231
FXUS65 KBOU 270522
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1122 PM MDT Tue May 26 2026

.KEY MESSAGES...

- Wednesday appears to be the most active day with more widespread
  showers and thunderstorm coverage with locally heavy rainfall
  possible due to slow movement of thunderstorms.

- After somewhat of a lull Thursday, thunderstorm potential will
  increase again Friday through the weekend with a chance of
  severe thunderstorms over the plains.

&&

.DISCUSSION /Through Tuesday/...
Issued at 202 PM MDT Tue May 26 2026

Current water vapor satellite imagery shows a shortwave trough in
southwestern U.S. embedded in the flow of an upper level closed
lower over the coast of California. Southerly flow aloft over
Colorado has allowed mid-level moisture to be advected into the
region, with showers now initiating over the mountains. Expect
showers and thunderstorms to increase in coverage over the high
terrain this afternoon. Modeled Skew-T soundings show a highly
saturated environment, with PWAT values between 0.40" and 0.60".
With modest instability over the high terrain, some stronger storms
could produce heavy rain. However, given the expected fast storm
motion, concerns are minimal for flooding at this time, unless we
get training.

Across the plains, surface observations have shown southeast winds
gusting between 30-40 mph this morning. With current ACARs soundings
showing relatively steep lapse rates, expect these gusty winds to
persist as daytime mixing continues. Overall lack of decent
instability across the plains will limit chances for widespread
precipitation to occur this afternoon. However, hi-res guidance does
indicate potential for a few showers and isolated thunderstorms for
the Palmer Divide and I-25 Corridor late afternoon and evening. With
DCAPE values projected to reach up to 800-1000 J/kg, gusty outflow
winds will be the main threat.

The next few days will likely see a blocking pattern set up across
the U.S. with the upper level closed low situated over the western
U.S. and blocking high over the Great Plains. This will leave
Colorado under relatively weak flow aloft between these two
features. On Wednesday, global and regional guidance are in good
agreement of the aforementioned shortwave trough slowly trekking
across the forecast area, providing synoptic lift for a round of
showers and thunderstorms for the plains and mountains. Sounding
guidance has continued to indicate a warm moist vertical profile,
with PWAT values above the 90th percentile. And, given weak flow
aloft, storm motion will be slow as evident in hodographs. Thus,
localized heavy rain will be the main concern for tomorrow. However,
there is also a conditional threat for a landspout to occur if we
get a DCVZ and enough sunshine for low-level instability to build.
There is still some question if we can get a Denver cyclone to
form tomorrow morning, and with the expected incoming cloud cover
we might not get enough instability that some models suggest.

Showers may continue into the overnight hours of Wednesday night,
before gradually ending by sunrise on Thursday morning. Temperatures
should rise to the upper 70s across the plains as the upper level
shortwave exits the region. With upsloping, we could have another
round of showers and thunderstorms mainly for the Front Range
mountains and foothills. Given continued weak flow aloft, storms
will be slow moving and thus localized heavy rain is possible again.

By Friday and into the weekend, ensemble guidance indicates the
upper level low over western U.S. weakening and getting absorbed by
the flow of the upper level ridge. With continued southeast flow at
the surface, low-level moisture will be continuously advected into
the region. Soundings show better instability building over the
plains, with mid-level flow turning more south/southwesterly
resulting in better shear profiles. This will allow better potential
for strong to severe storms Friday and particularly Saturday
afternoon.

Weak southwest flow aloft will dominate the flow pattern Sunday and
into the beginning of the week, with an upper level ridge still in
place over Central U.S. With low and mid-level moisture still in
place, guidance does indicate potential for continued showers and
isolated thunderstorms for the forecast area. However, given overall
weak flow and forcing, severe threat is very low at this time.

&&

.AVIATION /06Z TAFS through 06Z Thursday/...
Issued at 1116 PM MDT Tue May 26 2026

SSE winds will be in place overnight and will continue thru Wed
aftn. Only expect some mid and higher level cloud cover overnight
but ceilings will drop down to around 6000 ft by 16z. By 19z,
there will be a chance of showers along with a slight chc of -tsra
thru the aftn hours. If a heavier shower or tstm were to occur
ceilings may briefly drop down to 3500 ft. By 23z winds will
become more SE and continue into Wed evening. There will continue
to be a chc of showers with a slight chc of -tsra thru 04z.
Ceilings will remain around 6000 ft.

&&

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

&&

$$

DISCUSSION...MAI
AVIATION...RPK

NWS BOU Office Area Forecast Discussion