514
FXUS63 KMQT 061743
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
143 PM EDT Mon May 6 2024

.KEY MESSAGES...

-Complex mid-week weather pattern with rain chances increasing
 on Tuesday and multiple passing low pressures keeping rain in
 the forecast through the end of the week.

&&

.SHORT TERM /THROUGH TODAY/...
Issued at 142 PM EDT Mon May 6 2024

Upper air pattern consists of a 500 mb trough in the central Rockies
and a shortwave in the mid Mississippi River Valley. The trough
heads northeast and develops a closed 500 mb low that moves into the
Dakotas by 12z Tue. Weather will be quiet through tonight with very
few changes made to the going forecast.

&&

.LONG TERM /TONIGHT THROUGH SUNDAY/...
Issued at 448 AM EDT Mon May 6 2024

The extended forecast is largely dominated by a trough currently
over the Rockies and its complex evolution and influence on the few
sfc lows moving across the CONUS through the upcoming week. We then
see a bit of a pattern shift over the weekend where model guidance
begins to diverge, but cooler and drier southeast flow over the
Great Lakes is expected this weekend into next week.

Starting tonight, the trough will be negatively tilted over the
Central/Northern Plains with ridging over the Great Lakes. The
trough deepens over the northern plains supporting cyclogenesis over
the western Dakotas. Cyclogenesis will also be ongoing over Kansas
supported by a shortwave rotating northeast along the deep trough as
well as the left exit region of a ~115 kt upper level jet. While the
northern sfc low deepens as it retrogrades into Montana and the
southern more weaker sfc low moves northeast into the Mid-
Mississippi Valley, weak high pressure is shifted northeast from the
Great Lakes. Taking that all into account, dry and quiet weather
holds for the UP with lows in the 40s under a some high level
clouds. Cooler temps are forecast for the eastern UP.

Moving onto Tuesday, the trough forms a closed off low over the
Northern Plains as the shortwave continues northeast from Iowa to
the Upper Great Lakes. At the sfc, the weaker low will have lifted
into the western end of the Great Lakes Basin by Tuesday evening
occluding as it approaches near our CWA. While there still is some
spread yet on this track, expect an occluded front to lift north
through the UP late Tuesday morning/early afternoon bringing with it
a round of showers. With the incoming occluded front, high temps in
the upper 50s to upper 60s are expected earlier in the afternoon
with higher temps holding on longer in the east. The HRRR is the
fastest to bring in showers around 12-1 PM EDT while the NSSLWRF is
closer to 3-4 PM EDT. The better chances for showers arrive later in
the day when the shortwave swings north over the UP. Instability
will be lacking and bulk shear is low (20-35 kts); the NAM Nest and
HRRR show the highest MUCAPE values with a thin stream of up to ~200-
400 j/kg of MUCAPE lifting with the shortwave. Given the set up,
strong thunderstorms can be ruled out, but a few rumbles of thunder
are possible along the WI/MI state line. If the drier solution is
favored, a longer period of mixing ahead of precip will yield lower
RHs in the upper 20s to low 30s in the northern half of the UP save
for the Keweenaw. Gusty southeast winds up to 20-30 mph will also be
a fire weather concern. That said, anticipated precip does look to
bring some relief with a few hundreths to 0.25" of rain; a few areas
in the south central may see up to 0.5-0.75". With uncertainty in
precip arrival time and mixing, will need to monitor the potential
for elevated fire weather conditions in future forecast packages.

The sfc low then begins to meander east through the Great Lakes
Basin Tuesday night into Wednesday with periods of showers possible
during that period. A third low pressure develops over the Southern
Plains Tuesday night with the support of weak embedded shortwaves and
the right entrance region of the upper level jet. As the mid level
closed low weakens on Wednesday, so does the sfc low as they both
move southeast. Meanwhile the southwestern sfc low is moving
northeast with the upper level jet. The two sfc lows look to phase
together mid day on Wednesday over the Mid-Mississippi Valley. At
the same time, chances for showers continue in the UP as a shortwave
drops south across the region.

Wednesday night and Thursday have two potential solutions given the
uncertainty in the guidance at this point in the forecast. The first
one being a brief dry period Wednesday night followed by showers
across the southern half of the UP on Thursday as the new low
pressure tracks east along the southern edge of the Great Lakes
Basin. The other possibility is that this sfc low`s track is further
south and showers stick to the south of the CWA, letting dry weather
hold through the rest of the work week. Determinist GFS and ECMWF
seem to favor the drier solution, but opted to leave in some chance
PoPs in for now. Will continue to monitor if this drier trend
continues.

There is growing confidence in anomalous ridging setting up over
British Columbia this weekend with broad anomalous troughing over
the eastern CONUS. This would set up the Upper Great Lakes for
northwest flow with shortwaves and clipper type lows providing the
next precip chances. Given the significant spread in the guidance
this weekend onward, opted to leave the NBM slight chance PoPs as is.

&&

.AVIATION /18Z TAFS THROUGH 18Z TUESDAY/...
Issued at 1237 PM EDT Mon May 6 2024

VFR conditions will continue to prevail with the area under the
influence of high pressure.  IWD will have MVFR conditions late in
the forecast period.

&&

.MARINE...
Issued at 448 AM EDT Mon May 6 2024

With high pressure over the Upper Great Lakes, resulting stability
will keep winds mainly below 20 kts through Monday night. The
exception to this would be over the far western portion of the lake
near the Duluth Harbor where some northeast channeling may yield
some gusts up to 25 kts. An approaching low pressure Tuesday morning
will force northeasterly to east winds to funnel over the western
half of Lake Superior to 25 kts by noon Tuesday with a few gusts to
30 kts in the far west and along the Minnesota shorelines. With
probability of winds exceeding 34 kts below 20% and the short
duration of the highest winds, opted for no Gale Watch. Winds across
the east half of the lake increase to around 20-25 kts Tuesday
afternoon. A brief break in 20+ kt winds is expected Tuesday night.
Periodic chances for winds in the 20-30 kt range dot the forecast
through Thursday as multiple weak low pressure systems pass through
the Upper Great Lakes region, but uncertainty still remains.

&&

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

&&

$$

SHORT TERM...07
LONG TERM...Jablonski
AVIATION...07
MARINE...Jablonski