000
FXUS65 KBOU 260541
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1141 PM MDT Thu Apr 25 2024

.KEY MESSAGES...

- Less intense showers overnight.

- Cooler on Friday, with scattered showers continuing.

- Significant snowfall likely (70-80% chance) in the mountains
  Friday night through Saturday night, widespread rain showers
  over the plains

- Warmer and drier early next week

&&

.UPDATE...
Issued at 719 PM MDT Thu Apr 25 2024

With the northeast corner of Colorado now in cooler air, the
severe threat has ended and the Tornado Watch has been cancelled.
There may still be some strong storms clipping the eastern border
with small hail, gusty winds, and brief heavy rain. Further west
we`re seeing a minimum in shower activity around Denver now as
we`re between the low level moisture/instability and the
wraparound dynamic forcing that will come later tonight. We are
seeing weaker convection rotating northward from around Colorado
Springs, so there could be some increase in showers and a few
storms over the next couple of hours. There should be increased
shower activity again behind the low as it moves east later
tonight. No big changes to the forecast, but we`ll try to refine
this timing a bit better.

We`ve also dropped the Red Flag Warning for eastern Elbert and
Lincoln counties as the cooling temperatures and decreasing winds
have taken conditions below criteria.

&&

.SHORT TERM /Through Friday/...
Issued at 233 PM MDT Thu Apr 25 2024

Satellite shows a potent/negatively tilted trough axis centered
near the Four Corners region. This trough is expected to continue
to deepen as it ejects into the central plains later this evening.
Meanwhile... a few thunderstorms have developed in Washington
county in the last hour or so. The edge of our CWA is also roughly
the edge of the favorable environment for severe weather. This
threat should continue through the next few hours before shifting
east into Nebraska/Kansas.

Further west, some weak showers have developed across the high
country and foothills, though this activity has remained fairly
weak so far. This should gradually become a bit more organized
this evening as the trough axis pivots across the state. There`s
still some uncertainty if Denver/I-25 corridor get into any
showers/storms later this evening, with CAMs offering many
solutions but zero answers. At least some scattered showers will
continue overnight in the wake of the trough, especially across
the mountains. Some light mountain snow is also expected with a
couple inches of slushy accumulation possible above 10000ft.

Friday will be a bit of a transition day in between systems, as
the first trough axis cuts off and stalls over the central
Plains/Midwest, while another trough approaches from the west.
Cool northwesterly flow on the back of the initial trough will
keep temperatures cooler and breezy across the plains. With
moisture increasing again in advance of the second trough, there
should be a gradual increase in showers later in the afternoon yet
again. Still this won`t compare to the rain and snow coming this
weekend... which you can read more about below.

&&

.LONG TERM /Friday night through Thursday/...
Issued at 233 PM MDT Thu Apr 25 2024

Much cooler and wetter weather is expected over the weekend as a
closed upper low tracks from the Four Corners Region across Southern
and Central Colorado. Snowfall rates should increase in the
mountains during Friday evening as QG ascent and moisture
increase ahead of the upper low. Precipitation should also
increase across the plains as upslope flow develops behind the
passage of a weak cold front. The heaviest precipitation Friday
night should be focused from the Continental Divide eastward
across the foothills and Front Range Urban Corridor. Models are
suggesting enough convective instability during the evening to
produce a few thunderstorms leading to higher precipitation rates.
There may be a lull in the precipitation during the early morning
hours with precipitation ramping back up again by sunrise as the
flow around the mid and upper level low results in increasing
moisture and easterly upslope flow along and east of the
mountains. Widespread precipitation is expected to continue across
most of the forecast area through the Saturday evening as the
upper low slowly drifts east to northeast across the state. Models
are showing 2 to 3 inches of QPF from the Front Range Mountains
eastward across the Front Range Urban Corridor and Palmer Divide
with lesser amounts further east across the plains. The mountains
should see snow amounts from 6 inches to possibly over 2 feet
with the heaviest amounts over the Front Range Mountains above
10,000 feet. Therefore, have issued a Winter Storm Watch for these
areas effective Friday evening through late Saturday night. There
is also the potential for a few inches of snow across the higher
portions of the Palmer Divide as well.

Precipitation should decrease across Northeastern Colorado on
Sunday with some gusty winds to 30 mph as the upper low moves into
the Northern Great Plains States. Across the high country, periods
of snow showers should continue due a moist westerly flow aloft.
Warmer and drier weather is expected Monday through Wednesday due
to some weak ridging aloft. However, scattered (25%- 40%) snow
showers will still be possible each day over the higher mountains.

&&

.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.

&&

.FIRE WEATHER...
Issued at 233 PM MDT Thu Apr 25 2024

Moisture has been slow to mix out along and south of I-70 this
afternoon, but recent trends over the past couple of hours suggest
that rapid drying is ongoing. Some unofficial stations across
southern Lincoln county have approached RFW criteria in the past
hour, and this is expected to be the case across the current Red
Flag Warning area through mid/late afternoon. Will keep the
current highlight in place.

Cooler weather is expected on Friday. Despite increasing
northwesterly winds, RH values should remain high enough to avoid
critical fire weather conditions.

&&

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

&&

$$

UPDATE...Gimmestad
SHORT TERM...Hiris
LONG TERM...JK
AVIATION...Cooper
FIRE WEATHER...Hiris