557
FXUS63 KDLH 181133
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
633 AM CDT Wed Sep 18 2024

.KEY MESSAGES...

- A couple more days of warm and muggy conditions

- Chance (30%) of storms some strong to severe entering from the
  west late this afternoon.

- Better chances for showers and storms (60%) Thursday. Slight
  risk (2 out of 5) of severe for the region with all hazards
  (large hail, damaging winds, tornadoes) possible in the
  afternoon and evening.

- More seasonable temperatures return Sunday and linger into next
  week

&&

.DISCUSSION...
Issued at 326 AM CDT Wed Sep 18 2024

Current Conditions/Today:

A deepening upper level low over the Northern Rockies with a
weakening Rex Block across the Appalachians has spurned another
robust LLJ across the Midwest. Activity isn`t quite as high as the
previous night due to lack of forcing. However, there is still
enough to give a few echoes extending from the Twin Cities and up
into Aitkin. The better dynamics still look to be over the Dakotas.
But these storms wil likely not be able to sustain themselves into
our area as the LLJ weakens. The rest of the morning and early
afternoon will be similar to what we`ve seen the past couple days.
Winds out of the south with temperatures and dewpoints a bit higher
than what we normally see for this time of year.

Afternoon/Overnight Storms:

This afternoon and overnight could see some more active weather with
storms developing across our west. While the main frontal boundary
remains off to the west, strong warm air advection out ahead
combines with an upper level shortwave and divergent jet to
promote storm growth. The strongest storms are expected to be
during the late afternoon and early evening hours with the
primary hazards being damaging winds and hail 1 inch in
diameter. A strengthening LLJ could help to maintain storm
chances through the night and carry them over into Thursday
morning, however severe chances quickly drop off after 10 PM
amongst most of the high res guidance. The NAMNEST is a bit of
an outlier right now keeping stronger storms past midnight.

Thursday Severe Storms:

Thursday has potential to be quite an active weather day. We will
see lingering showers and convection in the morning hours but is
largely expected to dissipate by late morning. There is fairly high
agreement in having the environment recover in the afternoon building
dewpoints into the mid and upper 60s. This sets us up for some
fairly high instability (MLCAPES > 2000 J/kg). We will also have
bulk shear values of over 40 kts helping to provide the much needed
tilt for storm longevity. The focal point for convection will be the
cold front moving west to east in the afternoon and evening hours.
CAMs are in good agreement with the development of a line of storms,
however placement of the line varies from our western counties to
our central ones. The initial threat will be large hail. Steep
mid level lapse rates greater than 7.5C/km will increase updraft
strength producing quarter to ping pong sized hail. Hodographs
also show some low level veering in the winds leading to some
tornado potential. As the event continues storms may cluster
into more of a linear complex shifting the threat to more
damaging winds. The current outlook from SPC has the area in a
slight risk for severe (2 out of 5).

Friday into next week/Cool Down:

Storms will have vacated the region for Friday with highs dropping
into the mid 70s. The temperature drop isn`t done quite yet though.
Another cold front is poised to move through Saturday bringing some
showers and storms (currently non severe). By Sunday highs drop into
the 60s and low 70s. Beyond Sunday models are diverging on the
handling of the next upper level low out of the southwest. For now,
we are carrying some 20-40% PoPs and maintaining the more seasonable
temperatures.

&&

.AVIATION /12Z TAFS THROUGH 12Z THURSDAY/...
Issued at 630 AM CDT Wed Sep 18 2024

A few isolated showers across MN this morning as the LLJ weakens.
Through the day we are expecting VFR conditions with some gusts out
of the south upwards of 20 kts. The latest models runs have been
backing off the storm chances for this afternoon and making it more
of an overnight feature. We will also have the LLJ to contend with
once again bringing low level shear across the region once again
overnight.

&&

.MARINE /FOR NEAR SHORE WATERS OF WESTERN LAKE SUPERIOR/...
Issued at 326 AM CDT Wed Sep 18 2024

Southeast winds today with speeds up to 10 kts. Thunderstorm chances
return after midnight. The best chance for storms will be tomorrow
afternoon and evening, some of which will be strong to severe. Winds
will also increase a bit out of the southeast with some gusts up to
20 kts at times. For the open water discussion, refer to the
NWS Marquette Area Forecast Discussion at weather.gov/mqt.

&&

.DLH WATCHES/WARNINGS/ADVISORIES...
MN...None.
WI...None.
MARINE...None.

&&

$$

DISCUSSION...Britt
AVIATION...Britt
MARINE...Britt