938
FXUS65 KBOU 220910
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
310 AM 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.
  Elevated to critical conditions expected 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.

&&

.UPDATE...
Issued at 306 AM MDT Wed Apr 22 2026

Made some minor adjustments to temps and winds. Not sure about
tstm threat over the far northeast plains this aftn. Low level
moisture looks to mix out by mid aftn with no defined convergence
zone. However, can`t completely rule out an isold high based
storm with gusty winds due to decent DCAPE.

&&

.DISCUSSION /Through Tuesday/...
Issued at 1127 PM MDT Tue Apr 21 2026

Hot, dry, and windy will be the name of the game today as
southwest flow increases across the forecast area ahead of an
approaching trough currently moving across the Great Basin. Our
latest warming trend will max out this afternoon as highs are
expected to climb into the 80s once again across the plains, and
60s for our high mountain valleys before returning to near
seasonal norms through Saturday. Critical fire weather is expected
across the majority of the forecast area by late morning as
enhanced downslope winds, drying, and warming is brought on by a
deepening lee surface trough. A prolonged period Red Flag Warning
is in effect beginning at 10 AM Wednesday morning through Midnight
tonight as continued enhanced downslope winds will make for slow
relative humidity recoveries. Overall, expecting southwest winds
to gust between 30-45 mph (strongest in the afternoon hours when
mixing is greatest) with very low relative humidity values in the
low single digits across the plains and South Park. This will make
for rapid fire spread if a fire were to start. Outside of the
fire weather concerns, our northeast corner may see a few late
day/evening thunderstorms as a dryline retrogrades westward
nudging 50-55 degree dewpoints up against our Nebraska and Kansas
borders. The SPC has kept Sedgwick and Phillips Counties in a
Marginal Risk for tomorrow for if we do see a storm develop, large
hail and strong winds would be the main hazards, though most CAMs
show the main activity staying just east and north of our CWA
boundaries.

A cold front is expected to slide across the forecast area Wednesday
night. Additionally, a restrengthening of 700mb flow is expected
late Wed night/early Thurs morning as a 60-70kt jet max straddles
the WY/CO border. This will increase winds at ridgetop, and while
pressure gradients are in place (~10 mb difference between GJT-DEN),
the main ingredients we look for in a high wind type mountain wave
event, aren`t quite adding up to more than a slim chance that
mountain wave amplification will be suffice to send stronger winds
down into the lower foothills. We are expecting some stronger gusts
to make their way down into our typical upper-foothill windy spots
for a few hours early Thursday morning where 55-60 mph gusts will be
possible between roughly 6AM to 9AM.

With the aforementioned poor overnight relative humidity recoveries
expected for our lower elevations and South Park, another critical
fire weather day is on tap for Thursday. Despite seeing much cooler
temperatures behind the front, windy conditions are expected to
persist as subsidence and efficient mixing will keep enhanced
winds in place with relative humidities ranging from 10% to 17%
across the lower elevations on Thursday afternoon. A Fire Weather
Watch is in effect for all of the lower elevations from 10AM to
8PM and will likely be upgraded later today.

By Friday, fire weather conditions should start to improve as a
backdoor cold front stemming from a building surface high over
South Dakota and Nebraska looks to bring improved RH into at
least the northeastern plains, but just how far west it makes it
could determine the need for any additional fire weather
highlights. At this time, confidence is higher in South Park, the
Palmer Divide and our southern plains being the likeliest to see
elevated to critical fire weather conditions, but would like to
wait for the hi-res guidance to come into play before making any
decisions.

With an upper-level low progged to sit over Southern Canada
through the weekend, smaller scale disturbances are expected to
move through the larger scale flow keeping at least some potential
for light precipitation across the forecast area through the
weekend. Sunday looks to be our best shot at any real measurable
precipitation as a shortwave brings Pacific moisture into the
Rockies, but we will have to see how things trend between now and
then.

&&

.AVIATION /06Z TAFS through 06Z Thursday/...
Issued at 1120 PM MDT Tue Apr 21 2026

Winds were gusty out of the south at DIA but should decrease by
07z. Otherwise winds will be drainage overnight. SSW winds will
increase in the 15z to 16z period with gusts up to 25 mph. SSW
winds will continue thru the aftn with gusts from 30 to 35 mph at
times. The winds will switch to a more westerly direction by 01z
with gusts up to 30 mph thru early Wed evening. Finally, VFR
conditions will continue thru the period.

&&

.FIRE WEATHER...
Issued at 1127 PM MDT Tue Apr 21 2026

Critical fire weather conditions are expected today as gusty
southwest winds and very low relative humidity values coincide
across our lower elevations, Front Range Foothills, and South
Park. 30-45 mph gusts are expected during peak heating this
afternoon, though critical thresholds are expected to be met early
and persist through late tonight, therefore, a prolonged Red Flag
Warning is in place from 10 AM this morning to Midnight tonight.
Poor overnight recoveries are expected tonight that will bring
another day of critical fire weather conditions to the same
locations on Thursday. Currently these areas are under a Fire
Weather Watch, but this is expected to be upgraded to a Red Flag
Warning later today.

There are uncertainties with how widespread critical fire weather
conditions will be on Friday as a backdoor cold front should allow
for cooler temperatures and higher RH to filter into the plains
through the day. Confidence is higher in critical fire weather
conditions developing for South Park, the Palmer Divide, and
Lincoln County at this time, but will need to see how things trend
as hi-res guidance comes into play today.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning from 10 AM this morning to midnight MDT tonight
for COZ214>216-238>251.

Fire Weather Watch from Thursday morning through Thursday
evening for COZ214-216-238>251.

&&

$$

UPDATE...RPK
DISCUSSION...9
AVIATION...RPK
FIRE WEATHER...9

NWS BOU Office Area Forecast Discussion