415
FXUS65 KBOU 201814
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1214 PM MDT Wed May 20 2026

.KEY MESSAGES...

- Unsettled Wednesday through Friday with scattered to numerous
  showers and a few storms.

- Warming and drying trend for the weekend.

&&

.DISCUSSION /Through Tuesday/...
Issued at 109 AM MDT Wed May 20 2026

Cooler temperatures and rain chances are expected to continue
through the workweek. An upper level trough will remain to our
west/northwest through Thursday. Ahead of the trough, we`ll see
decent large scale lift. And with the moisture already present
thanks to the rain the past few days, this will be enough to
produce some scattered showers and thunderstorms during this time.
For today, instability is on the lower end (MLCAPEs 400 J/kg or
less), so we`re not expecting any severe storms this afternoon.
The one thing we will need to keep an eye on the potential for
landspouts. High res models have a Denver cyclone developing near
the urban corridor this afternoon and we do have some weak
surface CAPEs in that area, so landspouts are not out of the
question. For Thursday, coverage and intensity of storms look a
bit higher. Moisture will be ushered into the area at the surface,
QG lift ahead of the trough will be stronger, and we could see
some breaks in the clouds in the late morning allowing for some
surface heating and increased lapse rates/instability for
Thursday afternoon. The highest chance of stronger storms will be
in our southeastern counties where the better shear and
instability overlap. Right now, the main hazard looks like large
hail, but we can`t rule out an isolated tornado or strong winds as
well.

The upper level trough will move over the area and off to the
northeast overnight Thursday into early Friday. A cold front will
also move through overnight, dropping temperatures a few degrees
for Friday. Rain chances will continue on Friday as a secondary,
weaker trough develops to our northwest and moves over the area
late Friday into Saturday. Coverage and intensity of showers and
storms will be lower than what we`re expecting on Thursday.

After that secondary trough moves through, upper level ridging
will start to build over the area. A warming trend will begin on
Saturday, with highs reaching into the upper 80s for portions of
the plains by Monday. The warming trend will be halted on Tuesday
as another trough approaches from the west, cloud cover increases,
and precip chances return to the mountains and potentially the
plains.

&&

.AVIATION /18Z TAFS through 18Z Thursday/...
Issued at 1210 PM MDT Wed May 20 2026

Current observations show a Denver cyclone set up just to the
west of KDEN. This cyclone is expected to shift southward over the
next few hours leading to N/NNE winds by early this afternoon at
all three sites. Current radar shows showers ongoing to the west
of KBJC in the mountains. There is still strong agreement that
showers and storms should move in from west to east affecting all
three terminals this afternoon starting as early as 19z and
lasting into the early evening. Visibility could lower to MVFR or
IFR at times as this rainfall moves through.

Otherwise, winds will shift around to drainage by this evening at
all three TAF sites. Low clouds are expected to continue
overnight given the presence of deep low- to mid-level moisture.

For tomorrow, a Denver cyclone is forecast to setup near/over
KDEN once again. The evolution of this feature will in turn affect
the SHRA/TSRA chances. For now, we expect showers and storms in
the vicinity of the terminals by around 19z to 21z. These showers
and storms should last well into the evening. We have left out any
mention of -TSRA for now, but there is a chance (15-20%) given
the decent instability expected. Visibility could once again lower
to MVFR or IFR at times as this rainfall moves through. There is
also the possibility of some breaks in the clouds, especially in
the afternoon tomorrow at KDEN, so have raised ceilings to around
12,000 ft AGL for now. Finally, gusty winds are possible tomorrow
afternoon with any storms that do move near the three sites.

&&

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

&&

$$

DISCUSSION...AP
AVIATION...MV

NWS BOU Office Area Forecast Discussion