659
FXUS63 KABR 131156 AAA
AFDABR

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
656 AM 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 649 AM CDT Sat Jul 13 2024

See below for an aviation forecast discussion for the 12Z TAFs.

&&

.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 /12Z TAFS THROUGH 12Z SUNDAY/...
Issued at 649 AM CDT Sat Jul 13 2024

Terminals KABR,KATY,KPIR,KMBG

Briefly MVFR cigs at KATY this morning. Otherwise, VFR conditions
are forecast through the end of the TAF period. Rain showers (and
a few thunderstorms) continue to push southeast across the Black
Hills and surrounding areas. It`s possible that some of this
activity could spill over into KPIR terminal airspace through late
this morning. The rest of the day should be dry, with a chance of
thunderstorms tonight that could impact KMBG/KPIR. Low confidence
on precipitation forecast so left any mention out of the TAFs at
this time.

&&

.ABR WATCHES/WARNINGS/ADVISORIES...
SD...Heat Advisory from 1 PM CDT /noon MDT/ this afternoon to 8 PM
     CDT /7 PM MDT/ this evening for SDZ006>008-010-011-017>023-
     033>037-045-048-051.

MN...Heat Advisory from 1 PM this afternoon to 8 PM CDT this evening
     for MNZ039-046.

&&

$$

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