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279
FXUS63 KMQT 250640
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
240 AM EDT Sat May 25 2024

.KEY MESSAGES...

- Showers, with some thunder, return early this evening and
  shift east overnight followed by clearing skies late.

- Approaching low pressure system brings isolated shower or
  thunderstorm chances to the far west Saturday evening then
  widespread rain chances late Sunday into early Monday.
  Rainfall amounts over 1 inch are possible by Monday evening.

- Below normal temperatures and a drying trend for much of next
  week. Patchy frost possible Thursday morning.

&&

.SHORT TERM /THROUGH THIS AFTERNOON/...
-- Changed Discussion --
Issued at 240 AM EDT Sat May 25 2024

Upper air pattern consists of a 500 mb closed low near Lake Winnipeg
this morning which meanders slowly northwest into western Ontario by
00z Sun. There is some 850-500 mb q-vector convergence and some
moisture that comes into the west late in the day while earlier
moisture and q-vector convergence moves out across the cwa this
morning. Showers will continue to move out this morning and then the
next wave comes into the far west by late this afternoon. Appears
like this next wave would be in the southern part of a deformation
zone from the closed low that gives the far west a glancing blow.
Could be some thunder with this elevated convection. Overall, did
not make too many changes to the going forecast.
-- End Changed Discussion --

&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...
Issued at 459 PM EDT Fri May 24 2024

The primary feature of interest for the long-term period is an
unseasonably strong low pressure lifting northeast across the region
Sunday and Monday. The UP stays on the chilly side of this system
leading to widespread soaking rain with embedded thunderstorms
possible, but nothing severe. A chilly Canadian ridge builds Tuesday-
Wednesday, lingers on Thursday, then shifts east Friday-Saturday. In
addition to being very dry with some fire wx potential, this air
mass appears cool enough to raise frost/freeze concerns. Frost seems
mostly likely/widespread Thursday morning, but may develop across
the west Wednesday morning.

Beginning with Saturday morning, rain showers should exit the far
eastern area early in the day leading to an almost completely dry
day. Mostly sunny skies allow temps to warm to around 70F amidst
breezy west-southwest winds that should limit lake breeze activity
to the eastern UP. A 30-40 knot southwesterly low level jet noses
into the western CWA around sunset with more than half of HREF
members initiating shower and thunderstorm activity across our
western tier of counties. The convective environment is CAPE
deficient with HREF means only rising to around 250 J/kg, but the
ensemble maximum approaches 1000 J/kg. The most likely outcome is
any storms that form should be limited to beneficial rain, but gusty
winds and small hail are possible if CAPE ends up being more
favorable. Probably broad-brushed PoPs too much for this time frame
since it may only occur far west, but wanted to increase from
previous forecast and kept QPF light. There is potential for QPF
>0.25" with the strongest or most persistent activity.

Sunday starts off dry with a surface low over eastern KS that
quickly moves northeast to southern WI by 00z Monday. Slowed PoPs a
bit on Sunday to account for the typical progressive bias in
NBM guidance. Also focused Sunday`s PoPs across the western UP
in the vicinity of an axis of frontogenesis extending north from
the surface low. The primary area of rainfall arrives Sunday
evening and EFI guidance shows the best signal for heavy
rainfall (>1 inch in 24 hours) across the eastern UP. Meager
CAPE combined with impressive dynamics results in chances for
embedded thunderstorms, but the primary associated hazard is to
increase rainfall rates. Dew points well above lake water temps
combined with rain and strongly convergent synoptic flow are all
favorable for a potentially dense advection fog event.

Steady rain chances shift east of the UP on Monday as showery
chances arrive across the west. These shower chances are forced by a
decaying upper level disturbance that digs southeast across the UP
Monday night and Tuesday. It`s too early to dig into the details,
but fairly chilly mid-levels suggests steep lapse rates and
diurnally enhanced rain shower chances. Precipitation amounts appear
light and should end Wednesday morning -if not sooner- as a cool and
dry Canadian surface ridge builds southeast into the area. This
ridge appears to park itself over the Great Lakes region for several
days resulting in a stretch of prime springtime weather with highs
in the 50s/60s and lows in 30s/40s beneath mostly sunny skies. There
is a threat for frost with this chilly air mass so folks with
sensitive vegetation should monitor forecasts accordingly.

&&

.AVIATION /06Z TAFS THROUGH 06Z SUNDAY/...
Issued at 111 AM EDT Sat May 25 2024

Occluded front is currently moving across Upper MI, and shra will
end with its passage. With front already passed IWD, expect VFR to
prevail at that terminal thru the fcst period. Gusty winds to around
20kt will occur overnight and to around 25kt today. Shra and
potentially some tsra will develop this evening over western Lake
Superior. IWD may be affected, but confidence is low attm. At CMX,
front will pass in the next hr or two, bringing a wind shift from
easterly to gusty westerly to 25-30kt. LLWS will also end with
fropa. MVFR cigs may linger to mid morning under the upslope
westerly winds at CMX, but VFR will prevail thereafter. CMX has a
better chc of being affected by shra and possible tsra this evening.
Included shra mention, but no thunder given the lower confidence of
thunder impacting the terminal. At SAW, with the shra that have
occurred, upslope sse wind should result in IFR cigs setting in over
the next hr or so. Improvement to VFR will occur within 2 hrs after
fropa. VFR will then continue thru the end of the fcst period.
Westerly winds will be gusty to around 20kt at SAW today.

&&

.MARINE...
Issued at 459 PM EDT Fri May 24 2024

Northeast gales to 40 knots continue across the far western lake
with east winds of 20 to 30 knots across most of the central lake
this afternoon ahead of a low pressure currently near Grand Forks,
ND. East winds up to 30 knots gradually shift to the north-central
lake tonight ahead of a cold front that shift southwesterly.
Southwest winds around 25 knots are expected across the west half of
Lake Superior on Saturday morning before decreasing to 20 knots or
less by the evening and continuing through the rest of the weekend
as a high pressure ridge builds over the area. Another system tracks
northeast across the Great Lakes region Sunday night and Monday with
generally northerly winds of 20 to 25 knots, mainly across the
eastern half of the lake.

&&

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

&&

$$

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