National Weather Service Forecast Discussion

Thornton Weather Forecast   
Today's Forecast Story   
967
FXUS65 KBOU 020028
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
628 PM MDT Wed Apr 1 2026

.KEY MESSAGES...

- Mountain snow will continue through this evening, with travel
  impacts for higher passes during heavier snow.

- Numerous rain showers are expected on the plains this afternoon
  and evening. Isolated thunderstorm or two possible.

- A brief warm up Thursday, with potential for locally critical
  fire weather conditions.

- Windy and cooler Friday with another round of snow for the
  mountains. Plains look to be dry (80% confidence).

- Dry and warming trend expected over the weekend and into next
  week.

&&

.DISCUSSION /Through Wednesday/...
Issued at 236 PM MDT Wed Apr 1 2026

Forecast remains generally on track, with current radar showing
ongoing mountain snow showers and developing scattered light rain
showers on the plains. The upper level shortwave is currently
entering western Colorado, as evident on water vapor satellite
imagery. It will continue trekking east this afternoon/evening, with
colder air being advected into the mountains. This will result in
mountain valleys likely seeing a transition from rain/snow mix to
all snow later today, with better snow-to-liquid ratios for the
high terrain. However, this will still be wet and heavy snow as
SLRs are only expected to reach up to around 13:1. Additional
accumulations of 2-8" is expected across most of the mountains,
with localized higher amounts likely for Park Range, as that area
has more favorable moisture content and synoptic lift.

For the plains, lee-cyclogenesis is still favored to develop over
southeastern Colorado this afternoon with the arrival of the upper
level shortwave. This will help bring a round of more widespread
rain showers through this evening. Overall, precipitation will be
light. However, with hi-res guidance continuing to show
instability building this afternoon, and ACARS soundings showing
abundant moisture being advected into the plains (current PWAT
values of ~0.54", which is above the climatological 90th
percentile for this time of the year), thunderstorms and briefly
moderate to heavy rainfall is expected at times. Ensemble guidance
still in agreement of QPF amounts generally ranging between
0.05-0.25", with localized higher amounts up to 0.50" under the
heavier showers. However, there is a low chance (~30%) of QPF
amounts higher than 0.50", particularly for the northeastern
plains.

Precipitation should gradually end across the forecast area
overnight tonight, as subsidence increases aloft. Flat ridging on
Thursday will bring warm, dry, and breezy conditions for the
mountains and plains. Ensemble guidance is still in agreement of
temperatures rising back up tot the low 70s across the plains.
However, downslope winds could aid in compressional heating and
raise temperatures slightly higher than forecasted. Gusty
southwest winds (up to 35-40 mph at times) along the southern and
eastern plains will promote elevated-to-briefly-critical fire
weather conditions. However, these conditions will be heavily
dependent on the precipitation (amount and location) this
afternoon. Have decided to keep Fire Weather Watch as is, as
Lincoln County and the eastern portions of Elbert county are still
expected to receive minimal rainfall amounts, and will allow the
next forecast package to see if there is a need to upgrade,
expand, or cancel the watch.

The next system is progged to arrive Thursday night, with a 500-mb
closed low trekking just north of Colorado. This will bring
another round of mountain snow through Friday, particularly for
our northern mountains, as the best QG lift, mid-level
frontogenesis, and upper level jet line up. As of right now,
snowfall amounts are not impressive, but next few forecast
packages may warrant a Winter Weather Advisory if guidance
continues to trend towards higher QPF amounts. For the plains, a
dry but strong cold front will traverse the region overnight,
bringing wind gusts up to 40-50 mph at times through Friday
afternoon. Combined with marginal relative humidity values, this
could bring another round of elevated fire weather conditions.
However, relative humidities still look to be marginal, hovering
around 15-20%.

Dry and warming conditions are expected through the weekend and
early next week as weak ridging aloft dominates the weather pattern.
Ensemble guidance is in good agreement of temperatures reaching up
in the 60s each day through Monday, with the heat peaking mid-week
with temperatures in low 70s. Daily elevated fire weather concerns
are possible for South Park and portions of the plains, however
relatively weak winds will be the limiting factor.

&&

.AVIATION /00Z TAFS through 00Z Friday/...
Issued at 627 PM MDT Wed Apr 1 2026

Recent observations show a line of showers extending over KDEN and
KAPA and moving east, as well as ceilings lowering to around
4000ft-6000ft under the rain showers. Some additional showers
could make their way off the Foothills and east over the airports
early this evening but we expect rain activity to taper off by 04Z
or slightly earlier. Winds remain mainly from the north across the
region with some small variations due to weak outflows.

Model guidance suggests a moderate (40%) chance for fog later
tonight between 06Z and 10Z so we decided to introduce a TEMPO
group for lower ceilings (500ft) as well as visibilities around
3-5SM. Otherwise, clouds will clear by sunrise and winds will
gradually turn to SW-SSW. Mostly clear skies are expected
tomorrow, and there is potential (70% chance) for some higher wind
speeds aloft to mix down to the surface resulting in brief
periods of 25kt gusts late in the afternoon at 21Z-01Z.


&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 9 PM MDT this evening for COZ031-
033-034.

Fire Weather Watch from Thursday afternoon through Thursday
evening for COZ246-247.

&&

$$

DISCUSSION...MAI
AVIATION...AA

NWS BOU Office Area Forecast Discussion