859
FXUS65 KBOU 171905
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
105 PM MDT Thu Jul 17 2025

.KEY MESSAGES...

- Scattered showers and storms, mainly across Park County and the
  Palmer Divide.

- Active pattern continues into the weekend, with scattered
  afternoon showers and storms each day. Higher chances for rain
  across the Front Range mountains and foothills.

- Warmer and drier trend for early next week.

&&

.DISCUSSION /Through Thursday/...
Issued at 105 PM MDT Thu Jul 17 2025

Best chance for showers and thunderstorms through this evening
will be across Park County and eastward across the Palmer Divide.
Heavy rain, small hail and wind gusts to 50 mph will be possible
with the stronger storms. To the north across the higher terrain,
it will be drier with less instability. Showers and storms here
will be isolated and weaker. Isolated showers/storms are still
possible for the urban corridor and eastern plains. Convection
then comes to an end this evening as the airmass stabilizes.

For Friday, scattered showers and thunderstorms form over the
higher early afternoon and then spread eastward across the plains
through mid evening. Instability is somewhat limited, less than
800 J/kg, so storms are expected to stay sub-severe. However,
DCAPE values reach 1000-1500 J/kg, so can`t rule out a couple
strong to severe wind gusts. Precipitable water values are near
normal, so brief heavy rain will be possible from the stronger
storms.

Southwest flow aloft will prevail around an upper level high over
the south central and southeast part of the county this weekend.
Appears there is a shortwave trough embedded flow aloft for
Saturday. Precipitable water values will be 120-140% of normal, so
we should see a decent amount of showers and thunderstorms
Saturday afternoon and evening. As far as severe weather goes,
there will be a ribbon of better low level moisture and
instability across the plains. Some models keep it over far
eastern Colorado, while the NAM brings this moist and unstable
airmass westward to the foothills over northern Colorado. So this
will be something to watch for the next couple of days.

We slowly begin our warming and drying trend on Sunday. Moisture
decreases a little, but enough is expected to bring isolated to
scattered showers and thunderstorms during the afternoon.
Temperatures will warm a few degrees with high temperatures mainly
in the lower 90s across northeast Colorado.

For early next week (Monday and Tuesday), the upper level high
over the southern part of the country retrogrades westward. Across
Colorado, 500mb heights increase, leading to warmer temperatures.
Decent agreement between the ECMWF and GFS ensembles that drier
moves into the area with precipitable water values falling below
normal (60-90% of normal). Chances for showers and storms will be
low, with mainly high based showers/storms over the higher terrain
both days. High temperatures climb into the mid to upper 90s
across northeast Colorado.

For Wednesday and Thursday, the high is expected to drift
slightly eastward, leading to an increasing southwest to southerly
flow aloft. This will increase subtropical moisture over the area
leading to a better chance for showers and thunderstorms. Highs
are expected to take a step back with readings in the lower 90s
across northeast Colorado.

&&

.AVIATION /18Z TAFS through 18Z Friday/...
Issued at 105 PM MDT Thu Jul 17 2025

VFR to prevail through tonight and Friday. Will continue with the
prob30 for thunderstorms 23-02Z. The better chance for storms
will be south of Denver and will go with a tempo for storms at
APA. As far as winds go, weak northerly winds turn east to
southeast towards 21Z. Winds increase and shift southerly with
gusts to 30 knots around 00Z Friday. These gusty winds linger
through the evening hours before decreasing after 06Z. For
Thursday, weaker northerly winds are expected by 16-18Z. Scattered
afternoon showers and thunderstorms should develop with about a
30 percent chance one moves across an airport.

&&

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

&&

$$

DISCUSSION...Meier
AVIATION...Meier