266
FXUS65 KBOU 131124
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
524 AM MDT Wed May 13 2026

.KEY MESSAGES...

- Summerlike warmth with dry weather this week, with highs in the
  80s for the lower elevations Wednesday through Sunday. A few
  highs in the 90s possible Wednesday across the urban corridor.

- A few afternoon showers possible today through Friday, mainly
  across the Front Range mountains and foothills. Wednesday will
  have the best coverage with a few late afternoon storms
  possible.

- Elevated fire weather conditions will develop across the far
  eastern plains of Colorado on Wednesday. Another round of
  elevated to critical fire weather conditions possible for
  portions of the plains, especially the Cheyenne Ridge, North
  Park and South Park on Thursday.

&&

.DISCUSSION /Through Tuesday/...
Issued at 234 AM MDT Wed May 13 2026

After a relatively "cool" day on Tuesday, warmer temperatures will
return on Wednesday as the well-advertised upper level ridge shifts
east. The axis of the mid-level thermal ridge is progged to be over
Colorado by this afternoon, with 700-mb temperatures reaching up to
14-15 dg C. Hi-res guidance has continued to indicate temperatures
reaching up to 90F at DEN, however incoming cloud cover could keep
temperatures just shy of 90 dg.

Elevated fire weather conditions are possible today for portions of
the high elevations and far eastern plains. Increasing southwest
flow aloft with an upper level shortwave passing over Idaho/Montana
will lead to breezy conditions across the mountains. Relative
humidity values are expected to fall in the low teens for North Park
and Middle Park in the afternoon. However, winds should stay below
25 mph throughout the day, only periodically gusting stronger. For
the far eastern plains, lee-cyclogenesis will promote southerly
winds gusting up to 35 mph throughout the afternoon. However, some
low-level moisture will be advected into the eastern plains, keeping
relative humidity values around 20%. For these reasons, have held
off on any fire weather highlights at this time.

Another concern for Wednesday will be a round of virga showers (and
possibly a few weak thunderstorms). CAMs show the best potential
for convection for the Front Range and adjacent plains this
afternoon. Despite the best instability located northwest of the
forecast area (more towards Idaho/western Wyoming), DCAPE values
of 1200-1500 J/kg will support outflow winds up to 50 mph with the
stronger storms.

On Thursday, another round of elevated to critical fire weather
conditions is likely across the mountains and northern plains.
The upper level shortwave will pass north of Colorado, leading to
a more westerly flow aloft. Models indicate cross-barrier flow
increasing to 40-50 kts, particularly over northern Colorado. This
will lead to gusty winds over the mountains and off the Cheyenne
Ridge. With relative humidity values expected to drop between
9-12%, have decided to issue a Fire Weather Watch for North Park
and portions of the northern plains, as those locations will see
the combination of low RH and strongest winds. South Park will
likely see elevated fire weather conditions as well, however have
held off on any highlights for that area as wind speeds remain
uncertain at this time. There is still some uncertainty with fuel
status, particularly for North Park, so the decision to upgrade to
a Red Flag Warning will be dependent on if green-up has occurred
or not.

Above normal temperatures are forecasted to last through the
weekend, with mostly dry conditions set in place. Daily elevated
fire weather conditions are possible with a dry airmass in place,
however winds don`t look as strong compared to Thursday. A pattern
shift is looking likely by Sunday and into early next week as models
try to resolve an upper level disturbance, bringing measurable
precipitation to the Front Range and portions of the plains Sunday
and Monday. NBM PoPs have increased to 40-60% chance for both days.
This seems reasonable at this time, given that model guidance has
come into better agreement on the evolution of the upper level
shortwave. With the passage of this system, expect cooler
temperatures on Monday, with ensemble guidance indicating highs in
the low 60s!

&&

.AVIATION /12Z TAFS through 12Z Thursday/...
Issued at 516 AM MDT Wed May 13 2026

VFR conditions expected through the TAF period. Lighter southwest
winds will slowly take place in the next hour or so for DEN and
APA, while BJC should continue to see light northwest winds. As
the convergence zone shifts east, light (generally under 10 kts)
and VRB winds will take place by mid-morning. There is some
uncertainty in regards to wind direction after that, with guidance
either keeping VRB winds through the early afternoon, or
transitioning to an easterly component. It will likely depend on
how the cyclone evolves north of DEN.

Virga showers and isolated thunderstorms are still possible this
afternoon, however there is still some uncertainty with where the
storms set up and how numerous they will be. Due to the
uncertainty, have kept the PROB30 for all terminals (with an
earlier start time for APA and BJC, 20Z-21Z). If a high-based
shower were to materialize, gusty VRB outflow winds are expected.

Behind the convection this evening, winds should transition to
drainage flow by 03Z/04Z. However, BJC could see southeasterly
winds tonight instead of light southwest winds.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Fire Weather Watch from Thursday morning through Thursday
evening for COZ211-238-242-248-250-251.

&&

$$

DISCUSSION...MAI
AVIATION...MAI

NWS BOU Office Area Forecast Discussion