Lyons, Colorado Weather Forecast Discussion

465
FXUS65 KBOU 061731
AFDBOU
Area Forecast Discussion
National Weather Service Denver/Boulder CO
1131 AM MDT Mon Oct 6 2025
.KEY MESSAGES...
- Scattered rain showers in the foothills and I-25 Corridor this
  afternoon and evening. A few snow showers possible over the
  mountains
- Cool Tuesday with some partial clearing.
- Above normal temperatures return for Wednesday and continue
  through Saturday.
&&
.DISCUSSION /Through Sunday/...
Issued at 248 PM MDT Sun Oct 5 2025
Satellite shows clouds increasing along the Front Range in the
upsloping post-frontal airmass this afternoon. A few showers were
developing in the higher terrain, about as scheduled. KFTG 88D
Vad wind profiler now shows upslope has deepened to 10,000 ft MSL,
and there should be at least a little further deepening this
evening. However, speeds will remain relatively weak at 10-15 kts.
While moisture is relatively limited, there is weak QG lift and
continued upslope to overcome that. Thus, we do expect precipitation
to become more widespread during the evening hours with these
features in place. However, given the moisture limitations we
think this will remain an upslope focused event favoring the Front
Range north of I-70 (drier south). Finally, it should be noted
the right entrance region of a passing jet max and also some weak
frontogenesis could result in a couple of heavier bands, and
models seem intent in focusing on this from western Boulder County
into the Mummy Range - where higher elevations are expected to
see several inches of snow. Snow levels will be lowering with
further cool advection. The northern Front Range Foothills around
Red Feather Lakes should see snow levels drop to 8,000 feet later
this evening, but only to around 9,000 feet farther south toward
the I-70 Corridor. Thus, most impacts will be to the higher passes
including Cameron Pass and Trail Ridge Road in RMNP (the latter
already pre-emptively closed). Also, couldn`t rule out some
slushy roads along higher elevations of the Peak to Peak Highway.
Precipitation intensity is expected to decrease overnight as the
upslope component weakens, but a weak and shallow upslope
environment means we`ll likely see areas of light drizzle linger
into Monday morning. Low clouds and weak upslope will stick around
for the day, resulting in chilly conditions with high temperatures
only reaching the lower to mid 50s on the plains, and a few spots
may see temps not even hitting 50F!
We`ll have another chance of showers redeveloping Monday
afternoon, but overall the forcing seems weaker than tonight.
There is a hint of a jet streak but frontogenesis seems limited.
That said, a few models were showing another banded precipitation
even sneaking out of the foothills and across Denver metro for the
evening hours. We have increased PoPs a bit for this.
The low clouds are likely (70-80% chance) to hold in Monday
night, limiting and frost or Frost Advisory potential. Then slight
warming should occur Tuesday, before a stronger warming trend
still occurs for Wednesday through the end of the week. Overall,
temperatures will be several degrees above normal Wednesday
through next weekend. Chances of precipitation will hold off until
the end of the week (Friday and beyond), and even then most
chances would be confined to the mountains as we`ll be under the
influence of ridging and southwest flow aloft. The confidence of
this decreases toward Sunday as ensembles differ on speed of the
next weather disturbance.
&&
.AVIATION /18Z TAFS through 18Z Tuesday/...
Issued at 1131 AM MDT Mon Oct 6 2025
Low clouds to persist through tonight with ceilings mainly 1500
to 3000 feet. We may see some brief improvement this afternoon
with ceilings up to 4000 feet. Rain showers and lower ceilings
will be possible 21-04Z. The PROB30 covers this well. Winds to
turn northeast this afternoon through 00Z Tuesday. The winds are
then expected to turn to the southeast 02-04Z and stay southerly
through about 12Z Tuesday. A Denver cyclone is expected to form
and bring northerly winds after 12Z Tuesday, which may lower
ceilings below 1500 feet.
&&
.BOU WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
DISCUSSION...Barjenbruch
AVIATION...Meier

NWS BOU Office Area Forecast Discussion