932
FXUS65 KBOU 072342
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
542 PM MDT Sat Jun 7 2025

.KEY MESSAGES...

- Afternoon showers and thunderstorms from Sunday into next week
  with a warming trend and above normal temperatures Tuesday
  through the rest of the week.

- Watching the potential for 90 degree temperatures next weekend
  and beyond.

&&

.DISCUSSION /Through Saturday/...
Issued at 131 PM MDT Sat Jun 7 2025

The rest of the afternoon will be mostly sunny and dry. GOES-19
shows just how dry and stable it is out there across the area.
Mostly clear skies and light winds should result in good
radiational cooling tonight across the area, with temperatures
cooling into the low 50s across the urban corridor, upper 40s
across the eastern plains and foothills, and upper 30s in the
mountain valleys.

A strong trough moves across the Canadian border on Sunday, and
helps drive a cool front across the plains before sunrise Sunday
morning. Stratus should form in it`s wake, covering most of the
plains of Colorado and into the eastern foothills. With the
shallow nature of the front, and the fact that the pressure
gradient is weak behind it, the front should wash out leaving
east winds across the plains. The high June sun should mix out the
stratus around midday, and instability will increase rapidly
during the afternoon hours with partly sunny skies. The post-
frontal airmass contains some low-level moisture, as dewpoints
are expected to be in the mid 40s. The 12Z HREF ensemble mean has
900-1200 J/kg SBCAPE across the eastern foothills, I-25 corridor,
and Palmer Divide by mid afternoon, and close to 0 east of a Fort
Morgan to Limon line. 0-6 km wind shear is 35-40 kts, so any
storms that form over the higher terrain and move southeastward
should be organized and one or two could become supercells. We
thus expect one or two severe storms Sunday afternoon, with gusts
to 50 mph and maybe up to golfball size hail. Storm coverage for
now looks to be isolated, especially across the plains.
Shower/thunderstorm activity should move out of our area by late
evening, clearing from northwest to southeast. Lincoln County
could have showers lingering through about midnight. High
temperatures on Sunday will be in the low to mid 70s across the
plains, and low 70s in the mountain valleys.

On Monday Colorado has weak NW flow aloft with a strong
extratropical cyclone over the Great Lakes. The upstream ridge
for now looks to remain over the Sierras. The surface pressure
gradient favors continued northerly flow, but anticyclone-ing off
the Cheyenne Ridge should result in northeast flow along the I-25
corridor and eastern foothills. There doesn`t look to be much
low- level moisture to work with (dewpoints in the low 40s), but
with upslope and some moisture return, afternoon showers and
thunderstorms are expected to form across the high country and
move southeast. Instability looks limited overall, and the storms
probably won`t get too far east given much stronger stability
across northeast Colorado. Best chances of convective rainfall
would be along and south of I-70, especially the Palmer Divide and
South Park. Lightning, small hail, gusty winds to 40 mph, and
brief heavy rainfall are the main impacts expected. With some cold
advection aloft temperatures are expected to be a little below
average, with highs in the upper 70s across the plains and I-25
urban corridor, with 60s to low 70s in the mountain valleys.

On Tuesday, lee troughing across Wyoming will result in a return to
southerly flow across the plains. At the same time, a 700 mb ridge
begins to spread over Colorado, and warmer temperatures aloft will
likely offset any increase in low-level moisture with the southerly
flow.  Afternoon thunderstorms are possible in the high country, but
with weak northwest to north flow aloft, they won`t make it very far
to the east. Instability should be enough to support lightning and
gusty winds.  With the ridge building overhead and less convective
cloud cover overall, temperatures should have no problem warming
into the mid 80s across the plains, with 70s in the mountain valleys.

Wednesday through Friday continues to look warm with
afternoon/evening showers and thunderstorms each day. West-
southwest flow aloft continues through the end of the work week
but there should be enough moisture for storms to form over the
high country and move east. Low-level moisture is not impressive,
but with PW 0.7" east of the Divide, even close to 1.0" near the
Nebraska/Kansas border, there should be enough moisture overall
for isolated storms to make it eastward across the plains. By far
the best chances will remain across the high country and Palmer
Divide. High temperatures each day across the plains and I-25
corridor should be in the mid to upper 80s, with 70s in the
mountain valleys.

We can`t resist looking towards next weekend and beyond because
it looks to be very different from the first half of June. The
subtropical ridge could be overhead extending south over New
Mexico starting next weekend (June 14-15). Climatologically this
is fairly typical for Colorado, where often around mid-June the
atmosphere dries out significantly under a quasi-stationary ridge
and the heat lamp turns on as the annual peak of solar insolation
is approaching. Available ensemble guidance (EC, GEFS, Canadian)
all are hinting that could occur starting this weekend, and
continue well into the following week. Ensemble mean high
temperatures point to 90s across the plains and I-25 urban
corridor for the weekend and well into the following week.

&&

.AVIATION /00Z TAFS through 00Z Monday/...
Issued at 531 PM MDT Sat Jun 7 2025

VFR conditions will prevail for all terminals into tonight through
at least 10Z Sun. Current WNW winds, with occasional gusts to ~20
kts, will weaken 02-03Z this evening and turn to the typical
southerly drainage pattern. Overnight, a weak frontal boundary
will bring a shift to more northerly flow. Expect this to
initially emerge in the form of NW/NNW winds after ~08Z, with an
eventual turn to a NE component closer to sunrise. Low stratus
will move into the area coinciding with the arrival of these NE
winds, with CIGS to 020 expected, and ~30% chance of lowering to
015. Still anticipate stratus scattering out between 17-18Z as is
typical. E/ENE winds should prevail through the afternoon. True
scattering may be temporary, as SHRA should develop by mid
afternoon with periods of BKN CIGS ~050. Instability will likely
be limited given the morning stratus, so not entirely sold on TSRA
potential, but the possibility is there nonetheless, so the
PROB30 groups seem reasonable for now. 22Z would be the earliest
for any convective activity at KDEN (leaning closer to 23Z), and
may extend through 02 or 03Z.

&&

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

&&

$$

DISCUSSION...Schlatter
AVIATION...Rodriguez