583
FXUS65 KBOU 122054
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
254 PM MDT Sun Apr 12 2026

.KEY MESSAGES...

- Critical fire weather conditions expected today and Monday over
  the southern portions of the forecast area and the plains near
  the Wyoming border.

- Continued above normal warmth Sunday and Monday with a few,
  mainly alpine late day showers.

- The next system will bring cooler temperatures and a decent
  chance of precipitation to the forecast area Tuesday and Tuesday
  evening. Some minor travel impacts possible mountain passes.

- Another system capable of widespread precipitation looking
  possible by the week`s end.

.DISCUSSION /Through Sunday/...
Issued at 242 PM MDT Sun Apr 12 2026

Water vapor imagery shows our next expected weather system
currently spinning off the coast of northern California. Another
less defined disturbance is visible just on its heels, with
guidance showing these features merging as they progress eastward
across the Great Basin and into the Central Rockies over the next
few days. The extended forecast period looks to remain fairly
active this week, with elevated to critical fire weather
conditions mixed in with multiple chances for mountain snow and
low elevation precipitation.

It`s a rather nice day across the forecast area today, albeit a
little breezy across the southern foothills, mountain valleys, and
along the Palmer Divide and adjacent plains. Temperatures are
already in the 70s across the plains and 50s in the foothills and
mountain valleys. With the breezy and dry conditions in place, the
main concern for today is with elevated to critical fire weather
conditions. Today`s Red Flag Warning remains in place until 8 PM for
the southern portion of the forecast area as well as eastern Larimer
and northwestern Weld Counties. Relative humidities are already in
the teens across the majority of our lower elevations and even along
the I-70 mountain corridor , so even where winds are expected to
remain below critical thresholds, elevated fire weather conditions
are fairly widespread across the forecast area.

For tonight, southwesterly flow aloft starts to increase ahead of
our next approaching upper-level trough. There will be enough mid-
level moisture to bring some very light snow shower chances to the
northern mountains. Cooler temperatures aloft will start to filter
in on Monday as the trough moves much cooler temperatures our way.
Gusty southwesterly winds are expected to increase by late morning
while relative humidity values drop as low as 10% across portions of
the plains. Due to another day of breezy winds and low RH, have gone
ahead and upgraded the Fire Weather Watch to a Red Flag Warning for
all fire zones except for Washington County where winds will be more
marginal. Like today, with low RH values expected to be below
critical thresholds for all of the plains, there will be widespread
elevated critical fire weather conditions in place, with some brief
patchy critical conditions possible to develop outside the RFW
areas, so everyone should continue practicing good fire safety.

Ensemble trends have shown a bit of a turnaround over the past few
model runs, showing an increase in QPF for Tuesday`s expected trough
passage, leading to higher confidence in some Advisory level
snowfall totals for our mountains. Moisture will start to ramp up
late Monday night across the higher elevations, with deeper moisture
not expected to make it over the lower elevations until late Tuesday
morning, with the best QG forcings and cold front expected Tuesday
afternoon and evening. Expect increasing chances for mountain snow
through the day on Tuesday, shifting to the plains by the afternoon
in the form of rain showers with some scattered thunderstorms
possible. The current forecast would indicate the need for a Winter
Weather Advisory for accumulations of 4 to 9 inches possible for
elevations above 10,000 feet with this system, though will hold off
to see what the hi-res models show and monitor the upwards trend for
one more model run before making and decisions. For now, it`s safe
to say those traveling into the high country on Tuesday should
expect winter driving conditions.

Warmer and drier conditions are expected behind Tuesday`s weather
maker, as a brief period of upper-level ridging looks to develop on
Wednesday. Cross sections show little moisture remaining over the
lower elevations by Wednesday morning, and with gusty winds possible
over the eastern plains as a lee trough shifts eastward, there could
be some elevated fire weather concerns for the afternoon.

By Thursday, southwesterly flow aloft starts to ramp up again ahead
of another upper-level trough dropping out of the Pacific Northwest.
At the surface, another lee trough is expected to develop over
eastern Colorado. Critical fire weather concerns will be on the menu
once again as RH drops into the single digits over portions of the
plains, and winds increase over the higher terrain.

For Friday and onward, this next upper-level trough looks to bring
greater chances for a decent spring system, but much is still
uncertain this far out.

&&

.AVIATION /18Z TAFS through 18Z Monday/...
Issued at 1142 AM MDT Sun Apr 12 2026

VFR conditions are expected throughout the TAF period. We are
currently transitioning out of drainage flow as the inversion has
mixed out according to ACARS soundings. There is some uncertainty
on the winds for this afternoon. We have kept in WSW/W winds with
gusts around 20-25 kts at all three sites starting between 19z
and 22z this afternoon. KAPA is expected to see the strongest
gusts. There is a small possibility (20-30%) that the stronger
winds do not materialize this afternoon.

Winds will lighten up this evening and turn to drainage. They
are expected to stay at 10 kts or less through tomorrow around
18z to 21z. We expect another transition from drainage to a WSW/W
wind tomorrow afternoon. Wind gusts will once again be around
20-25 kts at all three sites starting around 19z to 21z. The onset
of these stronger gusts could be an hour or two earlier at KAPA
and slightly stronger than at KBJC and KAPA.

&&

.FIRE WEATHER...
Issued at 242 PM MDT Sun Apr 12 2026

Today`s Red Flag Warning remains in place until 8 PM for
the southern portion of the forecast area as well as eastern Larimer
and northwestern Weld Counties. Relative humidities are already in
the teens across the majority of our lower elevations and even along
the I-70 mountain corridor, so even where winds are expected to
remain below critical thresholds, elevated fire weather conditions
are fairly widespread across the forecast area. Due to another
day of breezy winds and low RH expected on Monday, have gone
ahead and upgraded the Fire Weather Watch to a Red Flag Warning
for all fire zones except for Washington County where winds will
be more marginal. Like today, with low RH values expected to be
below critical thresholds for all of the plains, there will be
widespread elevated critical fire weather conditions in place,
with some brief patchy critical conditions possible to develop
outside the RFW areas, so everyone should continue practicing good
fire safety. A weather system is expected to bring mountain snow
and widespread precipitation to the lower elevations on Tuesday.
Despite the increased moisture, we may still see some critical
fire weather conditions develop over southern Lincoln County on
Tuesday before the better moisture arrives, where wind gusts
between 30-35 mph will be possible coinciding with RH at or just
below critical thresholds.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning until 8 PM MDT this evening for COZ214-216-238-
241-246-247-249.

Red Flag Warning from 11 AM to 8 PM MDT Monday for COZ214-216-
238-241-242-246-247.

&&

$$

DISCUSSION...9
AVIATION...MV
FIRE WEATHER...9

NWS BOU Office Area Forecast Discussion