613
FXUS65 KBOU 161838
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1238 PM MDT Sun Aug 16 2026

.KEY MESSAGES...

- Scattered thunderstorms expected this afternoon and evening. A
  few of them could become strong to severe, with strong winds,
  large hail, and heavy rainfall.

- Warming and drying trend for Monday and Tuesday, but still
  isolated gusty pm storms/virga.

- More active weather day shaping up for Wednesday with scattered
  severe thunderstorm threat.

- Warmer again through the coming weekend with above normal
  temperatures. Drier Thursday and Friday, but some monsoonal
  moisture likely returns by the weekend.

&&

.DISCUSSION /Through Sunday/...
Issued at 1238 PM MDT Sun Aug 16 2026

Rich, low level air remained in place across the plains this
afternoon. This along with daytime heating is building MLCAPE
into the 1000-1800 J/kg range. Local ACARS soundings still show a
pretty healthy cap in place, but we are warming and should at
least get close to convective temperatures. The most likely area
for convective initiation of course is over the mountains (already
ongoing), but also the higher terrain of the Palmer Divide and
Cheyenne Ridge. Storms will likely move in a southeasterly
direction once they develop, and a weakening cap is expected to
allow propagation across the plains and portions of the I-25
Corridor. Bulk shear will be increasing to 30-35 kts, so enough
shear and instability is present for a few supercells. Thus, large
hail and damaging winds will be a threat with any storms through
mid evening. It should be worth noting that we`ll be under the
right entrance region of an upper level speed max, so weak forcing
should help coverage a bit so we did bump pops up ever so
slightly, with the highest odds of storms over the northeast
plains and Palmer Divide. That upper level speed max could also
aid storms to last a bit longer into the evening than normal.

We still expect clearing skies overnight, and enough lingering low
level moisture for some patchy fog over the plains and in the
high mountain valleys.

Monday will feature warmer and drier weather as the ridge axis
retrogrades to the west-northwest. That puts our forecast into a
drier westerly flow aloft, and mid level temperatures will also be
warming. Highs are expected to reach the upper 80s to lower 90s
over the plains and I-25 Corridor. We`ll still likely have enough
lingering moisture and strong daytime heating to support isolated
late day convection. The airmass along the I-25 Corridor would be
more supportive of just isolated late afternoon/evening sprinkles
and microbursts as DCAPE grows to ~1500 J/kg. Similar weather
conditions although further warming of a few degrees is expected
for Tuesday. Also, a late afternoon frontal passage will likely
be enough to support growing high based shower/storm coverage into
the Tuesday evening and overnight hours.

Wednesday is still on track to be slightly cooler with increased
chances of storms again as the post frontal airmass will be cooler
and more moist. Average MLCAPE from various models suggest
1000-2000 J/kg, while bulk shear is an impressive 40-50 kts so a
growing severe storm threat will be in the picture.

Thursday and Friday are shaping up to be drier again as the ridge
amplifies, this time across Colorado and eastern Utah. That means
a stronger thermal ridge and high temperatures pushing well above
normal...into the lower to mid 90s across the plains and I-25
Corridor. While the ridge should hold fairly steady across the
Central Rockies through at least next weekend, ensembles have good
agreement for an increase in monsoonal moisture under the ridge.
That would support a return to scattered afternoon and evening
shower/storms as well, with the greatest chances holding over the
mountains at least until early next week.

&&

.AVIATION /18Z TAFS through 18Z Monday/...
Issued at 1136 AM MDT Sun Aug 16 2026

As of 1745z, cumulus clouds are starting to build in the
mountains and the foothills to the west of the three sites with a
scattered deck pushing into KBJC. There is still a cap in place as
seen on ACARS soundings and radar is just starting to show some
returns in Park County. Given the fog that was in place this
morning as well as the cap still in place, we have held off on the
PROB30 from starting until 22z at KDEN and then lasting until
about 3z. Gusty winds, lowering ceilings, and heavy rainfall
(briefly limiting visibility) are possible from any storm that
passes near or directly over the TAF sites. Some CAMs are showing
showers and thunderstorms lingering a bit after 3z, but confidence
is low in this scenario at this time.

There is also some uncertainty on the winds tonight. For now, we
have gone ahead with an E to SE wind this evening before winds
turn to drainage by about 7z. Several CAMs depict outflow
boundaries from storms to the east moving through the metro early
this evening potentially affecting KAPA and KDEN. If this were to
occur, winds could shift more to an east or northeast direction
and briefly gust to around 20 kts.

For tomorrow, winds will start to turn clockwise before settling
on a northeast direction early in the afternoon. Model soundings
show DCAPE values reaching up to 1,500 J/kg and some mid-level
moisture lingering. So, we expect the possibility of virga showers
and dry microbursts starting around 21z and lasting through the
early evening (potentially a bit after the TAF period). These
could bring gusty winds and ceilings lowering to about 12,000 ft
AGL with little to no rainfall expected. Have now included a
PROB30 for this possibility.

&&

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

&&

$$

DISCUSSION...20
AVIATION...MV

NWS BOU Office Area Forecast Discussion