958
FXUS65 KBOU 170538
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1138 PM MDT Tue Sep 16 2025

.KEY MESSAGES...

- Scattered showers and thunderstorms through this evening. A
  severe storm is possible in the northeast corner.

- Shower/t-storm potential will linger into Wednesday, with cooler
  conditions through Thursday.

- Drier weather Thursday onward, with warmer temperatures
  beginning Friday.

&&

.DISCUSSION /Through Tuesday/...
Issued at 242 PM MDT Tue Sep 16 2025

Complicated situation this afternoon, but the main features are
the warm moist air ahead of a boundary from Limon to Julesburg.
The best moisture/instability/low level convergence is centered
right along the state line east of Julesburg and Holyoke and north
from there, and we`re seeing storms developing there in the last
hour. There`s a zone in between this energy rich air and the
cooler air close to the Front Range, west to around Fort Morgan
and Limon, that could still support strong storm development with
heating this afternoon. The severe threat looks lower in these
areas though, and rain cooled air is spreading southward from
about I-76 across this zone.

Further west, there may be just enough CAPE to sustain
thunderstorms, or perhaps the storms will weaken coming off the
mountains, but there should be decent coverage of showers in the
late afternoon and evening based on mid level instability and some
weak QG forcing. This will diminish by midnight, but the tail end
of the lift may still be dragging across the area through the
night. There`s a chance of some low cloud/fog development if
there is enough clearing or enough rain, but it`s looking like the
drying might be substantial enough to keep this out of Denver.

Wednesday we`ll start with cool and relatively drier air. It may
take most of the day to generate shower activity, but it will be
cool enough aloft that there should eventually be another round of
showers and storms. Then there`s some lift from another shortwave
dropping south across the plains to keep the threat of showers
going overnight. Thursday is a transition day as drier air is
moving in, but there will still probably be some diurnal showers.

For Friday and the weekend, we`ll have drier northwest flow as a
ridge builds to our west. Temperatures will warm and convection
will be at a minimum, though some isolated mountain showers are
still possible. Early next week, there will likely be another
shortwave dropping somewhere across the plains. It may be enough
to bring some cooling for a day or two and a chance of showers, or
it may have little effect. Meanwhile, the ridge will likely be
building more strongly just to our west so any cooling will
probably be temporary.

&&

.AVIATION /06Z TAFS through 06Z Thursday/...
Issued at 1130 PM MDT Tue Sep 16 2025

Showers and thunderstorms have moved east of Denver area
terminals at this time, and no additional convective development
is expected overnight. Primary forecast concern relates to
progression of stratus through the morning hours. There is likely
to be oscillation between SCT and BKN mid-level cloud bases,
030-050 over the next 3-5 hours. Nearing sunrise, potential for
more persistent CIGS closer to 025-030 will increase, mainly
10-15Z. Lower CIGS down to 015 can`t be ruled out, but confidence
in this scenario is low. Winds will be light through this period,
but should generally favor a more NW direction. A more
persistent/robust NW flow would help promote the lower CIG
possibility.

For Wednesday, there`s moderate to high confidence in the
prevalence of NE winds 07-12 kts from mid-morning through at least
mid-afternoon. Mid-level moisture will arrive late and provide
~30% chance of -SHRA (lesser instability will lead to lower TSRA
potential versus Tuesday) beginning near 23Z. CIGS 040-060 are
favored to persist well into the evening as this activity moves
through.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

DISCUSSION...Gimmestad
AVIATION...Rodriguez

NWS BOU Office Area Forecast Discussion