Area Forecast Discussion
Issued by NWS Pueblo, CO

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FXUS65 KPUB 222108
AFDPUB

Area Forecast Discussion
National Weather Service Pueblo CO
308 PM MDT Sun Apr 22 2018

.SHORT TERM...(This evening through Monday)
Issued at 252 PM MDT Sun Apr 22 2018

...Afternoon and Evening Showers and Storms Near the Mountains...

Satellite starting to showing some good cumulus development over the
mountains at this hour.  High res models continue this trend through
the remainder of the afternoon into the evening.  CAPE is building
over the higher terrain but not by much, just into the hundreds of
J/kg.  Instability is also building, too, with LIs expected into the
-1 to -2 range by late in the day.  High res models indicate a few
isolated to scattered showers and storms forming next few hours. The
primary threat from any thunderstorm will be lightning and possibly
some locally heavy snow showers at the higher elevations, generally
above 10,000 feet. Don`t expect much, if any, activity will make it
to the I-25 corridor this evening.

On Monday, the process of building CAPE and increasing instability
will continue.  By late afternoon, northern portions of the forecast
areas could see CAPES of 500 approaching 1,000 J/kg and LIs reaching
-2 to -4.  Values over the southern portions of the forecast area
look similar to today.  Plus, an approaching upper level disturbance
may begin to provide some forcing over northern portions of the
forecast area late in the day.  This means an even better chance for
some afternoon showers and isolated storms, primarily over and near
the mountains.  Additionally, parameters for convection look better
extending eastward across the plains along the Palmer and Raton
Ridges.  So, there will be the possibility of some isolated late day
activity in those areas as well.  The primary thunderstorm threat
will continue to be lightning.

.LONG TERM...(Monday night through Sunday)
Issued at 252 PM MDT Sun Apr 22 2018

Models very different through the extended period, especially
beyond Thursday. Ensembles tend to support the GFS solution
through the extended period, so have leaned that way for this
forecast package.

Monday night through Tuesday...both the GFS and ECMWF drop an
upper disturbance out of the Northern Plains, south across
Colorado and Kansas through this period. A strong cold front will
arrive Monday evening and clear the Plains overnight. Models in
good agreement with a band of precipitation developing over
northern Colorado Monday night, and slowly dropping it south
across the Plains on Tuesday, clearing into New Mexico Tuesday
evening. It looks like there is cold enough cold air with this
system to bring snow to the Palmer Divide Monday night, with rain,
possibly mixing with snow, even down to Pueblo by Tuesday morning.
Temperatures should warm enough on Tuesday that rain will be the
preferred precipitation type across the Plains. Snow over the
mountains will likely be confined to the Central Mountains Monday
night, with areas further south generally missing out. At most,
mountain areas will only see a couple of inches by the time the
system exits to the south.

Wednesday into Thursday...high pressure over the western states
will shift east across Colorado. Models develop at least isolated
convection over the mountains on Wednesday due to residual
moisture and weak instability. Lightning will be the primary
threat on Wednesday. Temperatures will also begin to warm, with
highs in the 60s across the lower elevations Wednesday afternoon.

By Thursday, models really begin to diverge. The GFS and ECMWF
both have a weak shortwave trough dropping south. The GFS is
further east and much quicker with the system, keeping most of the
area dry. It would bring a few shower and thunderstorms to the
mountain areas, but that would be it. The ECMWF is further west
and a bit slower with the system. This would bring a stronger
cold front to the Plains along with another round of rain and high
elevation snow for much of the region Thursday and Thursday night.
Current ensemble means seem to support the GFS at this time. But,
this time period needs to be monitored due to the potential for
increased precipitation.

Friday through Sunday...model differences continue into the
weekend. The GFS moves an upper disturbance across the area over
the weekend. Moisture embedded in the southwesterly flow ahead of
the system would keep active weather across southern Colorado
Friday into Saturday, with a windy day and potential high fire
danger on Sunday as the system moves across the area. The ECMWF
builds high pressure across the area over the weekend with dry,
warm conditions, but little fire weather potential and very
limited chances for precipitation. Mozley

&&

.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 252 PM MDT Sun Apr 22 2018

Limited moisture and instability will allow for the formation of
some isolated to scattered showers and thunderstorms, primarily over
and near the mountains, through Monday.  The prospects for showers
and storms on Monday look a little better than for today and they
will extend farther east onto the plains, along the Palmer and Raton
Ridges by late in the day.  Primary storm concerns will be lightning
and local sub-VFR flight conditions in convective showers.  Could
also be some local gusty and erratic outflow winds associated with
showers.

At this point, it looks like showers and storms will not be an issue
at the KCOS, KPUB and KALS terminals through 18Z Monday.  However,
the KCOS and KALS terminals may see showers or storms develop in the
vicinity beginning after 18z Monday.  KPUB will likely remain dry
through the forecast period.

&&

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

$$

SHORT TERM...LW
LONG TERM...MOZLEY
AVIATION...LW



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