Area Forecast Discussion
Issued by NWS Pueblo, CO

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FXUS65 KPUB 152103
AFDPUB

Area Forecast Discussion
National Weather Service Pueblo CO
303 PM MDT Tue Aug 15 2017

.SHORT TERM...(This evening through Wednesday)
Issued at 302 PM MDT Tue Aug 15 2017

Upper trof moving into western CO will continue to translate eastward
across CO tonight through Monday morning.  Low level moisture across
the plains has been slow to erode out of the I-25 corridor
particularly from PUB northward where dew points have maintained in
the lower 50s as of 1 PM.  Southern I-25 corridor has seen dew
points drop into the 40s as dry air has started to mix down.
Meanwhile...mountain areas are seeing dew points in the upper 20s
and 30s.  By far the deepest low level moisture is expected to
remain entrenched to the east of LHX where dew points will stay in
the mid 50s/lower 60s. This will yield CAPE values in the 2500+ J/kg
range. With forcing from the upper trof approaching, along with
convective temperature being reached, various high res models
develop thunderstorms along the I-25 corridor which will push
eastward and intensify across the southeast plains during the late
afternoon and evening as they move into higher CAPE.  Deep layer
shears are a little on the weak side, around 25-30 kts, but with the
forcing from the system and such strong CAPE, one or two severe
thunderstorms will be possible across the plains through this
evening.  HRRR pushes most of the activity east of the border by 01-
02z, though northern sections of the southeast plains may see some
residual showers and thunderstorms along/behind a cold front which
will sweep through the plains tonight.

Wednesday will start out cloudy across northern and eastern portions
of the plains with a few lingering showers on the back side of the
system.  Upslope flow develops behind the system on Wednesday
however dew points are not terribly high across the I-25 corridor/se
Mts. Just some limited CAPE under 500 J/kg will be available across
the southeast mountains and plains Wed aftn.  Initially model
soundings look capped, however with afternoon heating the CAP erodes
across the plains, so really can`t rule out an isolated storm
anywhere across the se mts/plains, though coverage should be a lot
more limited with less forcing behind the system. Temperatures will
be a little cooler on Wednesday. -KT

.LONG TERM...(Wednesday night through Tuesday)
Issued at 302 PM MDT Tue Aug 15 2017

...Wednesday Afternoon through Wednesday Morning...

On Wednesday evening showers will continue to dissipate as the sun
sets. Dew point values should remain in the mid 50s through the
overnight. The NAM12 is suggesting small showers over the eastern
plains overnight, in response to high surface dew points and weak
easterly upslope flow.

Thursday afternoon looks to be a favorable day for severe weather
across the eastern plains. CAPE values along the Colorado, Kansas
border will range 1500-2000 J/Kg with favorable wind shear. The SPC
has issued a marginal severe thunderstorm outlook for south and
southeastern Colorado, which is consistent with our forecast,
especially three days from the event. Thunderstorm initiation should
begin in the later afternoon hours as a shortwave trough, embedded
in the upper-level west to northwest flow, propagates over the
thunderstorm conducive atmosphere. The biggest question will be the
timing at which the shortwave will move across eastern Colorado.
Thunderstorms should be into Kansas by the overnight hours.  The
threat for tornadoes isn`t out of the question, but dry lower levels
and weaker low level wind shear makes the atmosphere not favorable
for them.  The main concern will be strong thunderstorm winds and
large hail.

...Friday - Wednesday Morning...

The combination of an upper-level low pressure system over
California and a ridge of high pressure begins to build over central
Texas which will advect moisture over southeastern Colorado.  GFS20
suggest Friday will mainly consist of mountain thunderstorms in the
afternoon hours, but should dissipate before reaching the eastern
plains. Starting Saturday, the daily pattern will consist of
thunderstorms initiating over the mountains during the early
afternoon hours, followed by the thunderstorms propagating over the
southeastern plains. Starting Saturday evening, GFS 20 outputs
precipitable water values over the eastern plains will consistently
reaching over 1.25", granted the GFS is generally more moist than
what occurs, regardless, precipitable water values should be quite
high, conducive for daily thunderstorms.

-Skelly

&&

.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 302 PM MDT Tue Aug 15 2017

Will have to watch the potential for MVFR Cigs to spread
westward into the I-25 corridor and the KCOS and KPUB taf sites
Wednesday morning, but in the mean time expect VFR conditions to
prevail.  Isolated thunderstorms will develop over the mountains
this afternoon and move eastward during the late afternoon and
evening.  Northern portions including KCOS may see some lingering
showers and thunderstorms as the front moves through this evening.
Otherwise, southeast winds at KCOS and KPUB will shift around from
the northwest this evening as the front moves through.  Could be
some gusts to 25-30 kts with locally higher gusts possible near
thunderstorms.  KCOS will see the best chance for VCTS through the
evening.  KALS and KPUB will be more likely to stay dry through
tonight.  For now best chance for MVFR to IFR stratus looks to stay
around LHX and eastward late tonight through Wed morning.

Winds will shift around from the east for KCOS and KPUB on
Wednesday.  Another round of thunderstorms will develop over the
southeast mountains and plains Wednesday afternoon but coverage will
be sparse, with KCOS seeing the best chance for VCTS.  -KT

&&

.PUB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

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



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