971
FXUS65 KBOU 301746
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1146 AM MDT Mon Jun 30 2025

.KEY MESSAGES...

- Cooler today with storms focused over the southern foothills and
  South Park.

- Scattered thunderstorms and normal temperatures are expected for
  the Fourth of July.

&&

.UPDATE...
Issued at 216 AM MDT Mon Jun 30 2025

Best chc of tstms today will be mainly along and south of the I-70
mtn corridor and across the srn foothills.  A few strong storms may
occur over South Park and the srn foothills.  Storms will be rather
slow moving as well which may lead to localized flooding in a few
spots.

&&

.DISCUSSION /Through Sunday/...
Issued at 229 PM MDT Sun Jun 29 2025

Water vapor satellite shows a weak shortwave trough over Wyoming
with weak westerly flow aloft over Colorado. This flow and trough
are providing just enough lift and shear to allow for severe
convection in our area. The main reason for the strong to severe
storms in our area is due to moderate to strong instability with
surface CAPE values over 2,000 j/kg across the entire I-25
corridor and eastern plains with some areas above 3,000 j/kg
across the far eastern plains. This will support strong updrafts
and with just enough shear, a few storms may produce large hail
greater than an inch. It appears the may threat will end up being
severe wind gusts as strong storms will eventually merge into an
MCS once they get east of a line from Greeley to DIA. Wind gusts
up to 70 mph will be possible especially near Fort Morgan, Akron,
and Sterling.

The assumption is that the storms this afternoon and evening will
"work over" the environment such that strong storms are not
expected overnight tonight. Some slight chance PoPs were kept in
the forecast for the eastern plains since some high resolution
model data shows a few showers and storms. Having said that, the
QPF was largely taken out of the forecast for tonight.

On Monday, it appears there will be just enough low level
moisture to form stratus clouds in the morning hours across a good
portion of the I-25 corridor and eastern plains. With a strong cap
above the low level cool and moist air, it will take a very long
time for the boundary layer to mix out. Therefore, highs will
likely stay in the upper 70s across the I-25 corridor and plains.
Furthermore, it will likely be too stable anywhere from downtown
Denver and to the north and east for any showers and storms to
form so PoPs and QPF were lowered or taken out. Where it will
storm is over the southern foothills and Park County as the best
upslope flow and instability will be located there. Some of these
storms may produce heavy rainfall.

The center of a ridge aloft will be over Colorado on Tuesday and
Wednesday. Highs will warm up each day and there is good consensus
in the ensemble data that highs will reach the mid 90s across the
plains on Wednesday. SPC added an area of marginal risk for severe
weather across the far northeast corner of Colorado on Tuesday as
60+ degree dew points will create moderate instability.

Tropical moisture will be brought up to Colorado on Thursday and
Friday due to southerly flow. A trough will be roughly over
Arizona on Thursday and over eastern Colorado on Friday. The exact
timing of this trough will be very important to determine whether
Thursday will see widespread storms of if Friday will have
widespread storms. At this moment, models seem split roughly
50/50 so please stayed tuned to future forecast updates to get a
better idea of weather for the holiday.

&&

.AVIATION /18Z TAFS through 18Z Tuesday/...
Issued at 1146 AM MDT Mon Jun 30 2025

Stratus deck is breaking up on satellite as daytime heating occurs,
so further improvement is expected through 21Z with VFR
conditions developing. Any thunderstorms this afternoon and
evening should stay closer, if not totally confined, to the
higher terrain southwest of Denver as the low levels are quite
stable. Winds are starting light and variable, but should pick up
a more easterly diurnal component 20Z-24Z. Then look for a slow
return to normal south/southwest winds overnight into Tuesday
morning. High based showers and storms are possible Tuesday after
22Z (30% chance) so have included that for now. Gusty/variable
winds to 35+ kts will be the main threat to aviation.

&&

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

&&

$$

UPDATE...RPK
DISCUSSION...Danielson
AVIATION...Barjenbruch