National Weather Service Forecast Discussion

Thornton Weather Forecast   
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361
FXUS65 KBOU 080826
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
226 AM MDT Mon Jun 8 2026

.KEY MESSAGES...

- Cooler temperatures today, but increasing risk of severe storms
  for portions of northeast Colorado. Considerable uncertainty in
  how temperatures affect convective evolution.

- More heat ahead, with the hottest temperatures Tuesday. Highs
  generally in the lower to mid 90s across the I-25 Corridor, but
  just shy of 100 over the northeast plains.

- Widespread critical fire weather conditions expected (>80%
  confidence) in fuel-prone areas by Tuesday, potentially (60%
  chance) lasting into Wednesday.

- Brief heat relief expected Thursday, before a more substantial
  cooldown for the weekend.

&&

.DISCUSSION /Through Sunday/...
Issued at 221 AM MDT Mon Jun 8 2026

Latest radar imagery shows convection ongoing over the far
northeastern counties into Nebraska. A cold (cool) front will push
through early this morning from north to south briefly causing
northerly winds to gust to around 25 mph at times. By late morning
into the early afternoon, winds will turn to be east to even
southeast. This will bring in some moist air from the I-25
corridor to the east with dewpoints expected to reach the 50s.

The biggest changes to this forecast include an increasing risk
for severe weather this afternoon. Isolated to scattered storms
are expected to initiate near the Denver metro around 1pm to 3pm.
The Storm Prediction Center has included nearly the entire I-25
corridor and plains in a slight (2/5) risk. MLCAPE values are
forecast to be around 1000 to 1500 J/kg for the I-25 corridor and
around 2000 J/kg for the eastern plains. 0 to 6 km bulk shear will
be around 50 kts. The greatest threat for today will be large
hail- 2 inches in diameter or larger. The aforementioned front
should stall somewhere near the Palmer Divide. Locations near this
feature could see enhanced low-level vorticity and the threat for
a tornado or two given that 0 to 3 km storm relative helicity
values could be around 100 to 200 m2/s2.

Once the storms move off to the east, they will organize into a
line and this will bring an increased wind threat for the eastern
plains. The severe threat will rapidly wind down between 6pm and
9pm from west to east across the area.

Something important to note is that the latest high resolution
model guidance is bringing this morning`s cold front in stronger.
This could cause significantly lower high temperatures for today,
especially in the northeast counties. For now, we generally have
temperatures in the low to mid 80s for the plains, but some
locations could struggle to reach the 80s. Additionally, morning
stratus across the area could limit high temperatures. Thus, we
will be monitoring the strength of the cold front and any morning
clouds. The cooler temperatures could result in a stronger cap,
which could in turn lower the risk for severe storms if this
scenario plays out.

For Tuesday, we will quickly transition back to hotter and drier
conditions given SW flow aloft and downsloping winds. High
temperatures will reach the mid to upper 90s. The record high at
Denver International Airport is 95 F, which would be within reach.
Overall, ensemble guidance has continued the trend of running
cooler than the deterministic models, which are showing high
temperatures on Wednesday much higher for the eastern plains.
Elevated to critical fire weather conditions are possible. See the
Fire Weather Discussion for more details. Another weak cold front
will move through on Tuesday night.

Wednesday could be another day to watch for elevated to critical
fire weather conditions. Highs on Wednesday will be a few degrees
"cooler" than Tuesday, but will still be around 90 degrees for the
plains. A stronger cold front will move through on Wednesday
night, briefly dropping high temperatures for the plains into the
80s. Zonal flow aloft will be in place for the remainder of the
week with high temperatures generally in the upper 80s to low 90s.
The next decent chance for any measurable precipitation could
come on Saturday with a trough moving in from Canada. We continue
to see trends in model guidance that more seasonable temperatures
could occur for the end of the weekend into early next week.

&&

.AVIATION /06Z TAFS through 06Z Tuesday/...
Issued at 1201 AM MDT Mon Jun 8 2026

Winds are attempting to turn more northwesterly and should stay
that way or just be light and VRB through about 13Z. Then we
expect a frontal passage with shot of increasing N-NE winds, and
some stratus potential. There`s about a 30-40% chance we go BKN
around 1000 feet given upstream moisture profiles but rather late
arrival of the front after sunrise. However, if front is earlier
or stronger, then the chance of MVFR ceilings will be higher
13Z-17Z, so something to watch closely.

Next challenge will be thunderstorms. Again, this largely depends
on the strength of the front and extent of stratus. At this point
the greatest risk for storms is expected to be mainly south of
KDEN, so we`ll maintain the PROB30 from 21Z-24Z at KDEN and KBJC,
but added TEMPO to KAPA given closer proximity to where we think
convective initiation will occur. There is potential for a severe
storm if we build enough heat and instability. East winds will
turn more E-SE ahead of storm development and then hold (outside
of storm influences) through about 06Z. Then winds are expected to
turn more southerly and keep most threat of any stratus or fog
development tonight outside of the Denver area TAF sites. Only
about a 20% probability at this time.

&&

.FIRE WEATHER...
Issued at 221 AM MDT Mon Jun 8 2026

Elevated to critical fire weather conditions are possible for
Tuesday and Wednesday across the area. A Fire Weather Watch
remains in effect for Tuesday afternoon. Winds could gust to 30 to
40 mph and relative humidity will drop into the upper single
digits and lower teens on Tuesday afternoon. The fuel status is
still a bit uncertain given the recent precipitation across the
area- we hope to get updates from our partners today to help
decide if a Red Flag Warning will be warranted. Wednesday could be
another day to watch for elevated to critical fire weather
conditions with winds and relative humidity forecast to be similar
to Tuesday. Spotty elevated to critical fire weather conditions
remain possible on Thursday and Friday given the expected low
relative humidity and a few hours of gusty winds each afternoon.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Fire Weather Watch from Tuesday afternoon through Tuesday
evening for COZ238>251.

&&

$$

DISCUSSION...MV
AVIATION...20
FIRE WEATHER...MV

NWS BOU Office Area Forecast Discussion