Area Forecast Discussion
Issued by NWS Pueblo, CO

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FXUS65 KPUB 191729

Area Forecast Discussion
National Weather Service Pueblo CO
1129 AM MDT Sat May 19 2018

.SHORT TERM...(Today and tonight)
Issued at 410 AM MDT Sat May 19 2018


A small, but potent, closed 500 mb circulation was located over far
northeast Colorado at 3 am this morning. This system was bringing
copious amounts of rain to the greater ne Colorado region. Over
southeast Colorado, scattered showers with a few ltg flashes were
noted over the far southeast plains. Over the interior mtns it was
dry with areas of high cloudiness, mainly north of highway 50.


500 mb circulation is expected to wobble across the ne Colorado
region today. This will likely allow the precip shield associated
with the low to push south, and showers will be possible across the
El Paso county region, and possibly norther Crowley and Kiowa county
during the day today. Showers and isold tsra will also be possible
across the central mtns and Teller county. Some very high elevation
snow is also possible.

Additionally, gusty north to northeast winds will allow for upslope
flow to occur across the Raton Mesa and the Wet mtns this afternoon,
and showers and isold tsra will also be possible across these

Over the remainder of the plains today gusty north winds will
prevail with winds in the 20 to 35 mph range throughout the day. An
isolated strong/marginally svr storm could occur over the plains
today per latest SPC outlook but confidence of this occurring this
afternoon is low.

With temps aloft rather cool, any storms today will be capable of
producing quite a bit of small hail. The best chance of this
happening will be over the east slopes of the southern mtns,
especially the Wet Mtns, the Spanish Peaks and Pikes Peak area.

Max temps today will be rather cool most regions. Over the plains,
50s will occur across N El Paso county while L70s are expected over
far se Colorado. Valleys will be in the 60s to around 70F.


Upper low over ne Colorado will begin to lift off to the northeast.
Any showers over the region should dissipate after sunset, with the
exception of some lingering showers along the Palmer Divide during
the late evening hours.

.LONG TERM...(Sunday through Friday)
Issued at 410 AM MDT Sat May 19 2018

Sunday through Tuesday night...An upper trough is forecast to dig
south across the western US coast on Sunday, developing into a
closed low over central/southern California by Monday afternoon and
shifting east over the Great Basin by Tuesday afternoon. Further
east over Colorado, weak ridging and generally weak southwest flow
aloft will give way to periodic disturbances. These disturbances
combined with adequate moisture remaining in place will allow for
daily afternoon/early evening thunderstorms to develop over the
eastern mountains. A few of these storms have the potential to
advance east onto the plains, but weak forcing should keep coverage
isolated each day. Further, marginal instability and shear should
keep storms sub-severe. Temps on Sunday will be relatively cool,
with highs expected to reach only around 70 across the plains and
high valleys, and mid 60s in the Colorado Springs area. Temperatures
rebound into the mid to upper 80s across the plains, and mid 70s in
the high valleys and Colorado Springs, Monday and Tuesday. Winds at
the surface will become breezy from the south/southeast each
afternoon across the plains as lee troughing tightens the surface
pressure gradient.

Wednesday through Thursday...Models agree to lift the Great Basin
upper low to the northeast north of Colorado. This allows a drier
airmass to funnel into southern Colorado, decreasing afternoon
thunderstorm activity slightly. Intense daytime heating will mix the
dry air to the surface, and combined with gusty winds, may lead to
areas of critical fire weather conditions each day, particularly
across the eastern mountains and southeast plains. Temperatures will
be slightly warmer, with highs near 90 each day across the plains,
and closer to 80 across the high valleys and Colorado Springs.

Friday...NWP solutions diverge during this period. The ECMWF
deepens another upper low just off the central California coast,
and establishes a ridge over the eastern Rockies. This solution
keeps the forecast area very warm with diurnal thunderstorms each
day. The GFS also brings down the upper low, but much slower,
keeping the ridge over the west coast and northerly flow with
embedded disturbances over the eastern Rockies. This is a slightly
wetter and cooler solution. The Canadian is more in line with the
ECMWF, but keeps the low further north. The GFS ensemble mean is
closer to the ECMWF solution as well, but with considerable
spread. Given these model differences, forecast confidence is low
during this period and beyond, but leans toward the eastern
rockies ridge scenario.


.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 1122 AM MDT Sat May 19 2018

VFR stratus will remain across the plains with another round of
thunderstorms staying confined mainly to the mountain areas
through early afternoon. A storm or two will drift eastward into
the adjacent plains during the late afternoon and while stability
will likely cause dissipation, VCSH will be possible at both KCOS
and KPUB after 21 to 22z. Showers and thunderstorms will diminish
for most areas by 03z. Wind shifting around from the southeast
will allow for some MVFR cigs to develop across the plains
overnight affecting both KCOS and KPUB through 16-17z.

KALS will remain VFR with winds shifting around from the southwest
and becoming gusty this afternoon before switching round from the
east this evening. A stray storm or two will be possible in the
San Luis valley, but odds are too low to put mention in the TAF at
this point. -KT




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