Boulder, Colorado 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

622
FXUS65 KBOU 250702
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
102 AM MDT Fri Apr 25 2025

.KEY MESSAGES...

- Severe threat winding down this evening.

- Cooler tonight through Friday with light rain showers/drizzle.

- Critical fire weather conditions Monday afternoon for the
  eastern plains.

- Mild and dry next week.

&&

.UPDATE...
Issued at 547 PM MDT Thu Apr 24 2025

Severe storm threat is diminishing as storms continue to push
east into a slightly more stable and capped environment on the
eastern plains. Still a low end threat for the next hour or so
(mainly into Lincoln County) but radar is starting to show these
trends already underway. There has been some redevelopment back
into the I-25 Corridor, but additional rounds that do develop will
be in an environment where most instability has been used up.
Still unsettled through the evening with scattered showers, but
thunderstorm coverage and intensity is on the wane.

&&

.SHORT TERM /Through Friday/...
Issued at 147 PM MDT Thu Apr 24 2025

Southwest flow aloft will prevail while an east-southeast low
level flow advects moisture into eastern Colorado. This has
resulted in mostly cloudy skies and cool temperatures over most of
the eastern plains with a stable airmass in place. The increase
in moisture made it to the urban corridor with dew points in the
40s. Skies were mostly sunny this morning allowing temperatures to
reach the mid 60s to lower 70s. RAP model continues to show
MLCAPE of 1000-1500 (J/kg) across the urban corridor and nearby
plains. A cyclone has formed over the south part of the Denver
area. Along this convergent boundary we are seeing towering
cumulus and should see storms form along it by mid afternoon.
Additional storm development is expected over the northern urban
corridor mid to late afternoon. Large hail, up to golfball size
will be the main threat. Isolated wind gusts to 60 mph and a brief
tornado will also be possible. Storms will weaken as they head
into a less unstable airmass over the eastern plains.

The threat for severe storms will end early to mid evening as the
airmass stabilizes. However the chance for showers and
thunderstorms will continue through the evening, mainly over
northern Colorado behind a cold front pushing south into the area.
Showers and storms end by midnight as the colder air behind the
front stabilizes the airmass. Moisture and colder air moving into
northeast Colorado will saturate the airmass leading to low
clouds, fog, and drizzle after midnight and into Friday morning.

Easterly low level flow will keep low clouds with areas of fog
and drizzle going for much of Friday morning, and perhaps into the
afternoon in and near the foothills due to upslope flow. Highs
will be chilly with upper 40s to lower 50s across northeast
Colorado. This will stabilize the airmass over the foothills and
eastward. The mountains become slightly unstable with MLCAPE
climbing to 500 (J/kg). This is expected to lead to widely
scattered showers and thunderstorms over the mountains. As the
convective tracks eastward and encounters the cool and stable
airmass, the showers and storms are expected to dissipate.

&&

.LONG TERM /Friday night through Thursday/...
Issued at 147 PM MDT Thu Apr 24 2025

Broad but relatively weak southwesterly flow aloft will
overspread the region on Saturday ahead of a closed upper low
moving into California, entraining enough mid-level moisture in
the afternoon to support isolated to scattered afternoon
showers/thunderstorms, generally favoring the higher terrain. At
the surface, healthy southerly winds will promote ample warm
advection, returning temperatures to above normal values region-
wide.

As the low lifts northeast through the Great Basin, southwest
flow along its leading edge will increase into Sunday, helping to
push highs potentially into the 80`s for the lower elevations,
with limited change for the high country. Precipitation chances
will be buffered substantially under much drier low-levels.
There`s growing confidence in critical fire weather conditions
across a broad portion of the forecast area for Sunday afternoon,
particularly the southern half where humidity will be lowest.

By Monday, the primary low is slated to transition into more of
an open wave, with a secondary low shearing off the southern tip
of the trough. It`s a messy pattern which inherently carries
greater uncertainty as far as how things play out through the
week, but for Monday we`ll at least be looking at considerably
cooler temperatures following a frontal passage and greater
afternoon precipitation potential, most pronounced in the
mountains. Our southern plains could hold onto some fire weather
concerns too depending on the frontal timing.

Details are fuzzier Tuesday onwards, with general west to
northwest flow prevailing aloft and potentially punctuated by a
few shortwaves and opportunities for spring-like convection most
afternoons, albeit there are no strong signals.

&&

.AVIATION /06Z TAFS through 06Z Saturday/...
Issued at 1159 PM MDT Thu Apr 24 2025

The low clouds and fog/mist are here for the night and DEN and APA
have visibility around 1 SM with ceilings around 200 feet. There
is not expected to be much change in these conditions tonight. BJC
currently has higher visibility and ceilings but conditions should
trend towards 1 SM visibility and around 200 foot ceilings there
as well. The question is, when does the fog go away and then when
do ceilings increase? The best estimate is that the fog will
dissipate between 13-16Z at all terminals. Ceilings will slowly
increase and then southeast winds may allow the ceilings to
increase out of IFR and even to VFR between 17-19Z. Models are
starting to disagree more with what happens during the afternoon
and evening hours Friday. Some keep low clouds over the terminals
and some have mostly clear skies. The recent trend towards
stronger southeast winds gives more confidence that less/higher
ceilings will last for much of the afternoon and evening. Friday
night, low clouds and mist are expected to fill in once again.
Neither visibility nor ceilings should be as low as tonight but
IFR conditions are a possibility.

&&

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

&&

$$

UPDATE...Barjenbruch
SHORT TERM...Meier
LONG TERM...Rodriguez
AVIATION...Danielson