Louisville, Colorado 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

737
FXUS65 KBOU 222033
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
233 PM MDT Fri Aug 22 2025

.KEY MESSAGES...

- Cooler, wetter pattern through most of next week.

- Locally heavy rain from a few storms tonight, Saturday, and
  Sunday, but every day provides unique forecast challenges.

- More widespread showers and storms Monday, some with heavy rain
  and localized flooding potential.

- Active weather remains through much of next week, with scattered
  showers and storms each day - most numerous over the mountains.

&&

.DISCUSSION /Through Friday/...
Issued at 233 PM MDT Fri Aug 22 2025

Satellite and radar show one shortwave and area of convection
moving across the Front Range early this afternoon, a bit too
early to support more widespread and stronger storms. In addition,
the cold front that moved through earlier today packed more of a
cooling punch, limiting instability. That said, there`s still
forcing that will push east across the plains into the evening
hours. It appears the main threat of any severe storms would be
shifting far southeast where stronger surface heating occurred.
That`s essentially along and south of the frontal boundary
extending across southeast Elbert, Lincoln, and southeast
Washington Counties. Meanwhile, precipitable water values are
still climbing as dewpoints have pushed into the upper 50s and
lower 60s over most of the plains. So even though other showers
and storms won`t be as intense, they will still be capable of
producing locally heavy rain. They just appear smaller and thus
won`t last as long in any one given area.

For overnight and into Saturday morning, the amount of
instability weakens, but we`ll still have a threat of locally
heavy rain from any showers/storms as the lower atmosphere becomes
nearly moist adiabatic in the low levels and warm cloud depths
deepen. The CAMs are all over the place and very little agreement
(some with stronger storms this evening, others with heavier
showers/storms overnight, and still others like the HRRR with
heavy rain on the plains Saturday morning). At this point,
there`s very low confidence in any one solution. As a result,
we`ll keep a rare but needed extended period of rain chances in
the forecast overnight through Saturday morning.

By Saturday afternoon, the airmass is actually expected to
stabilize on the plains and I-25 Corridor with a capping
inversion and some drying/stabilization aloft. The expected
morning stratus/showers will limit warming and thus the cap should
be able to hold strong through the afternoon and limit any
redevelopment. The mountains should fare better, but probably only
along a relatively narrow sweet spot of moisture and instability
along the Front Range mountains and Park County. Meanwhile, it
stays drier over much of Grand and Jackson Counties. Some of the
showers/storms will still have a reasonable chance to push onto
the adjacent plains late in the day or evening.

Sunday appears to become more active again as the low level
airmass is expected to recover and destabilize. There`s still
quite a bit of uncertainty here, but all ingredients will be in
place for stronger/a few severe storms and locally heavy rainfall.
MLCAPE should grow to 800-1500 J/kg, with sufficient bulk shear.
We`ll have more on the potential for heavy rain and flooding in
the Hydrology section of this discussion.

The greatest risk of heavy rainfall and localized flooding issues is
still expected to occur Monday. There is still good agreement in
the ensembles that this is the day when all heavy rain/flash flood
ingredients come together. Those include; 1) PW increasing to
around 1.25", or 150-200% of normal and near climatological
maximums. 2) moist adiabatic/skinny CAPE profiles, 3) Deep warm
cloud depths potentially as deep as 8,000 ft, and 4) sufficiently
slow storm motions of 15-25 mph, but just enough shear/upslope to
keep storm cold pools (as weak as they may be) balanced with
storm motion. It still appears the heavier rain threat should be
shifting slowly south/southwest of our forecast area through
Tuesday and Wednesday, but there is still some uncertainty
depending on how progressive the trough/ridge pattern is. It`s not
impossible the heavy rain producing storm threat doesn`t increase
again Thursday or Friday, but that could very well depend on a
shortwave or two riding across the top of a flattening ridge.

Temperatures will remain well below normal through the entire week
ahead. If more widespread precipitation and stratus does occur,
either Monday or Tuesday could end up with highs staying near/below
70F on the plains and I-25 Corridor. We are essentially a lock
for 70s or cooler those two days, and then only upper 70s to lower
80s at most in the lower elevations on all the other days in the
week ahead.

&&

.AVIATION /18Z TAFS through 18Z Saturday/...
Issued at 1044 AM MDT Fri Aug 22 2025

Cold front had pushed across the TAF sites, with enhanced NNE
winds behind it gusting to ~20 kts. Main concern today is
thunderstorms, the best chance of which still exists 22Z-03Z, but
give or take an hour due to stability concerns and faster arrival
of shortwave (see .Update section above).

Lower confidence still exists tonight into Saturday morning with
regard to any showers and storms. However, there is good agreement
for widespread stratus development after 06z, with IFR cigs
likely developing 09Z-16Z. Stratus should then slowly lift but IMC
conditions will likely persist through the day Saturday to due
abundant moisture and a lower stratocu deck. The highest chance of
rain on Saturday could be in the morning with weak but deep
upslope in place, rather than the afternoon when we actually
stabilize further.

&&

.HYDROLOGY...
Issued at 233 PM MDT Fri Aug 22 2025

For tonight and Saturday morning, locally moderate to heavy rain
will be possible even from the weaker convection on the plains and
I-25 Corridor. That is mostly supported by nearly moist adiabatic
lapse rates in a weakly forced upslope. For the most part, this
is a relatively shallow layer, however there is some chance
(30%) of deeper convection over the northeast plains that could
produce storms with 1-2"/hr rain rates as warm cloud depths grow
to ~5,000 feet. The potential for locally heavy rain Saturday
afternoon should be confined to a relatively narrow corridor from
the Front Range mountains into Park County.

Sunday will feature a chance of stronger storms and locally heavy
rainfall as well, and a little greater threat as long as
convective temperatures can be met. Precipitable water values
start to grow again after a decrease Saturday, and by Monday reach
150-200% of normal. Monday remains our main target day for
potential flash flooding day, as discussed above. There are still
questions regarding if sufficient instability will remain, but it
wouldn`t take much considering the other environmental
characteristics favorable for heavy rain - like warm cloud depths
potentially reaching 8,000 ft.

The main threat of locally heavy rain likely pushes back into the
mountains Tuesday and Wednesday, but still a small threat on the
plains.

&&

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

&&

$$

DISCUSSION...Barjenbruch
AVIATION...Barjenbruch
HYDROLOGY...Barjenbruch