FXUS65 KPUB 040507

Area Forecast Discussion
National Weather Service Pueblo CO
1107 PM MDT Sun Jul 3 2022

.SHORT TERM...(This evening through Monday)
Issued at 320 PM MDT Sun Jul 3 2022

Key messages:

1. Scattered to numerous thunderstorms expected into this evening,
main risks will be lightning and locally heavy rainfall.

2. No change in the weather pattern for Monday, with widespread
afternoon/evening storms over the mountains, scattered to
isolated coverage elsewhere.

Another round of afternoon/evening convection across the area today,
though storms look a little weaker than yesterday, perhaps due to
lee surface trough on the plains and subsequent wly downslope flow
along the I-25 corridor behind it. Low shear (0-6km values of 20 kts
or less) also playing a role in keeping storms relatively weak,
though one or two cells could become strong/low end severe in the
more unstable air and better wind regime east of the lee trough on
the plains and along the Palmer Divide. Again expect main risk with
convection into the evening will be locally heavy rainfall,
especially with some training/redevelopment along weak boundary from
Trinidad to La Junta. Expect most activity to fade away toward
sunset, though latest HRRR does drag some convection off the
mountains into the Interstate 25 corridor 9-11 pm. May also see
some showers linger back over the southwest mountains into Monday
morning, as deeper moisture lingers through the night.

On Monday, not seeing much change to the upper level or surface
pattern across the area, with continued feed of mid-level moisture
in place while weak lee surface trough hangs out over the eastern
plains. Expect convective coverage/strength to be similar to Sunday,
with highest pops over the mountains, and least chance for storms
over the far ern plains near the KS border. Little change in
precipitable water, so again locally heavy rainfall the main storm
threat. Max temps will continue a very slow upward climb over the
plains, while mountains/valleys see little change.

.LONG TERM...(Monday night through Sunday)
Issued at 320 PM MDT Sun Jul 3 2022

Key messages:

1) Fourth of July evening, scattered PM thunderstorms for several
locations may create another light show other than only fireworks
for some. A few stronger storms could produce flash flooding in
urbanized areas and over burn scars.

2) Widely scattered PM thunderstorms will be possible over the most
areas from Tuesday through Thursday. PM storms will be more isolated
for Friday through Sunday and mainly over mountains. Flash
flooding will be possible, especially over burn scars and urban

3) Temperatures will be warm on Tuesday, with a slight cooling trend
Wednesday through Thursday, then becoming much warmer Friday through
next weekend.

Detailed discussion:

Fourth of July evening...

Latest HRRR shows a majority of the late evening thunderstorm
activity on Monday being mainly over the I-25 corridor. The NAM 4km
Nest keeps most of the convection confined more to the central
portions of the I-25 corridor and along US-50 and just south.
Analyzing the NAM12 lapse rates, steeper lapse rates appear to be
over the Palmer Divide and the Raton Mesa. The model also shows a
very high concentrated area of CAPE over the southern Sangre de
Cristo Mountains of over 2000 J/kg in some areas. Given relatively
higher shear of nearly 30kts as opposed to the surrounding areas,
there could be a possible stronger or severe thunderstorm form just
after 6 PM over this area and move out over the adjacent plains,
possibly impacting locations such as Trinidad and Aguilar just
before sunset, or right around the time for firework viewing. Some
of the thunderstorms over the northern areas of the Sangre de Cristo
Mountains, as well as the Wet Mountains, could also impact portions
of the I-25 Corridor in Huerfano and Pueblo Counties. The Palmer
Divide area looks like it could also be dealing with a thunderstorm
right around sunset that will be moving into Lincoln County. Given
the better shear and steeper lapse rates in this area, it is
possible that a storm could become severe. However, soundings around
this time for Colorado Springs reflect high LCLs with an inverted V
signature, so the main threat would be gusty outflow winds to
possibly 60 mph. With elevated cores above -20C, some hail will be
possible, although CAPE appears to be only around 600-700 J/kg over
most of El Paso County, so hail will likely not get bigger that pea
size. The better potential of severe storms will exist further south
over the southern Sangre de Cristo Mountains, where torrential rain
could bring about flash flooding, especially over the burn scars.
Hail potential will also be a bigger threat in this area, with
possibly nickel size (or greater if storms become severe). As these
storms move over into the adjacent plains and the southern I-25
corridor, there could be localized flash flooding in the urbanized
areas. Storms could move out into the central and eastern plains,
but should continue to weaken by midnight. Low temperatures for
Monday night will be generally in the 60s for the plains, to the 40s
and 50s for higher country.

Tuesday through Thursday...

Ensembles and deterministic models have been consistent for the past
several days with the long wave pattern during this period in the
forecast, showing troughing over the northwestern CONUS remaining
nearly stationary and keeping the ridge over central CONUS. As the
ridge overhead begins to flatten slightly, along with weak
perturbations moving through in the longwave troughing upstream, the
monsoonal moisture plume will shift back to being more over
southeast Colorado, which will provide more widely scattered to
numerous PM thunderstorms to develop over most areas of the CWA for
Tuesday through Thursday. Tuesday will be quite warm, especially
over the plains, under a stronger ridge. As troughing upstream helps
to weaken the ridge and also allow for more moisture to move in over
the region, there will be a slight cooldown from Wednesday through
Thursday. With the enhancement of mid-level moisture over the
mountains coupled with weak shear, there will continue to the the
threat of storms remaining nearly stationary. This could result in
potential flash flooding, especially over burn scar areas, for all 3
days during the afternoon and evening hours.

Friday through Sunday...

By Friday, as the ridge begins to build back again over the region
and the upper level high over western Texas begins to slightly
retrograde further back to the west, the moisture plume will also
shift back to the west with a more north to south orientation of the
ridge axis and keep any thunderstorm initiation confined to the
mountains with a more northward mid-level flow. There will continue
to be possible flash flooding concerns over the burn scars due to
weaker mid level shear. Saturday will be very similar, with a
slighter chance of thunderstorms over the plains and storms being
more isolated over the mountains and confined mostly to the central
mountains. Temperatures on Friday and Saturday will also be much
warmer under the strengthening ridge with near 600 dm heights
centered over western Colorado showing up on the ECMWF at the 500mb
level on Friday. The GFS is now in better agreement with the ECMWF
when it comes to the 500 mb heights being closer to 600 dm. The
models tend to differ much more going into the weekend, with the
ECMWF showing the ridge strengthening over the region and forcing an
upper level low to become cut-off over northwest CONUS, whereas the
GFS has the ridge flattening and troughing upstream beginning to
push over the area on Sunday. If the ECMWF resolves this better, the
monsoonal plume will remain more confined to the mountains with much
drier and warmer temperatures for the plains. If the GFS resolves
this better, the plume will be forced back to the southeast and
allow for a better chance of thunderstorms over the plains with
cooler temperatures overall.  -Stewey


.AVIATION...(For the 06Z TAFS through 06Z Monday night)
Issued at 1106 PM MDT Sun Jul 3 2022

Latest radar imagery does depict isolated showery development
continuing across parts of southern Colorado at this this time.
While this may persist at the start of the period, expect any
remaining showers to diminish with no real impacts expected through
the morning hours. VFR ceilings will likely remain in place early
this morning, but expect coverage to lessen with really only high
level clouds persisting. After a dry morning, a similar setup with
scattered showers and isolated thunder across southern Colorado is
expected this afternoon through mid evening. At this time, ALS and
COS have the higher chances of seeing any precip during that time.
Mainly light winds this morning into the middle part of the day,
with wind speeds increasing this afternoon out of the southwest for
ALS and east southeast across PUB and COS.





NWS PUB Office Area Forecast Discussion