946
FXUS65 KBOU 032055
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
155 PM MST Tue Mar 3 2026

.KEY MESSAGES...

- Off/on snow in the mountains through this evening with some
  travel impacts, especially over/near higher passes.

- Low elevation rain showers likely through this evening. An
  isolated thunderstorm or two possible across the Front Range
  foothills and I-25 corridor.

- Critical fire weather conditions possible across the plains on
  Thursday due to mild, dry, and breezy conditions.

- Potential for colder storm system with more widespread snow
  Thursday night through Friday, although uncertainty in amounts
  remains.

&&

.DISCUSSION /Through Tuesday/...
Issued at 125 PM MST Tue Mar 3 2026

Water vapor satellite shows the center of the upper level low over
northern Colorado this afternoon (quite close to Hayden/Craig). In
our CWA, we`ve seen scattered, somewhat organized clusters of
showers through most of the day, with even a couple of lightning
strikes noted over the past few hours. The last several cycles of
the HRRR attempt to develop one more cluster of convection over
the Front Range/I-25 corridor this evening as the center of the
upper low continues to drift closer to Denver. Additional rainfall
is likely for most of the I-25 corridor (>70% chance of measurable
precipitation), but amounts advertised by some model runs (e.g,
the 18z HRRR) are likely a little overdone. Still, any additional
rainfall would be a welcome sight. Rain should end late this
evening, but there could be some patchy fog across the plains and
Denver metro late tonight into Wednesday. BUFKIT soundings suggest
some FG potential, even though the explicit model output does not
show much.

Today`s upper low should transition back to an open wave as it
shears out and drifts east of the forecast area by Wednesday,
while a brief period of ridging develops. Temperatures should warm
back into the upper 50s to mid 60s during the afternoon, with
light winds for most locations.

The next storm system approaches the area by Thursday, leading to
a complicated setup for both fire weather (Thursday) and winter
weather (Friday) across our CWA. Strong southwesterly flow aloft
is expected to develop Thursday as a sharp shortwave swings
towards UT/AZ by Thursday afternoon. Mid-level temperatures also
warm a bit, and with deep mixing... high temps should easily reach
the mid 60s to low 70s for the lower elevations. The main question
will be if enough wind mixes down for critical fire weather
conditions across the plains... but for more detail see the Fire
Weather section of the AFD below.

The forecast pattern gets much more complicated Thursday night
into Friday. The primary shortwave now looks to close off near the
Four Corners or southwest Colorado. Most of that energy splits
off and ejects into the central CONUS, while some of the wave is
sheared off and shoved southwestward into the desert southwest, as
a 130kt jet streak and accompanying shortwave drops in from
British Columbia. As the primary wave ejects, a sharp cold front
drops into the region during the day with a brief period of
north/northeast upslope that would favor precipitation across most
of the mountains and into the I-25 corridor.

There is generally better agreement that the primary piece of the
wave will eject out into the Central Great Plains by Friday
evening, but with the interaction between the primary trough axis
and the secondary shortwave dropping in, it seems plausible, if
not likely, that the model consensus today is temporary. This is
also hinted at by today`s ensemble runs. In fact, a majority of
the global deterministic models today (e.g., ECMWF, UKMET, ICON,
GDPS) fall well outside the interquartile range of QPF for DEN
from their respective ensemble systems. It will be worth watching
if we see any noteworthy shifts in the ensemble distribution over
the next 24 hours or so... but for now our forecast QPF (and snow)
is much closer to the GEFS/ECMWF ensemble mean. Stay tuned!

The pattern looks a little more straightforward for this weekend,
as Colorado is split between the cutoff low to the southwest, and
the stronger flow across the northern Rockies. Generally quiet and
mild weather is anticipated during that time.

&&

.AVIATION /18Z TAFS through 18Z Wednesday/...
Issued at 1108 AM MST Tue Mar 3 2026

Radar has filled in with convective showers, and there have also
been isolated thunderstorms. Low clouds were filling in as well
with a northerly flow and weak upslope component, in addition to
the aid of all the showers. We`ll keep prevailing MVFR conditions
with local IFR for the duration of the afternoon and evening,
likely lasting til about 03Z. Probability of a Thunderstorm (TS)
is still low at any given TAF site (less then 20%).  Even after
the showers end, it appears we`ll see a modest (60%) chance of
light fog and 3-4SM vis with low IFR ceilings til about 06Z-08Z.
Light drainage winds are then expected to develop which should
bring clearing skies but also a low (10-15%) chance of thicker fog.
At this point, we still think enough downslope drainage component
is expected to keep VCFG out of the local TAF sites including
KDEN. Odds would be much higher for fog farther north - closer to
KGXY and KFNL.

North winds have established themselves and should hold through
02Z before gradually weakening and turning around to the
west as previously discussed. VFR will prevail for Wednesday with
mostly clear skies and winds slowly transitioning from S-SE-E
14Z-22Z.

&&

.FIRE WEATHER...
Issued at 125 PM MST Tue Mar 3 2026

Critical fire weather conditions are possible on Thursday as warm
and dry conditions develop once again. There is good agreement
that RH will fall to the 10-15% range for the Palmer Divide and
Lincoln county, though there is less certainty with winds. With
southwesterly flow aloft, this tends to favor the development of a
Denver cyclone... which should shelter most of the Denver metro
from the stronger winds but may also accelerate the low level flow
to the south and east. GEFS Hot Dry Windy Index plumes generally
fall between the 75-90th percentile near Limon, with much more
spread north of I-70. There was enough confidence to support a
Fire Weather Watch for the Palmer Divide and adjacent plains to
the east, but an eventual upgrade to a Red Flag Warning will be
highly dependent on the wind forecast as we draw closer to the
event.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 8 PM MST this evening for COZ033-
034.

Fire Weather Watch Thursday afternoon for COZ241-245>247.

&&

$$

DISCUSSION...Hiris
AVIATION...20
FIRE WEATHER...Hiris

NWS BOU Office Area Forecast Discussion