Area Forecast Discussion
Issued by NWS Pueblo, CO

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FXUS65 KPUB 150359
AFDPUB

Area Forecast Discussion
National Weather Service Pueblo CO
859 PM MST Sat Jan 14 2017

.UPDATE...
Issued at 858 PM MST Sat Jan 14 2017

Made some adjustments to the pops for tonight, mainly over
northern portions of the forecast area. Also updated the first 24
hrs of the fire wx grids using the 00z run of the NAM.

&&

.SHORT TERM...(This evening through Sunday)
Issued at 326 PM MST Sat Jan 14 2017

...High impact storm to affect most of southern Colorado with
heavy snow mountains...and a mix of snow and ice plains...

Upper low has finally turned eastward and headed inland on the Baja
Peninsula. There is fairly widespread precipitation across the
desert southwest ahead of the upper low.  Models in fairly good
agreement tracking the upper low to the east northeast across old
Mexico then hooking more northward into southeast NM by 00z monday.
Track looks a tad farther south...and while 12z NAM was faster
spreading the next round of precipitation northward into the
southeast plains overnight...18z NAM run has slowed the northward
progression of the precipitation shield and jives better with the
GFS.

So should be fairly quiet this evening...though with southerly flow
into the eastern San Juan mountains...should continue to see some
off and on light snow.  Next wave of heavier precipitation should
spread northward into the southern portions of the forecast area
after 06z to 09z.  This wave spreads northward into the most of the
plains by 15z-18z before lifting northward into east central CO
during the afternoon. While most of the precipitation will fall as
snow across the mountains and valleys and I-25 corridor...model
soundings show nice WAA overrunning colder air at the surface...
conducive to freezing rain across the plains...mainly east of a line
from La Junta to Kim. A lot will be determined by temperature
though...with surface Ts right at or slightly below freezing.
A degree or two warmer or colder could mean more or less icing
potential. Soundings start to cool aloft towards 12z...with freezing
rain pulling east of KLHX by early morning...then towards the KS
border by 00z.

Biggest impacts will be across the eastern most
counties...Kiowa...Bent...Prowers...and Baca counties.  Should
between .20 and .50 of rain...with the possibility of up to .75 in
far southeast Baca counties.  Farther west...across
Crowley...Otero...and most of Las Animas counties...ice accumulation
of .02 to .20.  With additional snowfall Sunday night and Monday on
top of ice accumulations...winter storm warning seems the best way
to go for all of the southeast plains.

Have issued winter weather advisories across the San Luis
Valley...the Central Mts/Upper Arkansas river valley...Pikes
Peak...Fremont county...Wet Mountain Valley and the northern I-25
corridor of El Paso and Pueblo counties.  There will likely be waves
of snow...with the heaviest falling Sunday morning.  Could be a
quick 2 to 4 inches over this area during the morning...with locally
higher amounts across southern portions of the San Luis valley. With
additional snowfall expected into Sunday night and Monday as the
system approaches...(see discussion below) this will be a long
duration event...so although there will be a lull in the action
tomorrow afternoon...more impacts will be possible into Sunday night
and Monday.

There are quite a few challenges with the forecast.  Some concerns
are that a shift in the storm track to the south could cut back on
precipitation amounts with the first wave of precipitation tomorrow
morning.  Getting the temperatures correct at the surface will also
mean all the difference for precipitation type.  Models have around
an inch of QPF falling over portions of Baca county through the day
tomorrow...which if temperatures remain slightly colder could mean
more ice accumulation than currently forecast.  Will just have to
see how the forecast evolves...but bottom line is...check the
forecast often...and don`t head out if you don`t need to. -KT

.LONG TERM...(Sunday night through Saturday)
Issued at 326 PM MST Sat Jan 14 2017

...Snow diminishing through the day Monday...

Sunday night-Monday night...Latest models coming into better
agreement with the ending the overunning phase of this storm system
across southern Colorado late Sunday afternoon, and transitioning to
a more dynamic phase as the upper low moves into the western Texas
Panhandle around 00Z Monday, and continues to lift north and east
into north central Kansas by 18Z Monday. Still some differences on
trowal position and phasing energy associated passing northern
stream trough, though conceptually should see trowal and deformation
band precipitation developing across the southeast mts and plains
Sunday night with main band of snow lifting out into northwestern
Kansas through the day Monday, as developing north to northeast mid
level flow keeps light snow in the upslope favored areas of northern
portions of Teller and El Paso Counties, as well as the southeast
mountains and southern I-25 corridor. For now, kept current warnings
and advisories in place, with highest snow totals of 4 to 8 inches
across the higher elevations of the eastern mountains Sunday night
through Monday afternoon, with 3 to 6 inches across the rest of the
higher terrain. Current snow grids also have 2 to 4 inches across
the Palmer Dvd and Raton Mesa and out across the far southeast
plains for the Sunday night through Monday afternoon timeframe, with
1 to 3 inches across the rest of the lower elevations. Will see
breezy northerly winds developing over the higher terrain and across
the eastern plains through the day Monday, with snow showers
diminishing from north to south Monday afternoon and evening as
northern stream trough continues to dig across the rockies.

Tuesday-Saturday...Operational models having a hard time in
resolving northern and southern stream energy and stayed close to
GFS ensemble mean, which develops moderate northwest flow aloft
across the region Tuesday which becomes more westerly through
Wednesday, keeping the area generally dry and warm, with at and
above seasonal temperatures expected.  Southwest flow aloft develops
across the area Thursday, as another eastern pacific system digs
across the Great Basin, bringing chances of precipitation to the
ContDvd into Friday, and possibly the rest of the area on Saturday.

&&

.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 326 PM MST Sat Jan 14 2017

Weak southerly flow has kept IFR cigs in KALS all day...and think
this will continue into the overnight hours with next wave of snow
moving in after midnight.  More challenging CIG forecast for KCOS
with southerly flow upsloping on the southern slopes of the Palmer
Divide possibly leading to MVFR to IFR cig development during the
evening.  KPUB is more likely to remain VFR.  Next wave of
precipitation will spread northward into all three terminals towards
12z-15z.  A quick 1-3 inches of snow will be possible for KALS
Sunday morning...with 1-2 for KCOS and KPUB.  CIGS/VIS will be IFR
to even brief LIFR at KCOS and KPUB through the morning...with
improving VIS during the afternoon as the snow band lifts northward
and all three terminals experience a lull in the activity during the
afternoon. Fairly widespread freezing rain event is expected from
KLHX eastward on Sunday with widespread IFR to LIFR conditions in
dangerous icing. Mts will remain obscured for the majority of the
day on Sunday with SN. -KT


&&

.PUB WATCHES/WARNINGS/ADVISORIES...
Winter Storm Warning until 11 AM MST Monday for COZ072>075-079-
080-087>089-093>098.

Winter Weather Advisory from 5 AM Sunday to 11 AM MST Monday for
COZ058-059-061>063-076>078-081>086.

Winter Storm Warning until 11 AM MST Monday for COZ066-068-099.

Winter Weather Advisory until 11 AM MST Monday for COZ065-067-
069>071.

Winter Weather Advisory until 11 AM MST Monday for COZ060.

&&

$$

UPDATE...28
SHORT TERM...KT
LONG TERM...MW
AVIATION...KT



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