612
FXUS63 KMQT 130846
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
446 AM EDT Tue Aug 13 2024

.KEY MESSAGES...

- Warm and mostly dry weather today and Wednesday though some
  isolated lake breeze showers and thunderstorms are possible
  this afternoon.

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

&&

.SHORT TERM /THROUGH THIS AFTERNOON/...
Issued at 148 AM EDT Tue Aug 13 2024

Mostly clear skies look to continue across the area early this
morning as a high pressure block moves overhead today. Satellite
imagery is possibly picking up on the first patches of fog over Luce
and Delta counties as of the time of this writing. However, given
the dry airmass overhead, thinking fog will be limited to being
patchy in nature before dawn this morning, and mainly being limited
to the south central and east. Once the sun comes up, expect the fog
to quickly erode away.

Expect another mostly sunny/dry day again, with temperatures being
almost a near repeat of yesterday (just maybe a hair warmer). There
is also a small (10-20 percent) chance that we could see some
showers and thunderstorms along the lake breezes this afternoon as
there is ample instability in the atmosphere to work with. However,
given the lack of a forcing mechanism, save for maybe the lake
breeze, I have my doubts as to whether convection will fire off or
not. In addition, CAMs soundings show the boundary layer being a
tall inverted-v, meaning that there will be quite a bit of dry air
to be overcome before precipitation hits the surface. However, this
also means anything that gets started at the surface could keep
building up to the tropopause given the lack of CIN in the
atmospheric profile and the strong low to mid level lapse rates.
Rain chances are zero percent behind the lake breezes this afternoon
as the airmass will be too stable to support localized convection.

&&

.LONG TERM /TONIGHT THROUGH MONDAY/...
Issued at 444 AM EDT Tue Aug 13 2024

Positive height anomalies prevailing across Canada this week will
suppress southward a branch of the westerlies across the Lwr 48 with
that flow relatively progressive, lower amplitude for the next few
days. Late this week, that flow will buckle with mid-level ridging
building northward thru Alberta/Saskatchewan. In response, a group
of shortwaves approaching the Great Lakes will consolidate into an
amplifying trof into the Great Lakes region and eastern U.S. Fri
thru early next week. For Upper MI, this evolution of the flow with
troffing developing thru the Great Lakes region will bring shra to
the area Thu thru Sat. While all day rain is not expected, potential
right now appears high for all of Upper MI to see at least light to
mdt rainfall over the course of the 3 days. Ensemble guidance
suggests a 25-50pct probability of pcpn amounts of an inch or more
by Saturday evening, greatest w to s central. The rainfall is needed
as the pattern has turned drier over the last few weeks. A large
portion of Upper MI is running at 25-70pct of normal rainfall over
the last 30 days with the largest areas under 50pct over the w half
of Upper MI. As for temps, above normal high temps will continue
into Wed, then readings will be around normal or a little blo normal
thru the weekend and into early next week as mid-level trof passes,
followed by lingering nw flow.

Beginning tonight, isold convection that develops this aftn may
linger a little past 00z, but otherwise, the night will be dry. Some
patchy fog may again develop tonight as we are now into late summer,
and when quiet/cool nighttime conditions occur, patchy, shallow fog
often forms, especially near swampy areas, rivers/streams, lakes due
to their warm waters. Fog development would be more likely to occur
if some rainfall occurs this aftn/early evening. Expect min temps
mostly ranging thru the 50s F. Some of the traditional interior cool
spots may slip into the upper 40s F, and some lakeside locations
will stay above 60F.

On Wed, concern is again the potential of isold aftn convection.
However, models all show a drier column and weaker instability Wed
aftn compared to this aftn. Although a few models do show isold
convection developing, will ride with a dry fcst for Wed given the
less favorable environment. High temps on Wed in many locations will
be a few degrees warmer than today. Expect upper 70s to mid 80s F.
Dry weather continues Wed night with temps falling back to the mid
50s to mid 60s F.

During Thu/Thu night, mid-level troffing and a group of unorganized
shortwaves progressing across s central Canada/Northern Plains will
shift to the western Great Lakes. At the sfc, low pres will develop
into WI. A healthy surge of isentropic ascent and 850-700mb moisture
transport ahead of the trof may send associated shra into western
Upper MI as early as around 12z on Thu. Otherwise, expect shra to
progress w to e across the area as the forcing advances eastward
during Thu and thru Thu night. Precipitable water increasing to 150-
170pct of normal, weak instability developing aloft, and warm cloud
depths increasing to around 12kft to increase warm rain processes
will combine to support some potential of locally hvy rainfall.
Thunder likely to be limited to isolated coverage given the weak
instability.

Showers will continue on Fri as troffing/potential weakly closed off
mid-level low drift over the western Great Lakes while associated
sfc low slowly moves e across northern WI or Upper MI. With ocnl
shra and abundant cloud cover, high temps should be held to mostly
the upper 60s/lwr 70s F. If sfc low tracks across WI/southern Upper
MI, could end up being a gloomy, low stratus kind of day across the
w and n central with upslope ne to n winds.

As the troffing continues drifting eastward on Sat, expect shra
coverage to diminish compared to Fri. Abundant cloud cover should
remain, holding high temps to the upper 60s to mid 70s F. Dry
weather should then set in for Sun with trof slipping a little
farther e. Mon should also be a dry day, then next shortwave
dropping se in continued nw flow downstream of ridging from NM/TX to
the NW Territories may approach on Tue or Wed, bringing the next chc
of shra/tsra.

&&

.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 305 AM EDT Tue Aug 13 2024

UPDATE: Current satellite and webcam imagery shows patchy fog
failing to develop up into the north central U.P. early this
morning. Therefore, I`ve removed the FG chances from KSAW. -TAP

Mainly VFR conditions for the duration of the TAF period.  However,
there is a chance for MVFR or worse fog at SAW again early this
morning.  Will highlight this in a tempo from Tue 08-12Z. Elsewhere,
confidence remains too low to include mention of fog at IWD or CMX.
And probabilities are also too low for shower/thunderstorm mention
this afternoon at any TAF site at this time.

&&

.MARINE...
Issued at 444 AM EDT Tue Aug 13 2024

Light winds less than 15kt will continue across Lake Superior today
under sfc high pres. Winds will increase slightly on Wed, but still
under 20kt as the high pres begins to slip eastward. Thu/Fri, low
pres 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.

&&

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

&&

$$

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