Area Forecast Discussion
Issued by NWS Pueblo, CO

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FXUS65 KPUB 151758
AFDPUB

Area Forecast Discussion
National Weather Service Pueblo CO
1058 AM MST Sun Jan 15 2017

.UPDATE...
Issued at 944 AM MST Sun Jan 15 2017

Challenging forecast with regards to snow amounts and precip
types. The switch over to snow has already occurred at KLHX...and
with time freezing rain line should shift eastward towards the
CO/KS border by 23z. Soundings look a little colder in the warm
nose aloft than they did yesterday...so could even see some sleet
along the transition line as it marches eastward today. Will keep
up winter storm warnings out east as this will be a mess of
freezing rain/snow combo. Looks like another .10 to .20 of
freezing rain will fall through the afternoon before the switch
over...with locally heavier amounts possible across Prowers and
Baca counties. Once switch over to snow occurs...could see
another 2-5 inches on top of what has already occurred with the
heaviest falling on the northern slopes of the Raton Ridge.

Snowfall forecast also a challenge for points westward. First wave
of snow didn`t prove as heavy as models had suggested yesterday
for the northern I-25 corridor (PUB to COS) and southeast Mts
(mainly wets and Teller)...though it did impact roads pretty good
in PUB. Nor did this wave spread as far westward up the Upper
Arkansas River valley of Chaffee and Lake counties. So forecast
challenge will be how far west will the deformation band will
impact as the upper low lifts northward through the TX/OK
panhandles overnight sending another round of snow into the
region. Models differ with this...with NAM more aggressive in its
westward extent of snowfall through tonight. Also looks like snow
will hang on longer into Monday with trailing energy from the
upper trof still moving across. Although snowfall rates don`t look
all that impressive...may have to extend highlights for the
southern mts/srn I-25 corridor (Huerfano and Las Animas counties)
and the northern slopes of the Raton Ridge based on impact where a
couple more inches may still fall through early Monday evening.
-KT

&&

.SHORT TERM...(Today and tonight)
Issued at 345 AM MST Sun Jan 15 2017

...High Impact Winter Storm To Affect The Region Next 24 Hours...

Currently...

Numerous showers were noted over the plains. Nearly all of the temp
observations at 3 AM were at or below freezing, so this precip is
freezing rain. The showers were convective in nature with dBz
values reaching to around 40. Quite a bit of lightning was
occurring south of the fcst areas in NM and TX phdl. Widespread light
snow was occurring in the mtns with some snow in the San Luis
Valley (SLV).

Today...

Bands of precip will move south to north most of today across the
region. Temps are likely to remain at or below freezing most areas
of the plains today. Careful examination of soundings indicate
thermal profiles generally along the I-25 corridor will primarily
favor snow while areas from roughly La Junta to Kim eastward will
favor freezing rain most of the day. This freezing rain/snow line
will generally move east later  today, reaching the KS border around
00 - 01 UTC.

Primary forcing for precip today will be warm air advection as
southerly flow in the lower levels of the atmosphere will
predominate. This will allow for mainly banded precip to move S to N
across the area throughout the day. Models hint at 2 primary bands,
one this morning and another later today. There may be a break in
the precip during the early afternoon time period across the
plains. However...areas near the KS border will likely see more
precip as better forcing is over this region.

Snow will continue in the mtns along the contdvd, but is expected to
be generally on the lighter side. The only exception will be the San
Juans were heavier snow will be possible

Icing is going to be an obvious issue today. However with temps in
the low 30s, the accretion rates may not be all that great.
Nonetheless, the far eastern plains will likely see a widespread
freezing rain event, with the greatest icing occurring along the
CO/KS border, especially in eastern Baca and Prowers counties.

Tonight...

Conceptually, flow goes northeasterly at 700 mbs and this should
favor the mtns/plains interface. I have increased POPs this general
region and we should see several inches of snow along the I-25
corridor region. Winds are not going to be that strong so shadowing
which occurs generally across S El Paso and N Pueblo counties may
not occur. Overall, the heaviest snowfall on the plains should occur
in the greater Spanish Peak/Raton Mesa region. Another heavier band
will likely occur with the trowal/waa which occurs along the KS/CO
border tonight. As mentioned above, precip tonight should be all
snow for the most part as colder air advects in throughout the lower
atmosphere.

Note that I have made no changes to the ongoing hilites. /Hodanish

.LONG TERM...(Monday through Saturday)
Issued at 345 AM MST Sun Jan 15 2017

Models in good agreement through mid week with high ensemble
spreads heading into the weekend with low confidence in the last
half of the extended period.

Monday...the upper level winter storm system is forecast to eject
out of northwest Oklahoma, northeast into northern Missouri by
Monday evening. Models all in good agreement with light snow
across the region all day. Decreasing upper level support as the
storm system moves away from the area should keep snow across the
plains on the light side. Additional accumulations of around an
inch are possible over the Plains through Monday evening, while
mountain areas see an additional 2 to 5 inches. Temperatures will
be cool with generally mid to upper 30s for highs. Expect snow to
come to an end from west to southeast during the evening hours
with dry conditions heading into Tuesday.

Tuesday through Thursday...high pressure over the west coast will
transit the area through mid week. This will bring dry and mild
weather to southern Colorado. Expect temperatures to warm into the
50s by Wednesday and Thursday with light winds. Flow aloft will
shift southwesterly on Thursday, and there could be isolated snow
showers late in the day along the Continental Divide.

Friday and Saturday...the next upper level storm system is
forecast to move off the Pacific and into the Rockies Friday into
Saturday. There are differences between the GFS and ECMWF. The
ECMWF develops a closed low and tracks it across the area Friday
with a secondary disturbance across the region Saturday. Both
would bring mountain snowfall, but the Plains will all depend on
storm track. The GFS is much slower and holds off the initial upper
disturbance until Friday night. Its storm track is similar to the
ECMWF, but the secondary system, which the GFS is slower with as
well, is much further south with Continental Divide snow and dry
conditions across the Plains. Cooler temperatures are expected by
Saturday. Mozley

&&

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 1058 AM MST Sun Jan 15 2017

MVFR and IFR conditions expected at COS...PUB and ALS through the
rest of the day, with moist southerly flow and bands of precipitation
moving across the area.

One band looks to move across ALS early afternoon with another band
through evening hours, with terminal snowfall accumulations of 1
to 2 inches possible through the period. IFR/LIFR conditions with
mist/fog likely overnight before cigs rise through the late morning
with VCSH continuing through the day Monday as weak upper trough
moves across the Rockies.

COS and PUB...One band of showers lifting out across COS attm,
with another band moving across PUB through the mid afternoon.
Another band looks to lift up across PUB and COS through evening
hours, with terminal snowfall accumulations of 1 to 2 inches
possible through the period. IFR/LIFR conditions with mist/fog
likely overnight before cigs rise through the early morning with
VCSH continuing through the day Monday as weak upper trough moves
across the Rockies.

&&

.PUB WATCHES/WARNINGS/ADVISORIES...
Winter Storm Warning until 11 AM MST Monday for COZ066-068-
072>075-079-080-087>089-093>099.

Winter Weather Advisory until 11 AM MST Monday for COZ058>063-
065-067-069>071-076>078-081>086.

&&

$$

UPDATE...KT
SHORT TERM...HODANISH
LONG TERM...MOZLEY
AVIATION...MW



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