643
FXUS65 KBOU 241757
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1157 AM MDT Sat May 24 2025

.KEY MESSAGES...

- A conditional severe threat today across most of the plains and
  I-25 corridor.

- Higher shower and storm coverage through the Memorial Day
  Weekend, along with cool temperatures.

- Gradual warming next week with more typical shower/storm
  coverage each afternoon and evening.

&&

.UPDATE...
Issued at 325 AM MDT Sat May 24 2025

Forecast for today regarding severe thunderstorms across the urban
corridor and eastern plains has not become any more clear over the
past 12 hours. A cyclone has formed bringing northwest to west winds
to a good part of the Denver area keeping the low clouds from moving
in. Models show this cyclone staying in place, but varying in
strength through the morning and this could limit the amount of low
clouds. If this were to occur, chances for strong to severe
thunderstorms would be fairly high with a moist and unstable airmass
in place. For areas north of Denver, low clouds have formed.

One change for today...even though the easterly push last evening
did spill a little over the Continental Divide, there`s not enough
of an easterly push to keep moisture in place. Drier air will mix
out of the low level moisture by this afternoon. Precipitable water
values fall below a quarter inch so it will be very dry. Therefore,
removed the mentioned of showers and thunderstorms for today and
tonight west of the Continental Divide.

&&

.SHORT TERM /Through Saturday/...
Issued at 302 PM MDT Fri May 23 2025

For the most part, things continue to progress as expected this
afternoon. Across the metro, it`s been a little slower to warm up,
with the near-surface inversion just a touch stronger than
guidance had suggested. Temperatures have made it into the upper
70s/low 80s so far, and high temperatures are still expected to
make it into the low/mid 80s for most locations later this
afternoon (high so far at DEN is 82F).

Meanwhile, the more interesting part of the forecast will unfold
over the next few hours. Convection has already developed across
Elbert county, where SPC Mesoanalysis suggests the inversion/cap
has eroded better than anticipated. With guidance not handling
this well, it`s difficult to say how this will evolve as it drifts
towards the better moisture/instability axis, but at least a
marginal severe threat exists along/south of I-70 into Lincoln
county this afternoon and evening.

The convection north of Cheyenne still looks to be the main show
this afternoon. Guidance has been remarkably consistent, with a
dominant supercell or two eventually emerging from the currently
disorganized TS, which then turn right and drop southeastward into
the northeast corner of Colorado. Though there remains some
modest capping in the region, continued daytime heating along with
some surface moisture convergence should continue to erode what
little cap remains. In general, the parameter space is largely
favorable for severe convection, with MLCAPE exceeding 2000 J/kg
along with ample deep layer shear. There may be some brief
potential for a tornado or two, with some sort of boundary noted
on KFTG radar near STK-AKO.

As we move onto tonight, deep boundary layer moisture is expected
to advect into the region as east-southeasterly flow strengthens
(potentially aided by convective outflow across eastern Colorado).
While this will increase surface dew points into the upper 40s/low
50s across the Denver metro, it will also lead to widespread
stratus... making tomorrow`s forecast difficult.

We`ll almost certainly start the forecast period socked in stratus
across most of the lower elevations. Guidance, like just about
every other time we have this setup, provides a large range of
solutions but little in the way of any clear signal. There are
generally two schools of thought here, depending on your
perspective. The first would be that the continued southeasterly
surface flow eventually forces some stratus breakout by mid/late
morning, leading to widespread destabilization across the I-25
corridor and adjacent plains by midday. Guidance in this camp
paints quite a favorable setup across most of the metro and
plains, with good CAPE/bulk shear profiles and curved hodographs.
If this were the case, scattered supercells would be a favored
storm type with hail as the primary threat. On the other hand, a
deeper stratus deck that doesn`t manage to burn off would lead to
significant capping (12z NAMnest solution) with a few weak
thunderstorms across the lower elevations. As is normally the
case, we`ll likely have a better idea by tomorrow morning.

Temperatures will be cooler than today either way, but should
reach the upper 60s to low 70s.

&&

.LONG TERM /Saturday night through Friday/...
Issued at 302 PM MDT Fri May 23 2025

Cooler weather will prevail for Sunday and Memorial Day as an
upper trough continues to slowly move eastward towards the CWA.
Sunday looks to be the coolest day of the week, as a thicker
stratus deck is likely to form Saturday night (especially if
additional moisture/precip is added from convection). There`s
enough forcing to support widespread showers and a few storms in
the afternoon with skinny CAPE profiles across the lower
elevations.

The overall pattern doesn`t change significantly Monday, with
temperatures again in the 60s and additional chances for afternoon
showers/storms. We probably won`t have a good handle on any
timing/severity of storms for another day or two, so those with
outdoor activities planned should continue to check back for
further updates.

Model solutions gradually diverge into next week, though most
ensemble guidance would suggest at least chances for
showers/storms during the afternoon/evening hours... not all that
atypical for late May in Colorado. A gradual warming trend is
expected through the week, with potentially warmer weather looming
as we get to next weekend with hints of a larger ridge developing
in that timeframe.

&&

.AVIATION /18Z TAFS through 18Z Sunday/...
Issued at 1153 AM MDT Sat May 24 2025

Satellite pictures are showing the Stratus deck over DIA starting
to break starting to break up a bit at this time. Ceilings are
coming up a bit as well. Best short range model consensus is that
convection could get to DIA around 22Z, so will leave the PROB30
group in there. Models are not in agreement concerning pops
overnight at DIA. There is still the potential for fog from around
06Z to around 15Z, so will keep that in as well. Cross sections
show ceilings should be down low by 06Z and stay that way well
into Sunday. Will go with OVC012 or lower.


&&

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

&&

$$

UPDATE.......Meier
SHORT TERM...Hiris
LONG TERM....Hiris
AVIATION.....rjk