Severe Thunderstorm Warning 259, NWS Denver/Boulder, CO

Area Forecast Discussion
National Weather Service Denver/Boulder CO
211 PM MDT Wed Jul 22 2026

.KEY MESSAGES...

- Storm coverage and intensity increases today and Thursday as
  monsoonal moisture moves into the region. Storms will be
  capable of producing locally heavy rainfall along with a
  localized threat of flash flooding.

- Storm coverage expected to decrease again by Friday into this
  upcoming weekend, although mountain areas should see at least
  scattered storm coverage each afternoon and evening.

- Temperatures will rise back into the upper 90's to lower 100's
  over northeast Colorado for the weekend into early next week.

&&

.DISCUSSION /Through Wednesday/...
Issued at 209 PM MDT Wed Jul 22 2026

Today and tomorrow will bring beneficial rainfall to a majority
of the area with an isolated risk of flash flooding. High
temperatures will reach the low to mid 90s once again today across
the plains. There are already several storms ongoing across the
high country and the Palmer Divide. Storms today will migrate into
the plains by mid-afternoon and push east into the early evening.
Scattered showers and thunderstorms will likely continue across
our area through at least midnight tonight.

Low-level flow is currently southeast which is continuing to
provide ample moisture to our area. Additionally, we already have
MLCAPE of 500-1000 J/kg and 20-30 knots of bulk shear as of early
this afternoon. Storms will be outflow dominant, so any storm
could produce gusty winds up to 50-60 mph with the highest risk
across the plains.

PWATs are at 150-200% of normal today and will approach
climatological record high values on Thursday. We have a low
flooding risk today given slow storm motions and the warm cloud
layer depth approaching 5000 feet. The highest risk of flooding
will be across the high country, mainly for burn areas and also
where storms train or for areas that received significant rainfall
yesterday (and thus have lower flash flood guidance).

A shortwave moves through tomorrow during the day which should
provide a slight increase in rainfall coverage tomorrow afternoon
as well as high temperatures in the upper 80s for the plains.
Storms will once again form in the high country by late morning to
early afternoon and then move into the plains during the
afternoon and evening. Storm motion will be faster than today
(around 20 kts) given increased flow aloft, but tomorrow still
carries a low risk for flash flooding. Additionally, the warm
cloud layer should be deeper than today allowing for more
efficient warm rain processes. Tomorrow will likely be the 3rd day
in a row of rainfall for some areas. Rainfall rates could once
again approach 2-3 inches per hour, so the WPC is now highlighting
most of our area in a slight (2 out of 4) risk for flooding.

In summary, there are several ingredients in place that lead us
to be concerned about the potential for isolated instances of
flash flooding in our area, but also some ingredients that will
lessen the extent of the threat. Given the nature of these storms,
there will be varying rainfall totals across short distances.
Overall, additional rainfall totals across the area will generally
be around 0.25 to 0.75 inches with some isolated totals of 2-3+
inches by Thursday evening.

The high pressure will build back into the area starting Friday
and strengthen through the weekend. The last several model runs
have been keying in on the heat peaking on Sunday. This is when
temperatures across the plains could reach 100 degrees F once
again, given the thermal ridge aloft will be near 20 C and
centered over our area. Record highs could be in play and a Heat
Advisory could be needed as we get closer to the weekend. A chance
for scattered showers is expected to continue through the weekend
for the high country.

By Monday and Tuesday, models show the ridge weakening and
shifting slightly off to the southeast. At the same time, moisture
from the remnants of Bertha could be pulled into the Southwest
United States and into western Colorado. This will be something to
watch as this could bring an increase in rain chances, mainly for
the high country. Otherwise, highs should still be in the mid to
upper 90s for the plains through much of next week.

&&

.AVIATION /18Z TAFS through 18Z Thursday/...
Issued at 1136 AM MDT Wed Jul 22 2026

Convection this afternoon remains the primary concern of the TAF
period. KDEN recently reported an observation of 87F/55F, with
ACARS soundings showing MLCIN quickly decreasing across the metro.
Continued destabilization is likely over the next couple hours,
with convection likely to develop sometime between about 20-22z.
Forecast soundings would suggest the potential for at least some
brief TSRA/+TSRA at the terminals, with relatively high confidence
that this would occur sometime between 22-01z this afternoon.
Scattered showers or a few thunderstorms could continue into the
evening hours.

Some guidance is fairly bullish on developing low stratus late
this evening (~05z), with that potentially continuing through the
overnight hours. This looks like it would be highly dependent on
today's convection, so at this time the only change was to add in
a FEW010 group to DEN for most of the night.

A reasonably similar forecast pattern is expected tomorrow.
Guidance continues to advertise a favorable environment for slow
moving SHRA/TSRA tomorrow afternoon, with the best chance of any
storms coming after 21z Thursday.

&&

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

&&

DISCUSSION...MV
AVIATION...Hiris