797
FXUS65 KBOU 031808
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1108 AM 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 likely through this evening, with highest
  rainfall amounts north of I-76.

- 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.

&&

.UPDATE...
Issued at 351 AM MST Tue Mar 3 2026

Radar indicates moderate snow showers are ongoing in the mountains
of our forecast area this morning. Cameras show I-70 is snow-
covered at the Eisenhower Tunnel and Berthoud Pass and other
mountain passes are snow-covered as well. This initial wave of
snow is out-performing model expectations and is setting up
conditions for greater travel impacts. Models within the HREF
have increased their QPF output for today. Meteorologically
speaking, this makes sense due to a slow moving shortwave trough
providing forcing to our forecast area with steep lapse rates and
plenty of low level moisture in place. This combination of factors
will allow for moderate snow to continue over the Front Range
Mountains and higher foothills through this evening. A Winter
Weather Advisory was issued for 6-14" of snow with the heaviest on
the northern peaks.

Across lower elevations, there is growing confidence that rain and
a few thunderstorms will form later this morning. PoPs and QPF
were increased mainly in Larimer, Weld, and Morgan Counties. High
resolution model guidance suggests some locations could receive
over an inch of rain in those counties due to the slow-moving
nature of the rain/storms.

&&

.DISCUSSION /Through Monday/...
Issued at 1152 PM MST Mon Mar 2 2026

Current water vapor imagery shows an upper level shortwave trough
over southwestern Wyoming/northeastern Utah. This weak system
will trek into Colorado by Tuesday morning, with moisture
advecting into the region. Scattered mountain snow showers will
continue overnight tonight and throughout the day Tuesday. Given
how warm we have been lately, snow levels will be around 8000-8500
ft overnight, before dipping down to 7000-7500 ft with the
arrival of cooler air from the shortwave. The overall snowfall
forecast for the mountains were not changed significantly from the
previous forecast, with highest snow accumulations limited to
elevations above 10,000 ft.

The biggest change to the forecast is the precipitation amounts for
the northern plains. Recent guidance now favors the 500-mb
vorticity max right over the plains Tuesday, with good mid-level
forcing throughout the day (mid-level lapse rates will be around
7-8 dg/km). The surface lee cyclone continues to trend farther
south than previous runs, which will allow moisture to be pulled
further south into the northern plains. Hi-res guidance now favors
some areas receiving upwards of 0.50" of QPF by throughout
Tuesday, with a few solutions indicating 1.00". Due to this, have
increased amounts for areas north of I-76. Unfortunately, Denver
area will not see the bulk of this precipitation, as guidance
still favors ~0.10" of QPF. Expect rain showers across the
foothills and plains throughout the day Tuesday before gradually
ending northwest to southeast overnight.

Upper level ridging will return to the state Wednesday and Thursday,
with increased southwest flow aloft on Thursday ahead of an incoming
trough. Temperatures will rebound to the 60s by Wednesday and
possibly lower 70s by Thursday. ECMWF ensemble has consistently been
warmer than the GEFS, with 36 out of 50 members showing max
temperatures between 70-72 (compared to the GEFS, where all 30
members show max temperatures between 62-68 degrees). With these
warm temperatures and dry conditions, elevated to critical fire
weather conditions are possible on Thursday, particularly the Palmer
Divide and eastern plains, where lee cyclogenesis could promote
gusty winds.

Guidance continues to be in good agreement of a shortwave trough
breaking into two pieces of energies on Friday, with the weaker one
ejecting into the northern Great Plains, and the other one trekking
towards southern California and becoming a closed low. Cold air will
advect into the region, with 700-mb temperatures dipping to -6 to -9
dg C. Moisture will begin to stream into the region by late Thursday
night into the mountains, and Friday morning across the plains. At
the surface, a lee cyclone will strengthen slightly and trek
northwest, with a cold front pushing through the plains.
Precipitation is possible across the forecast area, as GEFS and
ECWMF ensembles have consistently shown measurable QPF with the
latest few runs (and even snow!). However, how much moisture is
still the question, as it will depend on the exact track of the
ejecting trough. As of now, the ECMWF has a slightly southerly track
than the GFS, which brings more moisture and colder air into the
region.

By the weekend, we will likely have weak flow aloft as Colorado
looks to be in between the two systems. Dry conditions and warmer
temperatures should prevail for the mountains and plains.

&&

.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.

&&

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

&&

$$

UPDATE...Danielson
DISCUSSION...MAI
AVIATION...20

NWS BOU Office Area Forecast Discussion