Area Forecast Discussion
Issued by NWS Pueblo, CO

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FXUS65 KPUB 221737
AFDPUB

Area Forecast Discussion
National Weather Service Pueblo CO
1137 AM MDT Fri Sep 22 2017

.SHORT TERM...(Today and tonight)
Issued at 433 AM MDT Fri Sep 22 2017

Deep upper trough remains in place over the wrn U.S. early this
morning as SW flow aloft strengthens across Colorado. Have already
seen strong winds over the higher peaks as of 10z, with gusts to 45
kts at mountain AWOS stations near Monarch and La Veta Passes. Lower
elevations have become breezy in spots as well, with sporadic gusts
in the 20-30 kt range across the San Luis Valley, the Lower Arkansas
Valley and along I-25. As a result of the wind, temps are all over
the map, with readings still in the 70s around Pueblo and La Junta
at 10z.

For today, upper trough moves very little, leaving strong SW flow in
place across the state into the afternoon. While dewpoints will rise
a few degf over the area versus yesterday, humidity will still fall
to around 15 percent for several hours along the I-25 corridor and
across the adjacent plains in Crowley/Otero counties, and with
strong winds expected, Red Flag conditions look likely from late
morning through the afternoon. Regarding convection, best bet for
storms looks to be across the San Juan/La Garita mountains where
moisture/dynamic lift and favorable swly orographic flow come
together to produce sct/nmrs -shra/-tsra from this afternoon into
the overnight hours. Other area to watch will be the far eastern
plains, as low level moisture returns and CAPE climbs back above
1000 J/KG along the KS border after 21z. SPC marginal risk looks
reasonable given CAPE and 40-50 kt 0-6km shear, with mainly a high
wind threat in/near fast moving storms. Remaining mountains and
interior valleys may see a brief/windy tsra late in the afternoon as
mid-level moisture and weak lift develop. Max temps today will cool
just a couple degf versus Thu numbers, though readings will remain
well above average areawide.

Tonight...threat of tsra will continue over the mountains,
especially the San Juans where strong swly flow remains in place.
Given 700 mb temps around 4C or warmer, any snow should be limited
to the higher peaks above pass level. Over the eastern plains, low
level moisture continues to work westward, and with strengthening
low level jet providing some lift, expect a chance of storms to
persist through much of the night, mainly to the east of I-25.
Again, there may be a marginal threat of a severe storm or two
toward the KS border, wind strong winds the main threat.

.LONG TERM...(Saturday through Thursday)
Issued at 433 AM MDT Fri Sep 22 2017

...A much cooler and unsettled weather pattern expected into early
next week...

Saturday-Sunday...Operational run of the GFS remains faster and
further north with the Great Basin upper low ejecting across
northwestern Colorado and into the northern Rockies, with the GFS
ensemble mean closer to the slower and a further south EC and NAM
solutions. With that said, have followed more of an EC/NAM blend
with scattered to numerous showers and thunderstorms across the area
Saturday/Saturday night, as lead short wave translates across south
central Colorado. Best low level moisture remains out across the far
southeast plains, though models are keeping the best CAPE south and
east across northeastern New Mexico, northwestern Oklahoma and
southwestern Kansas. The latest run of the NAM does indicate better
instability in southeastern Baca County Saturday afternoon, with
ample shear to support the potential for strong to severe storms
producing large hail and damaging winds. Locally heavy rainfall will
also be possible with the stronger storms. Snow levels remain
relatively high through the day Saturday, though can`t rule some
light accumulation`s across the peaks. As the upper low starts to
eject out across the area Saturday night, frontal boundary slides
south and west across the eastern plains, leading to continued
chances of showers and embedded thunderstorms across the area Sunday
and Sunday night with upslope flow in place and increased uvv as the
upper low moves into the northern Rockies. Temperatures aloft cool
with the passing upper low allowing for snow levels to drop to
between 9000 and 10000 feet, with a another 1 to 4 inches of snow
expected generally AOA 10K through Sunday night, especially across
the central and eastern mountains. High temperatures across the area
on Sunday to be mainly in the 50s and 60s across the lower
elevations, though could see temperatures warming into the 70s early
Sunday across the far southeastern plains.  Cool air in place Sunday
night will also support widespread subfreezing temperatures across
the high mountain valleys and the potential end to the growing
season in the San Luis valley.

Monday-Thursday...Main upper low continues to lift north and east
across the northern Rockies on Monday, with models indicating
secondary energy digging down the backside of the system into the
Great Basin through the day Monday. This will keep cool and
unsettled weather across the area, with isolated to scattered
showers expected, especially over and near the higher terrain.
Models continue to differ on strength and location of this secondary
energy, and will keep current cool and unsettled weather in the
forecast, especially over and near the higher terrain, into the
middle of next week, with a warming and trend into the end of the
work week. Overnight lows, especially Monday night/Tuesday morning,
look to continue to be at or below freezing across the high
mountains valleys, before slowly warming through the middle of the

&&

.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 1128 AM MDT Fri Sep 22 2017

Gusty southwest winds will occur at all 3 taf sites, kpub, kals
and kcos the rest of this afternoon. Otherwise it will be dry with
variable high clouds the rest of today into this evening.

For tonight...winds will weaken and ceilings will gradually lower
at all sites, however VFR conditions are anticipated.

Tomorrow, it appears we will have a better chance of high impact
weather as guidance is now showing a better chance of rain for the
I-25 corridor and mtns, and this will likely lead to lower cigs
and a chance of showers at all 3 taf sites by mid to late morning.
For now I do not have it too bad at the taf sites, but if the
guidance is correct, MVFR conditions will be possible by late
morning at all 3 taf locations.

&&

.PUB WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning until 7 PM MDT this evening for COZ227>232.

&&

$$

SHORT TERM...PETERSEN
LONG TERM...MW
AVIATION...HODANISH



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