793
FXUS65 KBOU 170527
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1127 PM MDT Thu Oct 16 2025

.KEY MESSAGES...

- Patchy frost tonight for the Palmer Divide, Lincoln County, and
  portions of Weld County.

- Seasonably cool (though slightly milder Sunday), with breezy
  winds most days through Monday, and 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 /06Z TAFS through 06Z Saturday/...
Issued at 1127 PM MDT Thu Oct 16 2025

VFR conditions will persist through Friday night. Winds have
settled down in wake of the easterly surge, and a fairly normal
transition is now underway that will take winds at KDEN and KAPA
from SSE to S to SW through 15Z. There is some uncertainty with
winds beyond 15Z, but overall moderate confidence (60-70% chance)
that winds eventually become more W-NW-N 17Z-20Z, before an
anticyclone develops and winds turn more N-NE-E 21Z-24Z. Even if
winds don`t conform to the above, they should stay light and less
than 8-10 kts. Then expect a gradual transition to normal S/SW
winds by 02Z-04Z this evening.


&&

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

&&

$$

DISCUSSION...BRQ
AVIATION...20