664
FXUS63 KDLH 151144
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
644 AM CDT Tue Jul 15 2025

.KEY MESSAGES...

- Multiple rounds of showers and thunderstorms are expected
  today into Wednesday. Rainfall amounts of 1-3" with locally
  higher amounts may lead to flash flooding concerns this
  afternoon into tonight, especially over northwest WI and Pine
  County in MN.

- Strong to severe thunderstorms will be possible this afternoon
  and evening with damaging winds to 60 mph and large hail up to
  1" in diameter being the primary hazards.

- Temperatures for the latter half of the week into the weekend
  will be more mild with additional chances for precipitation
  late Friday into Saturday.

&&

.DISCUSSION...
Issued at 526 AM CDT Tue Jul 15 2025

A line of thunderstorms has developed early this morning across the
northern portion of the CWA. 06z sfc analysis from WPC revealed a
warm front draped across northern MN, which has been the primary
forcing mechanism for this morning`s convection when combined with
the influence of a 30+ knot southwesterly LLJ at 850mb. This LLJ and
stalling warm front will continue showers and thunderstorms through
the early to mid morning hours today, mainly impacting northern MN.
High PWATs to around 1.7" as well as training storms this morning
has led to high rainfall rates and minor flooding concerns. In
addition, large hail to 1" will also be a concern for the next
several hours as MUCAPE values remain elevated in the 2000-2500 J/kg
range. Damaging winds are a minimal concern early this morning as
CAM model soundings show a stable layer in the low-levels and DCAPE
is only at 500 J/kg or less.

An active synoptic pattern is expected today as a series of
shortwaves propagate through the CWA within zonal flow at 500mb. At
the sfc, a quasi-stationary front over the CWA will provide
necessary forcing in additional to the larger synoptic lift. Deep
moisture advection is expected to occur today with PWAT increasing
to 1.5-2" by this afternoon, especially within the warm sector over
northwest WI and Pine County in MN. The orientation of this moisture
advection to the quasi-stationary cold front will likely result in
training thunderstorms developing this afternoon and continuing into
tonight as another LLJ around 30 knots in magnitude develops. CAMs
reflect this potential for training thunderstorms with decent
agreement on an overall pattern of training convection.

The primary concern for this afternoon into tonight is flash
flooding due to the high amount of PWAT, in the 90-97th percentile
per NAEFS and ECMWF climatology, and the potential for training
thunderstorms. Model soundings from the CAMs in KHYR show that a
deep warm cloud layer in excess of 10,000ft will be likely combined
with a long and skinny CAPE profile around 900-1200 J/kg. These two
factors are very favorable for heavy rainfall rates, which is
reflected in global ensembles showing signals for 1-3" inches of
rainfall by 12z Wednesday. In addition, probability matched mean QPF
from the 00z HREF suggest that locally higher amounts to 4" will be
possible over northwest WI, which could lead to flash flooding
concerns. With the ingredients in place for flash flooding, a Flash
Flood Watch was issued for most of northwest WI and Pine County in
MN due to the potential this afternoon through tonight. At this
time, the greatest uncertainty lies in exactly where these
training storms will develop due to spatial discrepancies in
the CAMs.

While flooding is the primary concern, severe thunderstorms will
also be possible this afternoon as instability increases in excess
of 1000 J/kg with 0-6km bulk shear of 20-30 knots. Primary severe
hazards this afternoon and evening will be large hail up to 1" and
sporadic wind gusts to 60 mph. A Slight Risk remains in effect for
portions of the CWA today due to this potential for strong to severe
thunderstorms. Overall, today into tonight will be a period to keep
an eye on the weather.

Precipitation will be slow to exit the CWA on Wednesday into
Wednesday night, with CAMs continuing to show additional rounds of
showers and thunderstorms on Wednesday. Wednesday`s precip will be
synoptically forced by a 500mb shortwave, which will move through
the CWA on Wednesday night. In the wake of this shortwave, a brief
period of high pressure will be possible on Thursday. This will
bring a brief break in the rain on Thursday before additional
chances for showers and thunderstorms arrive late Friday into
Saturday. Expect more mild high temps for the latter half of the
week into the weekend.

&&

.AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/...
Issued at 644 AM CDT Tue Jul 15 2025

A stalling cold front will bring multiple rounds of showers and
thunderstorms through the period. Mostly VFR conditions this morning
will be decreasing to MVFR and IFR later today as precipitation
occurs. Strong to severe thunderstorms capable of producing large
hail, damaging winds, and heavy rainfall will be possible this
afternoon and evening. MVFR and lower cigs will likely linger
tonight into early Wednesday morning for most terminals.

&&

.MARINE /FOR NEAR SHORE WATERS OF WESTERN LAKE SUPERIOR/...
Issued at 526 AM CDT Tue Jul 15 2025

Winds today will be around 10 knots or less before shifting
northeast and increasing on Tuesday night to 10 to 20 knots with
gusts to 25 knots, highest in the western arm and the Apostle
Islands. These winds will also generate waves in these areas of 2 to
5 feet. A Small Craft Advisory has been issued for these nearshore
waters starting late this evening. Winds then diminish to 5 to 15
knots on Wednesday night. Multiple rounds of thunderstorms are
expected today into Wednesday. A few stronger storms will be
possible this afternoon and evening across western Lake Superior.
Large hail and wind gusts to 50 knots are the primary concerns in
stronger storms along with cloud to water lightning and heavy
rainfall.

For the open water discussion, refer to the NWS Marquette Area
Forecast Discussion at weather.gov/mqt.

&&

.DLH WATCHES/WARNINGS/ADVISORIES...
MN...Flood Watch from 1 PM CDT this afternoon through Wednesday
     morning for MNZ038.
WI...Flood Watch from 1 PM CDT this afternoon through Wednesday
     morning for WIZ001>004-006>008.
MARINE...Small Craft Advisory from 10 PM this evening to 7 PM CDT
     Wednesday for LSZ121-143>148-150.

&&

$$

DISCUSSION...Unruh
AVIATION...Unruh
MARINE...Unruh