000
FXUS65 KBOU 221947
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
147 PM MDT Mon Apr 22 2024

.KEY MESSAGES...

- Cooler Tuesday, but then above normal temperatures again for
  Wednesday and Thursday.

- Stormier weather pattern in the works, starting late Thursday
  and peaking next weekend.

- Stronger storms possible northeast plains Thursday
  afternoon/evening.

&&

.SHORT TERM /Through Tuesday/...
Issued at 122 PM MDT Mon Apr 22 2024

For the rest of the afternoon, a few weak showers are possible
across the high country and northeast corner of Colorado. Snow
levels are all the way up to the highest mountain passes. Any
precipitation that reaches the ground will be very light, and no
precip is expected to reach the ground across the I-25 corridor.
Virga and gusty winds look to be the main impacts, though there
are already WNW winds gusting 20-30 mph across portions of the
plains. Winds will die down after 7 PM with decoupling.

Tonight a cold front moves across the plains from north to south
between 2-4 AM, and will probably reach up to 8500 ft across the
eastern foothills. We use the word "cold" lightly because
temperatures behind the front should only be 10 degrees cooler
initially. Lows across the plains should remain above freezing,
with 30s across most of the plains, but 40ish across the I-25
corridor, lowest foothill locations, and the urban heat islands.
The front does not impact the West Slope whatsoever, and with
partly to mostly cloudy skies, lows will be warm in the low 30s
across the mountain valleys. The air behind the front is dry so we
are not expecting any post frontal precipitation through late
morning Tuesday. Just ahead of the 500 mb ridge, there is weak
synoptic scale lift in place across the area, and above the
frontal boundary enough heating should result in isolated
afternoon/evening showers and thunderstorms. The snow level
should again be above 10kft, and with 100-300 J/kg SBCAPE in
place, there is a chance of a few rumbles of thunder. All told,
the chances of measurable precip are still pretty low across the
high county, between 20-40% for the valleys, and close to 50%
above 10kft. Amounts will be light.

Across the plains on Tuesday, behind the front light east winds
5-15 mph are expected throughout the day. Dewpoints will remain in
the low to mid 30s, and with the strong frontal inversion near 700
mb, there is zero SBCAPE and effectively no MUCAPE east of the
Rockies, so any convection that moves off the mountains will be
hard pressed to generate enough precipitation for it to reach the
ground. Virga and a few sprinkles may occur across the I-25
corridor. Increasing QG lift occurs Tuesday evening with better
precip chances across the plains (covered immediately below in the
long term section). With ample cloud cover and a cool post-
frontal airmass, expect highs Tuesday to remain in the low 60s
across most of the plains. The northern tier of counties should be
mostly clear to party cloudy, and thus a little warmer in the mid
60s. The mountain valleys will be above the frontal inversion,
blocked by the Rockies, and highs should be in the upper 50s to
around 60 until showers/isolated storms web bulb the temperatures
into the 40s where/when precip falls.

&&

.LONG TERM /Tuesday night through Monday/...
Issued at 122 PM MDT Mon Apr 22 2024

Scattered showers and isolated storms will linger into the
evening hours in the post frontal airmass. The loss of daytime
heating will stabilize the airmass, causing the convective
activity to weaken as it progresses eastward. Could see a few
showers linger past midnight over the far eastern plains. By
sunrise Wednesday morning, northeast Colorado will be dry.
Temperatures warm back up Wednesday as an upper level ridge moves
over the Central Rockies. Mostly sunny skies will help
temperatures climb into the mid to upper 70s. A weak wave rounds
the top of the ridge, and could bring a few weak showers and
storms to far northern Colorado Wednesday afternoon/evening.

Flow aloft turns southwesterly as the an upper level trough over
the Desert Southwest pushes the ridge east of the region. This is
expected to keep temperatures mild with highs in the 70s again. At
the surface, pressure lowers along the Front Range in advance of
the upper level trough. Southeast winds over the plains will
advect moisture into eastern Colorado pushing dew points into the
40s, and possibly lower 50s. Expect an area of decent instability
(SB CAPE 750-1500 J/kg) over eastern Colorado Thursday afternoon.
Lift from the trough will trigger showers and storms, some of
which could become strong to severe over the northeast plains.

For Friday, weak ridging will bring a dry start to the day.
Models show the airmass becomes unstable during the afternoon with
showers and weak storms possible. Expect cooler temperatures for
Friday with cold air advection behind Thursday`s system.

For the weekend, a large better organized system will be tracking
across the western half of the country. Temperatures are expected
to continue to cool off. We will likely (60-80%) see a round of
showers and mountain snow on Saturday. Some models (like the
ECMWF) speed up this system with dry conditions possible for
Sunday, so will have the highest PoPs on the Saturday. Heavier
precipitation (1-2 inches) remains possible this weekend, though
if the faster solutions pan out, amounts may end up on the lighter
side.

&&

.AVIATION /18Z TAFS through 18Z Tuesday/...
Issued at 1140 AM MDT Mon Apr 22 2024

VFR through the TAF period though there could be some SCT030 in
the light upslope late morning Tuesday. But first, the battle of
wind shifts is ongoing. There is a very weak cool front to the
north of KDEN, moving slowly south. This looks to impact the
airfield after 1830Z. To the west, a lane of stronger WNW winds is
moving toward KDEN. These gusty WNW winds have been in the
forecast for the past 24 hours from all the high res models. At
this time it looks like the strong WNW winds will reach KDEN
between 1930-20Z, but the time period of 18-20Z is very low
confidence in wind direction. After 20Z, confident the WNW winds
will win out across all the terminals, and may gust to 25 kts.
After 02Z, decoupling occurs, reducing winds to 8-14 kts generally
out of the west.

A stronger cold front will move southward, impacting BJC and DEN
around 09Z with a north wind shift 10-15 kts. APA should see the
shift 30 minutes later. It is dry behind the front, but some mid-
level moisture may work in resulting in SCT030 after 15Z. By 18Z,
the main cloud deck should be around 080 but it will be BKN or OVC
by then. Light east winds should prevail midday and into the
evening hours Tuesday.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

SHORT TERM...Schlatter
LONG TERM...Meier
AVIATION...Schlatter