138
FXUS63 KABR 080221 AAB
AFDABR

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
921 PM CDT Sun Jul 7 2024

.KEY MESSAGES...

- Isolated shower and thunderstorm chances (15-25%) remain in the
  forecast on both Monday and Tuesday, mainly during the afternoon
  and evening hours across northeastern SD into west central MN.

- Heat and humidity will be on the increase through the week into
  the weekend. By Friday/Saturday temperatures will be about 5 to 10
  degrees above average, with highs in the upper 80s to mid 90s and
  lows in the upper 60s to near 70 with dewpoints well into the 60s
  to near 70 degrees.

&&

.UPDATE...
Issued at 919 PM CDT Sun Jul 7 2024

Still some shower and thunderstorm activity occurring across parts
of central South Dakota, but expect this to diminish and go away
by 04Z or so. No changes made to winds or temperatures at this
time.

&&

.SHORT TERM /THIS EVENING THROUGH MONDAY NIGHT/...
Issued at 208 PM CDT Sun Jul 7 2024

The longwave trough remains over the central and northern CONUS with
the axis from northern MN and southwestward through the Southern
Plains through 00Z. As of 1PM, satellite imagery indicates a vort
max/mid low spinning over northern MN along with a vort
max/shortwave over north central SD. This shortwave and energy
behind the low/vort max in MN will aid in lift for convection. Still
pretty moist out as PWAT values are around an inch which is around
average for this time of year, according to NAEFS. Surface dewpoints
are currently in the upper 50s to the lower 60s this afternoon with
700mb temps around 2-3 degrees. Daytime heating continues to steepen
low level lapse rates with MU/MLCape values reaching to around 1000-
1300 j/kg or so with values up to around 1500 j/kg over far
northeastern to eastern SD into west central MN per HREF. Rap values
seem to be running a little higher. Several soundings indicate more
skinny CAPE profiles with mid level lapse rates marginal around 6-
6.5C/km-1 and minimal shear. It is interesting to note that NST
parameter at 18Z ranges from 0.5 across the CWA to values of 2-3
over northeastern SD into southeastern ND. So cold air
funnels/landspouts could be possible as we have surface vorticity/0-
3km ML Cape values of 100-170j/kg (highest over northeastern SD) on
top of each other, per SPC meso page.

HREF/CAMS indicates convection chances over much of the CWA through
this evening with pops ranging from 30-40%. Storm mode will be more
pulse "hit and miss" summer type thunderstorms, with storm motion
cyclonically around vort max and behind the low which is why the
grids are more widespread in coverage. Severe threat remains low as
2-5UH>75m2s2 does not show anything exciting compared to yesterday.
With the cooler air aloft and thermodynamics mentioned above, some
of these storms could produce small hail (if strong enough) with the
main threat being lightning. Pops will diminish with sunset.

For Monday, the longwave trough pushes just a bit east with a high
pressure system centered over the Rockies in the morning and over
the central and northern Plains by the evening. Once again daytime
heating and Cape up to 1000 J/kg (which is mainly limited over the
far eastern CWA, closer to northern axis of trough) along with dp`s
in the lower 60s, could bring some isolated storms in the afternoon
and evening. With this limited instability and skinny cape profiles,
pops chances are a bit lower ranging around 15% (manually added).
Lows tonight will be in the mid to upper 50s/60 and highs for Monday
ranging from the upper 70s to the mid 80s.

&&

.LONG TERM /TUESDAY THROUGH SUNDAY/...
Issued at 208 PM CDT Sun Jul 7 2024

With minimal differences among ensemble clusters, confidence in the
large scale pattern for the long term is relatively high and this
carries over to the other mass fields such as the temperature and
wind forecast. There is greater uncertainty in the precipitation
potential however.

The northern plains will initially be in an upper level northwest
flow pattern as a SW CONUS high builds. The surface pressure pattern
remains weak but models suggest low level moisture, with 60+
dewpoints (especially across our eastern CWA) will be fairly
persistent. This does introduce some uncertainty into the blended
model depiction of a mostly dry forecast through mid week. Instead,
we could be on the repeat cycle of afternoon pulse convection.
Either way, coverage and POPs would be quite low. Continued the
previous trend of including at least a low POP on Tuesday, however
this may need to be considered Wednesday and Thursday as well.

It will be late in the week before the ridge of high pressure
traverses eastward and above normal air spreads across the plains
states. Definitely not a high amplitude ridge however, and models
suggest a parade of ridge riders traversing the pattern. LREF
probabilities of 700 mb temps exceeding 14C are highest on Saturday
and Sunday, generally ranging from 70-80% from our southwest CWA to
30-50% across our northeast CWA. This suggests a fairly healthy CAP
for the weekend. Likewise, probabilities of surface temps exceeding
90 degrees is greatest for our western CWA, however current ensemble
progs suggest a 50% chance or less of realizing heat advisory temps.

&&

.AVIATION /00Z TAFS THROUGH 00Z MONDAY/...
Issued at 623 PM CDT Sun Jul 7 2024

Terminals KABR,KATY,KPIR,KMBG

Scattered showers and thunderstorms will continue across the area
this evening. Once the sun goes down, the precipitation will come
to an end with the loss of daytime heating. Periods of MVFR vsbys
are possible with the thunderstorms. Otherwise, VFR conditions
will prevail across the area tonight and through the day Monday.


&&

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

$$

UPDATE...Parkin
SHORT TERM...MMM
LONG TERM...Serr
AVIATION...Parkin