Area Forecast Discussion
Issued by NWS Pueblo, CO

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FXUS65 KPUB 230548
AFDPUB

Area Forecast Discussion
National Weather Service Pueblo CO
1148 PM MDT Fri Sep 22 2017

.UPDATE...
Issued at 707 PM MDT Fri Sep 22 2017

Updated grids to take down the Red Flag Warning at its natural
7 PM expiration time. There is still a slight chance for a
thunderstorm along the far eastern border...but latest HRRR runs
are keeping most of the convection just east of the area until
around midnight when a new round lifts northward into the area.
Meanwhile best chance for showers overnight will continue along
the Continental Divide with isolated to scattered showers
spreading northeastward into the Sangre De Cristos at times. Snow
levels will remain pretty high tonight...most likely above pass
levels...but a couple inches of sloppy wet snow will be possible
across the higher peaks.

Best chance for showers and thunderstorms across the plains will
spread in Saturday morning as energy lifts northeastward ahead of
the approaching upper trof. Soundings moisten up quickly Saturday
morning with scattered to widespread showers and a few embedded
thunderstorms forming across the plains. Main question for
tomorrow is how much will atmosphere destabilize across the
southeast plains during the afternoon. Mid level lapse rates are
not too impressive though depending on surface heating, there
could be an axis of higher CAPE east of a line from approximately
La Junta to Branson. Deep layer shear will be running around 40-50
kts...which is sufficient for rotating supercells. NAMNest
appears to develop some stronger convection across the far
southeast plains during the afternoon where atmosphere may
destabilize a bit better. Will have to watch how this evolves in
00z runs. Overall grids appear to be in good shape for now. -KT

&&

.SHORT TERM...(This evening through Saturday)
Issued at 251 PM MDT Fri Sep 22 2017

...Precip to return to most, if not all, of the region tomorrow...

Currently...

Breezy to windy over the area at 2 pm. Parts of the southeast plains
are gusting to 40 to 45 mph while most other lower elevations
regions are gusting to 25 to 35 mph. Red Flag conditions are
marginal at best as most areas have RH values in the 15 to 20%
range. Moisture in the midlevels is noted at mtn tops RH values are
quite high, above 70% (most of the higher San Juan mtn areas are 100%),
and quite a bit of mid lvl cloudiness is noted in teh water vapor
imagery. In addition, showers with isold thunder has been going
across the contdvd since earlier this morning. convective bubbles
were starting to develop over far se CO, and SPC mentioned one or
two stronger storms could form later this afternoon per latest
SWOMCD.

Rest of Today & Tonight...

Isolated thunderstorms will be possible over far southeast Colorado
this evening. As per latest discussion. one or two could be strong
to marginally severe. The best chance will be over Baca county as
best instability is located over this region. Later tonight showers
with isold thunder will slowly increase over the far SE Colo plains.

Showers with isold thunder will be possible this afternoon into
tonight across the San Juan mountains. This activity will also
increase at the night progresses. The best chance will be over the
San Juan mtns.

Over the rest of the area, it will remain primarily dry,

Tomorrow...

High amplitude 500 mb trough will continue to progress toward the
region and this system will likely bring a good chance of precip to
the area during this time period.

Guidance is pretty insistent on bring bands of rain with embedded
thunder across most if not all of the area during the day tomorrow.
Two areas of activity will be across the Contdvd region. The 2nd
area will be over the plains, with the overall best chance from
central/eastern Las Animas county NNE up to La Junta/Lamar regions. A
few strong storms could occur tomorrow as  dwpts will be in the 50s
and CAPE values will roughly be in the 1000 J/KG range, with deep
shear about 30-40 knots. SPC currently does not have the area
outlooked, but I would not be too surprised if parts of the se CO
plains are outlooked in later SPC forecasts.

As for QPF, several areas on the plains may see 0.50 to 0.75 inches
of rain tomorrow.

Snow will be likely across the higher elevations, with the
accumulating snow mainly above 11000 feet. 1 to 4 inches of new snow
will be possible at the highest elevations. Areas along the contdvd
will have the best chance of snow.

Temps tomorrow will be noticeably cooler than today, with highs
mainly in the m60s to m70s plains, and 50s and 60s valleys. Breezy
southerly winds will occur, especially over the far se plains and
mtns and valleys.

.LONG TERM...(Saturday night through Friday)
Issued at 251 PM MDT Fri Sep 22 2017

Active and cooler weather is expected into early next week. Models
are having a hard time through the middle of next week and there
is a high degree of run to run inconsistency leading to lower
forecast confidence. Ensembles spreads are high as well also
leading to lower confidence in the later half of the extended
period.

Saturday night...the upper level low sitting over Utah will
continue to lift energy northeast across Colorado Saturday night.
Strong to severe weather will be ongoing across the far Eastern
Plains and should push east into Kansas by midnight. Large hail,
gusty winds in excess of 60 mph and heavy rainfall will be
possible. For the rest of the area, showers and thunderstorms will
be continuing over the mountains, spreading east into the Eastern
Plains through the evening hours. Snow levels will lower some
through the overnight hours down to around 10 kft, especially
along the Continental Divide where a couple inches of snow are
possible on area peaks.

Sunday...currently this is where the most change looks to have
occurred in the forecast. Models have the upper level low starting
to track eastward into western Colorado through the afternoon. The
current model runs bring dry air north out of New Mexico and dry
slot southern Colorado. This has mixed the dryline further east,
over western Kansas and would bring our severe weather risk down
to zero through Sunday evening. This would also mean drier
conditions across much of the region, with the exception of the
mountain areas, where near continuous showers and thunderstorms
are expected into Sunday night. Warmer afternoon highs are also
expected with mid to upper 70s across the Plains. Low pressure is
forecast to develop near Pueblo by Sunday afternoon, and move east
to near Lamar overnight. This will send a cold front south across
the CWA by Monday morning. A few model solutions to develop light
precipitation across the Plains with the front late Sunday night.
Snow levels over the mountains will also fall to around 9 kft with
a few more inches of snow possible above that elevations.

Monday and Tuesday...the upper low is forecast to split, with
energy moving into the Northern Plains, and energy moving into
Arizona. This will keep southern Colorado under cool conditions
into early next week. Temperatures will be in the lower to mid
60s across the Plains. As far as precipitation, much will depend
on energy moving across moving around the upper troughs.
Southeasterly upslope flow across the region would favor the
Eastern Mountains, into the I-25 corridor. But this time period is
where uncertainty in the model solutions begins to develop.

Wednesday through Friday...big model differences through the mid
to late week period. The GFS keeps the split trough as such, with
a longwave trough over the Northern Plains, and weak troughing
over the Desert Southwest. Several disturbances would be forecast
to lift north out of New Mexico and produce rounds of
precipitation for the region. The ECMWF has the longwave trough to
the north, but drops a strengthening disturbance south into the
Great Basin through the end of the week. It has much better
chances for precipitation, along with much cooler temperatures
through the back half of the extended period than the GFS. Mozley

&&

.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 1148 PM MDT Fri Sep 22 2017

VFR conditions are expected to continue tonight for KPUB, KALS
and KCOS taf site).

On Sunday, increasing precipitation chances(including isolated
thunderstorms) in combination with lower ceilings cigs is
anticipated allowing for MVFR conditions at times, favoring the
KCOS taf site.

&&

.PUB WATCHES/WARNINGS/ADVISORIES...

NONE.

&&

$$


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