696
FXUS65 KBOU 041829
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1229 PM MDT Sat Oct 4 2025

.KEY MESSAGES...

- Becoming windy most areas Saturday with elevated fire weather
  conditions.

- Showers and a few storms graze the high country tonight, but
  become more numerous Saturday. A dusting of new snow likely
  (70%) for the mountains into Saturday evening.

- A few strong to severe storms over the northeastern plains
  Saturday pm, with the main threat damaging winds.

- Cooler Sunday through early next week...but warmer temperatures
  likely to return by mid/late week.

&&

.UPDATE...
Issued at 522 AM MDT Sat Oct 4 2025

Main shortwave trough continues to spin over far eastern
Nevada/southwestern Utah this morning, and this trough is expected
to lift out into Wyoming by tonight... bringing some active
weather to most of the region.

No significant changes were needed overnight, but there were a few
minor changes. First, the timing of showers/thunderstorms looks to
be just a little earlier than previously expected, and some PoP
adjustments were made to reflect that. Overall the chance of a
storm in the Denver metro is still fairly low (~30%), with higher
chances across the northern mountains into the Cheyenne Ridge.
Can`t argue with the SPC Marginal Risk over the northern half of
the CWA given the impressive kinematic fields, though I`m not
convinced we`ll have the right balance of instability/shear to get
more than a couple of gusts of wind.

Sunday still looks to be much cooler as a secondary cold front
backs into the area. Guidance has remained relatively consistent
with the upslope potential Sunday night, with fairly good odds of
>0.10" of QPF across the northern Front Range and I-25 corridor...
though the upslope/moisture combo doesn`t stick around for too
long Sunday evening/night.

&&

.DISCUSSION /Through Friday/...
Issued at 215 PM MDT Fri Oct 3 2025

Southwest flow will strengthen through Saturday as an upper level
low moves east across the Great Basin, and then ejects northeast
into Western Wyoming Saturday afternoon. 700 mb winds increase to
35 kts, so the windier areas (mountains, Palmer Divide, and
eastern plains) should see peak gusts of 35-40 mph as the airmass
will become well mixed by afternoon. Farther north (roughly from
Boulder - Fort Collins), winds will be slower to establish
themselves and in fact quite likely may not through most of the
day given some blocking and even potential for a backdoor cold
front. Regarding shower and storm chances, the increasing QG
forcing will aid development through the day, with the highest
coverage in the mountains spreading to the northern border area
where moisture is not as limited. Farther south and southeast
across the plains, it will be drier but still a low chance of a
high based shower/storm. However, given the strength of the
environmental flow and DCAPE near 1000-1100 J/kg, any high based
shower/storm will be capable of producing severe wind gusts to 60
mph. SPC has a Marginal Risk for now and that looks good, although
I wouldn`t be surprised to see that expanded a bit considering
synoptic scale lift to aid coverage.

Temperatures turn cooler behind passage of the cold front late
Saturday afternoon and evening, with winds turning more
west/northwest. The colder temperatures should allow for a dusting
of snow (<1") in most of the mountains before drier air pushes in
overnight.

For Sunday, we`ll be much cooler with highs in the 60s across the
plains as cool high pressure builds in from the Northern High
Plains. We`ll stay dry most of the day, but by late afternoon and
evening, a persistent and deepening easterly flow should support
shower development in/near the northern Front Range. Most
precipitation forecast right now is north of I-70, and amounts
mostly light (less than 0.2"). Snow levels are expected to drop to
around 8,500-9,000 feet with a light dusting above that.

The cooler weather will stick around through Monday and Tuesday.
While deterministic forecasts show highs in the lower to mid 60s
both days, there`s a 35-45% chance the plains and I-25 Corridor
stay 60F or cooler Monday.

Moderation then starts with a gradual warming trend offered up in
the ensembles by Wednesday with slightly above normal temperatures
then expected through the end of the week. The warmer
temperatures, and drier forecast, would be supported by good
agreement that upper level ridging will dominate our weather for
the Wednesday through Friday period.

&&

.AVIATION /18Z TAFS through 18Z Sunday/...
Issued at 1151 AM MDT Sat Oct 4 2025

Winds have steadily increased through the morning, with a
persistent southerly component in place across the TAF sites.
ACARS soundings show mixing is well underway with 35-40kt winds
measured at the top of the mixed layer. Still expecting convection
across the TAF sites this afternoon capable of producing VRB wind
gusts between 40-45kts. Hi-res guidance suggests one line of
storms will pass across the area between the 20-24Z time frame,
with winds diminishing after they depart to the east.

There are some uncertainties with what winds will do this evening
behind the line of convection. The current TAF depicts winds
shifting to the west and gradually weakening through the evening
before settling into drainage by 5/6Z. The latest hi-res guidance
is suggesting that there will be a more northerly push beginning
to make its way from north to south across the TAF sites around
1Z to 3Z before turning to drainage. If the northerly scenario
plays out, expecting winds to be much lighter (5-9kts).
Additionally, winds at KBJC may become more ESE and remain under
10kts between the 4-9Z if the westerly winds don`t win out.



&&

.FIRE WEATHER...
Issued at 215 PM MDT Fri Oct 3 2025

Southwest winds will increase Saturday, with gusts to 35-40 mph
expected across the mountains, high valleys, Palmer Divide, and
eastern plains (winds will be lighter through much of the day
Boulder - Ft Collins).  Fuels showed relatively mixed
susceptibility per latest info from land managers. Winds will
certainly reach critical levels but forecast minimum humidity is
forecast so stay above 15%, and in most locations 20% or higher.
Given the mixed fuel status and marginal humidity, we`ll hold off
on any Red Flag Warnings at this time. Still something to monitor
and take note of though given strength of winds.

&&

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

&&

$$

UPDATE...Hiris
DISCUSSION...Barjenbruch
AVIATION...Bonner
FIRE WEATHER...Barjenbruch