Area Forecast Discussion
Issued by NWS Pueblo, CO

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FXUS65 KPUB 150513

Area Forecast Discussion
National Weather Service Pueblo CO
1113 PM MDT Mon May 14 2018

Issued at 758 PM MDT Mon May 14 2018

Updated forecast to decrease pops for the southeast
mountains/adjacent southern I-25 corridor tonight through Tuesday
morning as latest short res models continue to suggest second
round of activity will be most widespread across Northern El paso
county this evening before blossoming across the eastern plains
to the east of LHX overnight. This is likely in response to
upglide over the front with intensifying low level jet helping to
realize some limited elevated instability. CAPE is not all that
great though, and actually looks quite a bit lower than runs from
yesterday...and this does not build confidence in the exuberant
hrrr runs which actually suggest the potential for a few strong
storms across the far eastern areas after midnight. As upslope
intensifies overnight some activity could develop westward into
the Raton Mesa region. Quite a bit of uncertainties with
pops have been trended down along their western fringe for now
and trended up for the far eastern plains. Don`t think
thunderstorm intensities will be all that strong after midnight
given limited instability but will be keeping an eye on this. -KT


.SHORT TERM...(This evening through Tuesday)
Issued at 251 PM MDT Mon May 14 2018

...Isolated severe storms possible today with showers/tsra tonight.
More storms possible tomorrow late...


At 2 pm, a cluster of strong to severe storms was moving east over
the Palmer Divide north of the NWS PUB CWA. Tail end of this
activity was affecting extreme norther El Paso county. Another weak
updraft was trying to fire west of Pueblo. HRRR still was trying to
initiate convection off the Wet mtns although latest runs do not
appear as vigorous as earlier runs. Latest mesoanalysis was
indicating about 500-1000 J/kg of CAPE over the plains and deep
shear was quite strong, running about 40/60 knots.

Rest of this Afternoon into Tonight...

Isolated svr tsra is main concern over the eastern plains. Question
is can storms overcome capping inversion? If they do, then potential
for svr activity is rather high given the quality shear and
sufficient CAPE over region.

Most latest guidance continues to indicate the potential for late
night tsra/showers over the s mtns/plains as disturbance moves
across the fcst area during the early morning hours. This
disturbance combined with plenty of llvl moisture and remnant CAPE
should allow for scattered tsra to occur, with small hail possible
with the stronger convection.

With activity over plains tonight, should see quite a bit of clouds
over the lower elevations towards sunrise.


Some remnant showers will still likely be ongoing after sunrise but
activity should decrease as the morning progresses.

With quite a bit of low clouds over the plains tomorrow morning
atmosphere will be slow to destabilize, so isolated to scattered
thunderstorms will likely get a slow start, with most activity
occurring during the late afternoon or maybe holding off into the
early evening hours. Overall best chance of storms will likely be
over the eastern slopes of the s mtns as best instability will be
realized this area during the afternoon time period.

It will be cooler tomorrow and expect max temps over the plains to
only reach into the U60s to L70s.

Over the interior mtns and valleys, there will be a better chance of
showers and thunderstorms than the last few days, especially over
the central mountain region. Over the SW mtns expect it to be mainly
dry with only isold tsra.

.LONG TERM...(Tuesday night through Monday)
Issued at 251 PM MDT Mon May 14 2018

The upper level low that has been affecting our region begins to
merge with another upcoming upper level low on Tuesday night. A
ridge will propagate into the region Wednesday afternoon and will
continue to affect the region into Thursday.  The previously
mentioned upcoming upper level low will continue to propagate
easterly during this time, and by Friday afternoon will eject off of
the Rockies and over the plains. The low pressure passage will make
for a cloudy and stormy end of the forecast period for the region.

Tuesday Night through Thursday...

A lingering isolated storm may continue into Tuesday night, but
should dissipate in the early morning hours on Wednesday. During the
day on Wednesday a ridge of high pressure continues to strengthen
over the region, resulting in warmer temperatures and relatively
light surface flow. A dry line develops over the eastern plains,
near the border of Kansas and Colorado, which may spark some
thunderstorms Wednesday afternoon. CAPE values are in the vicinity
of 1500-2000 j/kg, but the environment is lacking strong shear, as
analyzed by model resolved hodographs. The exact location of the dry
line is subject to change, so check back, but PoPs were added to
eastern plains Wednesday afternoon. Temperatures will span the 80s
over the plains, the San Luis Valley and the Upper Arkansas River
Valley should experience temperatures in the mid 70s, and Lake
County will have temperatures in the 60s.

The temperatures will be even warmer on Thursday, as the ridge
continues to strengthen over the region. Temperatures will straddle
the 90 degree mark across the plains. Near critical fire danger will
exist Thursday afternoon over the Spanish Peak / Raton Mesa region,
as a lee cyclone forms off of the southern Sangre de Cristo
Mountains. The winds will increase, the fuels are dry, and the RH
values will be marginal. The San Luis Valley will have strong enough
winds and low enough RH values, but the fuels are still moist enough
to be removed from critical fire criteria.

Friday through Monday:

Friday afternoon could also be a critical fire weather day for the
southeastern plains, Spanish Peak country, and the San Luis Valley.
The limiting factor will be how strong the winds are over the
Spanish Peak region, the limiting factor for the southeastern plains
will be how the low the RH values will reach, and finally, the
limiting factor of the San Luis Valley will be how moist the fuels
are. Later in the afternoon a cold front will pass over the region
as the main upper level low ejects over the plains. The cold front
will spark thunderstorms over the Palmer Divide in the afternoon
continuing to form behind the cold front as it continues to
propagate southeast.

On Saturday and Sunday, the backside of the low pressure center,
upslope flow may spark thunderstorms over the mountains during the
day, the storms should stay over the mountains, though, as the
environment over the plains is not conducive to support
thunderstorms. Widespread cloud cover will exist everywhere else,
which will inhibit daytime heating, so expect a cooler weekend.

Monday afternoon could be interesting day for thunderstorms, as CAPE
values are high and shear values are also high, but it is much too
far out to pinpoint thunderstorm development and intensity, so check
back as certainty increases.


.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 1107 PM MDT Mon May 14 2018

MVFR stratus will fill in across southeast Colorado overnight
affecting both KCOS and KPUB after 06z-08z. Isolated to scattered
showers and thunderstorms will be possible across the plains
overnight with the potential of producing IFR conditions with
brief -TSRA. Stratus will break for most areas by 18z Tues with
scattered thunderstorms developing across the southeast mountains
during the afternoon and drifting eastward into the adjacent
plains. KCOS has the greatest potential off seeing VCTS during the
late afternoon and early evening. Stratus will likely redevelop
for both terminals Tuesday night with MVFR conditions expected.

KALS will remain VFR with the return of southwest winds 15-25 kts
in the afternoon through early evening. -KT




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