293
FXUS63 KMQT 190738
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
338 AM EDT Thu Sep 19 2024

.KEY MESSAGES...

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

- A cold front brings scattered showers and a few thunderstorms
  late today into Friday. Some stronger storms are possible in
  western Upper Michigan this evening.

- Temperatures around normal are expected to return for next
  week.

&&

.SHORT TERM /THROUGH THIS AFTERNOON/...
Issued at 334 AM EDT Thu Sep 19 2024

Water vapor imagery and RAP analysis show troffing over the western
U.S. with one well-defined mid-level low over se Saskatchewan and a
second just off of the central CA coast. Some shra/tsra are
occurring across MN ahead of the former mid-level low. Mid-level
ridging is over the western Great Lakes. So, once again, it`s
another early morning just like the last several. With stirring s
winds closer to Lake Superior, it`s a 4th day in a row with early
morning unseasonable warmth in the downslope areas near Lake
Superior from western to n central Upper MI. As of 07z, temps are
still in the upper 60s F in that area. For the 4th night in a
row, Big Bay is the warm spot. Three nights ago, the temp at Big
Bay was 76 at 07z, 2 nights ago it was 75, last night it was
73F and this morning its 70F. Just like previous nights, temps
fall off significantly to the e and s. Across s central and
eastern Upper MI, temps are as low as the mid 40s F at
traditional interior cool spots as winds are decoupled, and a
dry column has further enhanced the radiational cooling, but
temps ranging thru the 50s F are generally the rule. With the
cool conditions, fog has once again developed in that area. The
areas of fog, locally dense, will burn off 1-2 hrs or so after
sunrise.

The Saskatchewan mid-level low and associated sfc low will drift
into southern Manitoba today. Trailing occluded front moving e
across MN will be the focus for late day convective development
within a sharp 850mb theta-e ridge and MLCAPE building to 1500-
2500j/kg. This main area of developing convection will remain w of
Upper MI thru about 00z. Earlier in the day, focus is on
convection over MN in association with low-level jet/theta-e
advection. Should see some additional development across MN over
the next several hrs on eastern edge of low-level jet where
theta-e advection is sharper. This convection should
weaken/dissipate as it approaches Upper MI late morning/early
aftn as low-level jet weakens. For now, have left pcpn mention
out of fcst. Trends will be monitored as the morning progresses
to assess whether pcpn needs to be introduced. Otherwise, expect
one more day with temps exceeding 80F over much of the fcst
area. Models indicate mid morning 850mb temps to be similar to
24hrs ago, so highs should be within a couple of degrees of
yesterday`s highs at most locations. Ongoing, lengthening dry
spell remains a concern for wildfire potential. Winds will be a
little stronger today than yesterday with gusts getting into the
15-20mph range across the w and n. Dry air mix down potential
today doesn`t appear to be quite as good as yesterday, so min RH
should bottom out around 35pct today. Will certainly be
something to monitor this aftn due to a little more wind today.

&&

.LONG TERM /TONIGHT THROUGH WEDNESDAY/...
Issued at 315 AM EDT Thu Sep 19 2024

Some active weather starts off the extended forecast tonight as a
cool front pushes in from the west, bringing with it showers and
thunderstorms over Upper Michigan. With MUCAPE between 1k to 2k J/kg
and 0-6 km bulk shear being around 25 to 35 knots, we could see a
few strong thunderstorms over the western U.P. this evening a couple
of hours after the sunset, with namely strong winds and large hail
being the main threats. However, as the front and precipitation
travel eastward with time tonight, the convection looks to outrun
the better CAPE and shearing, causing the strong storm threat to end
around midnight over the central U.P.. While rainfall amounts from
the front won`t be all that impressive (mainly between 0.10 and 0.30
inches), we could see a few isolated spots, mainly over the west and
central, that could see some localized soaking rainfalls as the
heaviest downpours move over them (PWATs will be around 1.50
inches). In addition to the rainfall, we could also see some record
warm low temperatures tonight as the antecedent warm air along with
the cloud cover will work to keep lows from reaching the 50s. The
showers and storms continue over the east half Friday as convection
redevelops behind the initial line. While not expected, there is a
small, outside chance (2% or less) that we could see a strong storm
or two over the central and east, even though the conditions are not
as ideal as what they will be over the far west this evening. Expect
slightly cooler temperatures too on Friday, with highs only being in
the 70s. The rainfall associated with the front looks to get out of
here by Saturday morning as weak ridging moves overhead.

More dry weather and well above normal temperatures return Saturday
as weak, localized ridging looks to keep precipitation and cloud
cover away. Expect to see high temperatures return into the upper
70s to low 80s once again Saturday, meaning that some spots in the
U.P. may flirt with tying or breaking their daily max temperature
record. However, as a cold front from our north and west phases with
a shortwave low lifting from the Plains through the U.P. Saturday
night and Sunday, we could see showers return to the area.
Currently, the expectation is that the rainfall from this will be
fairly light.

Temperatures will return to around normal next week behind this cold
front, with highs generally being in the 60s and lows in the 50s to
mid 40s later in the week. We may see additional rainfall over
mainly the central and east around next Tuesday as a low lifts from
the Southern Rockies into the Upper Midwest. However, model
agreement is still shaky at this time, so confidence in this
occurring is still pretty low (30-40% chance). Behind this low,
expect surface ridging to return to the Great Lakes region by the
latter half of next week.

&&

.AVIATION /06Z TAFS THROUGH 06Z FRIDAY/...
Issued at 127 AM EDT Thu Sep 19 2024

VFR conditions will prevail in this TAF period.

&&

.MARINE...
Issued at 315 AM EDT Thu Sep 19 2024

Light winds of 20 knots or less today give way to southeast to
southerly winds of 20 to 25 knots over the central lake this evening
as a cool front slowly trudges from west to east today through
Friday. This front will bring some showers and storms across the
lake, with some storms possibly being strong to severe over the west
(the main threats being strong, erratic winds and large, damaging
hail). As the front moves eastwards with time, expect the severe
threat to diminish, particularly by around midnight tonight EDT.
While winds generally decrease to 20 knots or less across Lake
Superior by Friday morning, the showers and storms continue along
the front through Friday night. Weak ridging over the area keeps
winds light Saturday before a cold front passes through Saturday
night and Sunday from the west. Currently, we could see
northwesterly winds gust to 20 to 25 knots behind the cold front
over the western half of the lake late Saturday night and Sunday. In
addition, expect to see some showers and a few thunderstorms with
the front`s passage Saturday night through Sunday, although the
convection isn`t a guarantee as some models do keep the lake rain-
free (50 to 60% chance of occurrence). Another low lifting from the
Southern Rockies may lift into the Upper Great Lakes around the
Tuesday time period too and bring stronger winds and thunderstorms
back across the lake, but uncertainty on this occurring is higher
(around 30 to 40% chance of occurrence).

&&

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

&&

$$

SHORT TERM...Rolfson
LONG TERM...TAP
AVIATION...07
MARINE...TAP