Johnstown, Colorado 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

708
FXUS65 KBOU 150556
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1156 PM MDT Thu Aug 14 2025

.KEY MESSAGES...

- Moisture increases today and Saturday with a higher chance of
  thunderstorms. Strong, gusty outflow winds a threat with the
  storms.

- Slight cooling into this weekend, but still above normal
  temperatures through the week ahead.

- Drier weather again later this weekend through most of next
  week.

&&

.DISCUSSION /Through Thursday/...
Issued at 240 PM MDT Thu Aug 14 2025

Water vapor imagery indicates upper level moisture is increasing
from the southwest, and that will continue through tomorrow as
deeper moisture arrives from the Desert Southwest. Initially, the
low levels are very dry and warm, and with deep layer mixing
DCAPE has grown to 1700-1800 J/kg. These are impressive numbers,
so the main threat from any of these high based showers and storms
will remain strong, gusty microburst winds of 40-50+ mph. That
threat will continue through early evening. A couple gusts
reaching severe criteria will be possible especially as storms
push east across the plains where stronger/slightly more organized
downdrafts are expected with higher instability.

On Friday, there is good agreement that precipitable water (PW)
values finally climb to or just above normal levels, ranging from
near 100% over the plains to 120% over the mountains. 700-500 mb
specific humidity increases to 5-6 g/kg, not terribly impressive
but still better than today. It will still be quite warm and dry
in the low levels (highs mostly in the mid 90s), so storms will
still be high based. At least there`s a better chance of storms
with measurable rainfall due to the increased total column water.
The same can be said for Saturday, although temperatures cool
slightly but will still be just above normal levels. There is a
weak shortwave noted, but timing is uncertain and it could come
through too early in the day to support any appreciable uptick in
storm coverage.

By Sunday, the airmass is advertised to start drying again in the
wake of Saturday`s shortwave and slight building of the ridge. PW
values are expected to drop to slightly below normal again. Thus,
storm coverage and propensity for measurable rainfall would
decrease. Models are uncertain with moisture building on the
plains for Monday and Tuesday, but it appears there`s some chance
of storms both days - even as the upper level ridge retrogrades
and amplifies in the Central Rockies.

That upper level ridge is expected to continue to build and
retrograde slightly into western Colorado and Utah through
Wednesday and Thursday. This will bring higher confidence in fewer
storms and warming temperatures. There high confidence that high
temperatures will be several degrees above normal, pushing back
into the mid 90s on the plains and I-25 Corridor.

&&

.AVIATION /06Z TAFS through 06Z Saturday/...
Issued at 1133 PM MDT Thu Aug 14 2025

There will be light drainage winds tonight that will give way to
light and variable winds during the morning on Friday. The main
concern is gusty outflow winds from thunderstorms Friday
afternoon. With increased moisture and instability, coverage of
showers and storms will be higher on Friday. This means multiple
outflow boundaries moving across all airports is likely and gusts
above 40 knots are possible. These storms are not expected to have
much of an impact on visibility or ceilings.

Winds will weaken during the evening on Friday and become drainage
overnight.

&&

.FIRE WEATHER...
Issued at 240 PM MDT Thu Aug 14 2025

A couple dry thunderstorms have developed in the mountains early
this afternoon, and will likely continue into early evening. This
will keep the threat of new wildfires in place, especially
considering how dry the near surface environment is (RH in the
teens outside of storms). Also, gusty outflow winds will occur
with most showers and storms. We`ll keep the Red Flag Warning
going until 10 pm for the potential new wildfire starts due to dry
thunderstorms.

Friday will still be quite warm and dry in the low levels, but
mid and upper level moisture will increase further. Therefore,
showers and storms with hopefully wetting rains will become more
numerous. There`s still a chance that a couple storms could be
dry, but not enough coverage to warrant another Red Flag. Saturday
should feature one more day of better shower and storm coverage.
Then drier and warmer weather is expected for Sunday through much
of next week, but winds will remain light through this period.

&&

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

&&

$$

DISCUSSION.....Barjenbruch
AVIATION...Danielson
FIRE WEATHER...Barjenbruch