Area Forecast Discussion
Issued by NWS Pueblo, CO

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FXUS65 KPUB 210539

Area Forecast Discussion
National Weather Service Pueblo CO
1139 PM MDT Thu Jul 20 2017

.SHORT TERM...(This evening through Friday)
Issued at 352 PM MDT Thu Jul 20 2017

Drier air has pushed in under the high which has shifted the focus
for thunderstorm development across the western and northern
portions of the forecast area.  The eastern San Juans and La Garita
mountains as well as Chaffee, Lake and Teller/El Paso counties will
have the best chance for showers and thunderstorms. H7-H5 specific
humidities are still running around +6 to +8 g/ locally heavy
rainfall will be the primary threats and flash flooding will be
possible on vulnerable burn scars, areas with susceptible soils
(like the chalk cliffs) and urban areas. Activity winds down after
04z, though some isolated showers will be possible over the
mountains through the early morning.  Most of the southeast plains
will remain dry this evening...though high res models send an
outflow boundary southward into the highway 50 corridor which could
spark an isolated storm or two.  Kept pops mainly confined to the I-
25 corridor counties for now as HRRR keeps majority of the activity
just north of the area through the late evening hours.

Friday will be a more active day across the district as the upper
high nudges eastward a bit allowing the monsoon plume to shift over
more of the mountains.  Front drops through the southeast plains
during the late afternoon and evening...likely reinforced by outflow
from thunderstorms that develop along the Palmer Divide. Once
again... El Paso county should see an uptick in thunderstorm
coverage given forcing from the front.  Threats from thunderstorms
will continue to be locally heavy rainfall capable of producing
flash flooding, wind gusts up to 50 mph and lightning.  However
given some pooling of CAPE along the Palmer Divide in the afternoon
in vcnty of the front, we could see one or two strong storms with
hail to near the size of quarters. -KT

.LONG TERM...(Friday night through Thursday)
Issued at 352 PM MDT Thu Jul 20 2017

Relatively active meteorological conditions are anticipated over
many portions of the forecast district at times...especially from
Friday night into this weekend and then again from Wednesday into
at least next Thursday.

Primary meteorological concerns include but are not limited to
temperatures, increased precipitation potential(including locally
heavy rain and localized flash flooding potential favoring this
weekend and then again from Wednesday into at least next
Thursday). The potential also exists that intense thunderstorms at
times may also be observed from Friday night into this weekend
and then again by later next week.

Recent longer term computer simulations, PV analysis and forecast
model soundings indicate that precipitable water values over many
portions of the Interstate 25 corridor should run around 1 inch
or slightly higher at times from Friday night into this weekend
and then again from Wednesday into next Thursday. In addition,
northerly surge moves across eastern sections Friday night,
helping to enhance precipitation potential from Friday night into
this weekend.

The combination of adequate atmospheric moisture, surface
boundaries, the daily orographic heating cycle and subtle upper
disturbances will be capable of producing enhanced precipitation
chances(including flash flooding potential at times) from Friday
night into this weekend.

Also, projected localized capes and LI`s nearing/exceeding 1000
J/KG and -5C respectively at times from Friday night into this
weekend will be capable of generating some intense thunderstorms
with a limiting factor once again being projected low-grade mean-
layer wind shears. As always, WFO Pueblo will monitor closely and
issue hydro/severe products as needed.

Finally, in addition to generally low-grade gradient winds during
the longer term, anticipate that near to slightly below seasonal
later July maximum temperatures should be experienced over many
locations from Saturday into Monday with near to above seasonal
maximum temperatures then expected from Tuesday into Thursday.
Also, projected minimum temperatures during the longer term should
remain above late July climatological averages over the majority
of the forecast district.


.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 1132 PM MDT Thu Jul 20 2017

Mostly clear skies over the southeast corner of the state
currently. Mid and high level clouds will gradually thin and
dissipate across the rest of Colorado overnight. On Friday, expect
scattered thunderstorms to develop over the mountains by early
afternoon. The thunderstorms will move off the mountains and onto
the plains after 22z. The far southeast corner of the state will
remain dry, but areas near the mountains will have a better chance
of a late day thunderstorm. Stark




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