Area Forecast Discussion
Issued by NWS Pueblo, CO

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FXUS65 KPUB 182232

Area Forecast Discussion
National Weather Service Pueblo CO
332 PM MST Wed Jan 18 2017

.SHORT TERM...(This evening through Thursday)
Issued at 253 PM MST Wed Jan 18 2017

Current water vapor imagery and upper air analysis is indicating
moderate north to northeast flow aloft across the region, as a weak
elongated upper low/trough continues to slowly lift north and east
across northeastern New Mexico. Water vapor imagery is also
indicting a strong eastern Pacific weather system spreading mid
and upper level moisture across the West Coast at this time.
Satellite imagery is indicating high level clouds spreading south
and west across the southeast plains with lows clouds persisting
across the central and southern portions of the San Luis Valley at
this time.

Temperatures as of 2 pm certainly an indicator of the greatest snow
cover across the plains, with mid 40s to mid 50s from Pueblo north
and west and mainly in the mid to upper 30s along a line from TAD to
LAA. Further west, temperatures were a mixed bag from the 20s to
40s, as of 2 pm.

Tonight and Thursday...Flow aloft across the region transitions to
more west to southwest through the day tomorrow, with the old cut
off low/trough continuing to lift north and east into the High
Plains, as short wave ridging builds across the Central Rockies into
the region ahead of the strong eastern Pacific system moving onshore
across the West Coast.

This should lead to generally dry and warm weather across the area
tomorrow, save for increasing chances of light snow across the
ContDvd through the late afternoon. With some warming aloft across
the area, should see temperatures at and slightly warmer than todays
readings. Thinking low clouds will persist across the SLV tonight,
with the potential for fog development once again with the moist
boundary layer conditions persisting. Could see lows clouds lifting
through tomorrow morning, with the increasing flow aloft.

.LONG TERM...(Thursday night through Wednesday)
Issued at 253 PM MST Wed Jan 18 2017

...Active weather in the long range with several systems expected to
bring rounds of snow to the mountains....

The next trof will move through Thursday night and Friday.  Snow
will ramp up along the Continental Divide with the Eastern San Juans
favored for heavier amounts due to southwesterly orographically
favored flow.  Upper trof appears to come through in waves...with
the first Thurs night...and the second perhaps stronger wave
expected on Friday. Models differ with the details...with GFS (and
to a lesser extent the ECMWF) deepening and closing off the upper
low across southeast CO briefly Friday morning...while NAM12 is more
progressive and open. So while NAM12 keeps the plains dry...GFS and
ECMWF print out some light QPF along the northern periphery of the
upper low across portions of southeast CO. Have leaned the forecast
towards the GFS...though don`t think amounts on the plains will be
all that heavy given the breezy to windy downslope flow. It will be
cooler for all areas on Friday...with brisk winds...though these
should stay under high wind criteria.  Focus for moderate snowfall
will shift from the southwest mountains into the central mountains
once the trof axis passes and flow aloft becomes more west to
northwesterly.  Snowfall totals with this first storm stay in the
advisory range for the Continental Divide...with heaviest accums
across the eastern San Juans.

It will be a brief reprieve in snowfall for Friday evening as the
next storm will moves in quickly on the heals of the
previous...ramping up snowfall again along the Continental Divide.
This one looks to be a heavier snow producer for the eastern San
Juans...and with not much of a break between systems...decided to go
out with a winter storm watch for the southwest mountains.  Eastern
San Juans will likely hit warning criteria...with a little more
uncertainty (and likely to be more in the advisory range) for the La
Garitas.  Since this event won`t start until the 3rd period...have
opted to go out with a watch for now in order to let later shifts
refine the timing.  Snow will also fall along the Sawatch and
Mosquito ranges...and these areas may also need an advisory at some
point as well. Both the ECMWF and GFS close off the system across
the TX and OK panhandles Saturday afternoon.  This would bode for
precipitation across southern sections of the forecast area Saturday
afternoon...with precip type likely to be a rain with a rain to snow
change over into the evening hours.  Temperatures may end up being
too warm for much in the way of accumulation across the
plains...unless the timing of the system slows down such that the
majority falls during the overnight hours.  Have shaded up pops for
southern areas for now...with main influence south of highway 50.

Yet another storm system is progged by long range models to move
through during the Monday and Tuesday time frame.  Lots of
uncertainty with this latter storm...with GFS taking it north across
CO...while EC is slower and farther south.  The farther north track
would suggest more wind than snow for the southeast plains...though
northern El Paso county could see a high impact wind driven snow
event if the GFS track is correct.  ECMWF is farther south
suggesting more of a southeast CO event. This event looks colder
than the previous two...which could mean more snow for the southeast
plains depending on the storm track.  Its too soon to pops
will climb into the scattered category for the east on Tuesday...but
will need to wait for better model consistency before we can clear
up the details. -KT


.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 253 PM MST Wed Jan 18 2017

VFR conditions with generally light diurnal wind regimes expected at
COS and PUB over the next 24 hours.

ALS...MVFR and IFR stratus to persist over night, with the potential
for patchy freezing fog developing through the late evening hours
with continued moist boundary layer conditions. Expecting stratus to
lift tomorrow morning with increasing flow aloft ahead of the next
eastern Pacific system which will spread light snow into the ContDVD
through the late afternoon.


Winter Storm Watch from Thursday afternoon through Saturday
evening for COZ066-068.



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