636
FXUS63 KABR 162005
AFDABR

Area Forecast Discussion
National Weather Service Aberdeen SD
305 PM CDT Sun Jun 16 2024

.KEY MESSAGES...

- Strong to severe thunderstorms are possible again late tonight
into early Monday. The main area of concern is along and south of a
line from Pierre to Watertown. Large hail will be the main threat
along with wind gusts between 60-70mph.

- The threat for strong to severe storms continues over the entire
forecast area Monday evening/early Tuesday, with large hail and wind
gusts between 60-70mph as the main threats.

- A moderate risk (40%) for excessive rainfall/flooding still exists
over far northeastern SD into west central MN, where 2"+ could fall
tonight through early Tuesday. Trends have been for lower confidence
that this area will face multiple rounds of thunderstorm activity,
however.

- Showers and storms will linger across the east on Tuesday, with a
chance for a few strong to severe storms during the afternoon.
Otherwise, quiet and dry conditions return by Tuesday night through
Wednesday night and/or early Thursday before another disturbances
moves into the region with increasing chances (60-80%) for showers
and storms late this week.

&&

.SHORT TERM /THIS EVENING THROUGH MONDAY NIGHT/...
Issued at 302 PM CDT Sun Jun 16 2024

Elevated convection has developed across the forecast area this
afternoon however dewpoint depressions are on the order of 30+
degrees and cloud bases exceed that of the ASOS Ceilomter...so
looking at just virga at this point.

Overnight tonight, CAMS support convection developing around 02-04Z,
though the focus for convective development has again trended more
south and east compared to previous runs. RAP MUCAPE values show a
gradient south to north across the CWA of around 1500/2000 j/kg and
about 500j/kg respectively, though what is much more impressive is
the shear which is 60-70kts. Pretty straight line hodographs support
a fast moving, splitting supercell environment with hail threat
across the southern CWA. 2-5km Updraft Helicity from the HREF points
to mainly right moving storms, and based off hodographs that should
cause the strongest storms to progress in a more or less eastward
direction, which is why CAMS are leaning towards a more eastward
progression of QPF compared to previous runs, which also means the
focus for heavy rainfall has also shifted, along with the more
organized threat for potential flooding, towards and south of the
Watertown area.

CAMS suggest convection is much less organized and with less
coverage elsewhere tonight/early Monday for the rest of the CWA.
Probabilities for just a half inch have fallen to only 40 percent for
Pierre and 20 percent for Aberdeen, and is negligible for Mobridge.
The probability for an inch accumulation for Watertown is 50
percent.

Focus then shifts to the second round of more organized convection
late Monday into early Tuesday. The main mechanism for severe storm
generation appears to be the development of a low level jet. The jet
intensity strength tops 60kts in the NAM with a focus up along the
Coteau. NAM MLCAPE is around 2000j/kg at 06Z up in that area and a
widespread 3000-4000j/kg MUCAPE thereafter. Shear is a more modest
40-50kts. BUFKIT still shows fairly stable boundary layer conditions
for most sites with an inverted trough across the area, and the
surface low doesn`t lift through until the early morning hours,
suggesting again mainly a large hail threat associated with this
outlook. CAMS also show a bit of random coverage of convection, so
at this point while heavy rain is still expected to present a
threat, its uncertain if storms will move over the same areas that
had previous convection/heavy rain. Thus, despite the WPC moderate
risk outlook, no watch at this time.

&&

.LONG TERM /TUESDAY THROUGH SUNDAY/...
Issued at 302 PM CDT Sun Jun 16 2024

The main forecast challenges in this period will continue to revolve
around the active pattern that has become entrenched across our
region as of late. We will get an initial break early from the
active storminess but it will be short lived as better opportunities
for showers and storms return the latter half of the forecast term.

Models are in fair agreement initially showing a sfc low pressure
system tracking across eastern SD into western MN Tuesday morning
with a trailing cold front passing west to east through our forecast
area during the day on Tuesday. Lingering showers and thunderstorms
will be possible during this time, especially east of the James
Valley through perhaps midday into the first half of the afternoon.
Guidance does hang onto some instability and decent shear in our
eastern zones into early afternoon. SPC has highlighted our far
eastern zones in a marginal(1/5) risk for severe weather. Timing
will be everything when it comes to the risk in our east by Tuesday
afternoon. That system will depart to our east by Tuesday night and
leave us with a fairly quiet, pleasant and mostly dry Wednesday. Sfc
high pressure will build in at that time. Sfc dew point temperatures
drop during the day into the 40s to low 50s with high temps mainly
in the 70s to near 80. Wednesday looks to be the nicest day of the
period.

The sfc high is progged to shift east of our area on Thursday. An
east to southeast low level flow is expected to develop. This return
flow will be the beginning`s of yet another active stretch through
the remainder of the period. Perhaps some of us will squeak out a
mostly dry daytime period on Thursday, especially our northern
zones. But, PoPs will be on the increase nonetheless by the latter
half of the day into Thursday night. Another sfc frontal boundary is
anticipated to set up shop in our southern zones or just to our
south later Thursday into Friday and perhaps into the beginning of
next weekend. Mid level flow will remain southwesterly that will
contain periodic shortwave energy that will rotate southwest to
northeast through the region the latter half of the week...a pattern
much similar to what is currently underway across our region. A good
chance for showers and storms will persist through at least Friday
and perhaps linger into Saturday. We`ll have to consider chances for
strong to severe storms again by late in the week as joint
probabilities for SFC CAPE/CIN and bulk shear show
increasing percentages for those favorable ingredients for storms.

&&

.AVIATION /18Z TAFS THROUGH 18Z MONDAY/...
Issued at 1219 PM CDT Sun Jun 16 2024

Terminals KABR,KATY,KPIR,KMBG

Primarily VFR conditions for all terminals. Convection tonight is
expected near the KATY terminal, with less confidence for
KPIR/KABR. Thereafter, as winds shift to northeast, lower CIGS
(MVFR) are expected to move in.


&&

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

$$

SHORT TERM...Connelly
LONG TERM...Vipond
AVIATION...Connelly