733
FXUS65 KBOU 061137
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
537 AM MDT Sun Sep 6 2026

.KEY MESSAGES...

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

- Temperatures will remain very warm, with only slightly cooler
  conditions starting Tuesday.

- Some potential for a brief cooldown next weekend?

&&

.DISCUSSION /Through Saturday/...
Issued at 1252 AM MDT Sun Sep 6 2026

A cluster of disorganized convection continues to backbuild across
the far northeastern corner of the state in these early overnight
hours. The axis of heavier rainfall has generally been just north
of our forecast area, along the Nebraska border... though radar
estimates have been as high as 2-3" in northwest Sedgwick county.
Guidance pushes most of this activity out of our CWA by about 09z,
and the Flood Watch will be allowed to expire then.

Sunday should be a bit quieter across the plains, as the better
moisture pushes westward into the I-25 corridor. With T/Tds near
90/50 during the afternoon, we`ll likely see MLCAPE increase to
around 1000-1500 J/kg by the afternoon hours. The flow aloft will
remain rather weak, with 0-6km/effective layer shear sitting near
20-30kt. The environment would support at least a marginal
hail/wind threat across the Front Range and urban corridor, but
would be conditional on any storms managing to develop during the
afternoon hours. The HRRR, along with both HREF and REFS members,
are fairly bullish with this potential, and I would expect at
least a couple of thunderstorms to develop around the Denver metro
between roughly 3-8 PM. High temperatures will again reach the
low to mid 90s across most of the plains.

Monday still looks to feature the best chance of precipitation
across most of the region. With similar moisture available, the
biggest change is the addition of some synoptic scale ascent, from
both a passing mid-level trough and the right entrance of a
70-80kt upper jet streak. While it`s possible that a majority of
the convection ends up to the south and east of Denver - as some
models currently hint at - the overall setup would still favor at
least some storms across most of the I-25 corridor. We`ll see if
any obvious trends emerge over the next 24-36 hours.

By Tuesday and Wednesday, the ridge across the south central CONUS
should begin to expand and flatten, bringing weak zonal flow to
the state. This should also push the deeper moisture off to our
south/west, and guidance has trended a little drier in this
period. Temperatures look to cool slightly, with highs in the mid
80s to low 90s. Zonal flow appears likely to persist through the
rest of the week, which will limit storm chances and keep
temperatures fairly steady in the mid 80s to mid 90s across the
lower elevations.

As we approach next weekend, guidance continues to hint at a
stronger trough/closed low pushing across the northern Rockies.
While we`d still end up on the dry side of this system, there`s
been a few runs that push some cooler air into the region by
sometime next weekend. However, while the deterministic forecasts
have been optimistic for those looking to get some relief from
this pattern, this is far from a guarantee. There is a significant
spread in 2m temperature forecasts from the past few ensemble
cycles from the GFS/ECMWF, and a good number of members
(approximately 40%) would favor above normal temperatures
continuing into mid-September. Still, it`s something to watch for
in an otherwise stagnant pattern.

&&

.AVIATION /12Z TAFS through 12Z Monday/...
Issued at 535 AM MDT Sun Sep 6 2026

VFR conditions are expected through the TAF period.

Instead of the typical drainage winds overnight, we`ve
predominantly kept a weak west/northwest direction at the
terminals, which is expected to continue through the mid-morning
hours. Winds are then expected to become more variable before
eventually settling on an east/southeast direction this afternoon.

Main concern in the TAF window will be the potential for TS
impacts after about 21-22z this afternoon. The last several cycles
of the HRRR have insisted on convective initiation somewhere in
the metro around 23-00z, which then lifts northeastward through
the evening hours. This solution is largely supported by the HREF
and REFS ensemble members. Given the relatively sparse convective
coverage, the PROB30 still seems appropriate for now, but may be
turned into a TEMPO later today if forecast confidence increases.

Once convection exits the area in the evening, winds are likely to
turn back towards typical drainage flow and continue into Monday
morning.

&&

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

&&

$$

DISCUSSION...Hiris
AVIATION...Hiris