590
FXUS65 KBOU 160740
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
140 AM MDT Sun Aug 16 2026

.KEY MESSAGES...

- Scattered showers and thunderstorms expected again on Sunday.

- Warming and drying trend for Monday and Tuesday.

- Another active day possible middle of next week.

&&

.DISCUSSION /Through Saturday/...
Issued at 136 AM MDT Sun Aug 16 2026

As of 1:30AM, we`re starting to see some patchy fog develop over
portions of Larimer and Weld counties, with areas of Laramie
county just to our north down to 1/4 mile visibility. Fog is
expected to develop further south in the next few hours,
potentially impacting the urban corridor, portions of I-25, I-70
and I-76. Visibilities down to 1/4 mile are expected for isolated
areas. A Dense Fog Advisory may be needed if the coverage of the
1/4 mile visibilities are great enough. The most likely timing of
fog near the urban corridor will be between 4AM and 8AM.

The upper level high, that was to our southeast, will start to move
west today. This will put us in more zonal flow aloft, which will
begin our drying trend. Precipitable water values today will
decrease, but will remain around 100% to 125% of normal. A weak
disturbance will move through the flow aloft to our south, providing
the best lift around the Palmer Divide and south. Surface winds will
be more from the southeast today. The SE surface winds will allow
for some weak upslope for our northern counties near the Cheyenne
Ridge. With the slightly lower PWs and less widespread lift,
showers and storms are expected to be lower in coverage today
compared to the past few days. Scattered showers and
thunderstorms will likely form around the Cheyenne ridge and
Palmer Divide areas today, moving east/southeast through the
afternoon and evening. The flash flooding threat will be lower
today, due to the decrease in PWs, decrease in coverage, and
increase in storm motions. However, with all the rain we`ve seen
lately there could still be some localized flooding concerns due
to the more saturated soils and lower flash flood guidance. We do
have a slight risk for severe weather again this afternoon. Low
level lapse rates will be steep today and 0-6km shear will be
sufficient for strong to severe storms to develop (~30 to 35
kts). But there is a potential bust factor with the severe
weather threat, due to the possibility of morning fog and low
clouds sticking around longer than expected and impacting
instability. Stronger storms will have the capability of
producing large hail, strong winds, and heavy rainfall.

A warming and drying trend is forecast for Monday and Tuesday. Upper
level ridging will start to build to our west as the upper level
high shifts more towards the four corners region. Temperatures on
Monday will warm closer to normal with much lower rain chances. On
Tuesday, models are still a bit up in the air, but a few of them are
hinting at a weak cold front Tuesday afternoon and evening moving
in from the north. The timing of this front will impact highs in
our northern plains counties for Tuesday and our precip chances
for Tuesday. We`ll see a brief cooling in the temperatures on
Wednesday behind that front, and an increase in rain chances as we
see increased moisture behind the front and maybe some surface
convergence from the stalled boundary. But then upper level
ridging really starts to build just to the west of our area for
Thursday and Friday, before shifting east over our area for the
weekend. Highs are forecast to sit in the mid 80s to mid 90s for
the plains for the end of next week.

&&

.AVIATION /06Z TAFS through 06Z Monday/...
Issued at 1134 PM MDT Sat Aug 15 2026

Winds overnight will primarily be light from the south/southwest
or variable. The one exception could be an hour or two of stronger
winds (10 to 15kts) from the northeast as an outflow boundary from
convection to our northeast moves through KDEN. We currently have
the boundary reaching KDEN around 09Z, but it is possible that the
boundary could weaken and wash out before reaching the airport.
Models are still hinting at low clouds and potential fog at our 3
TAF sites. KDEN is expected to have the worst impacts from the
fog today, but it could spread south and west towards KBJC and
KAPA. Visibilities below 1SM will be possible between 11Z and 14Z
this morning at KDEN. We have another chance of showers and
thunderstorms this afternoon, but coverage is expected to be lower
than the past couple of days, so we`ve opted for a Prob30 rather
than a TEMPO for the mid afternoon and evening.

&&

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

&&

$$

DISCUSSION...AP
AVIATION...AP

NWS BOU Office Area Forecast Discussion