563
FXUS63 KMQT 132237
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
637 PM EDT Tue Aug 13 2024

.KEY MESSAGES...

- 15-25% chance of lake breeze showers, ~15% chance of thunder today

- Patchy fog potential overnight, 20-40% chance of dense fog in
  the interior

- Wet period later this week with showers and maybe some
  thunderstorms developing Thursday, continuing Friday, then
  lingering, but diminishing on Saturday.

&&

.UPDATE...
Issued at 637 PM EDT Tue Aug 13 2024

Scattered showers and thunderstorms are wrapping up across the
western UP, and though some additional weak convection has fired
along the Superior lake boundary in the eastern UP over the past
hour, this is also quickly dying out. Expect clearing skies over the
next couple of hours, followed by a quiet night.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 114 PM EDT Tue Aug 13 2024

GOES-16 Channel 10 Low Level Water Vapor imagery shows mostly dry
conditions at the low levels for virtually all of the eastern half
of the CONUS except for a MCS traveling through MO. RAP
analysis shows broad high pressure over the eastern CONUS from
1016-1020 mb supported by ridging aloft over the central CONUS.
This has resulted in clear skies to start the morning over the
UP. Fairly typical summer weather should result today with high
temperatures in the upper 70s with a few typical warm spots
hitting the low 80s.

The main question of the afternoon forecast is whether or not
thunderstorms will form. Northwesterly flow aloft has advected in
some cooler air aloft to steepen lapse rates, allowing for SBCAPE to
grow to 500-1000 J/kg this afternoon and evening. Moisture may be
somewhat lacking though as efficient mixing will allow surface RHs
to fall as low as 35 percent inland today. CAMs show fairly typical
Great Lakes lake breezes today, so the battle will be between the
broad inhibition of the high pressure or the lift from the lake
breezes to see if any parcels can capitalize on the instability.
However, with flow below 20 kt nearly up to the EL, even if the
instability is realized, any showers or isolated thunderstorms that
do form will just be pulse thunderstorms as there is virtually no
shear to work with to organize and maintain said updrafts.

A quiet night is expected as any showers that do form will cease by
00Z. Another threat for patchy fog tonight as GLAMP gridded guidance
shows sub-mile visibility for much of the UP and the HREF shows 20-
40% probability of 0.5 mile or less visibility by 12Z Wednesday, but
given the inconsistency in fog with similar setups in previous
evenings, will continue to only put fog in the forecast and not go
with any headlines.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
Issued at 243 PM EDT Tue Aug 13 2024

Upper air pattern consists of a broad 500 mb ridge across the
southern half of the U.S. poking up into the Great Lakes with
troughing in the eastern U.S. and on the west coast 12z Wed. There
is also a shortwave in the northern plains 12z Wed which heads into
the northern Mississippi Valley 12z Thu. This closes off a 500 mb
low Thu night which slowly moves into the upper Great Lakes on Fri.
850-500 mb q-vector convergence and deeper moisture move into the
area on Thu and remain into Fri. This will bring in the next chance
for rain and could be widespread through Friday. Overall, did not
make too many changes to the going forecast.

In the extended, the GFS and ECMWF show a 500 mb ridge across the
southern Rockies into the plains 12z Sat with a trough over the
Great Lakes region. Ridging then builds into northern Rockies 12z
Sun with troughing in the lower Great Lakes and then the ridge moves
back into the northern plains by 12z Mon as troughing digs into the
ern U.S. Troughing then tries to drop into the upper Great Lakes 12z
Tue with a closed low. Temperatures are below normal for this
forecast period. Backdoor cold front hangs around the area as well,
but does look mostly dry.

&&

.AVIATION /18Z TAFS THROUGH 18Z THURSDAY/...
Issued at 114 PM EDT Tue Aug 13 2024

VFR conditions at all TAF sites will continue through the evening
hours. Some lake breeze -SHRA and isolated TSRA are possible (15-
25%) this afternoon but look to be too far inland to impact the VC
of the TAF sites. Overnight, patchy FG is possible (20-40%) and
could locally be dense at times, but with the inconsistency in
observing fog in similar setups the previous couple nights, category
reductions in vis will only be at SAW at this time with TEMPOs for
all sites. Otherwise, expect mainly light winds throughout the
period under 5 kt.

&&

.MARINE...
Issued at 243 PM EDT Tue Aug 13 2024

Light winds less than 20 knots remain through Wednesday night.
Thu/Fri, low pressure will develop e and ne into WI, bringing
increasing easterly winds to Lake Superior. Expect winds to
occasionally gust to 20-25kt, particularly Thu aftn and Thu night.
Exact track of the sfc low will determine whether these stronger
wind gusts continue on Fri. As the low departs, n to nw winds may
gust to 20-25kt late Fri into Sat, mainly across the e half of Lake
Superior. Winds then drop below 20 knots on Sunday.

&&

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

&&

$$

UPDATE...LC
SHORT TERM...GS
LONG TERM...07
AVIATION...GS
MARINE...07