949
FXUS65 KBOU 140822
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
222 AM MDT Mon Sep 14 2026

.KEY MESSAGES...

- Still very warm today, with isolated to scattered showers and a
  couple storms. Mostly light precipitation amounts.

- Unsettled pattern rest of this week, but plenty of uncertainty
  with regard to daily precipitation chances. Thursday still looks
  like the highest opportunity of measurable rain (50-70%), and a
  locally heavy rainfall threat.

- Cooler weather arriving for Tuesday. Temperatures bounce back
  Wednesday, but then average around seasonal normals through next
  weekend.

&&

.DISCUSSION /Through Sunday/...
Issued at 222 AM MDT Mon Sep 14 2026

Satellite shows a weak shortwave pushing across Colorado in these
early morning hours, with scattered showers and a couple
thunderstorms along and ahead of it. While these will attempt to
move onto the plains this morning with the associated lift, most
of these will weaken or dissipate in the downslope westerly flow
aloft. That stronger flow develops today as a deeper upper level
low tracks across the Northern Rockies. Water vapor imagery
indicates drying behind our first shortwave, so the chances of
precipitation are generally decreasing after this early morning
disturbance. That said, we will still have some low level
moisture and weak instability (MLCAPE 500 J/kg or less) over the
western slope and plains mainly southeast of I-76. That`s where
we`ll keep the highest PoPs (30-40%), but lower PoPs (10-20%)
elsewhere. Temperatures will still be quite warm given downslope
flow, and increasing westerly breezes. In fact, some gusts near 50
mph can be expected over the Front Range mountains, with a few
gusts (outside of showers) to around 30 mph possibly reaching
Boulder. The stronger downslope component should boost highs to near
90F across the plains for one last time this season (Denver has
had a total 65 90F degree days, the 4th most 90s since records
began in 1872).

Cooler weather arrives tonight as a cold front pushes across the
plains by or shortly after midnight. How much cooler for Tuesday
is still in question. The latest data indicates low level
moisture and thus stratus potential or extent of any low clouds
behind the front would be lacking, so we`ll likely have more
sunshine and thus be able to reach the lower to mid 70s over most
of the plains and I-25 Corridor. The lack of low level moisture
also means our precipitation chances, at least in the lower
elevations, will be limited. Mountain areas should fare better
with at least scattered shower/storm coverage given monsoonal
moisture builds again in southwest flow aloft.

Stronger ridging occurs Wednesday as the next upper level closed
low digs southward along the Pacific coast. This means warmer
temperatures with highs likely pushing back into the mid 80s for
the lower elevations. Once again, the highest shower and storm
chances will occur for the mountains given increasing moisture and
instability during the day, while the plains reside in a more
marginal environment for convection given warming aloft but some
moisture still available.

Thursday is still shaping up to be the most active day with an
embedded shortwave and deeper monsoonal moisture lifting
northeast across the forecast area. Precipitable water values
will likely range from 150-200% of normal, so can`t rule out
locally heavy rain. WPC Excessive Rainfall Outlook has portions of
our forecast area in Slight Risk, and this seems reasonable,
especially if we are able to moisten up the low levels.

There remains plenty of uncertainty in the forecast through next
weekend, as there is little confidence in the timing of the West
Coast trough eventually lift east/northeast across the Northern
and Central Rockies. As a result, this period remains rather
broad-brushed at this point, with continued chances of showers
and storms and temperatures averaging near normal.

&&

.AVIATION /06Z TAFS through 06Z Tuesday/...
Issued at 1144 PM MDT Sun Sep 13 2026

One last surge of outflow winds had moved through KDEN, which
is a brief shift to W-NW and then VRB through 07Z, before
settling into fairly normal S-SW winds overnight.

For Monday, an upper level disturbance is on track to produce a
chance of weak showers in the morning, with the best time frame
being 12Z-16Z. Aviation impacts are expected to be minimal with
ceilings well above 6000 feet and generally light winds.Confidence
is low regarding the wind direction after 16Z Monday. The HRRR
model continues to show gusty west winds up to 25 knots while
most other models show weak winds with different directions. We
think west winds are likely (>70% chance) at least after the
passage of the weak disturbance Monday morning, but the direction
becomes unclear after 18-20Z. We may just end up VRB so we opted
for VRB in the afternoon for now. Also, while the chance of
showers is limited due to lack of instability, it will still be
quite warm with high DCAPE. As a result, we`ll keep the PROB30
with VRB G30kts in the TAFS for the 21Z-01Z period. Cold front
will arrive after 06Z Tuesday, which would bring a low threat (20%
chance) of stratus impacts for the Tuesday morning rush.

&&

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

&&

$$

DISCUSSION...20
AVIATION...20

NWS BOU Office Area Forecast Discussion