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000
FXUS65 KBOU 230309
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
909 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.

&&

.UPDATE...
Issued at 903 PM MDT Mon Apr 22 2024

Minor adjustments to precip chances this evening to cover isolated
virga/high-based showers in the mountains and northern plains.
Front still slated to push through the plains during the early
morning hours, but no precipitation associated with it.

&&

.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 /06Z TAFS through 06Z Wednesday/...
Issued at 903 PM MDT Mon Apr 22 2024

VFR expected to prevail for all terminals through at least 18Z
Tue. Cold front remains slated to push through the Denver metro
near 02-03Z, bringing a shift to more northerly winds.

The post-frontal environment will bring lighter easterly winds
much of the day Tuesday. Could be enough moisture for FEW-SCT low
clouds around 3,000 ft AGL. Tomorrow`s chances for any
precipitation remain confined mostly to the late afternoon and
evening period, after ~23Z. Would not be shocking to see some
brief CIGS below 060 after 00Z during and following any showers,
but for now confidence is not quite there, so will maintain deck
closer to 080.

&&

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

&&

$$

UPDATE...Rodriguez
SHORT TERM...Schlatter
LONG TERM...Meier
AVIATION...Rodriguez