661
FXUS65 KBOU 291128
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
528 AM MDT Wed Jul 29 2026

.KEY MESSAGES...

- Showers and thunderstorms likely across the high terrain in the
  late morning, shifting to the plains by the afternoon.

- Strong storms could produce localized flash flooding,
  particularly for the burn scar and areas along and east of the
  southern I-25 Corridor.

- Drying out again later in the week. Heat returns by the
  weekend.

&&

.DISCUSSION /Through Tuesday/...
Issued at 301 AM MDT Wed Jul 29 2026

Another round of showers and thunderstorms expected today as above
normal moisture remains in place for one more day. Main concern
continues to be localized heavy rainfall producing flash
flooding, particularly for burn scar areas in the mountains, and
portions of the plains. Let`s break it down below:

Guidance continues to favor above normal precipitable water values
>1", which is above the 90th percentile for the Denver area.
Forecast soundings show tall, thin CAPE (a typical profile for
maximizing precipitation efficiency) with a relatively moist
vertical profile and a warm cloud layer depth of 4-5,000 ft. These
ingredients coupled with expected slow storm motion, will promote
heavy rainfall and localized flash flooding. A flash flood watch was
considered for portions of the plains, including the southern I-25
corridor and adjacent areas east. However, recent REFS 3hr LPMM
QPF is nowhere near as robust as it was for Tuesday`s convection
(suggesting 0.75"-1.25" along the urban corridor with the
strongest storms for today). The most likely reason for this is
due to the lack of decent instability compared to yesterday, with
most CAMs indicating >1000 J/Kg of MLCAPE for the urban corridor
(better instability farther east). For this reason, have held off
on a watch for now, but if models begin changing and aligning more
with the NAM (the more bullish model for today`s convection), the
next forecast package may need one.

Timing: Widespread convection is expected to begin by the late
morning/early afternoon across the high terrain, before spilling
onto the plains and trekking east throughout the
afternoon/evening. Best chance for the Urban Corridor to see
precipitation will be 2/3 PM and into the late afternoon. While
coverage in showers/thunderstorms are expected to be greater today
due to better moisture return, that does not mean that all areas
will see beneficial rainfall. Storms will shift into the far
eastern plains by early evening and continue through 10/11 PMish.
Some guidance does favor additional scattered showers for the high
terrain overnight Thursday due to an upper level shortwave.
However, coverage will be limited.

Models continue to favor a drying trend towards the end of the week,
with warmer temperatures returning by the weekend. Scattered showers
and thunderstorms are still possible Thursday and Friday, however
coverage will be limited. The upper level ridge in the southwestern
United States will begin to restrengthen, with 700mb temperatures
reaching up to 20-22 dg C by Sunday. Ensembles favor portions of the
plains reaching 100 F Sunday and possibly Monday.

&&

.AVIATION /12Z TAFS through 12Z Thursday/...
Issued at 520 AM MDT Wed Jul 29 2026

Winds are currently drainage and could continue for the next hour
or so before becoming light and VRB through the early morning
hours. Models seem to generally have some sort of easterly
component, varying between southeast to northeast. Observations
across the eastern plains, show dewpoint depressions around 0,
which have created patchy areas of fog. There is a low chance
(~20%) that fog could reach DEN and BJC as winds turn easterly
this morning. However, due to low confidence, have still kept it
out of the TAF for now. If fog does form over the airports,
daytime heating should clear it up quickly.

Widespread showers and thunderstorms are expected this afternoon,
with convection beginning around 20Z for BJC and 21Z for DEN and
APA. Gusty outflow winds of 40 kts and heavy rainfall reducing
visibilities will be the main concerns. Guidance does indicate
scattered showers behind the main line of convection, however
coverage is uncertain. For this reason, have kept the PROB30 as
is. Showers should end by 04Z/05Z tonight, with drainage flow
possible behind convection.

&&

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

&&

$$

DISCUSSION...MAI
AVIATION...MAI

NWS BOU Office Area Forecast Discussion