256
FXUS65 KBOU 121119
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
419 AM MST Fri Dec 12 2025

.KEY MESSAGES...

- Dry and mild today with elevated fire weather conditions across
  the lower foothills and urban corridor through tonight. Breezy
  across the higher elevations and foothills in particular.

- Well above normal temperatures and dry conditions will persist
  through at least Tuesday.

&&

.SHORT TERM /Through Friday/...
Issued at 220 PM MST Thu Dec 11 2025

Current surface observations across the high country show winds have
now decreased below high wind warning criteria, with the strongest
gusts up to 73 mph at the highest peaks of the Front Range. Winds
will continue to gradually weaken (gusts up to 50 mph) this evening
and into Friday morning as flow aloft decreases and turns more
northwesterly.

For the plains, downsloping winds of 40-50 mph has allowed ample
mixing this morning and afternoon. Relative humidity values are
currently ranging from 10-20% and likely won`t start improving until
after the sun sets. High-resolution guidance also indicates those
stronger downslope winds will weaken at that same time, with gusts
up to 25 mph through tonight. For this reason, still think critical
fire weather conditions will last through 5 PM, with localized
elevated fire weather conditions possible through the evening hours,
particularly where winds persist.

A weak cold front will pass through the plains overnight tonight,
bringing low-level moisture across the northeastern plains. Looking
at modeled Skew-T soundings, areas of patchy fog or low clouds are
possible Friday morning for areas east of Morgan and Weld counties.
However, if these conditions materialize, they will be brief as
daytime heating and downslope winds off the Cheyenne Ridge will
bring drier air over the area. With breezy winds up to 25-30 mph and
marginal RH values, elevated fire weather conditions are possible
Friday afternoon, mainly for the northern plains, I-25 corridor and
Palmer Divide. For temperatures, expect slightly cooler, although
still above normal, conditions across the forecast area. The plains
should reach up to the mid-to-high 50s, and the mountains/valleys up
to low 30s/mid 40s.

&&

.LONG TERM /Friday night through Thursday/...
Issued at 220 PM MST Thu Dec 11 2025

Winds will increase Friday night along the eastern slopes of the
Front Range Mountains once again as WNW-NW flow increases to 50-60
knots at ridgetop, reinforcing mountain wave activity. While there
are some uncertainties on how far down the slopes the strongest
winds will descend (Namnest shows a more easterly extent than the
HRRR), there was enough certainty to bump up winds late Friday
night into Saturday morning for the foothills in today`s forecast
package (started with blending in the NBM 90th%). With cross-
sections showing a weak mean state critical layer just above
ridgetop, we could see winds between 65-70 kts develop in our more
wind prone areas, with some of those gusts spilling into the
lower foothills. Will continue to monitor if any highlights will
be needed in the coming forecast package. The strongest winds are
expected during the time of highest relative humidity values,
which should limit the threat of critical fire weather conditions
developing, however, there may be some elevated fire weather
conditions as relative humidity values decrease through the
morning and before the winds retreat back up the eastern slopes by
the afternoon.

Aside from the winds, we are still on track for an extended period
of above normal temperatures and dry conditions for the forecast
area. An arctic airmass is expected to spread south into the central
US, though only graze the northeast corner of Colorado Saturday,
bringing overnight lows to near normal values over the far eastern
plains, while staying 5 to 10 degrees above normal across the urban
corridor. As the arctic air pushes eastward, upper-level ridging
will follow suit, finally disrupting the persistent northwesterly
flow over Colorado. With more zonal flow expected as a moisture
starved shortwave is progged to traverse the Rockies Monday into
Tuesday, expect afternoon temperatures to warm into the 60s starting
Monday.

Ensembles continue to agree that moisture will start to return to
the region by midweek in the form of light snowfall potential for
the northern mountains, with the plains expected to remain dry
through the extended period.

&&

.AVIATION /12Z TAFS through 12Z Saturday/...
Issued at 415 AM MST Fri Dec 12 2025

VFR conditions will prevail for all terminals through the TAF
period. Winds will continue to briefly return to drainage patterns
at KDEN and KAPA through sunrise following the weak early morning
frontal boundary. Westerly winds will mix down at the terminals
mid to late morning. Gusts should be lower than previous days,
generally under 20-25 kts, with exception of KBJC where they may
approach 30 kts on occasion.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

SHORT TERM...MAI
LONG TERM...9
AVIATION...BRQ

NWS BOU Office Area Forecast Discussion