326
FXUS65 KBOU 180813
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
213 AM MDT Tue Aug 18 2026

.KEY MESSAGES...

- Scattered showers and thunderstorms expected today and
  Wednesday. Isolated severe thunderstorm threat both afternoons
  and evenings.

- Above normal temperatures through the weekend. Drier Thursday
  and Friday, but some monsoonal moisture likely returns by the
  weekend.

&&

.DISCUSSION /Through Monday/...
Issued at 148 AM MDT Tue Aug 18 2026

A weak cold front is forecast to move through the plains late
this morning into the early afternoon. Our severe weather threat
today will depend on available boundary layer moisture and
therefore potential instability. Some models have the I-25
corridor mixing and drying out prior to the cold fronts arrival,
with a lag between the cold front and the higher dewpoints. While
others have dewpoints staying a bit higher for late this morning,
with higher dewpoints moving in right behind the front. Another
potential hiccup in the moisture/severe weather forecast for
today is an outflow boundary which could stall over the area. As
of 1:30AM, the boundary was moving through Weld county, with
dewpoints increasing behind it. If this boundary does end up
stalling over the area, it could keep moisture higher and act as
another source of lift. The dewpoints/surface moisture will play
an important role in instability today. Areas that see the higher
boundary layer moisture will have much better instability and
higher chances of severe weather, as 0-6km shear increase behind
the front. The highest chance for strong to severe storms today
will be in our far northeastern plains counties, with decreasing
confidence as we go further west. The primary hazards will be
large hail and strong winds.

Tomorrows convective activity looks like its trending further south.
Models now have the shortwave over southern Colorado, putting the
best rain chances in our southern counties and south. However,
models are showing what looks like a stalled boundary over our
area Wednesday afternoon. This could allow for surface convergence
and some isolated to scattered activity in our northern counties
as well. While coverage of storms is forecast to decrease for
Wednesday compared to today, the severe weather threat will
continue as shear remains high and instability increases.

The upper level ridge with build over the area Thursday into the
weekend. Temperatures will remain well above normal for this time
period, with lower rain chances for the plains on Thursday and
Friday. The higher terrain could still see some isolated activity
in the afternoons. Precipitable water values will start to
increase for the weekend, with models showing values approaching
150% of normal again by Sunday. The higher moisture and a
shortwave aloft will bring increased rain chances across our
forecast area for the end of the weekend and start of next week.

&&

.AVIATION /06Z TAFS through 06Z Wednesday/...
Issued at 1145 PM MDT Mon Aug 17 2026

Drainage winds will generally prevail for the next couple of
hours. Winds will start to turn more west/northwest around 08Z to
09Z, before becoming variable around 15Z to 16Z. Light and
variable winds will continue for the late morning to early
afternoon until stronger northeasterly winds move into the area
behind a weak cold front. Scattered showers and thunderstorms are
expected this afternoon. Uncertainty is still pretty high in both
coverage and location of this activity, so we`ve left the prob30
in there for now. But, we may need to update that to a TEMPO if
models continue to trend up with storm coverage Tuesday afternoon
and evening. There`s also a question on how long the showers and
storms will linger across the area before moving off to the
east/southeast, with some models keeping them around into the
early overnight hours.

&&

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

&&

$$

DISCUSSION...AP
AVIATION...AP