002
FXUS65 KBOU 230602
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1202 AM MDT Thu Apr 23 2026

.KEY MESSAGES...

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

- Brief period of strong winds possible Thursday morning across
  the Front Range Foothills.

- 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.

&&

.AVIATION /06Z TAFS through 06Z Friday/...
Issued at 1131 PM MDT Wed Apr 22 2026

Confidence in winds at all three sites is rather low thru Thu
aftn. Currently there is a front moving in from the northeast
which will affect DIA by 0630Z and APA by 0730z.  Winds behind
this feature will be ENE. Eventually the winds will become light
SE by 09z and then will trend to more westerly by 13z. Previous
data suggested winds will be gusty W/WNW by 16z thru the aftn.
However, current data suggests there could end up being some type
of Longmont Anti-Cyclone by early aftn which may cause varying
winds directions all aftn, especially at APA and DIA. Thus
confidence in directions is low at this time as winds could end
being more N/NNE at both APA and DIA by 19z. For BJC, will keep
winds mainly W/WNW from 15z thru Thu aftn. Finally, there is some
potential (10-20% chance) of some virga Thu aftn as well with a
few weaker microbursts possible.

&&

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

Overnight humidity recovery has been poor so far across most of
the lower elevations, with some ~10% RH values still observed at
the time of this discussion. Humidity should recover to around 30%
overnight as slightly cooler air starts to work into the region.

Though temperatures will be cooler on Thursday, 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, uncertainty in the wind
forecast continues into Friday. Only modest mid-level flow is
expected, with 700mb winds generally less than 20kt. Guidance does
have some brief enhancement of the winds during the afternoon,
timed with the passing of a weak trough moving across the forecast
area. We added South Park and southern Lincoln county into a Fire
Weather Watch where forecast confidence is just high enough.
Additional expansion is possible depending on trends to the wind
forecast.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning from 11 AM this morning to 7 PM MDT this
evening for COZ214-216-238>251.

Fire Weather Watch from Friday morning through Friday evening
for COZ214-247.

&&

$$

DISCUSSION...Hiris
AVIATION...RPK
FIRE WEATHER...Hiris

NWS BOU Office Area Forecast Discussion