925 
FXUS65 KBOU 070517
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1117 PM MDT Sun Sep 6 2026

.KEY MESSAGES...

- An increase in afternoon shower and thunderstorm coverage is 
  favored Monday for most areas.

- Temperatures will remain very warm, with only slight cool down
  or Tuesday and Wednesday.

- Some potential for a brief cooldown next weekend?

&&

.DISCUSSION /Through Sunday/...
Issued at 213 PM MDT Sun Sep 6 2026

Colorado remains sandwiched between an upper level high over the 
south central part of the county and a large trough off to the 
northwest. This will maintain southwest flow over Colorado and 
transport subtropical moisture into the area. Precipitable water 
values are 150-160 percent of normal. Low level moisture has 
increased since yesterday with dew points in the 50s across most 
of the urban corridor and northeast plains. This is yielding 
MLCAPE values of 500-1500 J/kg. Water vapor satellite imagery 
shows lift over the Great Basin associated with a jet streak. Over
Colorado, satellite imagery looks somewhat subsident. This lines 
up with model output, which shows isolated showers and 
thunderstorms later this afternoon and evening. Given the 
instability and 0-6km bulk shear of 25-35 knots a couple of severe
thunderstorms will be possible. Recent runs of the HRRR have 
pushed convection further north near Fort Collins and the Cheyenne
Ridge while most of the other CAMs indicate at least the 
potential for isolated showers and storms in the urban corridor. 

On Monday, the set-up will be similar to today's, with southwest 
flow aloft continuing between the ridge and trough. Flow aloft 
will increase as the jet off to the west moves over the Central 
Rockies. The right entrance region of the jet slides over 
Colorado, bringing an increase in cloud cover during the morning 
and likely providing lift for better coverage of thunderstorms 
Monday afternoon/evening. There is decent agreement that the best 
lift ends up over the eastern plains. MLCAPE will be lower, below 
1000J/kg, which is expected to keep most or all of the 
thunderstorms sub-severe.

An upper level trough will track from the Northern Rockies to the
Northern Plains on Tuesday. This will flatten the ridge that's 
been over the region. The ridging shifts south, becoming elongated
and stretching east-west across the southern part of the country.
Over Colorado, we'll see zonal flow. A shortwave trough embedded 
in the flow aloft will travel across the region. The 
better monsoon moisture begins to shift south of the area with the
development of the zonal. However, enough moisture is expected to
linger Tuesday for a round of afternoon/evening thunderstorms 
across the urban corridor and eastern plains. Cooler and drier air
is expected for Wednesday behind the exiting shortwave and under 
the zonal flow aloft. The cooling is subtle and high temperatures 
are still expected to be near to slightly above normal, with highs
in the lower to mid 80s across northeast Colorado.

Zonal flow aloft continues Thursday and Friday over the Central 
Rockies. This pattern will keep monsoon moisture south of the area
with dry conditions expected both days. Temperatures warm up 
again with high temperatures across northeast Colorado reaching 
the upper 80s and lower 90s.

For next weekend, eyes are on an upper-level trough/closed low 
forecast to track across the northwest part of the country. So 
far, models have shown very little run-to-run consistency with 
each model run being very different. On the bright side, at least 
the models have trended toward a large upper level trough or 
closed low. For Colorado, the biggest question is how far south 
this system will dig. As it stands now, most models keep the 
trough too far north for widespread precipitation. We will likely 
see a cold front push temperatures closer to normal. Given the 
forecast uncertainty, including a chance for showers in the 
forecast seems appropriate at this point. 

&&

.AVIATION /06Z TAFS through 06Z Tuesday/...
Issued at 1112 PM MDT Sun Sep 6 2026

An outflow boundary from earlier tstms near the foothills has
moved across with a wind shift to the W/WSW.  These winds should
become more SSW/S by 07z at APA/DIA with WNW winds at BJC.

On Mon, winds will be light and variable by 13z and then trend to
more easterly at BJC and DIA by 17z. At APA, winds will be from
the NW by 19z. There will be a chc of showers/tstms by 22z which
will linger thru 02z Mon evening.  For now have kept a prob30
between 22z and 02z with brief gusty winds up to 35 mph possible.

&&

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

&&

$$

DISCUSSION...BM/Schnell
AVIATION...RPK