974
FXUS65 KBOU 260239
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
839 PM MDT Sat May 25 2024

.KEY MESSAGES...

- Snow showers in the mountains with scattered slick spots
  overnight. Showers and isolated storms decreasing elsewhere.

- Only isolated late day mountain showers and thunderstorms on
  Sunday with dry conditions over the rest of the forecast area.

- Warm through the coming week. There will be limited late day
  thunderstorm activity on Tuesday with better coverage Wednesday
  through Friday. Strong to severe storms will be possible
  Wednesday and Thursday.

&&

.UPDATE...
Issued at 839 PM MDT Sat May 25 2024

Satellite shows a pretty vigorous shortwave moving from northeast
Utah into Northwest colorado this evening. Scattered to numerous
showers were occurring in the mountains in the upward forcing area
ahead of this feature, while a few showers and isolated storms
continued to push across the plains despite relatively dry low
levels. We`ll see showers continue for the next several hours in
the high country, resulting in another 1-3" for most areas above
9,500-10,000 feet. Temperatures get cold enough for even some snow
late tonight down to mountain valley floors. We`ve adjust PoPs
upward to account for the combination of upward forcing and
orographics.

On the plains, while showers are decreasing, we`ve delayed the
cessation due to the upward forcing in play. In fact, there could
even be a few showers lingering over the northeast corner of the
state through early Sunday morning.

Subsidence is still on track along the Front Range by late tonight
and Sunday morning, which will lead to mountain wave enhanced and
gusty winds in/near the foothills. Those will mix/spread onto the
plains for much of Sunday. But, sunshine and mostly dry
conditions will prevail with the large scale subsidence in place.

&&

.SHORT TERM /Through Sunday/...
Issued at 245 PM MDT Sat May 25 2024

Convection is continuing over the mountains and foothills,
mainly north of I-70 at this time. There are also scattered
showers and storms moving eastward across the northern half of
Weld County. Upstream of our CWA, the storms are producing 60 mph
gusts and some lightning.

Models bring the weak upper trough axis across the CWA tonight, then
fairly strong northwesterly flow aloft on Sunday.  The QG fields
show some upward vertical velocity this evening in front of the
trough axis, then downward energy moves in after 06Z continuing
through most of Sunday for the forecast area. Cross sections show a
mountain wave set-up from 09Z to 18Z on Sunday, so will hit the
winds pretty hard on the high mountains and foothills. The low
level winds briefly go to drainage patterns later this evening
after the convection, but then downsloping kicks in after the
upper trough moves eastward. Fairly strong northwesterly winds are
progged all day for the CWA on Sunday.

Looking at moisture, precipitable water values and low level dew
points drop off overnight with Sunday looking pretty dry for all
areas.  There is little to no CAPE progged on any of the models
for Sunday afternoon as well. For pops, will keep them high over
the alpine areas this evening, then decrease them overnight as
the upper trough moves across and east.   For the plains,
"scattered" pops will suffice with evening, with nothing overnight.
On Sunday, will go with 10-20%s over the high mountains in the
afternoon, otherwise the rest of the CWA will be dry. Temperature-
wise, Sunday`s highs look quite similar to this afternoon`s
readings.

&&

.LONG TERM /Sunday night through Saturday/...
Issued at 150 PM MDT Sat May 25 2024

The weather on Memorial Day will be about as nice as it can be.
Ridging aloft with subsident flow will lead to plenty of sunshine
and slightly above normal high temperatures. Temperatures will reach
the mid to upper 70s across the plain and in the 60s across the
higher terrain.

The axis of the ridge will be over Colorado on Tuesday. There
will be a slight increase in low level moisture but only isolated
showers are expected Tuesday afternoon and evening. Soundings
indicate steep lapse rates and a dry boundary layer so strong
winds will be possible from these showers.

A broad trough will move across the western US Wednesday through the
rest of the work week. There will be lee cyclogenesis across the
high plains and strong southeasterly flow will develop in the low
levels across the eastern plains. There will bring healthy
moisture return from the Gulf of Mexico and moderate to strong
instability will develop. It appears a dryline will setup between
DIA and Akron and this may provide enough low level forcing to
generate storms along it. Given the good instability and enough
shear, storms that form along the dryline could be strong to
severe with large hail and damaging wind gusts possible.

Models do not agree with the trough placement on Thursday but this
trough may provide strong forcing to our forecast area. The healthy
moisture and instability will continue to be across the eastern
plains. Depending on the trough location, there is potential or this
day to be an active severe weather day with several strong to severe
storms. On the other hand, the trough could end up being far away
from our forecast area and with less forcing and shear, there could
be minimal severe storms. Nonetheless, this period will need to be
watched.

A cold front appears it will move through our forecast area on
Friday. This will lower high temperatures and may lead to more
stable conditions. By next weekend, slight ridging will build back
in over Colorado with limited coverage of showers and storms and
warm temperatures.

&&

.AVIATION /00Z TAFS through 00Z Sunday/...
Issued at 555 PM MDT Sat May 25 2024

One round of scattered showers and a couple thunderstorms have
moved off to the east. There is another batch in western Colorado,
and these will attempt to move into the area again after 02Z.
These, too, will likely produce some gusty and variable winds, but
we`ll have a little lower gusts in the TEMPO group for these,
closer to 25-30 knots. The most likely time period would last
until about 04Z before we start to stabilize, but still a low
threat after 04Z due to additional showers/virga moving off the
mountains through at least 06Z. Eventually, winds will transition
more southwesterly overnight with clearing skies.

For Sunday, winds are expected to turn more west/northwest by
15Z-17Z with daytime heating and mixing, and then gust to around
25 knots off/on during the remainder of the day from the
northwest. The airmass will be too dry and stable for any shower
or storm threat Sunday. VFR conditions will prevail.

&&

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

&&

$$

UPDATE...Barjenbruch
SHORT TERM....RJK
LONG TERM.....Danielson
AVIATION...Barjenbruch