Severe Thunderstorm Warning 289, NWS Denver/Boulder, CO

Area Forecast Discussion
National Weather Service Denver/Boulder CO
256 PM 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 Wednesday/...
Issued at 253 PM MDT Wed Jul 29 2026

It is another afternoon of showers and thunderstorms across Colorado
as monsoonal moisture continues to raise precipitable water (PW) for
the region to values (1.0"-1.6") that greatly exceed the 90th
percentile of climatology. Numerous thunderstorms have already
developed over the Front Range and the urban corridor, with radar-
estimated totals with the strongest storms ranging from 1.00" to 2.0"
in one hour. Weak mean cloud layer winds (<10KT) will lead to
slow storm motions and torrential rainfall that may lead to
localized flash flooding, particularly over burn scars and areas
with antecedent soil moisture from Tuesday's storms.

We have issued a Flood Watch for flash flooding for the Palmer
Divide, where high-res model guidance has been a bit more bullish
with thunderstorm coverage and instability will be more robust
(MLCAPE ~1000 J/kg). However, localized flash flooding may occur
outside of the Watch if storm redevelopment occurs over the same
areas, and with any storms that become anchored to the terrain.
We expect showers and storms to start diminishing in coverage by 9
pm, with perhaps a few decaying thunderstorms lingering over the
mountains and the easternmost Colorado plains.

For tomorrow, the upper level ridge currently over the southwest
U.S. weakens, and westerly winds aloft cuts off the flow of
monsoonal moisture from the southwest. We expect shower coverage to
decrease, although afternoon showers will still be possible (20% to
35% chance) mainly over the highest peaks, northern foothills, and
the Palmer Divide. The northeast Colorado plains will still hold on
to PWs around 1.5" and dewpoints in the low 60s, so this is where
the better chance for a strong isolated thunderstorm will reside. We
are not overly concerned about flash flooding for tomorrow due to
the decreased rainfall coverage as well as faster storm motions,
with cloud layer mean winds around 20KT.

The passage of a shortwave trough will bring another chance for
isolated strong to severe thunderstorms on Friday, although
uncertainty remains regarding the convective setup due to the
mesoscale convective system (MCS) that model guidance has suggested
will track through central Nebraska in the early morning hours,
which could produce an outflow front that greatly alters convective
parameters for Friday. Nevertheless, decent northwest flow aloft (20-
30KT) and the advection of higher dewpoints from the central plains
due to easterly flow at the surface could lead to a few strong
storms that produce erratic gusty outflows up to 50 mph.

Long-range ensembles are in good agreement that the upper level
ridge strengthens to our west on Saturday, the atmosphere dries out,
and temperatures rise above normal once again. Triple digits and
heat concerns are becoming increasingly likely for Sunday and
Monday over the plains, including the Denver metro. Uncertainty
enters the picture halfway through next week due to a series of
shortwaves sliding through the Pacific Northwest, and a weakening
of the ridge over the Four Corners.

&&

.AVIATION /18Z TAFS through 18Z Thursday/...
Issued at 1139 AM MDT Wed Jul 29 2026

Scattered convection is likely to develop within the next couple
of hours, spreading east across the terminals between about 20-24z
this afternoon. Guidance is starting to back away from the
potential for TSRA at KBJC with slightly higher confidence at
DEN/APA. Could see impacts from both wind and brief visby
restrictions with any more organized storms. Some showers may
linger beyond 00z this evening though chances of impacts from that
will be lower.

Drainage winds should prevail this evening through most of the
overnight period, before becoming light and variable by Thursday
morning. There is a slight chance of additional showers/storms
near or after 18z Thursday, but coverage across the metro looks
far lower than today. Did introduce a PROB30 for -TSRA at DEN
tomorrow for now but may eventually remove that in future updates.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Flood Watch until 9 PM MDT this evening for COZ041-046-047.

&&

DISCUSSION...AA
AVIATION...Hiris

Preliminary Local Storm Report
National Weather Service Denver CO
1034 AM MDT Wed Jul 29 2026

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0204 PM     Hail             Lyons                   40.23N 105.27W
07/28/2026  M1.00 Inch       Boulder            CO   Cocorahs

            Delayed report via CoCoRaHS. Hail lasted
            approximately 12 minutes and dented some
            cars.

&&

Special Weather Statement
National Weather Service Denver CO
238 PM MDT Wed Jul 29 2026

COZ040-041-292115-
North Douglas County Below 6000 Feet/Denver/West Adams and
Arapahoe Counties/East Broomfield County CO-Elbert/Central and
East Douglas Counties Above 6000 Feet CO-
238 PM MDT Wed Jul 29 2026

...A STRONG THUNDERSTORM WILL IMPACT SOUTHEASTERN ARAPAHOE...
NORTHWESTERN ELBERT AND NORTHEASTERN DOUGLAS COUNTIES UNTIL 315 PM
MDT...

At 238 PM MDT, Doppler radar was tracking a strong thunderstorm near
Castle Pines, or 18 miles south of Denver, moving northeast at 10
mph.

HAZARD...Wind gusts up to 50 mph and penny size hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor damage to outdoor objects is
         possible.

Locations impacted include...
  Southern Aurora, eastern Centennial, eastern Highlands Ranch,
  Castle Rock, Parker, Lone Tree, The Pinery, Castle Pines, Franktown
  and Foxfield.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Monitor the weather situation closely and be alert for threatening
weather conditions.

Heavy rain is occurring with this storm and may lead to flooding. Do
not drive your vehicle through flooded roadways.

&&

LAT...LON 3950 10498 3967 10476 3950 10455 3934 10484
      3949 10499
TIME...MOT...LOC 2038Z 223DEG 6KT 3949 10483

MAX HAIL SIZE...0.75 IN
MAX WIND GUST...50 MPH

63

Special Weather Statement
National Weather Service Denver CO
248 PM MDT Wed Jul 29 2026

COZ040-292115-
North Douglas County Below 6000 Feet/Denver/West Adams and
Arapahoe Counties/East Broomfield County CO-
248 PM MDT Wed Jul 29 2026

...A STRONG THUNDERSTORM WILL IMPACT NORTHEASTERN DENVER...
NORTHEASTERN ARAPAHOE AND WESTERN ADAMS COUNTIES UNTIL 315 PM MDT...

At 248 PM MDT, Doppler radar was tracking a strong thunderstorm 5
miles southwest of Denver International Airport, or 12 miles
northeast of Denver, moving east at 10 mph.

HAZARD...Wind gusts up to 50 mph and half inch size hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor damage to outdoor objects is
         possible.

Locations impacted include...
  Northern Aurora, northeastern Commerce City, Brighton, Denver
  International Airport, D.I.A Terminal and Concourses, Barr Lake and
  Watkins.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Monitor the weather situation closely and be alert for threatening
weather conditions.

Heavy rain is occurring with this storm and may lead to flooding. Do
not drive your vehicle through flooded roadways.

&&

LAT...LON 3970 10483 3996 10485 3999 10455 3972 10456
TIME...MOT...LOC 2048Z 263DEG 8KT 3981 10475

MAX HAIL SIZE...0.50 IN
MAX WIND GUST...50 MPH

63

<!doctype html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <title>Service Notice</title>
  <link rel="stylesheet" href="index.css">
</head>
<body>
  <main class="wrap">
    <section class="card" role="status" aria-live="polite">
      <div class="status" id="status">Temporary Notice</div>
      <h1 id="headline">This service is currently unavailable.</h1>
      <p id="message1">
        The site you requested is temporarily down for maintenance or an unexpected outage.
      </p>
      <p id="message2">
        Please try again in a few minutes.
      </p>
      <p class="small" id="detail">
        If you are an administrator, restore upstream service and remove the redirect/fallback rule when normal operations resume.
      </p>
    </section>
  </main>
  <script src="index.js"></script>
</body>
</html>

<!doctype html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <title>Service Notice</title>
  <link rel="stylesheet" href="index.css">
</head>
<body>
  <main class="wrap">
    <section class="card" role="status" aria-live="polite">
      <div class="status" id="status">Temporary Notice</div>
      <h1 id="headline">This service is currently unavailable.</h1>
      <p id="message1">
        The site you requested is temporarily down for maintenance or an unexpected outage.
      </p>
      <p id="message2">
        Please try again in a few minutes.
      </p>
      <p class="small" id="detail">
        If you are an administrator, restore upstream service and remove the redirect/fallback rule when normal operations resume.
      </p>
    </section>
  </main>
  <script src="index.js"></script>
</body>
</html>