871
FXUS63 KABR 102326
AFDABR

Area Forecast Discussion
National Weather Service Aberdeen SD
626 PM CDT Mon Jun 10 2024

.KEY MESSAGES...

- High chances (>60%) for rainfall late this afternoon though the
  overnight with a passing frontal boundary. Strong to severe
  storms possible over central SD, with hail to around one-quarter
  inch and wind gusts around 60 mph. Severe threat diminishes
  rapidly east of the Missouri River.

- There is a 20-40% chance of showers and thunderstorms Wednesday
  into Wednesday night, mainly along and east of the James River
  Valley. Some storms may become strong to severe.

&&

.SHORT TERM /THIS EVENING THROUGH TUESDAY NIGHT/...
Issued at 237 PM CDT Mon Jun 10 2024

Convection has recently moved into northwest SD and will be watching
progression of this into the far western CWA over the next few
hours. Ribbon of moderate instability (MLCAPE 1000-2000 J/KG)
generally stays over western SD (UNR CWA) during the event, but some
of these higher values do nudge their way eastward over Corson and
Dewey counties by 00Z this evening. Later this evening, MUCAPE
values are only around 500 J/KG or less across central SD, and fails
to materialize much further east at all. So, with the lack of
instability later this evening, do not think the severe storm threat
will progress much further east than the Missouri River valley. That
said, with the frontal boundary pushing eastward, models do still
indicate general showers and thunderstorms advancing eastward across
the CWA, although perhaps diminishing in overall areal coverage as
it does so.

Aside from the "main show" precip event later this evening, we are
seeing an initial area of light rain across central SD within the
warm air advection region and mid-level cloud deck. Had to add small
PoPs for this as it looks to hold together for at least a couple
hours yet as it heads towards the James River valley.

Tuesday will bring dry conditions in the wake of tonight`s passing
frontal boundary. Rather warm air aloft and decent northwest mixing
winds should allow highs to climb into the 80s.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
Issued at 237 PM CDT Mon Jun 10 2024

Clusters agree well on a broad low amplitude ridge over much of the
central and northern CONUS starting out Wednesday morning with a
broad area of low pressure in Canada. This is leaving the Northern
Plains in zonal to slight northwest flow aloft with winds increasing
to 40-50kts (and 70-80kts at 250mb) towards the afternoon and
evening. 850mb to the surface, a trough will move in over the CWA as
it pushes east into MN towards evening. To the northwest of this, an
occluding surface low is forecasted to be over Alberta/Saskatchewan
border, with a cold front trailing over the western Dakotas/WY early
Wednesday morning. It will track east/southeast over the Northern
Plains, with much of eastern SD into western MN ahead of the cold
front by ~late afternoon into the evening.

With this synoptic setup, 850mb winds will be out of the southwest
(on the PVA side of this trough) east of the Mo River with GFS IVT
indicating ample amounts of moisture surging north and northeastward
on the warm side of the low. This will raise dewpoints well into the
upper 50s into the lower 60s along with max temps reaching into the
mid to upper 80s into the lower 90s (NBM forecasted high of 94 for
KABR!). This will make the atmosphere quite juicy with low/mid level
lapse rates increasing to 7-8C, per NAM/GFS, over eastern SD into
west central MN. EC Ens has finally caught up with the GEFS with
prob of CAPE>1000 j/kg ranging from 40-90%, highest over eastern to
southeastern SD into western MN at 00Z Thursday. Prob of CAPE>2000
j/kg is highest at 50-60%, with both ensembles pegging eastern/
southeastern SD into southwestern MN. Deterministic GFS has the
2000+ j/kg threat extending further west over the James Valley than
the ensembles. It is interesting to note that NAM has areas of 3000-
4000j/kg along parts of SD/MN border. So something to watch. Bulk
shear is consistent among the ensembles, increasing to 40-50kts by
the evening time. Latest NBM shows 20-40% pops around and east of
the James River late Wednesday afternoon through the evening. The
SPC has a Day 3 Slight Risk (2/5) from eastern SD into western MN
with a 15% hatched area indicating a 15% chance greater probability
of significant severe weather within 25 miles of a point in this
area, which means larger hail/higher wind gusts and the possibility
of tornadoes is not out of the question. This is still a couple days
out so things could still shift a bit. The past few model runs have
shifted this threat slightly east.

Another weak system right behind could bring more moisture for early
Thursday as NBM has 20-45% pops. Otherwise, the unsettled weather
pattern continues as confidence is increasing on a system that could
affect the area heading through the weekend with pops ranging from
30-60% as the mid level pattern switches to more of a -PNA setup.
Warmer than average temps continue through the end of the week into
the weekend.

&&

.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...
Issued at 636 PM CDT Mon Jun 10 2024

Terminals KABR,KATY,KPIR,KMBG

A line of thunderstorms at 2315Z from around MBG to just west of
PIR will continue to slide east around 45 mph. The main concern
with these thunderstorms will be lightning, some reduction of
visibility with blowing dust ahead of moderate to heavy rain.
Estimated rainfall along the line has been around 0.4-1". Expect
these storms to continue to weaken as they shift east, into a less
favorable atmosphere. Still, have included wind gusts of 30-40kts
at both PIR and MBG and will continue to monitor the upstream
observations. VFR and mainly dry conditions and lighter winds
will return to all locations by 06Z Tuesday.

&&

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

$$

SHORT TERM...TMT
LONG TERM...MMM
AVIATION...KF