197
FXUS65 KBOU 091814
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1214 PM MDT Sun Aug 9 2026

.KEY MESSAGES...

- Heat will linger into the first part of next week. A Heat
  Advisory is in effect for the northern I-25 Corridor and Denver
  metro until 8 PM this evening.

- Another round of high-based virga showers today. Wind gusts of
  30-45 mph will be common with the showers and a few gusts up to
  55 mph will be possible.

- Precipitation chances increase and temperatures cool mid to
  late next week.

&&

.DISCUSSION /Through Sunday/...
Issued at 1208 PM MDT Sun Aug 9 2026

Current satellite imagery shows increasing cloud cover over the high
terrain, with the radar already indicating a few virga showers
initiating off the Front Range. Virga showers are expected through
the early evening for mountains and I-25 corridor before moving east
through late evening. ACARS soundings today have a slight
increase in mid-level moisture compared to yesterday, which will
likely result in more shower coverage. However, due to the dry air
mass at the lower levels, little-to-no precipitation is expected
to reach the ground for the plains. Gusty outflow winds of 40-45
mph will be the main concern, however can`t rule out an isolated
stronger gust.

One thing we will keep our eye on later this afternoon and evening
is for any storm that tracks into the far northeastern plains.
Surface observations and CAMs this morning have consistently shown
better low-level moisture and thus better instability, with modeled
Skew-T soundings showing better shear profiles compared to farther
west. If a storm can tap into this environment, it could become
strong to severe. Hail and strong outflow winds will be the main
threat.

With the increase in moisture and cloud cover, we likely won`t be as
hot today as were were yesterday. However, highs should still get up
to the upper 90s, with the potential for DEN to break its record
high temperature (98 dg set in 2021). Surface observations show
current temperatures in the mid-90s, so we only need to heat up a
few more degrees. Barring any evaporative cooling over due to a
virga shower, we are on track to tie or break the record.
Overnight low temperatures should be cooler than last night, thus
have no plans on extending the Heat Advisory and will let it
expire this evening.

Heat will linger Monday and Tuesday, with the weather pattern
looking very similar to the past couple of days due to the upper
level ridge situated in the Desert Southwest. Both days will likely
showers and thunderstorms in the afternoon, with best chances for
precipitation in the high terrain given better moisture
availability. However, like the past couple of days, a few scattered
virga showers should spill onto the I-25 Corridor and east. Given
the overall lack of forcing, strong outflow winds will continue to
be the main concern.

The weather pattern begins to change on Wednesday, as the upper
level ridge that has been dominating our weather for the past week
begins to weaken and shift east. This will result in southwest
flow aloft for Colorado, with better monsoonal moisture being
advected into the region. Showers and thunderstorms will begin
increasing in coverage by Wednesday, however ensemble guidance
indicates we won`t get widespread beneficial rainfall till
Thursday/Friday. With above normal precipitable water values,
localized heavy rainfall will likely become a concern. But, it is
too soon to pinpoint exact location of biggest concern yet. WPC
has introduced a Slight Risk for much of the plains for Day 5
(Thursday) which seems reasonable at this time given how guidance
has been trending. Along with this precipitation, expect cooler
temperatures by Thursday and possibly lasting through the weekend.
NBM has trended slightly warmer with forecasted highs now in the
low 80s. These still may change in the next few days, as models
are still coming into agreement on exactly how much we will cool
off. GEFS has been consistently warmer that the ECMWF Ens. Expect
highs to be somewhere between low- mid 80s.

For the weekend and into the beginning of next week, ensemble
guidance looks promising in keeping the upper level ridge southeast
of Colorado, with a few embedded shortwaves in the upper level
flow. This should keep up relatively cool compared to this past
week, with almost daily chances of precipitation.

&&

.AVIATION /18Z TAFS through 18Z Monday/...
Issued at 1117 AM MDT Sun Aug 9 2026

Current winds are light and variable across the Denver TAF sites
late this morning. Expecting winds to increase as northerly flow
becomes more predominate in the next hour (by 19Z). The main
concern for today remains with high-based virga showers expected
to develop across the higher terrain and move eastward over the
TAF sites, with some development already occurring in the
mountains west of KAPA. Current ACARS soundings show DCAPE values over
1300 J/kg at this time, with forecast soundings showing that
increasing by a few hundred more J/kg through the afternoon. This
would support gusty outflows and microbursts around 35-40 kts as
virga showers pass. Winds are expected to transition to the
southeast around 2Z/3Z this evening before settling into drainage
for the overnight hours. There may be a rogue outflow or two
lingering between 2-3Z that would keep winds slightly more N/NE,
but confidence is high that we should see southeasterly winds by
3Z.

Similar conditions are expected for Monday with high-based showers
expected to develop across the higher elevations in the afternoon
and bring gusty outflow and microburst potential across all TAF
sites starting around 20Z once again, with gusts between 35-40 kts
possible.

Smoke is expected to persist through today and into Monday
morning, with significant improvements expected Monday afternoon
and evening.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Heat Advisory until 8 PM MDT this evening for COZ038>040.

&&

$$

DISCUSSION...MAI
AVIATION...9

NWS BOU Office Area Forecast Discussion