689
FXUS65 KBOU 161119
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
519 AM MDT Mon Jun 16 2025

.KEY MESSAGES...

- A few strong to severe storms possible today and Tuesday, with
  chances increasing Tuesday.

- Warm weather continues today, but cooler by Tuesday and
  Wednesday as a storm system moves through. At least a chance
  (30-50%) of showers/storms across the metro and plains.

- Strong signal for record breaking heat from Thursday into next
  weekend, along with potential for critical fire weather
  conditions.

&&

.DISCUSSION /Through Sunday/...
Issued at 237 PM MDT Sun Jun 15 2025

Fairly interesting convective setup this afternoon. A broad
instability axis has set up across far eastern Colorado this
afternoon, with surface T/Tds in low 90s/upper 50s to low 60s.
Unsurprisingly, the SPC Mesoanalysis shows as much as 3500-4000
J/kg of MLCAPE across the far northeast corner of the state.
Though the airmass is largely uncapped, we haven`t seen much in
the way of a cumulus field develop, though there has been a robust
attempt at convective initiation near the surface moisture/theta-e
gradient in the past half hour. Meanwhile, there`s been some
fairly strong showers aloft across the Denver metro, though these
have developed over the drier airmass over southwest Denver (where
Tds are in the mid 20s). There`s some fascinating moisture
gradients across the I-25 corridor, with some mid 40s to mid 50s
dew points noted from Broomfield towards Fort Collins.

It comes as no surprise that guidance isn`t handling every aspect
of this complicated Colorado setup. There is good agreement that
a broad cluster of convection will gradually congeal into a more
organized MCS/QLCS as it tracks across the Cheyenne ridge into the
northern/northeastern edges of our CWA later this evening, with at
least a modest wind/hail threat. I can`t help but wonder if the
convection will simply be too cold pool dominant (given only
modest 0-3/0-6km shear) for the higher end severe threat to
develop. One caveat will be the attempt at more isolated
convection in Morgan county, which could produce at least a
short-lived severe threat this afternoon if it can break through
the very weak cap still in place.

Beyond that... it`s hot today (high of 94F at KDEN), and will be
hot again tomorrow. Guidance is in reasonably good agreement that
there will be less convection across the I-25 corridor, with
temperatures once again climbing into the low to mid 90s. Where
better moisture resides to the northeast, a few strong to severe
storms will be possible. In general CAMs favor a few supercells
drifting southeastward off the Cheyenne Ridge tomorrow afternoon.

Tuesday will be the coolest day of the week. Deeper boundary layer
moisture is expected to advect in from the east Monday night into
Tuesday, leaving surface dew points in the 50s to 60s across the
lower elevations, along with a chance of some low stratus. A
shortwave is expected to track across the region during the day,
and should be the focal point for at least scattered
thunderstorms. Again, there is a good amount of uncertainty about
storm coverage that will need to be worked out in the next day or
so. Wednesday will see a return to slightly warmer temperatures
and should be fairly dry across the region.

Attention then turns to what could be a few days of near record or
record heat across the region from Thursday into the weekend, as
a broad ridge expands across the south central CONUS.
Deterministic guidance continues to be quite bullish with the
heat, advertising 2-3 days of temperatures of >100F over the
Denver area (and hotter across the plains). That signal is also
obvious in nearly every ensemble tool available... with GEFS/ECMWF
ensemble guidance showing normalized 700mb temperature anomalies
near 2-3 sigma (loosely translating to a recurrence interval of
once in every 10-30 years). ECMWF EFI values are >0.90 both Friday
and Saturday, which indicates good model certainty. All but one
ensemble member has >100F temperatures at DEN. While I still think
that some guidance is at least slightly overdone... there has been
little change in the overall pattern and heat headlines look
likely by as early as Thursday. Stay tuned.

In addition to the heat... there will also be some fire weather
concerns as we get towards next weekend, with a dry southwesterly
flow increasing as the ridge flattens and a broad trough axis
deepens over the west. There is the potential for at least a
couple of days of critical fire weather conditions, which will
need to be monitored closely as we get later into the week.

&&

.AVIATION /12Z TAFS through 12Z Tuesday/...
Issued at 519 AM MDT Mon Jun 16 2025

We`ll start off with westerly flow around 5-10 kts, and then look
for a transition to northerly with a push of northerlies
originating in the northern High Plains. We expect a fairly normal
transition to a more easterly component 18Z-00Z. However, we may
still see VRB gusty winds from isolated high based convection or
virga 21Z-01Z. We`ll keep the Prob30 with -SHRA and VRBG30kts in
the TAF to account for that. The chance of TS is only around 10%.
The next notable feature will be a cold front which should arrive
04Z-06Z Tuesday, with areas of stratus/MVFR ceilings expected
before 12Z.

&&

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

&&

$$

DISCUSSION...Hiris
AVIATION...Barjenbruch