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486
FXUS63 KMPX 211938
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
238 PM CDT Sat Sep 21 2024

.KEY MESSAGES...

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- Isolated to scattered showers and storms in central to
  southeastern Minnesota into western Wisconsin this afternoon
  and evening.

- Temperatures fall tonight into Monday before warming back up
through the rest of the week.
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&&

.DISCUSSION...
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Issued at 237 PM CDT Sat Sep 21 2024

A band of isolated showers is currently developing over east-central
MN early this afternoon ahead of cold front. Strong upper-level
diffluence above a pool of elevated instability ahead of the front
has allowed for rounds of convection throughout this morning. The
current activity is expected to increase in coverage and move east,
preceding the southeastward moving cold front, through this
afternoon and into this evening. A few thunderstorms will
develop and should become surface-based with time, especially in
southeastern MN and portions of west-central WI, where daytime
heating will uncap the boundary layer. For our southeastern CWA
counties, an isolated severe wind gust or large hail stone
cannot be ruled out within these storms given the 1000-1500 J/kg
of CAPE and about 35 knots of shear before storms exit to our
east this evening. Meanwhile, behind the cold front
northwesterly winds are gusting to 20 to even 30 knots within
the CAA. These winds will follow the southeastward moving front,
weakening some this evening into tonight. Temperatures will
also cool with lows falling into the mid 40s to lower 50s
tonight. Sunday will be a pleasant Fall day with highs in the
mid to upper 60s. Clouds and winds will be decreasing thanks to
subsidence occurring amid strong upper-level confluence. By
Sunday night, surface high pressure will move over the Upper
Midwest, allowing for clear skies and light winds. Night-time
lows will be cool due to the Canadian air mass and favorable
radiational cooling conditions. Low to mid 40s are forecast with
even a few upper 40s possible in eastern MN and northwest WI.
More great, sunny Fall weather is expected Monday with highs in
the upper 60s to lower 70s.

Forecast models do show an amplified trough arriving from the west
Tuesday. However, this trough passage is expected to be dry given
the lack of moisture in the forecast model soundings. In fact, the
entirety of the coming work week is looking dry owing to the lack of
any moisture return and overall forecast stable conditions.
Amplified ridging that is located over the northwest CONUS early
next week will translate east into central North America by
Friday. Low-level WAA will occur into the north-central CONUS
causing highs to warm into at least the mid 70s Wednesday
through next Saturday. Even a few 80s look possible in western
MN, so it appears we are not done with summer yet. Our next good
chance of precipitation isn`t hinted in the long-range guidance
until towards the start of October. However, model spread and
uncertainty are unsurprisingly large by this time.
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&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 111 PM CDT Sat Sep 21 2024

First round of storms is winding down, but a field of accas that
extends back into southeast SoDak indicates that the atmosphere
isn`t done with thunderstorms yet. There is a cold front from
STC down through MKT at 18z, with upwards of 2000 j/kg of
muCAPE present out ahead of it, with it certainly possible that
as that accas moves over the tongue of instability, it will pop
off more storms, hence why we left prob30s in place at
MSP/RNH/EAU for later this afternoon. Behind the front, we will
see gusty northwest winds deep into the evening, with gusty
winds coming back Sunday morning across western WI in
particular, where the pressure gradient will be the strongest.

KMSP...Given the accas field to the west, left the prob30 going
for the potential for on more round of storms to develop before
we completely loose the instability. Also, with the front moving
through this afternoon. A wind shift requiring a shift over to
north flow operations will be needed around 22z.

/OUTLOOK FOR KMSP/
MON-WED...VFR. Wind SE 5-10 kts.

&&

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

&&

$$

DISCUSSION...CTG
AVIATION...MPG