Flooding in Michigan, May 4 to 14, 2023

Area Forecast Discussion
National Weather Service Marquette MI
707 PM EDT Wed May 3 2023

.SHORT TERM...(The rest of this afternoon)
Issued at 124 PM EDT WED MAY 3 2023

With the stacked low now well to the east over New England, surface
ridging filling in the wake of the low is creating some quieter
weather for today. Trapped boundary layer moisture lead to low
clouds this morning that have now cleared out for the west half.
Clear skies will not last terribly long however as a weakening
shortwave over northwest Ontario that is evident on GOES 16 water
vapor imagery will pivot southeast into the western portions of the
CWA. The shortwave will be aided by weak isentropic scent in the
afternoon over the western UP and western Lake Superior. CAMs do
show light reflectivities reaching into the UP, so slight chance
PoPs have been added to the west, though even the 95th percentile of
the NBM has no measurable QPF through 00Z tonight, so any showers
that form will be nuisance, low-impact showers, or just virga.
While the lack of QPF will not be adding any runoff to the hydro
concerns, the more direct sun angle in areas of clearing skies
will certainly add more snowmelt to basins such as the Dead River
basin which are already running low on storage.

.LONG TERM...(Tonight through Wednesday)
Issued at 340 PM EDT WED MAY 3 2023

An strong omega block sets up over North America the rest of this
week through this weekend as troughing sets up over the Pacific and
Atlantic Coasts. Some strong ridging aloft is expected over the
North American mainland later this week through this weekend as
ensemble guidance shows height anomalies up to 3 times above normal
occurring around Hudson Bay during this time period. However, with a
low-level trough setting up to the west of us and ridging remaining
over Hudson Bay and most of the Great Lakes region the rest of this
week into this weekend, we could see repeated shortwaves affect the
U.P. for the next few days, bringing rainfall across to our already
saturated area; therefore flooding concerns are expected to persist
into this weekend.

As the troughing pattern continues to leave towards the East Coast
tonight into Thursday as high pressure builds in over central Canada
and Hudson Bay, a lingering shortwave drops from the Northland into
northern WI. This in turn brings rain showers across the west and
central tonight into Thursday. With temps staying above freezing
across most of the western half tonight, no wintry weather is
expected late tonight into early Thursday morning save for a slight
chance in the north central in the hills west of Marquette and
around Gwinn to Chatham and Rock; should there be any ice, expect
there to only be a glaze, mainly over elevated sfcs. In addition,
some patchy fog could be seen over the central and east late
tonight, with the the interior east half possibly having lows in the
upper 20s. As the sfc ridging over Hudson Bay fights the sfc
troughing over the Great Plains, rain shower activity looks to
continue on and off as WAA slowly creeps in across the region.
Therefore, while mostly cloudy skies are looking to remain over us
for the rest of this week into early next week, temps are expected
to rise with each passing day, getting into the 60s and 70s for a
high early next week (which would be above normal). This leads us to
the main concern for the extended period: flooding.

As temps rise and rain chances continue across the area late this
week into this weekend, snow melt and liquid added from the rainfall
raises river water levels across the western and north central U.P.;
in addition, some ponding of water may be possible in the places
where the rainfall occurs the hardest, as some embedded
thunderstorms may occur (particularly Friday evening). What is
concerning is an uptick in the expected precip amounts recently;
some model guidance has 1 to 2 inches of liquid falling over us by
the end of this weekend, with the NAM12km showing as much as 3
inches in spots! However, there is still some uncertainty as to
whether this will happen, as some model guidance has only trended
towards the higher precip amounts recently. Therefore, the Flood
Watch for areal flooding/ponding of water continues into Friday, as
soil moistures across the U.P. remain exceptionally above normal,
meaning that much of the snow melt and rainfall that occurs late
this week through this weekend should have a hard time getting into
the soil (thus ponding and river levels rising). Moving into early
next week, model guidance is less certain. However, there is a
signal in at least some of the guidance that precip continues into
the early part of next week. Should this occur, our flooding woes
would continue into early next week.
&&

.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 707 PM EDT WED MAY 3 2023

VFR conditions and high clouds are expected this evening. A weak
shortwave moving through Upper Michigan is expected to support
lowering ceilings at KCMX and KSAW overnight and Thursday and a low
probability of rain showers. Ceilings are only expected to dip to
MVFR at KCMX while KSAW may dip to IFR by Thursday afternoon. Low
MVFR or IFR visibilities due to fog may also be possible overnight
at KSAW. KIWD is expected to remain VFR.
&&

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 356 PM EDT WED MAY 3 2023

Light winds of 20 knots or less continue this afternoon through
tonight, until a shortwave low passes over the far western lake late
tonight/early Thursday morning. Behind the low, expect northeasterly
winds to pick up to 20 to 30 knots across the western lake, with a
few gale force gusts up to 35 knots being possible over the far west
during the afternoon. While winds may subside a little Thursday
night, expect the winds to rise again Friday over the western half,
with a few more gales being seen over the far west. As ridging
slowly builds into eastern Lake Superior this weekend, expect the
winds to slowly calm with time, although northeast to easterly winds
of 20 to 30 knots could be seen Saturday. Expect light winds of 20
knots or less to dominate from Sunday onwards next week.
&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
  Flood Watch through Friday morning for MIZ001>006-009>011-084.

Lake Superior...
None.
Lake Michigan...
None.
&&

SHORT TERM...GS
LONG TERM...TAP
AVIATION...JTP
MARINE...TAP

Hazardous Weather Outlook...CORRECTED
National Weather Service Marquette MI
349 PM EDT Wed May 3 2023

MIZ001>007-009>014-084-085-041930-
Keweenaw-Ontonagon-Northern Houghton-Baraga-Marquette-Alger-Luce-
Gogebic-Iron-Dickinson-Menominee-Delta-Southern Schoolcraft-
Southern Houghton-Northern Schoolcraft-
349 PM EDT Wed May 3 2023 /249 PM CDT Wed May 3 2023/

This Hazardous Weather Outlook is for portions of central Upper
Michigan and western Upper Michigan.

.DAY ONE...Tonight

A flood watch is in effect for western and portions of north
central Upper Michigan. Runoff from recent heavy precipitation and
melting of new snow cover over portions of the area may result in
flooding of rivers, creeks, streams, and other low-lying and
flood-prone locations.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday

A flood watch is in effect for western and portions of north
central Upper Michigan through Friday morning. Runoff from melting
snow over portions of the area may result in flooding of rivers,
creeks, streams, and other low-lying and flood-prone locations.

.SPOTTER INFORMATION STATEMENT...

Spotters are requested to submit precipitation and flooding
reports through early next week.

LSZ162-240>251-263>267-041930-
Lake Superior west of a line from Saxon Harbor WI to Grand
Portage MN beyond 5NM-Saxon Harbor WI to Black River MI-
Black River to Ontonagon MI-
Ontonagon to Upper Entrance of Portage Canal MI-
Upper Entrance of Portage Canal to Eagle River MI-
Eagle River to Manitou Island MI-
Manitou Island to Point Isabelle MI-
Point Isabelle to Lower Entrance of Portage Canal MI-
Lower Entrance of Portage Canal To Huron Islands MI Including
Keweenaw and Huron Bays-Huron Islands to Marquette MI-
Marquette to Munising MI-Munising to Grand Marais MI-
Grand Marais to Whitefish Point MI-
Lake Superior from Saxon Harbor WI to Upper Entrance to Portage
Canal MI 5NM off shore to the US/Canadian border including Isle
Royale National Park-
Lake Superior from Upper Entrance to Portage Canal to Manitou
Island MI 5NM off shore to the US/Canadian Border-
Lake Superior West of Line from Manitou Island to Marquette MI
Beyond 5NM from shore-
Lake Superior East of a line from Manitou Island to Marquette MI
and West of a line from Grand Marais MI to the US/Canadian Border
Beyond 5NM from shore-
Lake Superior from Grand Marais MI to Whitefish Point MI 5NM off
shore to the US/Canadian border-
349 PM EDT Wed May 3 2023 /249 PM CDT Wed May 3 2023/

This Hazardous Weather Outlook is for portions of Central Lake
Superior...Eastern Lake Superior and Western Lake Superior.

.DAY ONE...Tonight

No hazardous weather is expected at this time.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday

A few northeasterly gale force gusts up to 35 knots are possible
Thursday. See the latest Open Lake Forecast for additional details.

A few northeasterly gale force gusts to 35 knots are possible
Friday. See the latest Open Lake Forecast for additional details.

.SPOTTER INFORMATION STATEMENT...

The need for weather spotter reports is not anticipated at this
time.

LMZ221-248-250-041930-
Green Bay North of line from Cedar River MI to Rock Island
Passage-Seul Choix Point to Point Detour MI-
5NM East of a line from Fairport MI to Rock Island Passage-
349 PM EDT Wed May 3 2023

This Hazardous Weather Outlook is for portions of Northern Lake
Michigan.

.DAY ONE...Tonight

No hazardous weather is expected at this time.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

The need for weather spotter reports is not anticipated at this
time.

GS