812
FXUS65 KBOU 311817
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1217 PM MDT Fri Jul 31 2026

.KEY MESSAGES...

- Isolated thunderstorms possible in the afternoon. A few storms
  could become severe, with strong outflow winds and hail as the
  main threats.

- Heat returns by the weekend, with temperatures reaching up to
  the 100s on Sunday and Monday.

- Heat Advisory for the Urban Corridor and Greeley Sunday
  afternoon.


&&

.DISCUSSION /Through Thursday/...
Issued at 239 AM MDT Fri Jul 31 2026

Current nighttime microphysics RGB satellite product shows low
stratus clouds in Nebraska trekking southwest. Guidance does keep
the stratus deck from entering Colorado (besides possibly the far
northeastern plains) this morning, which will help build a
favorable set-up for today`s thunderstorm potential. Isolated
showers and thunderstorms are possible this afternoon, with
convection initiating in the mountains by late morning/early
afternoon before spilling onto the adjacent plains through the
early evening. Modeled Skew-T soundings show steep low and mid-
level lapse rates, with DCAPE values of 1300-1600 J/kg. This would
favor strong-to-severe outflow winds up to 60 mph, particularly
for the southern I-25 Corridor and Palmer Divide area where
instability will be best. SPC has a Marginal Risk (1/5) for severe
storms for that area today. However, any strong storm that
develops over the plains has the potential for strong outflow
winds as well. While confidence is low, there is also an isolated
hail threat with the strongest storms today. One hindrance to
today`s storms would be near-surface smoke from wildfires in the
northwestern United States. If smoke is able to advect into the
plains this afternoon, it could act as a cap for storm
development.

The upper level ridge will likely restrengthen over the Four Corners
region by this weekend, which will bring the return of drier and
warmer conditions. Ensemble guidance continues to indicate
temperatures reaching near or over 100 F for the Urban Corridor by
Sunday. With Heat Risk expecting to get up to 3 (correlating to High
Risk for much of the population, especially those sensitive and
without effective cooling) have opted in to issue a Heat Advisory
for much of the Urban Corridor and the adjacent northern plains
(including Greeley where temperatures could reach up to 105 F).
Monday will likely see similar temperatures and an additional
Heat Advisory may be needed in the next forecast package.

We will likely see a reprieve of hot temperatures by Tuesday, as an
upper level trough is progged to trek north of Colorado. Ensemble
solutions favor temperatures in the mid-to-high 80s for much of the
plains. We could also see scattered showers and thunderstorms by
midweek, however ensemble guidance does not seem too optimistic
about widespread measurable rainfall. Temperatures should climb
back to the mid 90s towards the end of the week.

&&

.AVIATION /18Z TAFS through 18Z Saturday/...
Issued at 1215 PM MDT Fri Jul 31 2026

Current observations show winds transitioning out of variable and
becoming light (< 10 KT) northeast over the Denver metro area. Winds
will remain light NE-E through the afternoon until storms begin to
develop near the airports at around 20Z-21Z. We have kept the PROB30
for -TSRA for the three airports until 01Z-02Z. However, shower
and thunderstorm coverage will be isolated in nature with the
primary concerns being lightning and gusty outflows up to 45KT.
Winds will return to the usual drainage S/SW drainage flow by 06Z
tonight before turning light and variable by mid morning.

Model guidance continues to suggest an increase in smoke
concentrations from the wildfires in the Pacific Northwest for
this afternoon, likely between 21Z and 03Z. Smoke concentrations
may increase again for a brief period around 15Z tomorrow morning
due to light northerly surface winds.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Heat Advisory from noon Sunday to 9 PM MDT Monday for COZ038>043.

&&

$$

DISCUSSION...MAI
AVIATION...AA

NWS BOU Office Area Forecast Discussion