Area Forecast Discussion
Issued by NWS Pueblo, CO

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FXUS65 KPUB 181728

Area Forecast Discussion
National Weather Service Pueblo CO
1128 AM MDT Fri Jun 18 2021

.SHORT TERM...(Today and tonight)
Issued at 444 AM MDT Fri Jun 18 2021

...Uptick in thunderstorms today with isolated severe thunderstorm
potential across northern portions of the southeast plains...

Cold front will push through the eastern plains today bringing a
gradual increase in low level moisture along and to its north.
Moisture return is rather slow though and soundings still exhibit
inverted V structures, particularly over the mountains and most of
the adjacent plains.  Exception will be across northern El Paso and
Kiowa counties where low level easterly winds may have more time to
advect higher dew points westward yielding CAPE values in the 700-
1500 J/kg range.  Deep layer shears (around 30 kts) look best across
northern El Paso county, and while gusty winds to around 50 to 60
mph could occur just about anywhere across the mountains and
southeast plains given dry low layers, chance of hail to around 1
inch may be more limited to northeast portions of the area.

Meanwhile, above normal temperatures will continue for all areas
with record to near record highs possible at KALS where the old
record of 90 degrees set in 1989 may come very close.  It appears
KCOS and KPUB should stay about 5 to 8 degrees shy of their old
records (PUB 104 in 2012 and previous years, COS 98 in 2012).

Finally, although winds will stay on the lighter side under the
upper high today, the hot weather will result in relative humidity
values dropping below the critical 15 percent threshold for fire
weather concerns. With high based thunderstorms expected this
afternoon, there could be some isolated dry lightning associated
with these. As fuels are not deemed critical just yet, no fire
weather highlights will be issued. But concern does increase for
fire starts as the hot dry weather begins to cure fuels. -KT

.LONG TERM...(Saturday through Thursday)
Issued at 444 AM MDT Fri Jun 18 2021


The upper-high will begin to propagate southwest on Saturday,
bringing in stronger northwest flow to our area aloft. This will
allow for the translation of some shortwave energy over the region,
which will assist in sparking thunderstorms during the afternoon
hours, especially over the mountains. Shear will be a bit on the
weaker side, both directionally and speed-wise, but CAPE is expected
to be around 1000 J/kg and with the right orographics along with the
moisture circulating around the upper-high convective development
should not be an issue. Currently, majority of models are resolving
storms initiating over the central mountains and parts of the
Continental Divide around midday Saturday before expanding and
moving east into more suitable atmosphere. Once storms progress onto
the plains they are likely to intensify, and the greatest threat for
severe weather will be in the evening when this occurs. Main severe
risks at this time appear to be up to 1.5 inch hail and 70 mph
winds. In addition, if storms manage to train over a burn scar flash
flooding could also be a concern. Finally, dry lightning will be
possible over the mountains during the afternoon hours, and although
most of the fuels are still green, it is worth noting the
possibility. However, no fire weather highlights will be needed at
this time.


A shortwave will propagate over the high plains late Sunday
afternoon, which will send a cold front south across the plains. The
timing of this cold front is still fairly uncertain between the
models, with the main arguments being between the front passing down
just after midday or later into late-afternoon to early-evening. The
difference in the timing of the front will make all the difference
for Sunday`s forecast. The earlier solution will bring down the high
temperatures on Sunday significantly while also increasing the
potential strength of thunderstorms across the plains, with direct
daytime heating accompanying the lift. As the front passes, gusty
northerly winds will set in over the plains, although gusts are not
expected to exceed 30 mph. High temps will be dependent on the
timing of the front, but our current forecast along with guidance
shows highs in the mid-90s over the plains and upper-80s over the
higher terrain.

Monday and Onward...

Monday will see a respite from the oppressive heat, with highs
dipping back down into the 70s-80s. This will depend in part on the
strength of the cold front on Sunday, but a noticeable cooldown is
expected regardless.

A drier period will occur from Tuesday through Thursday next week as
an upper ridge builds in over the area, with temperatures returning
to the upper-90s by the end of the week.


.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 1124 AM MDT Fri Jun 18 2021

KALS...a few thunderstorms are expected over the San Luis Valley
this afternoon. Gusty outflow winds will be the primary concern,
with gusts to near 30 kts possible. If a thunderstorm impacts the
terminal, briefly reduced CIGS and VIS are possible. Thunderstorms
should dissipate this evening, with VFR conditions into Saturday.

KCOS and KPUB...afternoon and evening thunderstorms will be
possible at both terminals. Gusty outflow winds will be the
primary concern with thunderstorms. Briefly reduced CIGS and VIS
are also possible. The threat for thunderstorms will diminish this
evening, with showers lingering through the evening. VFR
conditions will prevail into Saturday morning once thunderstorms
dissipate.  Mozley




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