940
FXUS65 KPUB 212049
AFDPUB

Area Forecast Discussion
National Weather Service Pueblo CO
249 PM MDT Fri Jun 21 2024

.KEY MESSAGES...

- A Flash Flood Watch remains in effect until Midnight tonight
  for the San Juan Mountains. More localized flash flooding
  possible across the remainder of the mountains through
  midnight.

- A few strong to severe thunderstorms possible over the
  mountains and valleys today with hail up to 1 inch and wind
  gusts up to 60 mph along with locally heavy rainfall.

- Drier and warmer pattern expected through Tuesday with
  isolated mainly mountain thunderstorms and temperatures
  reaching 100-105 again across the southeast plains next week.

- Another uptick in thunderstorms possible mid to late week.

&&

.SHORT TERM /THROUGH SATURDAY NIGHT/...
Issued at 239 PM MDT Fri Jun 21 2024

Anomalously high moisture over the region (PWATs 200-250%+ of
normal) ahead of a shortwave trough will provide plenty of fuel for
strong to severe thunderstorms across the mountains and valleys
through this evening with heavy rainfall and flash flooding the
primary concerns.  Soils are most saturated over the Eastern San
Juans were a little over an inch of rain fell yesterday afternoon
through last night. A Flash Flood Watch remains in effect for this
area until midnight. Cloud cover has hampered heating across this
area today as well as across portions of the central mountains which
has limited instability.  But as cloud breaks and surface heating
occurs, odds for severe thunderstorms will increase as the afternoon
and evening continue.  High res models develop a couple rounds of
convection, one which is moving through the mountains now, and
another which is associated with the stronger forcing with the upper
trough axis this evening through tonight.  This latter wave may be
the one to bring the heavier rainfall to the eastern San Juan
mountains.  Mean QPF from HREF suggests another inch of rain could
fall across the eastern San Juan mountains with up to 0.5 inches
elsewhere across the remainder of the mountains and valleys.  90th
percentile QPF shows up to 1.75 inches of rain across the Southwest
mountains and west slopes of the southern Sangre De Cristo range
which would be the higher side of possibilities.  Stronger shear and
CAPE today will lead to one or two strong to severe storms across
the mountains as well.  Storms have been and will continue to be
relatively quick moving (around 25-30 mph) but storm intensities
and antecedent soil moisture could result in flash flooding for the
more susceptible areas elsewhere across the mountains such as burn
scars, and the Chalk Cliffs.  Rock slides will be possible across
the steeper terrain as well.  So far rises on the gaged smaller
creeks in the eastern San Juans have remained within banks and below
action stage with additional room for rainfall.  So far it still
appears that storm intensity and rainfall rates may be the primary
driver for flash flooding for these areas.

As storms move off the mountains into the adjacent plains late this
afternoon and evening, storms will become more higher based as dew
points have been mixing out into the 40s east of the mountains.
Downdraft CAPE of 1000-1300 J/kg will lead to more of a high wind
risk (gusts to around 60 mph) from the stronger cells along the I-25
corridor, however some small hail (up to an inch) could fall along
the lower eastern slopes of the southeast mountains.

Activity should diminish after midnight as the trough axis shifts
eastward and drier air works in from the north.  Clouds and showers
will be latest to clear across the southern mountains.

Saturday will be drier and warmer, but there will still be
sufficient moisture for afternoon and evening showers and
thunderstorms.  These will be higher based and less conducive for
producing heavy rainfall and flash flooding.  However there may
still be sufficient lingering low level moisture to yield CAPE up to
1000 J/kg and deep layer shears are progged to be around 30-40kts.
So we may still have a strong storm or two over the mountains and
valleys depending on how quickly this low level moisture mixes out.
East of the mountains, thunderstorm chances fall off quickly and
these will be high based with gusty winds and lightning the primary
risks.  Thunderstorms will diminish quickly with loss of heating
Saturday evening.

&&

.LONG TERM /SUNDAY THROUGH THURSDAY/...
Issued at 239 PM MDT Fri Jun 21 2024

The heat continues to build for Sunday through Tuesday as the upper
ridge builds northward back over southern CO. H7 temperatures +18 to
+21 C will result in max temps back in the mid 90s to 105 degree
range over the southeast plains with 80s for the valleys and 60s and
70s for the higher mountains/mountain communities.  Monday and
Tuesday could see more Head Advisories for portions of the I-25
corridor and southeast plains depending on these details, and this
risk will be monitored closely.  Fortunately, winds look relatively
light which should mitigate any critical fire weather potential even
though relative humidity values will be quite low in the afternoons.
There will still be enough mid/high level moisture present for
isolated high based thunderstorms each day, mainly across the
mountains. Gusty winds and lightning with little to no rainfall
would be the primary risks.

Upper high picks up some subtropical moisture Wednesday into the
latter part of next week which will bring increasing moisture and
better chances for thunderstorms to the region especially Thursday
into Friday as moisture quality increases.  This will take the edge
off temperatures some, but temperatures will still remain hot with
highs 5-10 degrees above normal.  Models advertise another upper
trough for next weekend which shunt the moisture plume to the east
and south once again so any uptick in thunderstorms late week
appears temporary. -KT

&&

.AVIATION /00Z TAFS THROUGH 00Z SATURDAY/...
Issued at 239 PM MDT Fri Jun 21 2024

KALS: Thunderstorms will continue into the evening with -SHRA
lingering until midnight at KALS as a disturbance moves through CO.
Cigs could drop into the MVFR to even high end IFR range with +RA
should a strong thunderstorm directly impact the terminal.  Gusty
erratic winds up to 50 kts, and small hail would also be possible.
Thunderstorm risk diminishes after 02z though VFR cigs may continue
until early morning.  If clearing takes place earlier than
anticipated some patchy ground fog could occur, though confidence in
this still looks low.  VFR conditions with light winds and drier
conditions can be expected for Saturday.

KCOS and KPUB...Best chance for VCTS will be at the KCOS terminal
this afternoon between 23 and 01z.  Gusty erratic winds up to 40 kts
will be the primary concern.  KPUB will be less likely to see VCTS
but winds will become driven by outflows from weakening showers and
thunderstorms as they move off the mountains bringing a gusty
westerly wind shift into the terminal around 00z.  Winds will be
light after 02z and predominantly northwest to westerly at speeds
under 10 kts.  Tomorrow will be VFR with drier conditions and
diurnally driven winds.  -KT

&&

.PUB WATCHES/WARNINGS/ADVISORIES...
Flood Watch until midnight MDT tonight for COZ068.

&&

$$

SHORT TERM...KT
LONG TERM...KT
AVIATION...KT