National Weather Service Forecast Discussion

Thornton Weather Forecast   
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894
FXUS65 KBOU 291718
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1018 AM MST Mon Dec 29 2025

.KEY MESSAGES...

- Seasonal temperatures and dry conditions today.

- Expect a warming trend this week along with the dry conditions
  into Thursday.

- There will be a chance of snow in the mountains Thursday
  afternoon through next Sunday.  The plains will remain dry.

&&

.UPDATE...
Issued at 345 AM MST Mon Dec 29 2025

Fairly weak northwesterly flow aloft is expected across the CWA
today with weak subsident synoptic scale energy in place. After a
cold start this morning, temperatures should warm to near
seasonally normal highs this afternoon. Quite the change from the
significantly above normal readings we have been having for much
of this December. Dry conditions are expected today for all areas
with only minor changes to the sky, temperature and wind grids.

&&

.DISCUSSION /Through Sunday/...
Issued at 200 PM MST Sun Dec 28 2025

Current satellite imagery shows clearing skies as snow has
gradually come to an end this morning. It finally feels like
winter for the first time in a while, with current temperatures
ranging between 20s to low 30s across the plains, and single
digits to low 20s in mountains and valleys. The main concern for
the rest of the day will be gusty winds across the Front Range
mountains causing blowing snow and reduced visibilities this
afternoon. Mid and upper level flow will briefly increase this
afternoon/evening as the shortwave to our north dips slightly
south and treks east. Colorado is progged to be in the left
entrance region of the upper level jet streak, which promotes
subsidence. This is further supported with QG fields showing
healthy downward vertical motion for this afternoon. With short
range guidance indicating 700-mb winds reaching up to 50-60 kts,
gusts up to up to 60 mph are possible across the Front Range
mountains this afternoon (some areas already experiencing these
winds), and downsloping winds off the Cheyenne Ridge could gust up
to 45 mph at times. As the system continues traveling east
tonight, winds will weaken across the forecast area.

Temperatures will once again plummet to the low teens/20s this
evening as the sun sets, and then single digits and teens
overnight. Despite snow melting across the plains today, any wet
roads will refreeze, which will cause isolated slick travel
conditions tonight and possibly Monday morning. Expect
temperatures to warm up to seasonal normals on Monday, with dry
conditions and clear skies. Relative humidity values will dip into
the teens in the afternoon, however light winds (generally under
20 mph) will limit any fire weather conditions.

Quiet conditions and above normal temperatures will prevail for most
of the week as Colorado will be on the eastern edge of the upper
level ridge, with a surface high pressure over the western United
States. Towards the middle of the week, the axis of ridge will shift
over Colorado, which will allow temperatures to soar to the high 50s
and possibly the low 60s (Ensemble members` max temperature ranging
between 54-61 degrees). With northwest flow aloft throughout the
week, dry air will filter in and lower relative humidity values to
around 20% each day. Recent precipitation and relatively light winds
this week will keep widespread fire weather concerns at bay for now.
However, localized elevated fire weather conditions are possible,
particularly in areas that haven`t received precipitation.

Our next chances of precipitation come towards the end of the
week and weekend. Long range guidance has continued to indicate
the upper level ridge flattening as shortwaves embedded in the
flow enter the forecast area. With mid-level moisture advecting
into the region, orographic snow showers are possible for the high
country. However, there are still still differences between
ensemble guidance in terms of timing and evolution of the system,
so expect changes as we get closer to the event. For now, will
keep NBM PoPs as they are for Thursday and Friday. Unfortunately
for the plains, guidance has kept lower elevations dry through
next weekend.

&&

.AVIATION /18Z TAFS through 18Z Tuesday/...
Issued at 1015 AM MST Mon Dec 29 2025

VFR conditions will prevail for all terminals through the TAF
period. Light winds will favor an ENE direction through this
afternoon before a clockwise rotation towards southerly drainage
flow this evening. A similar diurnal wind pattern is expected
Tuesday.

&&

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

&&

$$

UPDATE...66
DISCUSSION...MAI
AVIATION...BRQ

NWS BOU Office Area Forecast Discussion