Area Forecast Discussion
Issued by NWS Pueblo, CO

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FXUS65 KPUB 171736

Area Forecast Discussion
National Weather Service Pueblo CO
1136 AM MDT Fri Aug 17 2018

.SHORT TERM...(Today and tonight)
Issued at 437 AM MDT Fri Aug 17 2018

Upper ridge remains in place over the area today/tonight, with short
wave energy cresting the ridge and dropping southeastward across CO
late in the day. Given slightly better upper support, should see a
modest expansion of tsra coverage over the mountains today, with
most models suggesting a few clusters of stronger storms migrating
eastward through the I-25 late afternoon/early evening. Best forcing
then shifts south during the late evening/overnight, with only
isolated weakening convection on the plains after midnight. SWODY1
has marginal risk of severe storms along and east of I-25 today,
though with 0-6km shear values running only around 30 kts, expect
mainly brief/low end severe storms, with best chance along I-25 as
mountain convection encounters axis of higher instability just east
of the higher terrain. Still a risk of some spotty pockets of heavy
rain, as steering currents remain rather light, with last few runs
of the HRRR pointing toward Pueblo/Fremont counties having a higher
potential for storm mergers leading to increased rainfall rates.
Given increased cloud cover/convection, max temps today should drift
downward a few degf from Thu readings.

.LONG TERM...(Saturday through Thursday)
Issued at 437 AM MDT Fri Aug 17 2018

Saturday...Active day with strong to severe thunderstorms expected.
The long-term forecast period begins with a steep ridge over the
western US coast and northwest flow over Colorado. Models are in
excellent agreement on the timing of a fairly potent mid-level
shortwave trough advancing through Colorado Saturday
afternoon/evening. The exit region of an associated upper-level jet
will also spread over the state. At the surface, a lee trough will
develop during the afternoon, and southerly flow will maintain high
dew points ranging from the mid to upper 50s across the I-25
corridor to low 60s over the far eastern plains. Large scale forcing
in association with the shortwave and jet combined with low level
convergence/pressure falls near the lee trough and daytime heating
will allow scattered to widespread thunderstorms to develop over the
eastern mountains and spread east across much of the eastern
Colorado plains during the afternoon and evening. Strong
northwesterly mid-level flow over surface
southerlies/southeasterlies will yield 0-6 km shear around 40 knots.
High surface dew points will lead to MLCAPE values on the order of
1500 j/kg across the eastern mountains and plains, with pockets over
2000 j/kg possible. Given these conditions, thunderstorms will be
capable of producing large hail and damaging winds. An isolated
tornado is also possible. SPC maintains a marginal risk for severe
across the eastern mountains and all of the eastern plains. Won`t be
surprised to see this upgraded. TPW ranging from 1" near the eastern
mountains to 1.5" over the far eastern plains will allow storms to
produce heavy rainfall as well, so flash flooding will be a threat,
especially over burn scars and urban areas. However, storm motion
will be quick enough to help dampen the threat slightly. Storms
should be along/east of the CO/KS border by midnight. High
temperatures will be in the mid to upper 80s across the plains, and
around 80 in Colorado Springs and the high valleys.

Sunday and Monday...Expect pleasant weather for most areas during
this period. Models agree on height rises behind the Sunday
shortwave with unidirectional north/northwest from the surface into
th upper troposphere. This pattern will help scour moisture out of
the region, and squash convective chances during this period. Only
isolated afternoon thunderstorms are expected over the high terrain
each day. Temperatures will be cooler, with highs in the low to mid
80s across the plains and high valleys, and mid 70s in Colorado
Springs. Surface winds will likely become breezy during the
afternoon into the early evening on Sunday across most of the plains
and Monday across the far eastern plains as low pressure deepens
well to the northeast of the state.

Tuesday through Thursday...High pressure re-establishes itself over
the southwest US, centered over AZ/NM, with mid-level northwest flow
reigning over Colorado. Surface flow becomes southerly/southeasterly
again, increasing moisture across the region. Periodic disturbances
in the northwest flow will lead to afternoon/evening thunderstorm
chances each day. Wednesday looks to be the most active day and most
likely to have convection spread across the plains as a fairly
potent shortwave moves across the state. With models currently
indicating near 60 surface dew points and 0-6 km shear of around 30
knots, strong storms will be possible. Temperatures during this
period will rise into the upper 80s to low 90s across the plains,
low to mid 80s in Colorado Springs, and low 80s in the high


.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 1127 AM MDT Fri Aug 17 2018

A weak upper level disturbance will combine with ample moisture to
trigger another round of afternoon and evening thunderstorms
across the flight area. The first storms of the day are developing
over the mountains now. Storm development over the mountains will
continue through the early afternoon hours before spreading onto
the plains during the mid to late afternoon hours. Thunderstorm
activity will continue across the plains through the evening

KCOS, KPUB and KALS will all see thunderstorms at or near the
terminals from the midafternoon through early evening hours.
Primary storm hazards will include lightning, wind gusts to around
50 mph, locally heavy rain, and pea to quarter size hail.  Low
clouds will be possible again tonight at the KCOS and KPUB
terminals depending on how convective outflow evolves this




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