769
FXUS65 KBOU 230021
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
621 PM MDT Wed Apr 22 2026

.KEY MESSAGES...

- Critical fire weather conditions and potential for rapid
  wildfire spread today due to gusty winds and very low humidity.
  Critical conditions expected again on Thursday.

- Dry and unseasonably warm weather continues today. Highs will
  be nearly 20 degrees above normal.

- Slight mountain wave amplification to bring strong winds to the
  higher foothills (mainly above 8,500 feet) Thursday morning.

- Pattern change to cooler and unsettled weather by this upcoming
  weekend.

&&

.DISCUSSION /Through Wednesday/...
Issued at 1157 AM MDT Wed Apr 22 2026

Current satellite imagery shows an upper level low over the
Pacific northwest trekking east. Increasing southwest flow aloft
over Colorado due to this low has led to breezy winds across the
mountains and plains this morning. With ACARS soundings showing
almost dry adiabatic lapse rates up to ~650 mb, breezy winds have
been allowed to mix down to the surface and will likely become
more widespread this afternoon as clearing skies and daytime
mixing continue. Forecast remains on track for widespread critical
fire weather conditions this afternoon and evening as surface
observations already show relative humidity values already
reaching the single digits in some areas.

Outside of fire weather concerns today, our far northeastern plains
(Sedgwick and Phillips counties) may see isolated thunderstorms late
this afternoon/evening. However, most recent hi-res guidance does
indicate the dry line staying east of our forecast area. If any
storms were to develop, gusty outflow winds are possible, given
decent DCAPE values.

Gusty winds are expected to continue overnight tonight and into
Thursday. Models seem to be trying to resolve a brief mountain wave
for the high elevations due to a 700-mb jet, creating cross-barrier
flow of 40-50 kts. This will likely result in winds gusting up to 40-
60 mph across the Front Range mountains and wind prone areas off the
Cheyenne Ridge. However, cold air advection will occur right
after, which will result in winds turning slight more
northwesterly and becoming more bora in nature. with subsidence
increasing aloft through the Thursday morning hours, recent hi-res
guidance do indicate a brief window where winds gusting up to
40-60 mph could be brought down to the Hwy 93 corridor due to
momentum transfer.

Despite cooler temperatures on Thursday (highs in the 60s),
widespread critical fire weather conditions will return due to gusty
winds and minimum RH values between 10-17%. In terms of
precipitation on Thursday, isolated mountain snow showers are
possible in the afternoon, with a low chance (less than 20% chance)
of virga showers for the Palmer Divide and Lincoln county area.

By late Thursday afternoon and evening, we will likely get a
reprieve of strong winds across the forecast area, as the axis of
the upper level trough traverses the region and weaker westerly
winds replace the stronger southwest/west. However, by Thursday
night and Friday, a 500-mb jet associated with the longwave trough
and subsequent low over Canada, will bring breezy winds back to the
Front Range mountains. In addition, throughout the day Friday, a
developing lee-side trough will create tightening of pressure
gradients and allow breezy winds across the plains again. This could
bring about another round of elevated-to-critical fire weather
conditions. However, a backdoor cold front looks to bring improved
RH into at least the northeastern plains, but just how far west it
makes it could determine the need for additional fire weather
highlights. Confidence remains higher in South Park, the Palmer
Divide and our southern plains being the likeliest to see critical
fire weather conditions. Will hold off on any fire weather
highlights for now, but will continue to monitor the situation.

The weather pattern into the weekend will be dominated by the upper
level closed low over southern Canada, with westerly flow aloft over
the region. Embedded shortwaves in the flow will keep the potential
for light precipitation across the forecast area. Sunday continues
to look to be the best shot for more widespread and measurable
precipitation, due to a more defined shortwave trough pulling in
Pacific moisture. As of right now, ensembles are in good agreement
of QPF amounts between 0.10" and 0.25" for the plains.

Behind this system, ensemble guidance indicates a brief warming
trend for Tuesday and possibly Wednesday as a weak upper level ridge
tries to build over the Rockies. However, this could be shortlived
as models try to hone in on another system by midweek.

&&

.AVIATION /00Z TAFS through 00Z Friday/...
Issued at 552 PM MDT Wed Apr 22 2026

VFR conditions expected through the TAF period. Latest ACARS
soundings show it`s warm and dry out there today, with DALR up to
around 500 mb and dewpoint depressions approaching 80F. WSW winds
are expected to remain gusty for the next few hours as 30-35 kt
gusts continue to mix down to the surface. Expecting winds to
decrease around 3Z and turn more westerly. While lighter winds are
anticipated overnight, a slight mountain wave amplification may
send some channels of stronger westerly winds across the airfields
periodically (15-25 kt) overnight, though there is low confidence
in the exact location these would occur. Westerly winds
restrengthen between 14-16Z and 25-35 kt west to WNW gusts
prevail through the evening. Much lighter winds are anticipated
overnight on Thursday.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning until midnight MDT tonight for COZ214>216-
238>251.

Red Flag Warning from 11 AM to 7 PM MDT Thursday for COZ214-216-
238>251.

&&

$$

DISCUSSION...MAI
AVIATION...9

NWS BOU Office Area Forecast Discussion