439
FXUS63 KUNR 141739
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1139 AM MDT Tue Jul 14 2026

.KEY MESSAGES...

- Very hot temperatures will continue through the week, with
  record high temperatures possible and dangerous heat.

- Critical to near-critical fire weather conditions will continue.

&&

.UPDATE...
Issued at 913 PM MDT Mon Jul 13 2026

00z KUNR sounding tells the story again this evening. Hot. 03z
surface analysis has high over IA with weak frontal boundary from
eastern MT into eastern UT. Water vapour loop had strong upper
ridge across the northern Plains into the upper Midwest. Plenty of
stars to be seen with very clear skies tonight.

Current forecast in good shape. Strong upper/thermal ridge will
move little through Wednesday, but then the upper ridge will weaken,
especially in the west where disturbances start to impinge on the
western edge of the CWA allowing monsoonal moisture to sneak in.
Result will be continued hot weather and a slow increase in PoPs
by the end of the week/weekend. However, confidence in PoPs is low
given convective nature as well as ensemble spreads for moisture
availability later in the period. Temperature spreads are tight.
Heat headlines on target.

&&

.DISCUSSION...(This Evening Through Monday)
Issued at 212 PM MDT Mon Jul 13 2026

Water vapor imagery shows moisture circulating around upper level
high pressure centered over the Central Plains. At the surface, high
pressure is centered over Alberta and Saskatchewan with another
area of high pressure over the middle Mississippi River Valley. A
stationary boundary extends between the two areas of high pressure
from western Ontario into northwest Wyoming. At 19Z, temperatures
are hot, with most sites in the 90s and a few sites already above
100 degrees. Winds are mostly south to southeast at speeds of 10
to 25 mph, with gusts around 35 mph.

The strong upper level thermal ridge remains in place today and
Tuesday before it starts to shift east and weaken on Wednesday, and
more-so by the weekend. Widespread high temperatures in the 100-107
degree range will continue on Tuesday, with temperatures expected to
cool a degree or two each day, Wednesday through the weekend. Winds
will remain gusty from the south and south east through Wednesday,
due to the tightened pressure gradient.

As the ridge begins to break down Wednesday, a surface low will
develop over eastern Montana and western North Dakota. A trough
extending from the surface low will drift through the forecast area
Wednesday night. With dry air in place, the only impact from this
will be a shift in the winds from the north and northwest.

Monsoonal moisture begins to stream into the Desert Southwest and
Intermountain West this week. Models indicate some additional
moisture may make its way into the forecast area by late week,
although anomalously high 500mb heights continue. This will lead to
the possibility of an afternoon or evening thunderstorm Thursday,
with slightly higher probabilities Friday through Sunday.

&&

.AVIATION...(For the 18Z TAFS Through 18Z Wednesday)
Issued At 1137 AM MDT Tue Jul 14 2026

Expect VFR conditions through the forecast period.

&&

.FIRE WEATHER...
Issued At 913 PM MDT Mon Jul 13 2026

Dry, hot and breezy conditions will continue through mid-week,
leading to critical fire weather conditions from the northeastern
Wyoming to the far western South Dakota plains. On Tuesday, breezy
south to southeast winds with gusts up to 35 mph will combine with
the very low humidity of 15% or less. This will continue to support
critical fire weather conditions. In addition, poor humidity
recoveries are expected each night. A Red Flag Warning continues
until Tuesday evening. The strong upper level ridge begins to break
down on Wednesday, however, critical or near-critical fire weather
conditions may still be possible. Therefore, we will continue to
monitor the potential for critical conditions for the second half of
the week. If monsoon moisture is available for the end of the
week, dry lightning may become a concern depending on low level
moisture availability.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...Heat Advisory until 9 PM MDT /10 PM CDT/ Thursday for SDZ001-002-
     012>014-025>027-030>032-041>044-046-047-049-072>078.
     Red Flag Warning until 9 PM MDT this evening for SDZ322>332.
WY...Heat Advisory until 9 PM MDT Thursday for WYZ054>056-058>060.
     Red Flag Warning until 9 PM MDT this evening for WYZ314>317.
&&

$$

UPDATE...Helgeson
DISCUSSION...MLS
AVIATION...Ivory
FIRE WEATHER...MLS/Helgeson