237
FXUS65 KBOU 162357
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
557 PM MDT Thu Oct 16 2025

.KEY MESSAGES...

- Patchy frost Thursday night for the Palmer Divide, Lincoln
  County, and potentially portions of Weld County.

- Seasonably cool (though slightly milder Sunday), with breezy
  winds most days through Monday, wand limited potential for any
  precipitation.

- Elevated fire weather conditions will be present most afternoons
  across lower elevations, and may be locally critical come
  Monday.

&&

.DISCUSSION /Through Thursday/...
Issued at 133 PM MDT Thu Oct 16 2025

The closed low now into Wyoming and associated upper-level trough
are keeping our region seasonably cool and rather breezy under
enhanced southwesterly flow aloft. Temperatures tonight should
cool enough under the post-frontal airmass to support patchy frost
across some of the lower elevations, with the highest confidence
for the Palmer Divide and east into Lincoln County. Opted for a
slight expansion of the Frost Advisory into the former as a
result.

With the shortwave still overhead Friday, temperatures will
remain relatively stable, if even slightly cooler in our eastern
plains in the absence of warm southerly surface flow. Should
otherwise be a mostly clear and dare I say quiet day. By Friday
night, stronger synoptic northwest flow will begin to impinge on
northern Colorado thanks to an amplifying longwave trough,
producing notably stronger winds over the high country initially
(gusts 45-55 mph being fairly widespread for higher exposed
terrain), then spreading into the plains during the day Saturday
behind a secondary cold front. Highs will fall below normal as a
result. One advantage of the frontal passage will be an increase
in dewpoints and thus humidity, which should limit fire weather
concerns despite the breezier conditions. The trough will not dig
sufficiently south to bring any meaningful precipitation however,
rather just scraping northeast Colorado and limiting the potential
for light showers (if any) to our northernmost mountains. Lows at
or slightly below freezing look increasingly likely Saturday
night/Sunday morning across a majority of the rural plains
following the frontal passage (not so much for the urban corridor
where downslope flow should taper the cooling), so highlights will
eventually be needed barring any significant changes to the
forecast.

The cooler weather takes a mini hiatus Sunday, as weak ridging
briefly expands into the state behind the departing trough.
Healthy subsidence accompanying the ridge will make temperatures
rebound well into the mid to potentially upper 70`s east of the
mountains, and buffer the winds temporarily under weakened flow
aloft.

Yet another trough enters the picture Monday, following a similar
track to Saturday`s. There has been a clear and consistent
northward trend in its track over the past 24-48 hours across
practically all guidance, including both ensemble and
deterministic solutions. Consequently, precipitation chances have
almost completely evaporated for our lower elevations, and are now
largely confined to our northern mountains. While some light snow
remains favored Monday afternoon into Tuesday there, amounts look
considerably less impactful. We`ll see if this trend continues. In
any case, will need to continue to monitor the potential for
locally critical fire weather conditions on Monday, as breezy
northwest winds should be relatively widespread. Moisture guidance
often lags behind in these situations, so wouldn`t be surprising
to see the forecast trend dry enough to meet critical thresholds
over time.

Beyond that, the pattern transitions to weaker zonal flow, with
limited opportunity for precipitation, and temperatures likely
quite close to seasonal averages.

&&

.AVIATION /00Z TAFS through 00Z Saturday/...
Issued at 539 PM MDT Thu Oct 16 2025

VFR conditions expected through the TAF period. Gusty NW winds
will prevail through this evening before turning VRB by 03Z and
drainage overnight.

For Friday, generally light winds will prevail throughout the day,
with models disagreeing on exact wind directions. Overall, expect
a gradual anticyclonic circulation, with winds turning from SW in
the morning to NE/SE by the evening. However, with downsloping
winds, BJC could stay W tomorrow.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Frost Advisory from 2 AM to 8 AM MDT Friday for COZ041>043-046.

&&

$$

DISCUSSION...BRQ
AVIATION...MAI

NWS BOU Office Area Forecast Discussion