202
FXUS63 KABR 190514 AAC
AFDABR

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
1214 AM CDT Thu Jun 19 2025

.KEY MESSAGES...

- There is a Marginal risk (level 1 out of 5) for severe
  thunderstorms Thursday night. Threats will be large hail and
  damaging wind gusts.

- There is a Slight risk (level 2 out of 5) for severe
  thunderstorms Friday evening and overnight right up along the
  ND/SD state line. Threats will be large hail and damaging wind
  gusts.

- An extreme heat watch is in effect for portions of
  central/northeast South Dakota into western Minnesota
  Friday/Saturday. Temperatures are forecast well into the 90s
  with heat index values near 100.

- A front coming through Sunday will cool things off, but with
  some uncertainty on timing. Locations to the east of the front
  will experience another afternoon in the 90s with heat index
  values near 100.

&&

.UPDATE...
Issued at 1208 AM CDT Thu Jun 19 2025

Update for 06Z TAF discussion below.

UPDATE Issued at 851 PM CDT Wed Jun 18 2025

There remains a cluster of showers/thundershowers across the
southeast CWA, but has been decreasing in strength/coverage over
the past hour. Did some more adjustments to PoPs to account for
radar trends, which included increasing rain chances (30-50%)
across the southeast CWA until about 02-03Z. Watching activity
further north across south central ND. Added slight chances (20%)
out that way, and will watch radar trends across ND over the next
hour. Otherwise, winds are all over the place across the CWA with
multiple outflows/boundaries from earlier convection. Overall,
winds will generally favor a southerly direction overnight as
things stabilize.

&&

.DISCUSSION...
Issued at 304 PM CDT Wed Jun 18 2025

NAM BUFKIT profiles are weakly unstable, a skinny CAPE low shear
environment, so cant rule out more pulse convection much like
yesterday. We`ve already seen a few isolated weak cells. Will just
go with a broad 20% between the Mo and James valley.

The main story is still the heat, and not much has changed on that
front. NBM temperatures are now well aligned with forecaster
expectations, so this is becoming a high confidence event with the
latest NBM showing just a slight incremental uptick in
highs/dewpoints (maybe 1 or 2 degrees). The main question is how
best do we handle the headlines, regarding such early season heat,
albeit at mostly advisory level across the central and east.
Additionally, forecast temperatures Friday night are still
relatively modest for a heatwave (below 70F), though the low level
jet setting up over the Watertown area may mean this area could
use some tweaking warmer. Overall its still a patchwork of periods
in which we hit advisory criteria, mainly on the east/southeast
side of this lee low that develops Friday into Saturday. And then
the question is how quickly it abates with that warm front
transitioning to an inverted trough with a low riding northwards
and becoming a `cold` front with passage on Sunday. Generally
consensus has been for the James valley, central SD and western
Minnesota being hot/humid enough to warrant a headline
Friday/Saturday. Some question for Sunday as the GFS has the
frontal boundary a little faster eastwards progression with the
12Z run. Whether this is the start of a trend or just an
aberration is up in the air at this point. NBM50th percentile it
actually 8F warmer than deterministic for Aberdeen given
uncertainty in the transition with this front. Will opt for a
watch to advanced messaging even though the follow up is probably
just going to be an advisory since its early season and of a
prolonged duration with some minimal recovery overnight.
Thankfully the corn isn`t in full evapotranspiration mode just
yet.

As for thunderstorm chances, Thursday heights aloft are increasing
in step with warmer temperatures aloft. 700mb temperatures increase
but only peak between +12C (south central SD) to +8C (far
northeast). Not a cap for certain, however NAM BUFKIT profiles
indicate mid level warming should outpace surface warming/dewpoint
advection and thus destabilization. The exception is down in central
SD where NAM BUFKIT profiles shows enough heating for surface based
convection - mixing up to a little over 10kft for this achievement,
which is also 2kft below the freezing level (3km NAM follows suit).
Will continue with NBM POPs as the warm advection continues through
the evening which could provide the focus for elevated convection
for north central/northeast SD/western MN, with a low level jet of
40-50kts oriented into far eastern South Dakota and Minnesota. NAM
BUFKIT supporting about 1500j/kg and 50kts of 0-6km shear, though I
realize the lowest km or two is beneath the inversion and thus most
of the shear aloft is unidirectional. Regardless the environment
will be favorable for large hail/strong winds, maybe even heat
bursts given the warm air aloft with NAM DCAPE upwards of 2000j/kg
into Friday morning across the eastern CWA.

For Friday afternoon/evening the surge of hot air aloft moves
overhead. There will be a north south gradient that parallels the
ND/SD state line as the lee low forms in Wyoming.  There is about a
5C gradient in 700mb temperatures along the state line meaning
somewhere along this gradient the CAP could be overcome with daytime
heating. There is also a subtle southwest flow shortwave topping the
ridge which could provide some upper level support. Ensemble CIN
values for Ellendale and Linton, at the lower end of box and whiskers
are in the teens/low 20s j/kg so its a possibility we could see some
convection develop along the state line. Its more probable based of
NAM BUFKIT soundings that the warm front will provide the necessary
ascent for storms which would end up more north of the border in
this scenario, with NAM also supporting continued high DCAPE (+2000
j/kg) in a high shear environment (50-60kts). Thus going thinking is
we on the periphery of the better storm environment, with storms
moving at worst parallel to the border, or likewise along the
gradient, remaining just outside the CWA.

&&

.AVIATION /06Z TAFS THROUGH 06Z THURSDAY/...
Issued at 1208 AM CDT Thu Jun 19 2025

Terminals KABR,KATY,KPIR,KMBG

VFR conditions are forecast to continue through the TAF period.

&&

.ABR WATCHES/WARNINGS/ADVISORIES...
SD...Extreme Heat Watch from Saturday afternoon through Sunday
     evening for SDZ007-008-011-019>023.

     Extreme Heat Watch from Friday morning through Saturday evening
     for SDZ006-017-018-033>037-045-048-051.

MN...Extreme Heat Watch from Saturday afternoon through Sunday
     evening for MNZ039-046.

&&

$$

UPDATE...13
DISCUSSION...07
AVIATION...13