747
FXUS63 KABR 130543
AFDABR

Area Forecast Discussion
National Weather Service Aberdeen SD
1243 AM CDT Mon Jul 13 2026

.KEY MESSAGES...

- A dangerous and prolonged heat wave will continue through this
week with temperatures and heat index values warming into the triple
digits each afternoon.

- An Extreme Heat Warning for north central SD and a Heat Advisory
for parts of central and northeast SD and west central MN continue
through Thursday.

- The combination of humidity dropping near or below 20%, wind gusts
of 20-35 mph, and dry fuels will lead to elevated fire danger
concerns across portions of north central SD this afternoon.
Therefore, the Fire Weather Watch has been upgraded to a Red Flag
Warning for Corson and Dewey Counties.

&&

.DISCUSSION...
Issued at 1242 AM CDT Mon Jul 13 2026

Main concern in the forecast is the prolonged heat wave through the
week along with fire weather concerns over portions of north central
SD this afternoon. No real change in the models with the impressive
ridge extending well into Canada with much of the central CONUS
underneath it and its elongated mid level high stretching from the
Southwestern US to the Great Lakes by 12Z this morning. This mid
level high actually will stretch even further eastward, encompassing
the Ohio Valley by Tuesday. Other then the top of the ridge
flattening a bit with a passing shortwave and amplifying again
behind it Tuesday and Wednesday across Canada, not much overall
movement with the ridge until Friday into the weekend as it will
retrograde westward and over the western CONUS and its mid level
high underneath over the Rockies. This will put the region in
northwest flow. With the heat dome effect, subsidence continues
resulting in a prolonged period of dry conditions through the end of
the week. Our next chance of any precip is not until the end of next
weekend/Monday associated with a potential front and even then pops
are 20% or less as of now with very low confidence on actual setup
or even moisture this far out.

Both mean geopotential heights and temperatures aloft are still
running about 2 to 3 standard deviation above climo through Thursday
and 1 to 2 standard deviation above climo Friday through the weekend
per NAEFS. For example, 850mb temps range from +23 to +29C at peak
heating through Friday with the warmest temps over central SD. This
runs at or above the 90th percentile with 99th percentile over north
central SD per climo (GEFS/GEPS/ENS mean). So surface highs will
continue to range in the 90s to the lower 100s through Friday with
the hottest temps up to 105 over north central SD. Looking far ahead
into the weekend we could finally be "cooling" down with highs
potentially below 100 ranging in the 90s and even upper 80s to lower
90s starting next Monday per NBM. As mentioned in previous
discussions, due to the warm bias in the NBM 5.0, MaxTs still run
about 1 to 3 degrees warmer than NBM 5.2 over the next several days.
The lowest spread (thus higher confidence) is across central SD and
highest spread (lower confidence) James Valley and eastward.
Sunday`s highs at KABR was 93 and KATY at 89 which was several
degrees below the forecasted high set in place Sunday morning. Even
Saturday was a bit cooler than forecasted due to this warm bias. So
I did drop MaxT by one degree James Valley and eastward to put highs
pretty much in the middle of what NBM 5.0/5.2 were forecasting. I
was hesitant on going any lower due to today being one of the
warmest days. Held off on adjusting temps Tuesday and onward for
now. Luckily MinT`s are less affected and vary only about a degree
across the CWA between NBM 5.0/5.2. Comparing models within the
HREF, HRRR seems to be the coolest and FV3 the hottest across the
CWA with the mean for maxT`s running near the NBM (and modified
changes). Dewpoints by peak heating will range in the upper 50s to
the upper 60s, highest east of the James River though Tuesday which
is offset from where the hottest and driest air will be over central
SD (where temps can rise over 100) with heat indices closer to the
actual temps. By middle of the week we see more drier air filter in
more eastward which will help tame heat indices a bit. So overall,
no changes made to the heat headlines which continue through
Thursday evening.

With the drier air over central SD, relative humidity this afternoon
will tank to near 20% or lower over portions of north central SD,
lowest over western Corson and Dewey Counties. As mentioned in
previous discussions, Geocolor indicates pretty dry (or drying)
fuels over these two counties. Adding in southerly wind gusts up to
35 mph here will result in elevated fire weather concerns. So went
ahead and upgraded the Fire Weather Watch to a Red Flag Warning for
Corson and Dewey Counties valid 19Z-01Z. Campbell was in the Fire
Weather Watch and based on Geocolor and recent rains they are more
on the greener side so dropped them from the watch/upgrade. RH/wind
gusts will need to be monitored this afternoon and the possibility
of any expansion of the RFW. Tuesday the humidity will be 25% or
less west of the James River, however, winds will be a tad lower. As
mentioned in previous discussions, areas east of the Mo are pretty
greened up with recent rains. So really Corson/Dewey may need to
watched for a potential fire headline.

&&

.AVIATION /06Z TAFS THROUGH 06Z TUESDAY/...
Issued at 1216 AM CDT Mon Jul 13 2026

Terminals KABR,KATY,KPIR,KMBG

VFR conditions will prevail at terminals through this forecast
cycle. Southerly winds will turn gusty by late morning through
the afternoon hours.

&&

.ABR WATCHES/WARNINGS/ADVISORIES...
SD...Heat Advisory until 10 PM CDT /9 PM MDT/ Thursday for
     SDZ005>008-010-011-017-018-021-033>037-045-048-051.
     Extreme Heat Warning until 10 PM CDT /9 PM MDT/ Thursday for
     SDZ003-004-009-015-016.
     Red Flag Warning from 1 PM to 8 PM MDT Monday for SDZ003-015.
MN...Heat Advisory until 10 PM CDT Thursday for MNZ039-046.

&&

$$

DISCUSSION...MMM
AVIATION...Vipond