Area Forecast Discussion
Issued by NWS Aberdeen, SD

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FXUS63 KABR 170154 AAB
AFDABR

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
854 PM CDT Mon May 16 2022

.UPDATE...
Issued at 850 PM CDT Mon May 16 2022

Overall the forecast looks on track. The latest HRRR continues to
show late night convection forming on the nose of an eastward
migrating moderate LLJ. That activity will likely persist in the
east through part of Tuesday. Temperatures look fine for now.

&&

.SHORT TERM...(This Evening through Tuesday Night)
Issued at 343 PM CDT Mon May 16 2022

The forecast challenge is timing, coverage and strength of overnight
convection.

At 2 PM CDT, abundant sunshine is noted over the entire CWA while
surface high pressure hangs on across the eastern Dakotas.
Southeasterly return flow winds have begun to develop west of the
James River valley this afternoon, while light and variable or light
northerly surface winds persist across far northeast South Dakota
and west central Minnesota. Temperatures have warmed into the 60s
and 70s.

The stage will be set for some elevated showers and thunderstorms
later tonight and continuing into the day on Tuesday. There is a
shortwave noted moving out of Idaho and timing it out, it should be
working through the CWA later tonight. There is a low level jet to
help focus convection, as well as some fine low to mid-level WAA and
adequate mid-level moisture advection happening tonight/Tuesday. Mid-
level lapse rates are forecast to steepen to 8+C/km across the
southern half of the forecast area. Elevated/cloud-bearing shear
environment appears to be supportive of rotating updrafts, and
MUCAPE tonight at KPIR is progged to increase from ~50J/kg to over
1000J/kg. Probably will just see some generic thunderstorms
overnight. But, given this set-up, would not be surprised if a few
storms end up producing some hail tonight.

Convection should weaken/wane by early Tuesday afternoon, leaving
the rest of the short term dry. Temperatures on Tuesday could be a
little cooler than the past couple of days, if it stays cloudy/rainy
for most of the day across the eastern half of forecast zones.

.LONG TERM...(Wednesday through Monday)
Issued at 343 PM CDT Mon May 16 2022

The main forecast challenge will be thunderstorm and severe
potential Wednesday night into Thursday. A shortwave trough will be
moving through ND and MN Wednesday morning and afternoon, and a dry
cold front will shift winds to the northwest through this time.
Breezy conditions are anticipated across the northern CWA, with high
temperatures in the 70s under partly cloudy skies. Meanwhile, models
are all in agreement about bringing in a larger, positively tilted
and deep upper-level trough from the northwestern US. By Wednesday
evening, sfc low pressure develops on the lee of the Rockies near
the SD/NE/WY borders. If a sufficiently strong LLJ can develop
overnight, thunderstorms may develop in a good shear environment.

A strong sfc low pressure system (990s mb) will then move across
South Dakota on Thursday. Out ahead of the low and in the warm
sector, environmental parameters do favor severe weather potential
by the afternoon/evening hours: low-level moisture with dewpoints of
60+F, steep lapse rates, sufficient instability and deep layer
shear, etc. The speed/timing of this system will be an important
factor for how much of the CWA has a chance for strong to severe
storms. A majority of the GEFS ensemble members are clustered into a
slower solution, which may place the low and cold front closer to
the James Valley by 00z (increasing the coverage of potential storms
in the forecast area), whereas the majority of the Canadian and
ECMWF members depict a faster solution, which would place the system
further east by that time (decreasing coverage of potential storms
in the forecast area). Future model runs will paint a clearer
picture on timing, and the overall threat potential.

A strong cold front passes Thursday evening/night, leading to gusty
northwest winds on Friday and much cooler air, with highs in the low
to mid 50s. Low temperatures may even approach or reach 32 F Friday
night and Saturday night across the area, especially if skies can
clear and winds can become light as large sfc high pressure builds
in. Something else to keep an eye out for is potential instability
showers and storms due to steep lapse rates from cold air aloft and
warmer air near the sfc Friday through Sunday, leading perhaps to
some graupel.

&&

.AVIATION...(For the 00Z TAFS through 00Z Tuesday Evening)
Issued at 606 PM CDT Mon May 16 2022

Terminals KABR,KATY,KPIR,KMBG

VFR skies/vsbys are expected through tonight. Scattered late night
showers and thunderstorms are also expected just about anywhere
over the region.


&&

.ABR WATCHES/WARNINGS/ADVISORIES...
SD...None.
MN...None.
&&

$$

UPDATE...TDK
SHORT TERM...Dorn
LONG TERM...Lueck
AVIATION...TDK


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