-- Discussion containing changed information from previous version are highlighted. --
969
FXUS63 KABR 220814
AFDABR

Area Forecast Discussion
National Weather Service Aberdeen SD
314 AM CDT Wed May 22 2024

.KEY MESSAGES...

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- Low risk for severe weather (marginal or 1/5) Thursday
  afternoon with showers and weak storms continuing into early
  Friday. Chance of precipitation ranges from 60-90%

- An unsettled weather pattern continues with additional chances
  of moisture Sunday into Monday (30-50%)

- Temperature guidance remains near to below normal Friday through
  Monday.

- Chance of frost (30-40%) for the northern portions of the forecast
  area Saturday morning
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&&

.SHORT TERM /TODAY THROUGH THURSDAY AFTERNOON/...
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Issued at 314 AM CDT Wed May 22 2024

Will be under a shortwave ridge for today, with the departing system
moving north of the Great Lakes while the next system starts forming
in Wyoming. Low level flow is west southwesterly, so expect to
overachieve a little on temperatures today, though we will see
increasing clouds as a weak shortwave moves into the west this
evening. This subtle wave, and mid level warm advection, will help
generate elevated convection early Thursday. Typical elevated weak
convection shouldn`t generate much more than some localized few
hundreds of moisture as CAMS show minimal coverage. The main focus
is on Thursday afternoon as the next wave moves in from Wyoming.
Very similar set up to the convective event that occurred on May 19
with a narrow ribbon of between 1-2k j/kg MLCAPE in central/north
central South Dakota with 0-6km shear near 50kts and favorable
looping hodographs.  There is still disagreement in the placement of
surface features though, with the surface warm front/occlusion and
cold front depicted in slightly different locations across the state
by the afternoon between deterministic guidance.
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&&

.LONG TERM /THURSDAY EVENING THROUGH TUESDAY/...
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Issued at 314 AM CDT Wed May 22 2024

Starting off the long term Clusters are in agreement with a
positive tilted longwave trough over the western CONUS with a
shortwave forecasted to be over WY, heading into the Northern Plains
around 00Z Friday. The center of the 850mb low should be over
~western to central SD by this time and surface low just
ahead/southeast of it. Return flow at 850mb will surge on the WAA
side of the low and wrap around to the northwest(trowel) through
early Friday. Dry and cooler air then filters in behind the low as
the whole system tracks northeast through the day into Friday
evening. This increase in moisture ahead of the front and in the
deformation zone looks to lie over the northern and northeastern
portions of SD. Lower confidence on where the dry slot will exactly
end up over the central parts of the CWA as the system shifts
northeast.

Latest NBM has pops increasing over the entire CWA from 60-90%
between 00Z-12Z Friday and between 20-65% from 12-18Z, as pops
diminish southwest to northeast. By Friday evening just lingering
pops (15-20%) over our extreme northeastern CWA as the low departs
the area. A high pressure system moves into the area behind it.
Highest QPF amounts per ensembles vary a bit with the highest
amounts over northern and northeastern SD and barely anything in
south central SD where the dry slot may end up. Prob of 24hr NBM
QPF>0.50" ending 00Z Saturday ranges from 25% over south central SD
to 60% over northeastern SD/western MN. Latest WPC shows a few
hundredths of an inch in south central SD up to an inch in parts of
northeastern SD possible. Like the last system, any wobble of the
low/dry air will affect QPF totals.

The next shortwave moves in over the Pacific Northwest Saturday as
NBM shows slight pops (15-25%) Saturday evening as a broad area of
low pressure sets up. Pops increase for Sunday/Monday (30-50%) as
this shortwave and developing low pressure moves over the Northern
Plains.

Cooler air from the north will keep temperatures at or below
average, as highs on Friday are forecasted to be in the mid to upper
50s to around 60. As the high moves in, lows are forecasted to dip
down into the upper 30s to the lower 40s. Depending on if the clouds
clear out and we get good radiational cooling (dropping the temps
even lower) we have the potential for patchy frost early Saturday
morning. NBM prob of 36 degrees or less runs around 30-60%, highest
over northern and parts of northeast SD with the Leola Hills with
the higher percent. I added this frost potential to the grids. For
the weekend into Memorial Day, temps will still be at or below
average with highs in the mid/upper 60s to the lower 70s. Temps warm
back up into the midweek, back into upper 70s and 80s by Wednesday.
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&&

.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 1226 AM CDT Wed May 22 2024

Terminals KABR,KATY,KPIR,KMBG

VFR conditions will prevail across the area overnight and through
the day Wednesday.


&&

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

$$

SHORT TERM...Connelly
LONG TERM...MMM
AVIATION...Connelly