cooler conditions expected Thursday
through the weekend under the influence of low pressure.

&&

.SHORT TERM /THROUGH THURSDAY NIGHT/...
Issued at 323 PM EDT Wed Jun 5 2024

GOES-16 Visible imagery shows clearing skies along the MI/WI state
line behind an advancing cold front, with the band of rain showers
from that front now mainly confined to the eastern half of the UP.
Through 1830Z, the only electrically active storm has been a sub-
severe cell that started in southern Menominee County and has
transited the Bay of Green Bay and is imminently arriving at the
Garden Peninsula. Under cloudy skies for much of the day, highs are
around 10 degrees cooler than yesterday, mainly in the low 70s.

Attention turns upstream this evening to the clearing in the
west, which already is showing signs of some cu development
supported by diurnal heating and a secondary shortwave evident
on RAP Analysis 500mb heights. The 12Z HREF showed much less
available instability relative to yesterday`s storms with only
around 500-1000 J/kg of SBCAPE available. Shear is right around
what it was yesterday with around 20 kt of effective bulk shear
and 50-100 0-3km SRH. It is worth noting that while instability
is surface-based, the depth of the mixed layer at the surface is
around 6,000 ft, so cloud bases are going to be relatively
high. Reflectivity paintball plots in the HREF show that CI will
begin in northern Wisconsin and push east into the UP around
20Z, somewhat losing energy as it progresses and maintaining
cellular form. Thinking hazards are once again isolated damaging
wind gusts and pea to quarter sized hail from "core dumps".
Less total precipitation is expected with this round of showers,
with HREF mean 6-hourly precipitation only around 0.2-0.4
inches. In the wake of showers, lows look to fall to the 50s
tonight, with winds staying out of the west.

&&

.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
Issued at 414 PM EDT Wed Jun 5 2024

Flow over and around N America through 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 through n
central Canada and across the Arctic Ocean, and then over
western N America will force mid-upper level troughing to
develop from s central Canada across the Great Lakes/eastern
U.S. This troughing will also force the mid-level low now over
northern Saskatchewan/Manitoba to descend across the Great Lakes
region beginning Thu. For Upper MI, this pattern evolution will
lead to periods of showery weather and 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. 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, the pcpn fcst
has much more uncertainty than normal. Overall, expect many
areas to be dry much of the time as showers are likely to be
scattered in coverage on most days. Thu is likely to be the day
with the most numerous shower coverage. With the mid-level
trough weakening and shifting e early next week, dry and warmer
weather is more likely to prevail for the first half of next
week, although a few of the 00z models hint at another wave
moving through the area in the Tuesday- Wednesday time frame
that may bring the potential for some light shower activity.

Beginning Thursday, the mid-level low now over central Canada will
dive se across the Upper Great Lakes by Thu. A shortwave attached to
the mid-level low circulation will track from northern MN se across
Upper Mi in the late morning/afternoon. Forcing associated with this
feature combined with the start of daytime heating will support a
rapid development/expansion of showers during the morning. The
showers 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 there before clouding
over and development of widespread showers. Under considerable
cloudiness, passing showers, rather stiff wnw winds and a 850mb
thermal trough 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 through n central ranging up to the lower/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 showers may
keep going in response to 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 between that
low and another mid-level low over s central Canada. This is
suggestive of fewer showers over western Upper MI on Fri compared to
Thu, with more areas likely to be dry through the day. To the e,
closer to the mid-level low, shower coverage will be greater. 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.

Sat, models seem to be coming into a little bit better agreement on
a shortwave trough moving through the area. MLCAPE values of 100-300
j/kg could maybe even support a rumble of thunder along the WI
border and south central late morning into the afternoon. Expect
scattered shower coverage with highs generally in the 60s, except
for some 50s readings near Lake Superior in a continued nw flow.

Sun, although model consistency isn`t great on exact details most of
the models hint at another shortwave/mid-level trough axis moving
through the area in the Sat night into Sunday time frame. Would
expect at least isolated showers from feature perhaps aided by some
weak isentropic ascent from the north as winds shifting from nw to n
bring a pocket of warmer 850 mb air into the area. North flow off
Lake Superior will result in 50s readings near the lake while 60s
readings will be more common inland.

With medium range models trending toward more ridging building over
the area on Monday behind the exiting mid-level trough, would expect
drier and warmer conditions on Monday with highs mostly in the 60s
to lower 70s, with warmest readings inland toward the WI border.
Models and ensembles then hint at a shortwave trough moving through
in the late Tue into Wed time frame which could result in at least
isolated showers again. Temps are expected to rebound to around
normal values for this time of year with highs mainly in the 70s
Tue into Wed.

&&

.AVIATION /18Z TAFS THROUGH 18Z THURSDAY/...
Issued at 134 PM EDT Wed Jun 5 2024

VFR prevails at all TAF sites to begin this afternoon. -SHRA has
moved out of IWD and CMX with SAW forecast to also clear out of
precip in the next hour or two. This evening, a second wave of
showers is expected to move in from the west, with some stronger
TSRA possible at IWD. VFR is expected to prevail through these
SHRA/TSRA. In the morning hours, low (20-40%) SHRA chances return to
the forecast along with likely (50+%) reductions in ceiling height
to MVFR, though models have trended later with the onset of MVFR
conditions over the last few model cycles. Expect winds to remain
primarily out of the west, occasionally gusty.

&&

.MARINE...
Issued at 414 PM EDT Wed Jun 5 2024

A low pressure trough moving in from the west could lead to a few
stronger thunderstorms developing over MN and moving out across
western Lake Superior late this afternoon/evening, posing a risk of
locally strong wind gusts. Late tonight continuing into Fri, steady
w to wnw winds generally at around 20kt with occasional gusts to
30kt will set in from w to e with the highest gusts over the east
half. A slight diminishing of winds will occur over the weekend with
sustained speeds falling back to around 15kt as winds shift from
northwest to north-northwest on Sunday. North winds should diminish
blo 15 kts on Monday as a high pressure ridge builds in from the
northwest.

&&

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

&&

$$

SHORT TERM...GS
LONG TERM...Voss
AVIATION...GS
MARINE...Voss