317
FXUS63 KMQT 190737
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
337 AM EDT Sun May 19 2024

.KEY MESSAGES...

- Borderline elevated fire weather conditions today with warm
  and very dry conditions, but winds on the lighter side.

- Leading edge of next round of showers could reach into the
  far western U.P. toward sunrise Monday.

- Frequent periods of showers Monday through late week, but mainly
  focused on Monday and Tuesday afternoon and Tuesday night.

- Above normal temperatures early in the week falling to below
  normal late week.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 336 AM EDT Sun May 19 2024

Today, sfc high pres ridging and an associated very dry air mass
will build into the Upper Great Lakes in the wake of last night`s
frontal passage. Full sun thru the morning will give way to
thickening mid/high clouds arriving from the w in the mid-late
afternoon ahead of a weak shortwave rippling thru the mid-level
ridge. Strong insolation will result in deep mixing into extremely
dry mid-levels. NAM soundings show late morning dewpoints at
800mb/~5kft AGL ranging from -20 to -40C, though this is the low end
of the model guidance. Even though moisture aloft does increase
during the afternoon, mixing potential still supports sfc dewpoints
falling thru the 30s F. Some locations will see upper 20s F. The low
dewpoint potential is also evident thru the local mixed dewpoint
tool and simply in some of the raw model guidance, which the HRRR
appears to capture quite well. With high temps fcst in the mid/upper
70s F across the interior, the low dewpoints will drive RH down to
around 20pct across much of the interior of Upper MI this afternoon.
The good news is winds will be on the lighter side, though a little
higher than previously expected. Sustained winds will be around 10
mph with gusts to around 15 mph. Winds will be strongest across the
Keweenaw where gusts to around 25mph are possible. Lake breeze
development should help limit fire wx concerns close to the Great
Lakes shorelines due to cooling conditions (temps falling into the
60s F), and higher dwpts, resulting in higher RH.

Tonight, the next significant shortwave and rainmaker, now over the
SW U.S., will be approaching through the Central Plains and Upper
Midwest late tonight. Increasing q-vector convergence and isentropic
ascent ahead of the shortwave could lead to some showers forming
over the far western U.P. around sunrise Monday morning. Model
soundings indicate that dry low-levels should keep much of the rest
of the U.P. dry through tonight. Expect min temps in the upper 40s
to around 50F. under mostly cloudy skies.

&&

.LONG TERM /TONIGHT THROUGH SATURDAY/...
Issued at 551 PM EDT Sat May 18 2024

An active pattern will continue across the U.S. during this week.
Troffing currently over western Canada into the northern U.S.
Rockies will amplify over the next few days, leading to western
Canada/western U.S. troffing this week. A series of shortwaves
dropping into this trof from the N Pacific will then eject e and ne
across the U.S., supporting the active pattern. For Upper MI, the
result will be several opportunities of rainfall this week. The
first is just beginning and continues into tonight. The second
follows late Sun night thru Mon evening, the third Tue aftn thru
Wed, possibly lingering into Thu, associated with the strongest low
pres of the week, and finally the fourth at some point Fri thru the
weekend. Models are in overall good agreement thru midweek. Timing
of the last system is most uncertain, but that`s expected given the
farther time range out in the model runs. So, expectation is for
overall above normal pcpn across Upper MI over the next 7 days. This
will work to ease still lingering drought over portions of western
Upper MI where, per the 5/16 U.S. Drought Monitor, severe drought
was still indicated, centered around the Porcupine Mtns, and also in
eastern Upper MI where moderate drought was still indicated from
eastern Delta to western Mackinac counties. As for temps, above
normal readings will be the rule thru Mon, warmest on Sun. Temps
will then trend downward to blo normal Thu/Fri, due to the flow
around the deep low that passes across the area midweek. A return
toward normal expected over the weekend.

Beginning tonight, a mostly narrow band of convection associated
with cold front still currently w of Upper MI will continue
progressing eastward with a tendency to diminish with time once it
reaches central Upper MI due to loss of daytime heating and
resulting waning instability. Risk of damaging winds/large hail
exists across roughly the w half of Upper MI owing to 500-1000j/kg
of MLCAPE over the next few hrs and deep layer shear of 30-40kt.
Last of the diminishing shra/tsra will exit the eastern fcst area 06-
09z. Skies will quickly clear from w to e after fropa. Expect lows
generally in the upper 40s to lwr 50s F across the area.

On Sun, sfc high pres ridging will move to the Upper Great Lakes
along with and an associated very dry air mass. Full sun thru the
morning will give way to some mid/high clouds arriving from the w in
the aftn. Strong insolation will result in deep mixing into
extremely dry mid-levels. NAM shows late morning dwpts at
800mb/~5kft AGL ranging from -20 to -40C, though this is the low end
of the model guidance. Moisture aloft does increase during the aftn,
but mixing potential still supports sfc dwpts falling thru the 30s
F. Some locations will see upper 20s F. The low dwpt potential is
evident thru local mixed dwpt tool and simply in raw model guidance,
HRRR most dramatically (it often captures mix down drying quite
well). With high temps in the mid/upper 70s F across the interior,
the low dwpts will drive RH down to around 20pct across much of
Upper MI Sun aftn. The good news is winds will be on the lighter
side, though a little higher than previously expected. Sustained
winds will be around 10 mph with gusts to around 15 mph. Winds will
be strongest across the Keweenaw with gusts to around 25mph there.
Will need to monitor for lightning strike started fires, especially
if rainfall from storms is more limited tonight. Lake breeze
development will limit fire wx concerns close to the Great Lakes
shorelines due to cooling conditions (temps falling into the 60s F),
and higher dwpts, resulting in higher RH.

Out of the amplifying mid-level trof over the western CONUS, next
shortwave will lift to the Upper Great Lakes on Mon, accompanied by
a surge of precipitable water up to ~190pct of normal. This increase
in moisture along with increasing isentropic ascent will lead to
shra/isold tsra and a widespread wetting rain across much of the
fcst area. EPS ensemble probabilities show much of the area, except
the Keweenaw, with a 30-50% chance of seeing 0.5 inch of rain from
this system. Shra will arrive late Sun night and end most areas Mon
evening. After a period of drier weather late Mon night thru Tue
morning, a notably stronger shortwave ejecting from the western trof
will reach the Upper Mississippi Valley Tue night. With this wave
potentially closing off a mid-level low, it may be slower to exit
across Upper MI into Ontario Wed/Thu. The GFS has been and continues
to be on the faster edge of the model solutions. This fcst leans
toward the slower consensus. Associated deepening sfc to 985-990mb
range will be in the vcnty of western Lake Superior Wed morning.
While the low track passing to the w of Upper MI will support the
widest coverage of heaviest rainfall to the w of Upper MI, mdt to
locally hvy rainfall will still be possible across the fcst area
during the period of strong isentropic ascent/strong 850mb theta-e
advection to the e of the low Tue night. Precipitable water
increases to ~200pct of normal as well. Expect widespread rainfall
across the area. EPS probabilities show a 30-70% chance for at least
a half inch of rainfall from this system with the highest
probabilities se and w. Shra coverage will diminish significantly
for Wed, some areas may slip in dry weather for much or all of the
day, especially e half. As the low lifts across northern Ontario,
isold/sct shra may linger under cyclonic flow on Thu.

Timing shra potential Fri/Sat is uncertain. For now, of the 2 days,
Fri has the better shot at being a dry day.

&&

.AVIATION /06Z TAFS THROUGH 06Z MONDAY/...
Issued at 657 PM EDT Sat May 18 2024

VFR conditions prevail thru this fcst period. A brief 2 hour window
through 02z at SAW and CMX could see some thunderstorms when a cold
front sweeps east across Upper Michigan.  Cloud cover also rapidly
diminishes behind the front with skies becoming clear by Sunday
morning.

&&

.MARINE...
Issued at 325 AM EDT Sat May 18 2024

Stable conditions will lead to light winds of generally 20 knots or
less prevailing over the lake into early next week, except for some
20-25 kt southeast gusts today over the east half ahead of an
approaching cold front. Thunderstorms are possible today into
tonight as the cold front marches across the lake. These storms may
contain small hail, gusty and erratic winds, and frequent lightning.
More thunder chances return late Sun night into Monday and then
again late Tuesday into Tuesday night as a series of disturbances
track northeast across the Upper Great Lakes region. Models and
ensembles indicate winds will ramp up Tue night into Wed as a
stronger low pressure center tracks across the western and northern
portions of the lake. Ensemble probabilities show a 40-60 pct chance
of gale force gusts to 35 knots late Tue night into Wed across
western and northern sections of the lake.

&&

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

&&

$$

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