003
FXUS65 KPUB 071000
AFDPUB

Area Forecast Discussion
National Weather Service Pueblo CO
400 AM MDT Fri Jun 7 2024

.KEY MESSAGES...

- Scattered showers and thunderstorms today with hot
  temperatures across the area.

- Severe thunderstorm risk increases for Saturday across the southeast
  plains with large hail, damaging winds and even an isolated
  tornado possible.

- Strong to marginal severe thunderstorm risk pulls westward
  across the southeast mountains and adjacent plains on Sunday
  with hail and heavy rainfall the primary risks.

- One more active day for thunderstorms across the mountains and adjacent
  plains Monday then another drying and warming trend returns
  through late week.

&&

.SHORT TERM /THROUGH SATURDAY/...
Issued at 348 AM MDT Fri Jun 7 2024

The upper ridge overhead will flatten somewhat today, leaving flow
aloft largely west-northwesterly. Surface flow will remain westerly
across the higher terrain, while southerly flow out east turns more
zonal throughout the day and into the afternoon hours. Our main
forecast challenge for today will be the extent of showers and
thunderstorms that form across the area as some embedded energy in
the flow translates overhead. Current short-term model guidance
shows scattered convection popping up across our area this
afternoon, initially over the higher terrain before quickly moving
east later in the day. Main areas of initiation will be the Central
Mountains, Palmer Divide, and Raton Mesa. Impact concerns will be
limited by lacking moisture at the surface with plenty of low-level
mixing. Models only show a few hundred J/kg of CAPE over and near
the I-25 corridor, and while these values do increase out east,
greatly varied in magnitude depending on which model you look at,
any storms that manage to intensify in this better air will move
into Kansas quickly. Additionally, forecast soundings show low
humidity at the surface, so storms today will likely be high-based
and fairly short-lived, with the main impact being gusty outflow
winds. If storms do manage to get some residence time in the more
unstable air closer to our eastern border, we could also see some
hail production.

Our other main forecast concern for today will be above average
temperatures across the area. Forecasted highs for today for the
plains reach the high-90s with a few locations in the triple digits.
Meanwhile, even the high valleys will see high-80s. Some model
guidance shows temperatures a few degrees higher, especially around
the I-25 corridor. Will have to monitor for heat-related impacts
should these conditions persist over the next few days.

Later tonight, a weak front will move its way in across the plains,
though overnight temperatures should stay relatively warm. However,
the influx of moisture and post-frontal upslope could set us up for
a more active weekend.

&&

.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
Issued at 348 AM MDT Fri Jun 7 2024

Still looks like a favorable set up for severe thunderstorms on
Saturday across the I-25 corridor and southeast plains. Active west
to northwesterly flow aloft continues into Saturday with another
shortwave moving through the flow in the afternoon.  Cold front will
drop through the southeast plains early Saturday morning with low
level flow becoming easterly by afternoon, advecting 50s to lower 60
dew points westward towards the mountains.  Timing looks a little
slower with the moisture advection which would impact CAPE values
along the I-25 corridor.  Latest HREF means show mid to upper 40 dew
points along the I-25 corridor around 21z as convection rolls off
the mountains.  However, some CAMs models bring lower to mid 50s
into the I-25 corridor with low 60s across the far eastern plains by
the same time.  This could mean CAPE values along the I-25 corridor
ranging from near 1000 J/kg on the drier side of the spectrum to
over 2000 J/kg on the higher side.  CAPE increases with eastward
extent across the plains with 2000-2500 J/kg near the eastern
border. Easterly flow beneath west northwest flow aloft will provide
ample deep layer shear (40 kts) for supercell development and 00z
HREF updraft helicity swaths maximize along and north of highway 50.
Overall, still looks like a few severe thunderstorms are likely
across the southeast plains Saturday afternoon and evening. Best
instability will be east of the I-25 corridor and this is also where
soundings show some enhanced curvature in the low levels where
easterly surface winds maximize. Can`t rule out an isolated tornado
or two. Thunderstorms will congeal into an MCS as it moves
southeastward into KS overnight, however westward propagating
outflow will spread stratus westward across the southeast plains
along with the potential for some isolated thunderstorms into the
overnight hours if any brief enhanced outflow can make use of the
terrain to break the cap. Overall pops should be tailing down
towards morning.

Plenty of low level moisture will be in place across the region on
Sunday for a repeat thunderstorm day, this time focused across
across the southeast mountains where best moisture and heating will
be coincide to trigger afternoon thunderstorms.  CAPE values up to
1500 J/kg look probable along and west of the I-25 corridor.  Deep
layer shears look a little weaker as the ridge aloft expands
slightly northward. Still looks like sufficient CAPE and marginal
shear for a few severe thunderstorms over and near the mountains.
Question will be how far east the severe risk will extend as model
soundings show a stout cap across the eastern plains.  Surface
heating will be the primary driver of how much CAPE will be present
east of the mountains.  Have leaned towards the NAM12 for these
details and decreased pops out east slightly where cap is likely to
maintain. One or two thunderstorm clusters will spread southeastward
off the mountains into the evening and overnight hours though think
the main MCS will develop farther south along the frontal boundary
across TX/OK.  Will maintain some scattered to likely pops into the
evening hours across the plains for now given uncertainties.  Will
also have to consider burn scar flash flooding potential this day as
this may be the first round of heavier rain of the season for those
areas. Our older burn scars have become more resilient and storm
motions and potential for hail may help mitigate this risk some. But
it will still require attention and monitoring.  Urban areas may be
at risk as well depending on clearing and available instability as
storms push off the mountains.

Otherwise, a couple days of below normal temperatures expected, with
coolest readings on Sunday, even across our western mountains as
moisture works westward into our high valleys and afternoon
thunderstorms mitigate peak heating.

Better forcing will move in for Monday in NW flow aloft for another
round of afternoon and evening thunderstorms.  Dew points begin to
drop off and focus for afternoon thunderstorms will  remain across
the mountains/adjacent plains.  Deep layer shears weaken a tad but
could be sufficient for a strong storm or two into the evening
hours.  Otherwise, plains dry out as dew points fall off and
temperatures remain below normal with highs in the 70s across our
lower elevations.

Upper ridge builds in for Tuesday through late week which will bring
another drying and warming trend.  Sufficient moisture will be
present for daily afternoon and evening thunderstorms over and near
the mountains but storms will become high based gusty wind makers,
and less efficient at producing rainfall.  Eventually a Pacific
system moves through the Desert Southwest bringing return southerly
flow, greater moisture and perhaps an uptick in thunderstorms by
Friday into next weekend.  There is quite a bit of variability in
timing of this system so will maintain the isolated to scattered
pops for now from model blends. -KT

&&

.AVIATION /06Z TAFS THROUGH 06Z SATURDAY/...
Issued at 348 AM MDT Fri Jun 7 2024

VFR conditions are expected at KALS, KCOS, and KPUB through 24
hours. Breezy southwest winds will set in across the area this
afternoon, with increasing chances for storms at KCOS and KPUB. The
best chances of storms impacting a TAF site will be at KCOS,
starting around 20Z and lasting into the evening. Passing storms are
expected to produce gusty outflow winds today, which could result in
short-term shifts in wind direction at KCOS and KPUB after 20Z.
Conditions will be closely monitored for changes.

&&

.HYDROLOGY...
Issued at 348 PM MDT Fri Jun 7 2024

Rapid snow melt will continue across the mountains leading to
elevated flows along the Arkansas River from Leadville to Canon
City through the weekend as well as on smaller creeks and
streams in and near the mountains. Flows are expected to remain
within banks along the Arkansas River but fast flows can still
be dangerous. Slightly cooler temperatures may decrease the snow
melt this weekend into early next week, however the potential
for heavy rainfall will increase Saturday through Monday for the
southeast mountains and plains. This could cause localized
flash flooding and push flows above the projected bank full
forecast for localized areas depending on where the rain falls.
Confidence in this scenario unfolding is low for the major
river stems for now. Continue to monitor weather forecasts
closely.

-KT

&&

.PUB WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

SHORT TERM...GARBEROGLIO
LONG TERM...KT
AVIATION...GARBEROGLIO
HYDROLOGY...MOZLEY