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560
FXUS63 KMPX 201947
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
247 PM CDT Fri Sep 20 2024

.KEY MESSAGES...

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Key Messages:

- Isolated showers and weak storms tomorrow into tomorrow night
favoring southeastern Minnesota. No strong or severe storms expected.

- Cooling down Sunday through the middle of next week, with highs
once again approaching 80 by the end of the week.
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&&

.DISCUSSION...
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Issued at 228 PM CDT Fri Sep 20 2024

Our picturesque day continues with sunny skies and the closest cloud
cover over northern Wisconsin as temperatures hover in the upper 70s
to near 80 as of 2pm. GOES satellite imagery shows what will
eventually be the boundary pushing through the area tomorrow just
reaching the western Dakotas as an upper level system moves
eastwards over the next 48 hours, bringing showers and weak storms
tomorrow into early Sunday before helping temperatures finally cool
down to more typical late September. The setup as the upper level
system arrives includes an occluded upper level low moving eastwards
through central Canada producing a broad area of h500 height falls
and CVA alongside a relatively weak low level jet. Compared to what
forecast models were producing a few days ago, the signal is far
weaker with forcing much more isolated such that the overall chances
for rain and storms has decreased, with the most favorable time
frames being the early to mid morning in central Minnesota and
eastern/southeastern Minnesota into western Wisconsin Saturday
afternoon through Sunday morning. Mean SBCAPE per the HREF is around
1000-1500 J/KG by 3-4pm over western Wisconsin and below 1000 for
most of Minnesota such that the bulk of thunderstorm activity is
likely to stretch from roughly Rochester through Ladysmith before
moving eastwards. Isolated showers and weaker storms are possible in
eastern Minnesota during the afternoon, however shear is relatively
weak as lower level wind speeds remain rather low with a lack of a
surface pressure gradient and weak low level jet. Overall, we are
expecting to see a few storms that likely remain below severe with
lightning being the only concern for those outdoors as the threat
diminishes quickly on Sunday post-fropa.

Temperatures become the main story into early next week as zonal
flow stagnates on the western side of the upper level system with
surface high pressure and subsidence keeping skies mostly clear and
allowing overnight temperatures to drop given the lower dew points
post cold fropa. The `coldest` day looks to be Monday with highs
struggling to reach 70 and lows in the upper 40s to low 50s before
we see another gradual warming trend with upper 70s to low 80s again
by the end of the week. Guidance has trended slightly colder over
the last 2 to 3 model runs, and if this trend continues we could
potentially see our final 80s of the year on Saturday. The longer
range ensembles are favoring low to mid 70s through the first week
of October with lows generally in the mid 50s in the Twin Cities
dropping near 50 otherwise with a lack of any significant weather
systems to bring at this point needed rainfall to the region. A few
areas have gradually been upgraded back to abnormally dry within the
weekly drought outlooks and this trend looks to continue as aside
from Saturday the rest of the period should stay almost completely
dry.
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&&

.AVIATION /18Z TAFS THROUGH 18Z SATURDAY/...
Issued at 1207 PM CDT Fri Sep 20 2024

A quiet TAF period is ahead of us as VFR conditions continue
with SKC becoming FEW/SCT250 later in the period. Winds
sustained at or just above 10kts around 270 will shift towards
180 with speeds lowering below 5kts after 00z. There is a chance
for a bit of LLWS as winds aloft increase after 04z, however
confidence was too low to include for now. Likewise, chances for
-SHRA/-TSRA by the end of the period were too low to include a
 mention for now.

KMSP...No additional concerns.

/OUTLOOK FOR KMSP/
SUN...VFR. Wind N 5-10kts.
MON...VFR, chc -SHRA. Wind E 5kts.
TUE...VFR. Wind S to W 5kts.

&&

.MPX WATCHES/WARNINGS/ADVISORIES...
MN...None.
WI...None.

&&

$$

DISCUSSION...TDH
AVIATION...TDH