484
FXUS65 KBOU 191819
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1219 PM MDT Sat Sep 19 2026

.KEY MESSAGES...

- Another round of scattered showers/t-storms this afternoon for
  the mountains and urban corridor.

- Numerous showers/t-storms over the plains, where some will be
  strong to severe throughthis evening, producing locally heavy
  rain, strong outflow winds, and hail.

- Trending drier Sunday into Monday, although scattered
  afternoon/eveningstorms may continue Sunday, particularly along
  and south of I-70.

- Cooler temperatures expected Sunday into Monday, before
  warmertemperatures return. Next week will bring a few
  additionalopportunities for precipitation.

&&

.DISCUSSION /Through Saturday/...
Issued at 1213 PM MDT Sat Sep 19 2026

In the foothills and areas west of I-25 (except Larimer County
where clouds slowed warming), temperatures have warmed into the
mid to upper 70s already, reaching their convective temperatures.
Thunderstorms have formed and are moving across parts of the
Denver metro area. MLCAPE for the urban corridor is 300-700 J/kg,
so the storms are expected to stay sub-severe. There is also some
drier air over eastern Boulder and Larimer Counties where dew
points have fallen into the 40s. We lowered PoPs slightly for the
west side of the urban corridor because of this. Hi-Res models
still favor numerous thunderstorms for the eastern plains this
afternoon and evening, but they have been inconsistent regarding
storm evolution and timing. There`s still a threat for severe
thunderstorms over the eastern plains, south of I-76 with large
hail and winds up to 60 mph. If northern parts of the urban
corridor miss this first batch of storms, a second batch could
form later this afternoon. By mid evening (8-9PM), storms are
expected to be finished, expect a few possible stragglers over the
far eastern plains.

Showers will be possible tomorrowmorning across northern
Colorado due to lift ahead of an upper level low moving across
Wyoming. These showers could continue into the afternoon over the
northeast corner of the state. The airmass will continueto cool
with the low nearby. Highs are expected to be in the mid 60s to
lower 70s. The cooler temperatures are expected to be found over
the northeast plains where cloud cover is anticipated most or all
of the day. Models have backed off on cloud cover some for
tomorrow afternoon along the I-25 corridor. Where temperatures
reach the lower 70s, MLCAPE is expected to reach 300-800 J/kg, and
be slightly higher along and east of the Palmer Divide. Storm
chances tomorrow will be lower due to less moisture, subsidence,
and possible capping. Though if storms can form, a couple severe
ones are possible over and east of the Palmer Divide where better
instability will reside.

The upper level low weakens and shifts east of the region on
Monday. Replacing it, will be shortwave ridging. Temperatures will
be slightly warmer than Sunday, but a little below normal with
highs in the lower to mid 70s across northeast Colorado. Looking
upstream, a closed low will move across southern California on
Monday. This low begins to weaken Tuesday as it runs into the
ridge. The low lifts northeastward Tuesday and Tuesday night. On
Wednesday, this now open trough will be over Wyoming. As it passes
north of Colorado, it could bring scattered showers and
thunderstorms sometime Tuesday afternoon through Tuesday night. If
it slows slightly, we could see them on Wednesday.

For Wednesday through Saturday, the large scale weather pattern
will feature a large upper level ridge over the central part of
the country and a longwave trough off the west coast. For
Colorado, we`ll see southwest flow for most of thisperiod with a
couple of minor fluctuations possible. Temperatures under this
pattern will be at or slightly above normal with highs in the mid
70s to lower 80s. Chances for precipitation will mainly come from
shortwave troughs and moisture lifting northward out of the
eastern Pacific and Mexico. There`s very little model agreement
identifying these shortwave troughs, precipitation chances will be
low at this time.

&&

.AVIATION /18Z TAFS through 18Z Sunday/...
Issued at 1213 PM MDT Sat Sep 19 2026

Current radar imagery shows a strong thunderstorm over the southwest
Denver metro area and in the vicinity of KAPA. We have adjusted the
TEMPO groups at KAPA and KDEN to reflect an earlier start to today`s
storm activity. Model guidance shows some disagreement regarding the
timing of the strongest storms, although it is likely that the brunt
of the threat will be east of KDEN by 00Z with some lingering
showers over the Denver metro until 02Z. Brief heavy rainfall may
lead to some visibility reductions under the storm cores, and gusty
outflow winds up to 35KT will be possible.

Winds tonight will turn to very weak SSW drainage flow, becoming
light and variable at times (

NWS BOU Office Area Forecast Discussion