Area Forecast Discussion
Issued by NWS Pueblo, CO

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253
FXUS65 KPUB 282109
AFDPUB

Area Forecast Discussion
National Weather Service Pueblo CO
309 PM MDT SAT MAY 28 2016

.SHORT TERM...(This evening through Sunday)
Issued at 253 PM MDT Sat May 28 2016

Current water vapor imagery and upper air analysis is indicating
generally weak westerly flow aloft across the region, with stronger
zonal flow across the Pacific Northwest through the Northern Tier,
as a weak wave in the southern stream is moving onshore across the
southern California coast. Water vapor imagery is also indicating a
minor disturbance embedded in the westerly flow aloft across the
state at this time. Regional satellite and radar data indicating
scattered showers and a few thunderstorms over the mountains and
spreading east across the immediate adjacent plains at this time.

Tonight and Tomorrow...No big changes in the ongoing forecast, with
scattered showers and storms across the higher terrain spreading
east across the eastern plains through the evening, before
diminishing overnight. Not a whole of instability across the area
today, though can`t rule out a few stronger storms producing small
hail, gusty winds and brief locally heavy rainfall through the early
evening.

Will see a slight increase in southwest flow aloft across the region
through the day tomorrow, as the southern stream system continues to
translate into the Desert SW. Increasing UVV and moisture ahead of
this wave looks to bring a better chance of showers and storms
across the area tomorrow afternoon and evening, with the best
coverage remaining over and near the higher terrain. The still is a
chance for strong to severe storms across the far SE Plains tomorrow
afternoon, as lee troughing across the southeast plains should bring
an increase in low level moisture. The 12Z run of the NAM was the
most aggressive with bringing the dry line back into the far se
plains, with progged capes of 2000-3000 J/KG around the western
Kansas border tomorrow afternoon. However, the 12Z runs of the GFS
and ECMWF keep the best moisture well into Kansas through the day
tomorrow. At any rate, the Day 2 SPC outlook keeps the far southern
plains marginal for severe weather, with large hail and strong winds
the main threats. Temperatures to warm slightly from today and
should be back to around seasonal averages tomorrow.

.LONG TERM...(Sunday night through Saturday)
Issued at 253 PM MDT Sat May 28 2016

Increased thunderstorm activity is expected along a dry line across
the southeast plains Sunday evening.  Still some differences in the
models in regard to the position of the dry line, with NAM farther
west into the southeast CO plains, and GFS and ECMWF farther
east. Suspect the more likely scenario is a blend of the two
camps, so will keep scattered pops across the far eastern plains
Sunday evening. Could see a marginally severe storm or two across
portions of Baca, Prowers and Las Animas counties where some
modest shear and CAPE will be located and area comes under some
weak forcing from shortwave ejecting out ahead of the upper trof
moving into the desert southwest. Low level jet across the plains
will back the moisture into SE CO Sunday night.

Better forcing will be in place for Monday afternoon and evening, as
desert southwest upper low slowly moves eastward, and an upper
trough digs down through northern Rockies into the nrn plains.
Once again, dryline is progged by models to mix eastward Monday
afternoon, however with upper level energy still off to the west,
suspect surface winds will remain a bit more easterly, keeping
higher dew points in across the plains. So perhaps a bit of an
increase in thunderstorm chances. Thunderstorms over the mountains
still look fairly high based with lightning and brief light to
moderate rainfall being the primary threat. Could be a marginal
chance for a strong to severe storm or two across the far
southeast plains with a little better CAPE.

A cold front drops through the plains Monday night, as the system
across the northern Rockies moves into the plains. Could see some
showers and thunderstorms continue along the front through Tuesday
morning. GFS and ECMWF drop through front into northeast NM by
Tuesday afternoon which serves to cool and stabilize the airmass to
the north of the front across southeast CO. NAM hangs the front up
along the Raton ridge which results in higher CAPE, less CIN and a
better chance for a severe thunderstorms Tues afternoon and
evening as the frontal boundary becomes the focus for convection.
This could lead to heavy rainfall Tuesday night along the NM
border. Think the GFS and ECMWF have the more likely scenario,
with post frontal upslope keeping best chance for showers and
thunderstorms across the southeast mountains and adjacent plains.
Could see some locally heavy rainfall across the mountains. But
for the southeast plains...instability will be key and will have
to see how this shapes up over the next day or two of model runs.
12z Model runs don`t bring as cool an airmass in with this system
as what occurred with the previous one, so snow levels appear to
stay around 9-10kft. However, there is still some time to settle
these details out. Either way Tuesday and Wednesday should end up
at least 10-15 degrees cooler than the temperatures over the
holiday weekend.

Upper ridge builds in over the western U.S. for the remainder of
week, though cool easterly surface flow takes time to transition to
southeasterly and advect higher dew points back westward into the
forecast area.  So majority of the thunderstorm activity appears to
stay restricted to the mountain areas for Thursday-Saturday, with
mainly gusty winds, some spotty light to moderate rainfall, and
lightning being the primary threats. -KT

&&

.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 253 PM MDT Sat May 28 2016

VFR conditions are expected at COS, PUB and ALS over the next 24
hours. Will continue to see scattered showers and thunderstorms over
and near the higher terrain through the early evening, with a few
storms still possible across the far southeast plains into tonight.
The best chances for storms to affect the terminals remains at COS
through 01Z, with gusty winds and lightning the main threats.
Clearing skies through the overnight hours, with a similar set up
is expected across the area tomorrow afternoon and evening.

&&

.PUB Watches/Warnings/Advisories...
NONE.
&&

$$

SHORT TERM...MW
LONG TERM...KT
AVIATION...MW



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