589
FXUS65 KBOU 250006
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
606 PM MDT Wed Jun 24 2026

.KEY MESSAGES...

- Numerous strong to severe thunderstorms expected today for the
  lower elevations, particularly late afternoon through tonight.
  Strongest storms may produce very large hail exceeding 2-3" in
  diameter.

- Additional round of strong to severe thunderstorms possible Thursday.
  Localized flash flood concerns will exist both Wednesday and
  Thursday.

- Critical fire weather conditions this afternoon in the mountains
  given warm, dry and breezy weather and the potential for
  isolated dry thunderstorms. Notably higher fire danger will
  develop this weekend as hotter and windier weather returns.

&&

.DISCUSSION /Through Wednesday/...
Issued at 147 PM MDT Wed Jun 24 2026

A rather conditional severe weather threat still exists across
most of the I-25 corridor and eastern plains this afternoon.

A broad belt of westerly/west-northwesterly flow aloft is evident
via GOES water vapor imagery and recent RAP analysis data.
Meanwhile, a well-defined surface boundary stretching from KAPA
through KDEN and into southeastern Weld County. While this
boundary has produced more of a shear zone than a true convergence
zone, there`s been plenty of differential heating along the
boundary. With the DEN ASOS on the "warm" side of the boundary,
we`ve seen T/Td reach 89/55F, with temperatures in the upper 70s
to low 80s across the western Denver metro.

At this point, it appears likely that we`ll see a first attempt at
convective initiation somewhere along the surface boundary in the
next couple of hours, with better probabilities of sustained
convection closer to Fort Morgan/Sterling. A recent ACARS
sounding, modified to the latest DEN observation suggest only
meager capping at 700-600mb remains, with ACARS and RAP
Mesoanalysis showing a fairly broad area of >3000 MLCAPE
stretching along and south of I-76. Combined with impressive deep
layer shear, any thunderstorms that can develop this afternoon
should quickly become strong to severe, with primarily a large
hail threat. Hodographs have slowly become more curved as the
low-level flow has increased, though overall hodographs are still
relatively straight-line and would favor splitting supercells with
the initial round of convection today. Still, there would be at
least a brief tornado threat, especially closer to any boundary
where sfc vorticity and effective SRH would be maximized.

A second round of thunderstorms is expected to develop in Wyoming
and move into our forecast area sometime between about 6-10 PM.
This should primarily be north and east of the metro (where SPC`s
enhanced risk is). I would expect this to be the more significant
of the two waves of convection given a weakening cap and rather
impressive skew-t/hodograph combinations advertised by the WoFS.
While again this threat appears to be mainly north/east of the
I-25 corridor, we can`t completely rule out strong to severe
storms this far west. Any sort of additional push of moist outflow
may be enough to break the remaining cap here, which has been
shown on and off by various high resolution models. We`ll see if
any more meaningful trends emerge this afternoon but the threat in
the Denver metro is highly conditional.

A more organized round of sub-severe showers and thunderstorms is
likely overnight tonight as a shortwave moves across the region.
There could still be a strong storm or two left depending on how
much instability lingers overnight, but the severe threat should
diminish quickly after midnight. A combination of some showers,
stratus, fog/mist, and haze from wildfire smoke will likely
develop overnight and linger into Thursday morning.

The shortwave should move across the area through Thursday, with a
cooler/more stable airmass behind it. There should still be widely
scattered showers and thunderstorms in the afternoon, though any
severe potential will be determined by how quickly things can
destabilize following the morning stratus/fog.

Drier southwesterly flow aloft should develop by Friday, leading
to less convection across the region. The warming/drying trend is
likely to continue into the weekend as a strong upper trough
advances into the Pacific Northwest region during the weekend.
Strengthening mid/upper level flow is expected to bring gusty
winds to most of the forecast area, with the strongest winds over
the higher elevations. The combination of above normal
temperatures, a dry airmass, and gusty winds will likely lead to
critical fire weather conditions across a large portion of the
forecast area... and Fire Weather Watches may be necessary soon.

Little change is expected in the longer term forecast period as
dry southwesterly flow aloft continues.

&&

.AVIATION /00Z TAFS through 00Z Friday/...
Issued at 552 PM MDT Wed Jun 24 2026

The DCVZ has been setup near KDEN for the entire afternoon and
has now sloshed back to the east and northeast of KDEN bringing
northwest winds for the time being. Some northeast winds could
start to make it into KDEN in the next hour or so given the
cyclone`s movement.

Short-term models remain in pretty good agreement that
precipitation will likely occur at least near all three sites this
evening. The latest WoFS runs and CAMs show rapid thunderstorm
development between now and 2z just to the north of KDEN and
moving to the south. Thus, we have now added a tempo group between
1z and 4z at KDEN and KAPA (with slightly later timing) to show
the increasing confidence of thunderstorms during this time
period. Thunderstorms could linger and/or redevelop through at
least 8z. Gusty outflow winds of at least 30 kts will continue to
remain possible with any storms near KDEN and KAPA especially.

Low ceilings/fog/haze/light rain are likely to develop overnight
and could last well into tomorrow morning. Ceilings could drop to
as low as about 005 generally after 10z. By tomorrow afternoon,
showers and thunderstorms should return to the area, but questions
remain on how unstable the atmosphere will be given the low
clouds likely keeping temperatures at bay at least in the morning.
Have added in a prob30 for -tsra the early afternoon for now at
all three sites.


&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning until 6 PM MDT this evening for COZ211>214-217-
218.

&&

$$

DISCUSSION...Hiris
AVIATION...MV

NWS BOU Office Area Forecast Discussion