558
FXUS65 KBOU 221133
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
533 AM MDT Mon Jun 22 2026

.KEY MESSAGES...

- Strong to severe storms expected for the plains this afternoon,
  producing large/very large hail, gusty winds, and possibly a
  weak landspout.

- Strong/severe t-storms to become more numerous Tue-Wed, with
  increasing potential for impacts to I-25 corridor and localized
  flash flooding. Temperatures to remain slightly below normal.

- Elevated to locally critical fire weather conditions in the
  mountains most afternoons, increasing in severity this weekend
  under building heat and strengthening winds.

- Drier and considerably hotter for the lower elevations starting
  Friday.

&&

.DISCUSSION /Through Sunday/...
Issued at 1220 AM MDT Mon Jun 22 2026

The last of the showers have dissipated, giving way to steady
clearing, although some low stratus and fog may creep into our
northeast plains before sunrise. A warm, moist and unstable
airmass remains in place today, most pronounced over the plains
with the dryline progged to nudge slightly farther west. A Denver
cyclone looks to develop early in the day and reinforce easterly
flow, which would help limit drying from daytime mixing which some
guidance remains rather bullish about. Bulk shear also appears
more favorable this afternoon for organized convection in the
plains, with values exceeding 45-50 kts. All of the lower
elevations may see thunderstorms this afternoon, although the
strongest storms capable of producing very large hail should
largely be focused east of the I-25 corridor within SPC`s Slight
Risk area. Initial convection may be helped along by the DCVZ, but
additional development will be possible through the afternoon
driven by established outflow boundaries. As for temperatures,
they`ll hold steady for the lower elevations under the easterly
flow regime, with the mountains seeing moderate warming given
rising heights.

A cold front early Tuesday will bring milder conditions to the
lower elevations, together with a renewed influx of low-level
moisture as lee cyclogenesis promotes strengthening of upslope
flow into the Front Range. Unsurprisingly, this will serve to
increase PW values into the 1-1.25" range across the lower
elevations. Combined with ample instability and favorable shear,
the environment will favor development of supercells with large
hail in the afternoon, and a widespread severe weather threat to
include the urban corridor. Meanwhile, much drier conditions will
be present in our mountains, where an opposite pattern of dry
westerly flow may promote critical fire weather conditions in the
afternoon.

Little changes on Wednesday, with the lower elevations holding
onto abundant moisture, instability and shear. Thus, expect
continued thunderstorm development in the afternoon, some of which
will become severe. Given the moisture availability and
successive days of convection, localized flash flooding will
become an increasing concern for the plains as the week
progresses. The severe weather threat looks to carry into Thursday
as well, before precipitation potential shifts to favoring our
high country on Friday as zonal flow increases ahead of a
developing trough over the West Coast.

Said trough looks to transition into a rather potent closed low
over the northern Rockies this weekend. The impacts are two-fold.
First, a considerable warming and drying pattern regionwide as
upper level ridging strengthens ahead of the trough, quickly
returning temperatures to above normal values and potentially the
hottest of the year so far come Saturday. Second, robust mid-level
southwest flow over the Four Corners region will promote a notable
increase in wind speeds, particularly for the high country,
lending increased confidence to a period of highly critical fire
weather conditions this weekend.

&&

.AVIATION /12Z TAFS through 12Z Tuesday/...
Issued at 524 AM MDT Mon Jun 22 2026

VFR conditions are expected to prevail for all terminals through
the TAF period, with low stratus/FG remaining confined to the
eastern plains this morning. Minor amounts of smoke may be present
above 3,000 ft AGL throughout the day, however concentrations
should be low enough to limit slantwise visibility concerns in the
absence of a more significant incursion of smoke.

As for winds, current drainage winds nudge to a SE/SSE component
this morning at KAPA and KDEN as a robust Denver cyclone spins up.
Confidence in prevailing wind direction is relatively high through
18Z, but falls precipitously thereafter as the cyclone attempts to
move east and convection begins to initiate. TSRA development is
most favored south of I-70 (i.e. KAPA) beginning near 18-19Z, but
may extend closer to KDEN as well. Convective outflows will
dominate prevailing winds in the afternoon and should mostly favor
a southeasterly direction where convection looks to be most
widespread.

In the evening, firm outflow-enhanced S/SSE winds look to take
hold for KAPA/KDEN with gusts 20-25 kts, only weakening during the
early morning hours. Although not indicated in model guidance, it
wouldn`t be entirely shocking to see redevelopment of SHRA or a
weak TSRA early evening as a result of preceding outflows. A cold
front will bring a transition to N winds shortly after sunrise
Tue.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Fire Weather Watch from Tuesday afternoon through Tuesday
evening for COZ212-213-217.

&&

$$

DISCUSSION...BRQ
AVIATION...BRQ

NWS BOU Office Area Forecast Discussion