432
FXUS65 KBOU 062325
AFDBOU

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

.KEY MESSAGES...

- Isolated thunderstorms late this afternoon and evening.

- 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 theCentral
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 thatthe 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
bettermonsoon moisture begins to shift south of the area withthe
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 andFriday 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 hightemperatures across northeast Colorado reaching
the upper 80s and lower 90s.

For next weekend, eyes are on an upper-level trough/closed low
forecastto 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 frontpush temperatures closer to normal. Given the
forecast uncertainty, including a chance for showers in the
forecast seems appropriate at this point.

&&

.AVIATION /00Z TAFS through 00Z Tuesday/...
Issued at 522 PM MDT Sun Sep 6 2026

VFR conditions will prevail for all terminals through the TAF
period. Over the next couple hours, additional convective
initiation is favored along the convergence zone in the NW Denver
metro, which should favor a period of NW/N outflow at the
terminals. Expect a return to drainage flow late this evening
after 04-05Z, lasting through early morning before transitioning
to light and variable winds. Cyclone formation tomorrow should
promote easterly flow for KDEN/KBJC. Convective forecast is rather
uncertain and generally favors greater activity due east of the
metro. Have reverted to a PROB30 for now given the lesser
instability compared to today.

&&

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

&&

$$

DISCUSSION...BM/Schnell
AVIATION...BRQ

NWS BOU Office Area Forecast Discussion