116
FXUS63 KABR 091541 AAB
AFDABR

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
1041 AM CDT Wed Jul 9 2025

.KEY MESSAGES...

- Slight risk for severe storms across the region today and
  marginal risk for severe storms on Thursday. Hail up to 2
  inches in diameter possible over central/north central SD by
  late this afternoon, with gusts over 70mph possible this evening
  into tonight.

- Heat and humidity today (especially over central South Dakota),
  with highs in the 90s and heat indices approaching 100 degrees.

&&

.UPDATE...
Issued at 1032 AM CDT Wed Jul 9 2025

Not much in the way of changes to the forecast through 00Z today.
Expecting hot and humid conditions across the region, especially
along and west of the James River into central SD. Heat indicies
may flirt with 100 degrees over central SD, so will keep an eye on
that. Still may be too marginal and small of areal coverage to
warrant a headline. Otherwise, will also be watching storm
development by late afternoon across western/central SD. No big
changes to timing in regards to when it moves/develops over the
west-river counties, still thinking 21-00Z (4-7pm CDT) or so.

&&

.DISCUSSION...
Issued at 352 AM CDT Wed Jul 9 2025

At 3 AM CDT, temperatures have cooled into the 50s and 60s across
the CWA. ACCAS clouds showing up over the central portion of the CWA
on the night-time microphysics product. So, perhaps isolated to
scattered elevated showers/thunderstorms may be developing within
the next few hours over portions of, at least, the James River
valley region. Winds are generally out of the southeast around 5 to
15 mph.

Throughout the 7-day forecast, (from Ensemble Clusters Analysis) the
flow pattern aloft continues to showcase the propagation of low
amplitude ridges/trofs over North America, meaning the continuation
of a somewhat active period of low level warm air and cold air
advection, frontal passages and mid/upper level shortwaves/shortwave
trofs over this region.

Starting off with today, outside of any morning elevated convection
firing on the leading edge of mid-level WAA and low level moisture
advection on a low level jet over the region, will be focused on two
boundaries over or near the CWA during peak heating when shortwave
energy over Idaho and Montana lift out of the Rockies and head for
the Dakotas. Models depict extreme instability (3000+ J/kg CAPE)
today/tonight out ahead of the boundary and generally around 25-
30kts of deep layer shear (underneath a high pressure ridge axis
aloft). Initially, CAM`s CI around 21Z may end up being delayed a
few hours, if +13C air at 700hpa (depicted in the NAM and RAP now)
is in fact in place over the boundaries in question. Mid-level lapse
rates are also progged at 7-9C/km this afternoon/evening. One of the
boundaries is a lee-side trof moving into the far western Dakotas by
late afternoon (almost taking on a dry-line look and feel of quite
dry (low dewpoints) behind the trof and rather moist upper 60s/low
70s along/ahead of the boundary. The other boundary, the lee-of-the-
Black Hills surface trof/low) is progged to be doing its thing down
across the I-90 corridor into south central SoDak by the end of peak
heating today. Guidance is still saying convection (multi-cells and
supercell structures expected initially with large hail potential)
develops by early this evening and moves east-southeast across the
CWA into the night-time hours potentially organizing into a linear
storm mode (strong/damaging winds gusts). SPC currently has the
western half of forecast zones in a slight risk (level 2 out of 5)
for severe thunderstorms this afternoon/evening.

Also, the latest iteration of heat indices continues to bring values
close to 100 over parts of central SD this afternoon, but as of now
it still seems potentially too brief/marginal to issue a headline
for heat (100+ degree heat indices), although something to monitor.

Heading into Thursday/Friday, one of these low amplitude low
pressure trofs aloft are progged to spread from the Pacific
Northwest over into the northern plains/southern Canada, bringing
with it additional precipitation chances. Generally speaking, the
CWA remains within a marginal risk (level 1 of 5) for severe
thunderstorms Thursday/Thursday night. Still looks to be plenty of
instability and steep lapse rates around heading into Thursday
evening. But, deep layer shear necessary to produce any sort of
organized severe weather threat Thursday afternoon/evening appears
to be lacking at this time over this CWA.

This upper level trof will sweep a strong cold front through the CWA
Thursday night into Friday morning. Some post frontal precipitation
Friday morning will be possible. Otherwise, the fropa will signal a
break for a few days in precipitation chances.  With winds through
the column taking on a northerly component to them heading into the
weekend, there could be a return of (Canada wildfire) smoke aloft on
Saturday (per the 00Z/09th RRFS Smoke and Dust model output).
Something else to monitor.

Ensemble Clusters qpf analysis reveals the majority of Friday
through Sunday should be precipitation free. The next noteworthy
fropa out in the extended is currently timed to push through the CWA
somewhere in the Monday night/Tuesday timeframe, and the Clusters
qpf analysis does show there is some lower-bound qpf potential there
on Tuesday. The Ensemble S.A. table for 850hpa anomalies also
suggests that beyond any potential warm up into the low 90s by
Monday, after the cold fropa early next week, cooler than normal
temperatures could be taking over for the rest of the week.

&&

.AVIATION /12Z TAFS THROUGH 12Z THURSDAY/...
Issued at 618 AM CDT Wed Jul 9 2025

Terminals KABR,KATY,KPIR,KMBG

VFR conditions will continue through tonight. Thunderstorms could
be near/over KPIR and KMBG in the early evening timeframe (~23Z
through 03Z). These storms have the potential for large hail and
severe thunderstorms wind gusts. Thunderstorms could be near/over
the KABR/KATY terminals in the late evening/early overnight hours
(~03Z through 07Z).


&&

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

$$

UPDATE...TMT
DISCUSSION...10
AVIATION...10