000
FXUS65 KBOU 260921
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
321 AM MDT Fri Apr 26 2024

.KEY MESSAGES...

- Cooler on today, with scattered showers continuing.

- Significant snowfall for the mountains and higher foothills
  tonight through Saturday night.

- Snow level 7000 to 8000 feet MSL.

- Rain Saturday/Saturday night lower foothills, Urban Corridor,
  and eastern plains with 1 to 3 inches of rainfall.

&&

.SHORT TERM /Through tonight/...
Issued at 304 AM MDT Fri Apr 26 2024

The first trough over the northeast plains early this morning,
is expected to lift into NE by 15z. Much of the precipitation
associated with this trough has shifted east of the urban corridor
and wrap around showers should impact the northeast plains the
rest of this morning. Elsewhere, a short wave ridge working its
way into central CO this morning will allow for just isolated to
scattered light showers through midday. Light to moderate QG
ascent early this morning will be replaced by QG descent or
subsidence by midday. Later this afternoon and tonight, the next
transition will kick in. The ridge will shift eastward, with
increasing mid/upper level QG ascent redeveloping ahead of the
next storm system. Increasing mid level instability this afternoon
will allow for primarily scattered showers this afternoon with a
few embedded thunderstorms. I do not anticipate any storms as
strong as what occurred yesterday, but small hail and gusty
outflow winds may accompany these storms. For tonight, increasing
QG ascent with a diffluent pattern ahead of the trough will allow
for snow to increase in coverage and intensity in the mountains,
especially after midnight. Consequently, a winter storm watch will
remain in effect starting tonight through Saturday night. Another
concern will be the higher foothills tonight, especially for
elevations above 8500 feet. The impacts will be strongest for
these areas after 12z Saturday, but snow could get started a
little earlier, so we included zones 35 and 36 in a winter storm
watch as well starting around midnight.

&&

.LONG TERM /Saturday through Thursday/...
Issued at 304 AM MDT Fri Apr 26 2024

Upper level low will be located near the Four Corners 12Z
Saturday. The low slowly travels east-northeast across southern
Colorado Saturday and Saturday night. The low eventually lifts
northeast of Colorado by Sunday morning. Models are in good
agreement on the track and timing of this system. Will see strong
lift from the low and an easterly upslope flow across the Front
Range. Rain and snow become widespread early to mid Saturday
morning and continues through at least Saturday evening.
Precipitation amounts for the Front Range and near by plains have
been running in the 1.50 to 3.00 inch range the last several model
runs. One challenging part of this system will be the snow level.
Wet bulb zero heights greatly vary in the models, anywhere from
7000 feet to a little over 9000 feet. With precipitation rates
expected to be moderate to heavy, will lower the snow level some.
Thinking the snow level ends up 7000 to 8000 feet. Will issue a
Winter Storm Watch for the foothills. Areas above 8000 feet are
expected to see mostly snow come Saturday with 12-18 inches
possible.

Rain and snow is expected to come to an end by Sunday morning
along the Front Range as the upper level low lifts northeast of
Colorado and a northwest downslope develops. Over the plains, rain
should linger into Sunday morning. Cross sections indicate there
should be enough moisture embedded in the northwest flow aloft to
produce snow showers over the mountains Sunday with rain in the
lower valleys. Additional snowfall is expected to be light on
Sunday so plan on ending the Winter Storm Watch at 6AM Sunday
morning. Some of the showers may survive onto the plains Sunday
with additional rainfall amounts on the light side (less than a
quarter inch).

Westerly flow aloft to prevail for much of next week, Monday
through Thursday. Main storm track will be north of Colorado with
the storm systems passing over the Northern Rockies. The first
wave next week passing north of Colorado is on track to be late
Monday. This will bring a chance for showers and storms to the
northern mountains. A cold front associated with the wave will
drop south across Colorado Monday night. Not much cold air behind
it with highs climbing back to around 70 degrees over northeast
Colorado on Tuesday. A second wave will pass north of the state
sometime Wednesday and it sends a cold front south across
northeast Colorado. There are some timing differences with this
system, so highs are a little more uncertain than other days. Best
lift and chance for precipitation stays north of Colorado, but
there`s a chance for isolated showers and storms
Wednesday/Wednesday night.

&&

.AVIATION /06Z TAFS through 06Z Saturday/...
Issued at 1132 PM MDT Thu Apr 25 2024

Scattered showers will decrease overnight, with ceilings mainly
between 4000 and 8000 feet. Localized MVFR ceilings and
visibilities are possible. As the showers decrease, then wind
may transition to westerly by 12Z Friday but overall confidence in
the wind forecast is low tonight. A break in shower activity is
expected during most of the day Friday with higher ceilings.
Northwest winds gusting to around 25 knots are expected most of
the time.

MVFR ceilings/visibilities will develop by 04z Friday evening as
rain showers increase in coverage and intensity overnight.
Easterly winds 8-12 kts can be expected at that time.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Winter Storm Watch from this evening through late Saturday night
for COZ033-034.

Winter Storm Watch from late tonight through late Saturday night
for COZ035-036.

&&

$$

SHORT TERM...Cooper
LONG TERM...Meier
AVIATION...Cooper

NWS BOU Office Area Forecast Discussion