475
FXUS65 KBOU 190646
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1246 AM MDT Tue Aug 19 2025

.KEY MESSAGES...

- Near normal temperatures today with hot temperatures Wednesday
  and Thursday.

- Isolated showers and storms are expected most days this week
  with minimal rainfall.

- Cooler and wetter weather arrives this weekend with the
  conditions lasting into next work week.

&&

.UPDATE...
Issued at 920 PM MDT Mon Aug 18 2025

Updated pop, wind, sky and weather grids based of current
conditions. Will keep 10-30% pops going for the most of the
plains and foothills north of I-70 through 06Z-07Z based on
current trends and high resolution models.

&&

.DISCUSSION /Through Monday/...
Issued at 224 PM MDT Mon Aug 18 2025

SPC upper-air maps show the upper-level ridge persists over the
southwestern CONUS this morning. There aren`t any big changes to the
synoptic pattern for today, but there are some mesoscale influences
that have lead the SPC to upgrade our northeastern corner to a
slight risk (2 out of 5) for severe weather this afternoon and
evening. As discussed yesterday, there will be greater instability
to work with today along with a little more moisture. This morning`s
upper-air maps also indicate a weak shortwave embedded in the 500 mb
ridge that will provide a little more vertical lift as it wiggles
its way across the region. CAMs are in decent agreement that storms
will likely initiate across the Palmer Divide, Cheyenne Ridge, and
Central Mountains this afternoon and make their way east across the
plains. With hi-res guidance showing DCAPE values ranging from 1000-
1900 J/kg, and forecast soundings showing inverted-v profiles, there
is certainly potential for some severe gusts (up to 70mph) to occur.
With 35 to 45kts of 0-6km bulk shear expected across portions of the
plains, should see some more organized storm potential, especially
for storms moving across the Cheyenne Ridge and far northeast corner
where the greatest shear values and dewpoints are expected. With
MUCAPE values ranging from around 500J/kg just east of the
mountains, to 2000J/kg+ along the Nebraska/Colorado border, hail
size will likely range between 1 to 2 inches with the stronger
storms, with potential for a little larger stones to fall the closer
you get to the border. Of course it needs to be mentioned that
morning convection has been persistent over the northeast corner and
this could have an impact on what happens later this afternoon and
evening.

Aside from the northeast corner convection, storms are already
forming over the Central Mountains and foothills of the Front Range,
with dime sized hail already being observed. Both ACARS soundings
and the SPC mesoanalysis page still show the majority of the lower
elevations capped at this time (1215 MDT), but CIN has been slowly
eroding through the morning. Will have to wait for this to fully
erode to see the above expectations come to fruition. But if storms
collapse as they enter the capped environment, we could still see
some significant microbursts as they come off the higher terrain.

Expecting similar temperatures to last night`s across the forecast
area. Skies are also expected to clear out from west to east as the
storms move out of the forecast area. Should be good conditions to
view the "Parade of Planets" that will be visible once again early
Tuesday morning.

As discussed over the past few days, Tuesday is expected to bring
slightly warmer and drier conditions as the upper-level ridge builds
over the Four Corners region. There will still be enough lingering
moisture around for afternoon showers and storms to develop,
however, coverage will be far less than the previous few days, and
the main potential will be for the Central Mountains and Palmer
Divide. With less instability and shear expected, storms should
remain sub-severe. As with the typical high-based environment, we
could still see some gusty outflows between 30-40 mph. Temperatures
across the plains will be in the low to mid 90s once again.

Wednesday looks to be the driest day of the week with the lowest
precipitation potential, but could still see some isolated afternoon
showers and storms develop over the higher terrain. Ensembles remain
consistent that an upper-level low will push ashore southwestern
Canada Wednesday, and we should see the ridge start to flatten out
on Thursday. Temperatures will peak on Thursday, when 700 mb
temperatures range from 17 to 21C across the forecast area. By
Friday, we should see a slight cool down as a cold front associated
with the aforementioned upper-level low makes its way into Colorado.
Moisture will also increase and we will have increased chances for
precipitation through the weekend. For those of you who welcome a
break from the heat, after Thursday`s high in the mid to upper 90s,
each of the ensemble means for the ECMWF, GFS, and Canadian do not
have another 90 degree high in place for our climate site (KDEN)
through September 3rd. Obviously a lot can change between now and
then, but for now, it looks like a cooling trend is on the
horizon.

&&

.AVIATION /06Z TAFS through 06Z Wednesday/...
Issued at 1158 PM MDT Mon Aug 18 2025

Showers and storms have ended at DEN and are not expected for the
rest of the night. Winds will shift towards drainage around 08Z.

Conditions will be much more stable on Tuesday than on Monday. A
cap will be strongest over DEN and it is unlikely any showers or
storms form over DEN. However, an outflow boundary may still move
through the terminal with gusts up to 36 knots. At BJC and APA,
convection coming off the higher terrain may move over the
terminals. The primary concern will also be strong wind gusts. The
evening will likely see southerly winds behind an outflow boundary
with more a of southeast component overnight.

&&

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

&&

$$

UPDATE.......rjk
DISCUSSION...Bonner
AVIATION...Danielson