Flash Flood Warning 27, NWS Denver/Boulder, CO

Area Forecast Discussion
National Weather Service Denver/Boulder CO
111 PM MDT Fri Aug 14 2026

.KEY MESSAGES...

- Flash flooding and a few severe storms will be the main threats
  through this evening, as another round of storms moves east-
  northeast across the forecast area.

- Monsoon moisture lasts through the weekend, bringing scattered
  showers and thunderstorms each day with locally heavy rain and a
  severe weather threat.

- Warming and drying trend still set to begin Monday.

- Another active day possible middle of next week.

&&

.DISCUSSION /Through Friday/...
Issued at 111 PM MDT Fri Aug 14 2026

Our main concern late this afternoon and evening will be another
round of strong thunderstorms, capable of producing flash flooding
and severe weather. Nearly full sunshine over the plains has
allowed the airmass to destabilize through early this afternoon.
Low level moisture was rather impressive with dewpoints holding in
the lower to mid 60s east of the I-25 Corridor. That's pushing
MLCAPE values into the 1000-2000 J/kg range per latest SPC
analysis. While bulk shear is marginal (only around 25 kts) for
organized severe storms, we have sufficient instability to drive
large hail and damaging wet microbursts from stronger storms.
While there was some drying noted in the 700-600 mb layer on the
most recent ACARS soundings, we still expect efficient rain
producers given low level moisture and updraft intensity, and
enough to warrant a Flood Watch for flash flooding in areas that
saw recent heavy rains - see HYDROLOGY section below for more
details.

Like most convective episodes, there will probably be some weaker
convection that lingers behind the initial stronger storms that
push east across the plains. Otherwise look for gradual clearing
overnight, but patchy fog/stratus development once again with a
very moist boundary layer.

On Saturday, deep layer shear increases as flow aloft strengthens
from the west-southwest. At the same time, we'll still have a fair
amount of low/mid level moisture present, which means growing
instability and another round of afternoon and evening storms.
Some of these may be severe again due to increased shear but
a little decrease in instability as some slight drying is still
forecast.

Sunday is shaping up to be another active weather day, and
potentially even higher than Saturday as persistent low level
easterly flow and moisture advection occurs over the plains. A
failure mode would be too much moisture/low level cloudiness over
the plains, but at the same time that could mean even greater
instability and more favorable shear profiles if we get enough
heating to break the cap.

We're still on course for drier weather Monday and Tuesday as the
ridge axis retrogrades slightly. That allows for a drier west-
northwest flow aloft and warm advection. High temperatures will
likely (>70% chance) return to 90F+ by Tuesday.

Wednesday should feature higher chances of storms again (30-50%
chance), as another front is scheduled to bring slight cooling
but moistening late Tuesday into Wednesday. We don't see much
change in the overall pattern through the end of next week, which
at this point favors fairly normal Colorado weather with near
normal temperatures and isolated to scattered afternoon and
evening storms each day.

&&

.AVIATION /18Z TAFS through 18Z Saturday/...
Issued at 1108 AM MDT Fri Aug 14 2026

Similar setup to yesterday. Sct tstms will develop between 20Z and
21Z and then move across the area thru 00Z or 01Z. Naturally if a
stronger storm were to hit one of the TAF sites visibility will
drop to 1 mile with brief MVFR ceilings. By 01z will see
decreasing activity, however, still can't rule out widely sct
showers/weaker tstms thru 05z so will keep Prob30 in TAFS.

As far as winds, expect light easterly winds outside of gusty
erratic winds from tsmts which may see bring gusts from 40 to 50
mph. For late this evening, winds will become light and variable
by 05z before going light drainage by 08z.

At this time, not expecting any low clouds or fog late tonight
thru mid morning on Sat.

&&

.HYDROLOGY...
Issued at 111 PM MDT Fri Aug 14 2026

While there was some mid level drying noted in the 700-600 mb
layer, instability is growing and precipitable water (PW) content
remains near 150% of normal. Warm cloud depths are expected to
average around 4,000-5,000 feet, just a tad less than yesterday.
Mean storm motion is expected to be a little higher as well,
closer to 15-20 kts as mean cloud layer flow has strengthen
slightly. Storms will still be efficient rainers today given the
above mentioned favorable parameters, but likely just a notch down
from yesterday. That still means we could see storms producing a
quick 1-2" in 30-45 minutes, and local totals pushing 3" where
storm mergers occur (per Local Probability Matched Means). Flash
flood guidance has dropped rather considerably in areas that saw
heavy rain yesterday, and enough to warrant another Flood Watch
for flash flooding in those locations.

For Saturday and Sunday, strong storms are expected again although
PW values are expected to nudge slightly lower (~125% of normal).
Locally heavy rains can still expected due to intensity of storms,
along with local flooding impacts mainly from training storms
since storm motions will be faster (20-25 kts).

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Flood Watch until 10 PM MDT this evening for COZ036-041-042-
044>049.

&&

DISCUSSION...20
AVIATION...RPK
HYDROLOGY...20

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