701
FXUS65 KBOU 201138
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
538 AM MDT Sat Jun 20 2026

.KEY MESSAGES...

- Critical fire weather conditions are expected for the mountains
  and high valleys today.

- Strong to severe storms possible across the eastern plains on
  today and Sunday.

- Scattered coverage of showers and storms on Monday and most of
  next week across the plains.

- Elevated fire weather conditions possible for the mountains and
  high valleys most of next week.

&&

.DISCUSSION /Through Friday/...
Issued at 217 AM MDT Sat Jun 20 2026

We`ve got quite an active day ahead of us, with critical fire
weather conditions expected across the mountains and high valleys,
and severe thunderstorms possible for our plains this
afternoon/early evening.

Current water vapor satellite imagery shows a shortwave over
Washington/Idaho. As this system treks east, it will help flatten
the well advertised upper level ridge that has been dominating our
weather pattern this past week. Winds across the high terrain will
strengthen, with westerly wind gusts up to 40-45 mph possible
throughout the afternoon. Due to the dry air mass in place,
relative humidity values will plummet to 9-15%. A Red Flag Warning
will be in effect from 11 AM to 9 PM today.

For the plains, a lee cyclone will develop in the morning ahead
the incoming shortwave. Easterly flow at the surface will advect
low-level moisture into the region, with dewpoint temperatures
reaching up to the low 60s across parts of the eastern plains.
Due to this, expect low clouds in the morning, which could affect
initial storm development in the early afternoon hours. However,
most hi-res guidance still favors the plains warming up to the low
90s. These hot temperatures combined with low-level moisture will
allow instability to build. Storms are expected to develop off a
boundary east of the Denver metro and track east through the
afternoon, where they will encounter an environment favorable for
all hazards. MLCAPE expected to build up to 2500-3000 J/kg, with
deep layer shear of 40-50 kts. With steep mid-level lapse rates,
supercells will have the ability to produce heavy rain, very
large hail, and strong outflow winds. With PWAT values up to 1.5",
localized flooding is possible. There is also a tornado threat,
particularly for our far northeastern plains, where LCLs will be
lower and SRH of ~150 m2/s2 is possible. Expect strongest storms
to be out of the forecast area by 6-8 PM. However, recent CAMs do
show the potential for additional thunderstorms exiting Wyoming
and entering the northeastern plains later tonight.

With the arrival of the shortwave on Sunday, additional showers
and thunderstorms are expected, but the strongest storms should be
confined to the far eastern plains. Forecast soundings show the
potential for elevated convection, with decent shear and mid-level
lapse rates indicating large hail as the main threat with the
strongest storms.

Next week continues to look active for the plains with daily
chances for precipitation with the passage of multiple shortwaves.
For Monday, there could be a few strong storms for the eastern
plains. However, instability and shear profiles do not look as
favorable as they do for the weekend. Unfortunately for the
mountains, the upper level ridge over the southwestern U.S. will
keep a dry air mass in place. Elevated fire weather conditions are
possible throughout the week.

Ensemble guidance is in good agreement of below normal
temperatures by Tuesday behind a cold front. Guidance has trended
slightly cooler (besides the GEFS), with forecasted highs now in
the upper 70s. However, warmer temperatures will return by the
later half of the week.

&&

.AVIATION /12Z TAFS through 12Z Sunday/...
Issued at 526 AM MDT Sat Jun 20 2026

Current satellite and observations show the low stratus deck near
DEN and BJC. With dewpoint depressions near zero, some fog has
formed over DEN and likely will stick around for a few hours
before daytime heating kicks in. Guidance has low stratus deck
through the morning hours before gradually eroding by 17Z/18Z.

In terms of winds, they are currently light and VRB due a weak
cyclone that has formed. Expect this to continue through the
morning before a more northwest wind (possibly northeast at APA)
materializes as the cyclone moves out of the area. Afternoon
showers and thunderstorms are expected today, however storms
should be just east of DEN and APA. VCTS is included in the TAF,
with gusty outflow boundaries impacting both airports. As
convection decreases in the evening, most guidance favors a brief
period of northwest winds, but models may be over mixing and
winds could stay northeast instead. BJC has the best potential of
seeing northwest winds this afternoon/evening.

A frontal boundary is expected to arrive between 03Z-05Z, which
will bring gusty northeasterly winds and low ceilings once again.
As of right now, expected ceilings as low as 1000ft, but could get
as low as 500 ft.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning from 11 AM this morning to 9 PM MDT this
evening for COZ211>214-217-218.

&&

$$

DISCUSSION...MAI
AVIATION...MAI

NWS BOU Office Area Forecast Discussion