855
FXUS65 KBOU 272022
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
222 PM MDT Wed May 27 2026

.KEY MESSAGES...

- Expect widespread showers along with scattered thunderstorms
  today. A few spots may see locally heavy rainfall. There will be
  a limited risk of flash flooding in the burn scars.

- Thursday will bring scattered showers and thunderstorms over
  the far northeast plains and in and near the foothills.

- Thunderstorm chances will increase Friday through Saturday,
  across the plains, with a chance of severe thunderstorms
  especially on Saturday.

- Afternoon showers and thunderstorms will be possible through the
  long-term forecast period with near-normal temperatures
  expected.


&&

.DISCUSSION /Through Wednesday/...
Issued at 214 PM MDT Wed May 27 2026


Current water vapor imagery shows an upper-level low continues to
spin over the Great Basin this morning, with a high amplitude ridge
in place over the Central CONUS. A disturbance moving through the
larger scale south-southeasterly flow over Colorado is aiding in
transporting Gulf moisture into the region, with some light showers
already visible on radar moving across the Palmer Divide and a a few
weak thunderstorms over Lincoln County early this afternoon (as of
12PM). These showers are expected to continue to move north-
northwest through the day keeping a steady stream of Gulf moisture
pumping into the forecast area. Widespread cloud coverage is
expected to persist through today with precipitation chances
greatest over the southern portion of the forecast area and along
the Front Range Mountains, where forecast soundings show a fairly
saturated moisture profile and PWATs are expected to approach values
between 150-200% of normal. With MLCAPE values generally ranging
from 250 to 500 J/kg through the afternoon, expect a few more
thunderstorms to be embedded within the overall shower coverage,
with potential for some heavier localized rainfall amounts of over
an inch possible with any passing thunderstorms (best shot for this
would be for areas in Lincoln County where shower coverage is
expected to be greatest), but this could be limited by the
aforementioned extensive cloud cover already in place. Temperatures
will be about ten degrees cooler across the forecast area compared
to yesterday, with 60s and 70s forecast for the plains and urban
corridor, and 50s and 60s for the high mountain valleys. Could see
some lingering showers persist through late tonight and early
Thursday morning for areas in the northeast portion of the forecast
area.

The synoptic pattern will largely remain unchanged for Thursday
outside of today`s upper-level disturbance shifting slightly
northward. Expecting temperatures to warm a few degrees over
today`s, with some afternoon showers and thunderstorms possible once
again. With a general lack of shear, not expecting storms to have
much potential to organize, but with elevated PWAT values still
remaining 150%-180% of normal, and MLCAPE approaching 1000 J/kg,
could see a few decent showers/storms in the afternoon.

By Friday, the upper-level low over the Great Basin will finally
start to make a move as it starts to eject to the northeast over the
Rockies. While moisture is expected to diminish (ensembles show
PWATs ranging between 100-150% of normal) as flow aloft starts to
shift to the southwest, there will still be enough moisture in place
to see some afternoon showers and thunderstorms, with the best
moisture now expected to reside along the northern portion of the
forecast area.

Saturday will bring the best shot for more organized storm potential
as we finally see an uptick in shear as 500 mb southwesterly flow
increases to 35 to 45 kts as the upper-level low continues to push
northeast along the Rockies. Though the southwest flow aloft is
expected to bring much drier air into the region, with PWATs
expected to drop to around 60%-80% of normal by the afternoon.
Expecting instability to increase throughout the day and our
northern corner to sit adjacent to a dryline where dewpoints in the
50s are expected. Can`t rule out some high-based convection becoming
strong enough for a severe storm or two to develop, and if the
dryline pushes any further west, these chances would become much
higher. Additionally, with the much drier air expected, we could see
some elevated fire weather conditions develop along our southern
most portion of the forecast area, where relative humidities are
forecast to drop into the low to mid teens.

Guidance still shows some slight differences in what becomes of the
upper-level low as it moves along the Northern Rockies, but we
should continue to see southwesterly flow aloft keeping drier air
flowing into the forecast area through the rest of the long-term
forecast period, with afternoon showers and thunderstorms possible
each afternoon and near-normal temps expected.

&&

.AVIATION /18Z TAFS through 18Z Thursday/...
Issued at 1128 AM MDT Wed May 27 2026

MVFR or borderline MVFR conditions are expected to prevail today
with ample mid-level moisture streaming in from the southeast. We
don`t expect the low-to-mid-level deck to break until Thursday
midday. When it`s not raining, CIGS should remain between 050 and
070 through this evening. However, there are chances of several
rounds of showers after 20Z. For now handling with a PROB30 for
-TSRA from roughly 20Z through 02Z. If any -TSRA or slightly
 heavier rain showers move over the terminals, CIGS are likely to
 drop to 040. Winds for the most part should be out of the
 southeast all day into the evening, turning more southerly after
 03Z. At DEN gusts could exceed 20 kt. If -TSRA occur, which is a
 low probability, then there could be some brief gusty winds to
 30 kts but again, a PROB30 should cover that potential.

All showers should either diminish or move out of the area after
03Z. CAMs have CIGs dropping to 030 at the terminals sometime
after 08Z, but those should be short lived once the almost June
sun mixes those low clouds out. On Thursday a weak Denver Cyclone
is expected which will reliably result in weak NW winds at BJC,
VRB at APA, and eventually ESE early afternoon at DEN after light
out of the SSE through Thursday morning. Only at DEN could the
winds exceed 10-12 kts Thursday afternoon. The TAFs don`t have it
yet, but we`ll likely need to introduce a PROB30 for -TSRA after
19Z. Instability will be higher Thursday (but still weak for this
time of year) than today.

&&

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

&&

$$

DISCUSSION...9
AVIATION...Schlatter

NWS BOU Office Area Forecast Discussion