207
FXUS63 KABR 020222 AAB
AFDABR

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
922 PM CDT Tue Jul 1 2025

.KEY MESSAGES...

- Scattered showers and thunderstorms (30-50% chance) expected
across the region late tonight through early Wednesday morning.
There is a marginal risk (level 1 out of 5) for severe weather over
the majority of the forecast area. Hail, up to around quarter size,
is the main threat. Wind gusts to 60 mph and brief heavy downpours
are also possible.

- Heat and humidity return to the region Wednesday through Friday,
with highs in the upper 80s and 90s, and dewpoints in the 60s to low
70s. Heat indices flirting with 100 degrees over central SD.

- A system late Friday/early Saturday will bring relief from the
heat and humidity in the form of storms (60-80% chance eastern
SD/western MN). Main concern is the potential for heavy rainfall.

&&

.UPDATE...
Issued at 900 PM CDT Tue Jul 1 2025

No changes planned to the tonight period forecast. By all
indications, there should be thunderstorms developing overnight
over the CWA. Got an upper level jet over the region for upper
support; at least one mid-level s/w impulse working through in
west-northwest flow; nose of a low level jet pointing into the
center of the CWA; persistent mid-level WAA/baroclinic zone over
the region over top of more than adequate low level moisture plume
moving north across the region. RAP analysis via BUFKIT reveals
MUCAPE values are likely to range between 1000-2000j/kg tonight
and cloud-bearing shear is progged to range from 30 to 45 knots.
That`s a recipe for hail-producing elevated supercell
thunderstorms. The latest GSM/CAMS/Ensembles all include
thunderstorms in their output for tonight (have been for a few
days now), and PoPs for convection are already in the forecast.
Maybe the atmosphere will under-achieve tonight, and precipitation
will only amount to a handful of light showers/weak
thunderstorms. But, won`t be surprised if some warnings get issued
later tonight.

UPDATE Issued at 728 PM CDT Tue Jul 1 2025

See below for an aviation forecast discussion for the 00Z TAFs.

&&

.DISCUSSION...
Issued at 253 PM CDT Tue Jul 1 2025

The ridge of high pressure that was over the area today will
shift eastward this evening with the center of the high over KS/MO
by 00Z. A lee trough sets up along the eastern side of the Rockies
northwestward through MT through at least Thursday morning. Aloft we
continue on the downstream side of the ridge, in northwest flow,
with a shortwave embedded within this flow over the region. However,
the bulk of the energy/lift will be near its southern axis over the
southern half of SD into NE (better chances for stronger storms
here) this evening as the wave tracks southeastward through the
morning hours. A LLJ will increase in strength late tonight with
speeds out of the southwest between 25-45kts with the northern
fringe of this jet reaching central SD and weakening through the
early morning hours. NAM is a bit further north with the LLJ than
GFS/EC who keep the nose over south central SD. This setup, along
with ongoing low level moisture/WAA, will lead to elevated showers
and thunderstorms firing up along and east of the lee trough over
the western half of SD/NE this evening, per HREF/CAMS. This
convection will track southeast, along with additional development
of storms, late tonight into the overnight over the area. By 12Z,
most of the convection is forecast to exit the CWA with maybe the
last of it over our far southeastern CWA as HRRR holds onto this
threat. MUCAPE will run between 500-1000j/kg and bulk shear of
30kts with pockets of 40kts. Some of these storms could be strong
to severe with hail as the main threat, up to the size of
quarters, and wind gusts up to 60mph as the secondary threat and
brief heavy downpours. The SPC has expanded the marginal risk
(level 1 out of 5) eastward that covers most of our CWA (with the
exception of the eastern half of Roberts County into MN).

Our attention then turns to the end of the week into Saturday as the
Northern Plains will be on the upstream side of the ridge/downstream
of a trough in southwest flow all the way to the surface. However,
winds aloft will be quite weak ranging between 20-30kts. Lee
troughing continues over the western Dakotas which lies south of a
low pressure system that will be over ~central Manitoba/Saskatchewan
border by 12Z Thursday. This low in Canada shifts east (and surface
trough) with a secondary lee low forming and pushing northeast and
over central ND by 12Z Friday. The low in Canada will continue to
track eastward and the secondary low southeastward into MN through
Saturday morning. Being in the warm sector, with south to southwest
winds from the surface to 500mb, will bring in ongoing warm and
moist air as dewpoints will range well into the upper 60s to the
lower 70s and 12-16C at 850mb with these values highest over the
eastern half the CWA by Friday afternoon and evening. This system
working with the warm and moist air will lead to showers and
thunderstorms developing over the CWA Friday through Saturday with
the highest pops of 60 to 80% James River Valley and eastward Friday
evening through early Saturday where this better moisture and
forcing lies.

NAEFS indicates PWAT values about 2 to 2.5 standard deviations above
climo with values up to 1.50-1.75" Friday evening through Saturday
morning east of the Mo River. With weak flow aloft and lots of
moisture in the atmosphere, heavy rain looks to be the main threat
with the showers and thunderstorms especially any storms that are
slow moving and/or training over the same area that could lead to
areal flooding or flash flooding potential. ERO outlook indicates a
marginal risk over our eastern CWA due to this potential where this
area has already received several inches of rain/flooding over the
past couple of weeks. Along and east of the Mo River mean CAPE, per
model blend of ENS/GEFS/GEPS, show values between 1000-2000j/kg with
MUCAPE in excess of 2,000j/kg James River Valley and eastward Friday
afternoon and evening with bulk shear pretty weak between 15-20kts.
So this weak shear and lack of lift aloft may put a damper on
widespread severe weather (or keep it isolated)as the higher shear
moves in behind the system and displaced from the better instability
ahead of the cold front.

It will be hot and muggy Wednesday through Friday with temps in the
upper 80s to the upper 90s and dewpoints in the mid to upper 60s to
lower 70s. The hottest day is forecasted to be Thursday with highs
well in the 90s to maybe even 100 degree readings over central SD.
Heat Risk is in the moderate to major category Thursday, with the
major category west of the James River. Heat Risk will mainly be in
the moderate category (with a few patches of major over KABR and
KATY area) Friday. This cold front will bring relief to the heat and
humidity with temps back in the 70s/80s and dewpoints back in the
50s to lower 60s. Otherwise Clusters indicates zonal flow aloft this
weekend in a ongoing -PNA pattern changing to a -PNA/split flow
pattern early next week. This leads to several passing shortwaves
over the area and ongoing chances of precip through at least
Tuesday. A ridge looks to build over the western CONUS/Rockies for
the middle of next week.

&&

.AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/...
Issued at 728 PM CDT Tue Jul 1 2025

Terminals KABR,KATY,KPIR,KMBG

VFR conditions are forecast for the TAF period, outside of
convection expected later tonight (visby may be reduced in heavier
downpours). High pressure will continue to shift southeast
overnight with isolated to scattered showers and thunderstorms
developing over portions of central and northeast South Dakota
tonight. These storms will spread/move southeast through early
Wednesday morning. Continued to use PROB30 to address this
potential.

&&

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

$$

UPDATE...10
DISCUSSION...MMM
AVIATION...10