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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS65 KBOU 210254
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
854 PM MDT Tue Apr 20 2021

.UPDATE...
Issued at 849 PM MDT Tue Apr 20 2021

Low to mid level cloudiness is increasing across the area and
mostly cloudy skies are still expected overnight. This should keep
lows a few degrees warmer than last night, which was accounted
for in the forecast. The next shortwaves are advancing east over
the Great Basin and south over the Rockies, and mid to upper level
moisture will increase ahead of them tomorrow. There still looks
to be enough lift and moisture to support scattered, light showers
across northeast Colorado tomorrow afternoon and evening. The
forecast is on track with only minor updates this evening.

&&

.SHORT TERM...(This evening through Wednesday)
Issued at 238 PM MDT Tue Apr 20 2021

A weak wave embedded in the northwest flow aloft is passing east
of Colorado. This is bringing gusty winds and clouds to the
northeast plains. Some of this cloudiness will creep westward
through the late afternoon and evening bringing mostly cloudy
skies for tonight. It will be another cold night, but the cloud
cover will help keep temperatures from reaching record lows. Most
locations are expected to bottom out in the 20s.

For Wednesday, two systems will affect the region, one dropping
out of the Northern Rockies and the other moving east across the
Great Basin. Both of these systems will be weakening as they track
across the Central Rockies. The piece from the north will help
reinforce the cooler air in place. Lift will be weak Wednesday,
but expect enough lift and moisture to be in place for light snow.
An easterly low level flow will provide weak upslope lift as
well. Snowfall amounts through Wednesday afternoon are expected to
be light with a few inches possible over the mountains and
foothills. Don`t expect any accumulation across the lower
elevations. Cold air will remain in place with highs only in the
30s across much of northeast Colorado.

.LONG TERM...(Wednesday night through Tuesday)
Issued at 238 PM MDT Tue Apr 20 2021

Light snow showers will continue across the mountains during the
overnight hours Wednesday under a weak deformation zone, ahead of
a relatively weak shortwave trough axis. The forecast trend has
been towards a drier solution over the past few model cycles,
especially over the plains. Still, there is enough lift around for
a couple inches of snow across the Front Range mountains and
Foothills. Snow showers will mix with rain over the plains, with
most locations seeing a half inch of snow or less.

The better forcing departs the area by Thursday morning and
should lead to a drier day over most of the plains. Temperatures
should also warm a bit as a warm air advection regime develops.
Despite the warmer temperatures, cloud cover should be fairly
widespread with mid-level moisture around. Across the mountains, a
few convective showers are possible with instability increasing
during the day. A few of these showers could spread east into the
urban corridor during the afternoon hours, but otherwise expect a
relatively quiet day.

Another trough passes across the area late Thursday into Friday,
with a separate round of showers likely across the higher terrain.
The strongest QG ascent is well to our south and the surface cold
front is pretty weak. There is enough moisture and instability
left in the mountains to continue some likely PoPs with lower
chances across the plains.

Warm weather finally makes a full return this weekend as ridging
builds into the region and warm/dry southwest flow increases.
Temperatures should make it into the 60s on Saturday and will
likely reach the 70s Sunday. Warm weather looks like it will try
to continue into Monday as guidance has pushed back the arrival of
the next storm system.

&&

.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 849 PM MDT Tue Apr 20 2021

Expect VFR conditions to persist until visibility decreases with
precipitation Wednesday afternoon as some weak weather systems
move over the central Rockies. Expect light showers in the
vicinity of the terminals by the early afternoon and MVFR
conditions with showers over the terminals by the late afternoon.
ILS conditions are also expected to persist through the TAF period
with broken to overcast skies and cloud bases at 4000 to 6000
feet. Light and variable winds this evening should turn
southeasterly overnight and remain southeasterly Wednesday, with
speeds generally under 15 knots.

&&

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

$$

UPDATE...Direnzo
SHORT TERM...Meier
LONG TERM...Hiris
AVIATION...Direnzo