168
FXUS65 KBOU 181736
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1136 AM MDT Mon Aug 18 2025

.KEY MESSAGES...

- Temperatures slowly climb each day during this work week and
  may reach the upper 90s by Thursday.

- Isolated showers and storms are expected most days this week
  with minimal rainfall. Isolated threat for severe potential over
  the northeast corner today.

- Looking like a slight cool down and moisture return by next
  weekend.

&&

.DISCUSSION /Through Sunday/...
Issued at 213 PM MDT Sun Aug 17 2025

As expected, drier conditions are in place across the region today
as shown in GOES-19 water vapor imagery. Additionally, the SPC upper
air maps show an upper-level ridge centered over the southwestern
CONUS/Mexico border this morning. This is expected to dominate the
weather pattern for the week as it shifts northward and builds over
the Four Corners region through the first half of the week,
bringing hot and dry conditions to the forecast area.

For today, with PWAT values ranging between .6 to .9" across the
forecast area, there is still some lingering moisture in place that
will allow for afternoon showers and storms to develop. Instability
isn`t very impressive today, but with hi-res guidance showing
between 300 to 500 J/kg of SBCAPE expected this afternoon, we expect
some weak thunderstorms and showers to develop over the higher
terrain. Activity is expected to generally be over the northern
mountains and Cheyenne Ridge areas where the most instability is
expected, but can`t rule out seeing something over the Palmer Divide
as well. Main threat from today`s storms will be gusty outflows
between 35-45 mph. Skies will clear out overnight tonight and
temperatures will be mild across the plains, staying between 5-10
degrees above normal.

Monday`s pattern won`t change much from today`s besides some
slightly higher instability expected. Dewpoints are looking to be
a few degrees higher than what we are seeing today, and ensembles
show PWAT values increase slightly across the Palmer Divide and
portions of the plains to near normal values. With the slightly
higher moisture and instability in place, it`s looking like there
will be a slightly better chance for afternoon showers and storms
to develop than what we are seeing today. With the highest
concentration of moisture and instability expected to coincide
over the Central Mountains and Palmer Divide we expect this to be
where scattered showers and storms will initiate in the early
afternoon, before moving across the lower elevations through the
evening. Hi-res guidance is starting to be very aggressive with
the magnitude of gusty outflows with these storms, as the latest
HRRR is showing 60+ mph. With DCAPE values expected to be around 1000
to 1200 J/kg, it seems that this is too aggressive for what we
are expecting tomorrow, and the Namnest seems to have a better
handle on this as it shows potential for 45-55 mph, which seems
reasonable given the setup. With dewpoints expected to remain in
the upper 50s to lower 60s over the northern corner of the state,
and 0-6km bulk shear around 35kts expected, can`t rule out an
isolated threat for hail and wind, and the SPC has introduced a
marginal risk for our three northeast corners for potential for
both of these hazards for tomorrow.

Not much has changed for the rest of the forecast period. Things
are still on track for the temperatures to gradually warm each day
through Thursday while the upper-level ridge remains in place. An
upper-level low is expected to come ashore southwestern Canada by
mid-week that will start to flatten out the ridge as it treks
across the southern tier of our neighbors to the north. This will
help bring cooler temperatures and moisture to the region as its
associated cold front drops south across Colorado by next weekend.

&&

.AVIATION /18Z TAFS through 18Z Tuesday/...
Issued at 1110 AM MDT Mon Aug 18 2025

Current light and variable winds should start to settle into a
more northeast/easterly component by 18/19Z. The main concern for
today remains the potential for gusty outflows/microbursts across
all of the Denver TAF sites from scattered afternoon showers and
thunderstorms across the area. ACARS soundings already show
around 1200 J/kg of DCAPE in place that would support strong gust
potential. While gusts between 35-40kts are what we are expecting
with showers and storms today, there is a low chance that slightly
higher gusts occur (~10% chance up to 50kts). If a stronger storm
occurs directly over the TAF sites, hi-res guidance suggests that
worst-case, VIS could drop as low as 2SM under the strongest
storms today.

Lingering storms over the Palmer Divide are expected to delay the
onset of drainage winds by a few hours, keeping southeasterly
winds in place at KDEN/KAPA through around 5-8Z. KBJC should see
more of a northerly turn before drainage kicks in late tonight.

Light and variable winds are expected for Tuesday morning before
making their diurnal turn to the east by the early afternoon.
Thunderstorms with gusty outflows will be a concern, once again,
for the afternoon hours, and a PROB30 has been introduced to
account for this hazard to end the TAF period.


&&

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

&&

$$

DISCUSSION...Bonner
AVIATION...Bonner