Area Forecast Discussion
Issued by NWS Pueblo, CO

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FXUS65 KPUB 221017

Area Forecast Discussion
National Weather Service Pueblo CO
417 AM MDT Wed Mar 22 2017

.SHORT TERM...(Today and tonight)
Issued at 415 AM MDT Wed Mar 22 2017

Upper ridge migrates eastward into the plains today, with deepening
sw flow across srn CO this afternoon and tonight ahead of the wrn
U.S. trough. At the surface, areas along and east of I-25 will see
areas of lower clouds this morning as upslope flow persists, with
gradual clearing in the afternoon as cooler air mass slowly retreats
and winds begin to take on a more sly component. Will keep Red Flag
Warning in place for the southern I-25 corridor as this area will
likely mix out first, though critical area may remain rather small
as surface low pressure develops between Trinidad and La Junta,
limiting the eastward spread of stronger winds. Farther west,
mountains and interior valleys will see thickening clouds today,
with perhaps an isolated showers along the Continental Divide late
in the afternoon as moisture begins to increase, though any daytime
precip will be very light. Max temps on the plains rather tricky
given stratus this morning and potential for east winds to persist
through the day, although with warm temps aloft, mixing should boost
readings into the 70s many locations by late afternoon as lower
clouds clear.

Overnight, mild conditions expected with clouds and increasing winds
as surface pressure continues to fall over the eastern plains.
Models keep most precip west of the Continental Divide through the
night, with just a few showers over the higher peaks into Thu

.LONG TERM...(Thursday through Tuesday)
Issued at 415 AM MDT Wed Mar 22 2017

.Thursday...Trough approaches the region with southwest flow
developing over the state. Over the eastern plains, low pressure
will develop in northeast Colorado with a dry line near the
Kansas border. Behind the dry line, southwest flow aloft will mix
to the surface with low humidities. Have issued a fire weather
watch for all of the eastern plains and Interstate 25 corridor.
With the dry line near the Kansas border, critical fire weather
conditions may not be present near the Kansas border. Some of the
models have the dry line moving into Kansas during the afternoon
which could result in critical fire weather conditions extending
to the Kansas border. SPC has a slight risk for severe convection
near the Kansas border, associated with the dry line. Main
threats appear to be hail and strong winds. Further west,
southwest flow aloft is favorable for orographic precipitation
over the eastern San Juan Mountains. Some model solutions, such as
the GFS, have snowfall reaching snow advisory criteria. Given the
uncertainty and marginal amounts, decided not to issue an advisory
at this time.

.Thursday night and Friday...Rapid cyclogenesis is forecast to
occur Thursday night somewhere over east central Colorado to
extreme northeast New Mexico. Moisture wraps around on the west
side of low center brining the potential for significant
precipitation to portions of eastern Colorado. Models still show
some differences in the location of the low with the EC being
furthest north and the fastest, while the GFS is slowest and
further south. There is not much cold air with this system and
snow levels should mostly stay around 6000 feet or higher. So far
the models have been consistent about the potential for
significant snowfall over the Palmer Divide and Pikes Peak region
and for strong northerly winds on the eastern plains. Have some
concerns for blizzard conditions along the Palmer Divide when the
heaviest snow is falling, but snow may be too wet to get
widespread blowing and drifting. Other challenge is the southern
Interstate 25 corridor, mainly from Colorado City and southward,
including the Raton Mesa. The GFS and NAM have been trending
towards a trowal on the west side of the low bringing significant
precipitation to this region. Much of the terrain in this area is
around 6000 feet, which will be close to the snow level. In the
deterministic grids, decided not to include too much snowfall
over this area at this time, given the uncertainty of the low
track. Probabilistic snow grids do a good job of capturing the
wide range in uncertainty. With the lack of cold air, suspect
snow level will lower to around 6000 feet during periods of
heavier precipitation when the atmosphere becomes isothermal. If
the precipitation stays lighter, snow level will be higher. Also
with the warm ground, heavier snowfall rates will be needed for
accumulation of snow. Quick look at 06Z NAM and GFS shows some
differences in low position and QPF, not helping to decrease the
uncertainty in the forecast!

.Saturday through Tuesday...Did not spend much time on this part
of the forecast. Models show a parade of weather systems through
next week with the potential for precipitation for the mountains
and plains with each system. A system on Sunday may briefly cut
off over eastern Colorado increasing chances for precipitation
over the plains and eastern mountains. Another system will affect
the region Tuesday or Wednesday, and models hint this system may
bring significant precipitation to the plains and eastern
mountains. --PGW--


.AVIATION...(For the 12Z TAFS through 12Z Thursday morning)
Issued at 415 AM MDT Wed Mar 22 2017

GOES-R fog loop shows stratus deck expanding over the plains as of
10z, and expect at least patchy MVFR stratus along and east of I-25
until midday. Western fringe of the cloud deck will likely produce
some IFR cigs/vis near the mountains and Palmer divide as clouds
push up against higher terrain.

At KALS...VFR today and tonight with SW winds gusting 20-25 kts this
afternoon and early this evening.

At KCOS...MVFR stratus will persist until mid/late morning, with
perhaps a brief period of IFR cigs 11z-14z. VFR conditions return
for this afternoon and overnight, with south winds gusting
20-25 kts 19z-02z.

AT KPUB...Brief period of MVFR cigs possible this morning as stratus
deck expands, then VFR returns by late morning as lower levels
mix out. VFR then likely for this afternoon and overnight.


Red Flag Warning from noon today to 7 PM MDT this evening for



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