980
FXUS63 KABR 131739 AAC
AFDABR

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
1239 PM CDT Sat Jul 13 2024

.KEY MESSAGES...

- There is a 20-30% chance of showers and thunderstorms across
  northeastern SD into west central MN this afternoon and evening.
  Additional thunderstorms are possible (20-40%) over the
  forecast area late tonight into Sunday morning. A few of these
  storms could become strong to severe during this time.

- High temperatures will be in the 90s through Sunday, with some
  areas potentially reaching the century mark this afternoon.

- There is a 30-60% chance of showers and thunderstorms across
  north central and northeast South Dakota into west central
  Minnesota by early Sunday evening. A few of these storms could
  become strong to severe.

- Temperatures will moderate with lower humidity for the first
  half of next week before readings warm back up toward the end
  of the week.

&&

.UPDATE...
Issued at 1235 PM CDT Sat Jul 13 2024

Aviation discussion updated below for the 18Z TAFs.

UPDATE Issued at 1025 AM CDT Sat Jul 13 2024

Rather complex scenario shaping up today in terms of cloud cover
and resultant high temps/heat indices, as well as thunderstorm
chances later today. Quite a bit of cloud cover across the CWA,
especially in terms of low clouds across the eastern CWA. By the
looks of satellite and latest HRRR low-cloud product trends, these
clouds across the east could linger into the afternoon. Highly
expect dissipation of these clouds at some point today, but it`s
unclear when. Further west, mid and high clouds associated with
the passing shortwave will put a wrinkle into temperature climbs
for the next several hours until this feature moves off later
today. But then, some of this cloud cover will be affecting the
eastern CWA. All that said, this does cast some uncertainty into
the high temperature forecast and resultant heat indices. For now,
will leave things as is in terms of high temp forecast and the
Heat Advisory. The day is quite long and we`ll see what these
clouds do by the mid to late afternoon. Will still be a rather hot
and humid day nonetheless, there just may be the chance we don`t
get quite as hot in places where cloud cover lingers the longest
into the afternoon.

As for convection, CAMs suggest much of the day should stay dry -
aside from the light rain/sprinkles moving into the western CWA
with the aforementioned shortwave energy. Did add/expand slight
chance (20%) PoPs for this into the late morning. A few solutions
suggest some thunderstorm development possible across the far
eastern CWA into western MN by late afternoon or early evening, so
will keep an eye on that. What may be more likely though, is some
degree of convection moving southeast into the CWA later tonight
with the energy skirting across the Canadian border.

Was also dealing with areas of fog this morning under some of the
stratus west/southwest of Aberdeen. Made several changes to the
grids earlier to account for the increased cloud cover, fog
insertion, and latest thinking in terms of precipitation.

&&

.SHORT TERM /TODAY THROUGH SUNDAY AFTERNOON/...
Issued at 408 AM CDT Sat Jul 13 2024

Ensembles continue to indicate the large mid level high settled over
the Rockies and Southwestern US with more of a quasi zonal flow to
the north of this high. Even warmer temperatures aloft to the
surface are expected through the weekend, thanks to this high. 700mb
temps by this afternoon will range between 12-14C and Sunday, up to
15C, highest over south central SD as winds will be from the
west/southwest. 850mb temps will range between 23-27C with similar
temps expected for Sunday and winds from the west to the south. With
daytime mixing, highs for today will range in the 90s, with some
areas across central SD reaching close or around 100 degrees.
However, HRRR Vertically Integrated Smoke Model does show another
round of elevated smoke moving in across the CWA from the
west/northwest. It does not look to get too thick so hard to tell if
it will impact temps at all. Highs for Sunday will be similar or a
couple degrees cooler (mainly over northeastern SD), but still
ranging in the 90s. It is moist out there with dewpoints ranging in
the upper 60s to lower 70s and continuing through Sunday. The
combination of heat and higher dew points will lead to heat indices
in the upper 90s to the lower 100s across central SD into areas of
northeastern SD. A heat advisory is in place for today over much of
the CWA, excluding our northwestern CWA. Similar heat indices for
Sunday with more of the upper 90s to around 100 across central to
south central SD. Collab with other offices decided to wait on
issuing a headline for Sunday at this point since there is one out
today.

Through the day, the shortwave that was overhead will continue to
push east/northeast and over MN/eastern Dakotas border this evening.
With moderate quasi zonal flow north of the high and south of a low
in Canada, models indicate ongoing shortwave energy moving in from
the west/northwest and over the Northern Plains. At the surface, a
trough will be centered over over central SD with a low over ND and
cold front extending westward. By this evening, this front will
extend over SD/ND border and northwestward into MT, stalling out, as
another surface trough sets up over central to western SD.
Overnight, this frontal boundary dips a bit south over central SD.

The heat and very moist air mass is leading to higher instability as
CAPE values will be increasing to over 2000 j/kg, east of the Mo
River, this afternoon and evening with shear around 30kts. EFI
indicates CAPE 0.5-0.8 with a shift of tails of 0 in this area. If
this instability can break the cap (according to HREF it should?),
the best area for convection will be across northeastern SD into MN
this afternoon/evening as HREF 2-5KM UH>75 shows this, indicating
organized convection. UH>150 does show a few paintballs over
northeastern SD indicating discrete cells. Several of the CAMs show
thunderstorms firing up over this area into MN as a linear
system/MCS forms over ~central MN and pushes south/southeast. CAMs
struggled with this morning`s convection and are struggling with
placement and timing of afternoon convection so confidence remains
lower on this and if it will occur. HRRR/HREF also shows clusters
turning into a line of elevated convection coming in from the
northwest and into our CWA late tonight. Confidence is higher on
this happening as there is stronger winds aloft with this next
shortwave. With ongoing sufficient instability and shear increasing
to 40kts over north central SD, the main threat would be large hail
with any discrete storms/clusters then becoming more of a wind
threat as the convection becomes linear. There is still a difference
in some of the CAMs on timing of this and intensity. There is a
slight risk (2/5) for severe weather for most of our CWA for this
afternoon into the overnight with a 15% hatched area for wind over
north central SD with the linear system.

&&

.LONG TERM /SUNDAY EVENING THROUGH FRIDAY/...
Issued at 408 AM CDT Sat Jul 13 2024

The flow pattern Sunday night is very zonal in appearance
(subdued/flattened upper level ridge over the western CONUS).
Tuesday through Thursday models/clusters have pumped the western
CONUS upper ridge back up and introduced an eastern CONUS/eastern
Canada long wave trof/upper level closed low. But by the end of the
period, the upper ridge may just be the dominant flow pattern
feature over the lower 48.

The main shortwave of interest continues to be progged to push
through the region Sunday night/Monday, dragging a notable airmass-
changing cold frontal boundary through the CWA. Much cooler/drier
air for Tuesday through Thursday. Then, potentially, a many days
long period of return flow southerly warm up/humidity return.

The airmass over this CWA Sunday night may be starting off rather
warm and humid. But by the middle of Monday, low level dry air
advection and cold air advection should be making a dent in all the
heat and humidity. But, prior to all that, it still appears as
though adequate deep-layer shear and instability is progged for the
Sunday night frontal passage. Tough to anticipate what type of
potential severe weather could be developing over the region Sunday
afternoon into Sunday night (including over this CWA), but a
significant wind-producing severe weather system could be in the
running.

Beyond that, with the flow pattern becoming increasingly
northwesterly and the boundary layer drying out/stabilizing for a
couple of days, it looks like pretty limited PoPs (generally less
than 25% chances) in the 7-day forecast until you get out toward
Friday and beyond.

&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 1235 PM CDT Sat Jul 13 2024

Terminals KABR,KATY,KPIR,KMBG

MVFR CIGs are on the decrease in KATY and should continue to see
them only in a FEW-SCT fashion through the afternoon, eventually
breaking up. VFR conditions are then forecast there, and at the
other TAF sites through the forecast period. Low confidence
thunderstorm forecast today/tonight, but what seems more likely is
seeing a cluster of TSRA/+TSRA move southeast into central or
north central SD tonight. Confidence on where this sets up, and
overall areal coverage of storms is not great. Will include a VCTS
mention at KMBG for the time being, where chances are highest.
Will examine again closer to the 00Z TAFs and may need to add TS
mention elsewhere.

&&

.ABR WATCHES/WARNINGS/ADVISORIES...
SD...Heat Advisory until 8 PM CDT /7 PM MDT/ this evening for
     SDZ006>008-010-011-017>023-033>037-045-048-051.

MN...Heat Advisory until 8 PM CDT this evening for MNZ039-046.

&&

$$

UPDATE...TMT
SHORT TERM...MMM
LONG TERM...Dorn
AVIATION...TMT