704
FXUS65 KBOU 211749
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1149 AM MDT Wed May 21 2025

.KEY MESSAGES...

- Warmer and drier for the rest of the work week.

- Thunderstorm chances and intensity increase this weekend.

&&

.UPDATE...
Issued at 1252 AM MDT Wed May 21 2025

Raised overnight lows a bit based on more cloud cover expected
and current temperature readings. Also put more cloudiness in
the grids with current satellite pictures in mind along with
latest model cross sections.

&&

.DISCUSSION /Through Tuesday/...
Issued at 158 PM MDT Tue May 20 2025

Main forecast concern will surround thunderstorm chances and
intensity as we head into the weekend. Until then, we`ll be in a
relatively dry and warm weather pattern.

On Wednesday, moderate west/northwest flow aloft and strong
mixing will bring another breezy day. Temperatures will warm a few
more degrees, with highs pushing slightly above normal - into the
mid 70s for most of the plains. Thursday will be even warmer as
the thermal ridge shifts closer to the forecast area, with highs
closer to 80F across the plains. Regarding shower and storm
chances from now through Thursday, anything will be high based
and light due to a deep and dry subcloud layer. A few of these
could produce gusty outflow winds to 40+ mph given the inverted-v
profiles and DCAPE growing to over 1000 J/kg.

Friday will almost certainly be the warmest day of the week ahead,
as the upper level ridge and thermal ridge shift across Colorado.
We expect highs to push into the mid to upper 80s on the plains,
with 70s in the foothills and high valleys, and mainly 60s in the
mountains. It will still be breezy at times, but spring green-up
is sufficient for fuels to be not receptive to fire spread at
this time. Low level moisture starts to increase on the plains,
and that will lead to increasing MLCAPE. It will be a battle
between sufficient moisture and instability for any stronger
surface based convection. Typically these scenarios can offer a
narrow ribbon where a couple stronger storms could occur, so
something to watch on the eastern plains for Friday late afternoon
and evening.

On Saturday, low level moisture is expected to increase further as
low level moisture gets pulled closer to the Front Range. This
occurs as surface pressure falls are expected ahead of an upper
level trough pushing east across the Great Basin and Northern
Rockies. That would be more favorable for stronger and potentially
a few severe storms. Sunday could see similar conditions,
although there is more uncertainty as cooler weather is more
likely to limit instability.

Considerable uncertainty exists for the eventual weather pattern
early next week, as we`ll be caught somewhere in between a trough
over the Midwest and a ridge building over the Great Basin and
Northern Rockies. Overall, that generally leads to a slow warming
trend but continued chance of showers and storms.

&&

.AVIATION /18Z TAFS through 18Z Thursday/...
Issued at 1135 AM MDT Wed May 21 2025

VFR through the TAF period. Main concern will be winds today and
tomorrow. Not much wind out there yet, but should start to see
some gusty northwesterly winds develop in the next couple of hours
as deeper mixing begins. There should be a gradual clockwise turn
through the afternoon and evening hours, with winds weakening by
00-02z.

Overnight winds look a little less certain as a weak northerly
push works against modest drainage. Ultimately may end up with
some weak east or variable wind before drainage establishes closer
to 12z. South to southeast flow should continue at DEN/APA through
most of the morning hours, with a Denver cyclone eventually
developing by the afternoon hours. Would also have some concern
for virga/outflow at some point tomorrow afternoon but not
confident enough to include in the TAF.

&&

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

&&

$$

UPDATE.......rjk
DISCUSSION...Barjenbruch
AVIATION...Hiris