437
FXUS65 KBOU 231805
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1205 PM MDT Thu Apr 23 2026

.KEY MESSAGES...

- Critical fire weather conditions today, possible again on Friday
  with dry and breezy conditions.

- Unsettled pattern by this weekend with chances for precipitation
  increasing.

&&

.DISCUSSION /Through Wednesday/...
Issued at 1201 AM MDT Thu Apr 23 2026

The pattern over the next several days will be dominated by a
strong upper low over Saskatchewan, that remains nearly stationary
through Monday or Tuesday of next week. A series of shortwaves
will pivot around this closed 500mb low... though a majority of
these will remain north of our forecast area until late this
weekend or early next week, when we finally see a more favorable
setup for precipitation.

SPC Mesoanalysis shows that a mid-level cold front is progressing
across the higher elevations at the time of this writing, and we
should start to see a transition to a brief bora-like wind event
through Thursday morning. Cross-sections show a marginally
favorable mountain wave setup for a few hours Thursday AM, with
cross barrier flow briefly around 40-50kt. That should translate
to a few peak gusts of 60-70 mph across the Boulder County
foothills, before quickly diminishing closer to noon as any wave
amplification breaks down. Though there may be a few rain/snow
showers across the high country, the main story of the day will be
fire weather. See the fire weather discussion for more details.

Friday also looks to be another day of elevated or critical fire
weather conditions. While the flow aloft remains fairly modest, a
passing mid-level trough and deepening lee cyclone may be just
enough for some gustier winds to spread across the lower
elevations Friday afternoon and evening. Temperatures will again
be mild with highs in the mid to upper 60s across most of the
plains. A cold front will attempt to push back into the area late
Friday or early Saturday bringing some moisture and slightly
cooler temperatures, which should limit the overall fire danger by
the weekend.

The pattern remains relatively uncertain this weekend into early
next week. Another shortwave is expected to drift in from southern
California on Saturday, and eventually get picked up by the
broader upper low over Saskatchewan by Sunday or Monday. That
should lead to one or two chances of widespread precipitation
across the region as a deep lee cyclone develops over southeastern
Colorado Sunday, before ejecting into the Great Plains by Monday.
A secondary, weaker shortwave may bring some additional moisture
on Monday. While the shortwave does take a favorable track for
northern/northeastern Colorado, guidance has continuously delayed
our chances of precipitation. Until we get a good ensemble signal
inside ~84 hours, confidence in seeing rain across the plains will
be lower than normal, despite what NBM and other raw model
means/blends would suggest. There`s higher confidence in getting
meaningful precipitation across the higher elevations, though QPF
amounts are still up in the air. At the very least, the cooler
pattern will continue to limit fire danger through early next
week.
the boundary will
not affect
&&

.AVIATION /18Z TAFS through 18Z Friday/...
Issued at 1202 PM MDT Thu Apr 23 2026

VFR conditions are expected through the TAF period. Wind speeds
have been elevated at all three sites this morning with some gusts
as high as 30 to 40 kts. Wind gusts should stay between 20 to 30
kts for the next several hours until around 01z with a low chance
(about 20%) of some gusts a little stronger than 30 kts. Currently
tracking a boundary/wind shift moving through southern Weld
county as of 1730z. This boundary should reach KDEN between 1915z
and 1945z and shift winds to a NNW direction. It is somewhat
uncertain if this boundary will reach KAPA and KBJC. A brief
period of mid-to-high level scattered clouds are expected this
afternoon between 19z and 01z, but no ceilings issues are
expected. After around 01z, winds will decrease in speed, but will
still be around 10 kts at all three sites.

Tonight, winds will turn to drainage between 04z and 06z with a
brief period of VRB possible just before that. Winds are expected
to stay under 10 kts. Tomorrow, winds will be W to NW at KDEN and
KAPA with gusts around 20 kts expected. The same wind speeds are
expected at KBJC, but winds will be SW.


&&

.FIRE WEATHER...
Issued at 1201 AM MDT Thu Apr 23 2026

Though temperatures will be cooler today, the dry airmass is
expected to remain over the area during the day, with minimum
relative humidity values falling to around 10-15% in the afternoon
hours. Some brief mountain wave amplification may lead to a
period of stronger winds in the foothills and immediately adjacent
plains late in the morning, but should quickly diminish as we
transition to more of a mechanical mixing regime by the afternoon
hours. Boundary layer flow isn`t particularly strong, but frequent
gusts of 20-25kt appear likely, especially over south Park and
along the Cheyenne Ridge. While recent trends suggest winds may
end up a bit weaker across portions of the Denver metro/Palmer
Divide, there should still be at least a couple of hours of
critical fire weather conditions across the existing Red Flag
Warning area.

Guidance over the past couple of days has trended a little
warmer/drier on Friday, resulting in minimum RH values falling to
near or below 10% across a large chunk of the plains, southern
Foothills, and South Park. However, there still may be periods of
gusty winds from the foothills across portions of the plains so
have added more zones to the previous Fire Watch.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Fire Weather Watch from Friday morning through Friday evening
for COZ214>216-238>247-249.

Red Flag Warning until 7 PM MDT this evening for COZ214-216-
238>251.

&&

$$

DISCUSSION...Hiris
AVIATION...MV
FIRE WEATHER...Hiris/RPK

NWS BOU Office Area Forecast Discussion