Area Forecast Discussion
Issued by NWS Pueblo, CO

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FXUS65 KPUB 181755
AFDPUB

Area Forecast Discussion
National Weather Service Pueblo CO
1055 AM MST Sun Feb 18 2018

.UPDATE...
Issued at 1031 AM MST Sun Feb 18 2018

Winds have been slow to come up though have been steadily
increasing this morning with a few high wind gusts reported in the
Black Forest area. Suspect mtn top winds weren`t strong enough
over southern sections of the area last night...and farther north
(Pikes Peak area) where winds were stronger we lacked sufficient
mountain top stable layer to reflect those winds down to the
surface. Forecast models always have a tough time picking up on
these nuances. HRRR suggests that any mountain wave activity
should break down by 18z...though deep mixing may keep some near
high wind gusts along the southern I-25 corridor into the
afternoon. All highlights are projected to come down at noon.
Tough call what to do as there could be another round of high
winds for the southeast mountains this evening into the overnight
hours. Looks like too much forward shear tonight for the Pikes
Peak region to get winds to surface, however NAM does show more
potential for a mountain wave with an inversion aloft across
southern portions of our area. May have to hoist another High Wind
Warning for the Sangres/Wets and southern I-25 corridor for this
evening through early Monday morning. Will make this call shortly.
-KT

UPDATE Issued at 605 AM MST Sun Feb 18 2018

Updated for minor short term adjustments.

&&

.SHORT TERM...(Today and tonight)
Issued at 353 AM MST Sun Feb 18 2018

...High Winds through mid morning for the southeast mountains and
adjacent eastern slopes mainly west of I-25...

...Critical Fire Weather Conditions expected for the southeast
plains and lower slopes of the southeast mountains today...

Currently...winds have started to come up early this morning over
areas like La Veta Pass.  Most areas are seeing gusts in excess of
45 mph at this time, but most areas peaking around the 5 am to 8 am
time period, which is slightly later than earlier runs. Temperatures
have remained warm along the lee slopes in the 40s, while areas out
east along the lower Arkansas Valley in the 20s.  Will continue to
monitor winds this morning.

Today...flow aloft is forecast to switch from westerly to
southwesterly by this afternoon.  The main concerns will be expected
strong winds for this morning into the afternoon hours.  As mixing
strengthens this afternoon, humidity values will lower and
temperatures will warm.  This will produce critical fire weather
conditions for the lower slopes of the Eastern Mountains, out into
the Plains where gusts will reach into the 30 to 40 mph range.  Any
outdoor burning should be postponed until another day.  For this
afternoon, highs will reach into the 60s and 70s due to the mixing.

Tonight...as an upper trough digs out west across the Great Basin,
energy embedded in the southwest flow will spread east into the
Continental Divide.  This fetch of moisture and favorable orographic
flow will favor the San Juan Range.  Further north, snow will
spread into the La Garita and Central Mountain Ranges.  The highest
totals will be over the San Juans through tonight, with less amounts
up north.  In addition, shear profiles indicate areas over the
Southern Sangre de Cristo range may see downslope winds by Monday
morning. Mozley

.LONG TERM...(Monday through Saturday)
Issued at 353 AM MST Sun Feb 18 2018

A strong upper level shortwave and associated jet stream will cross
over the region Monday and Monday night.  This wave looks moist and
vigorous. It will slowly drag the right rear entrance region of a
110-130+ knot upper jet across Colorado Monday afternoon through
Monday night.  The combination of moist southwest flow and prolonged
upper level lift from the upper jet should provide 18-24 hours of
wind-driven snow to the Continental Divide.  The southwest Colorado
mountains, particularly the San Juan Mountains, should do very well
with this storm with accumulations up to 2 feet or more at places
like Wolf Creek Pass.  Southwest flow is not quite as favorable for
heavy snow over the La Garita, Sawatch and Mosquito Ranges farther
north.  These Ranges tend to be blocked by the massive San Juan
Range to the south.  Additionally, the north-south alignment of the
Continental Divide in central Colorado favors WNW winds as opposed
to SW winds.  This is not to say that these Ranges won`t see snow,
but they will probably see about half of what the San Juan`s see,
generally up to about a foot, with locally higher amounts over the
higher southwest facing slopes.  The eastern mountain ranges will
also see some snow as the main upper trough and upper jet moves
across late Monday afternoon and night but mainly over the higher
elevations above 10,000 feet.  The Sangre de Cristos and Pikes Peak
above 10,000 feet could see 4-8 inches of snow.  Will hoist an
advisory for those areas beginning late Monday afternoon and
continuing through Monday night.  The top of the Wet Mountains could
also see a few inches of snow Monday night but not enough for an
advisory.

For everybody else, the main concern will be the wind.  Monday will
be very windy over most of southern Colorado.  In and near the
mountains, gusts of 50-60 mph will be possible.  This will result in
widespread blowing snow and poor visibilities through the mountain
passes.  Farther from the mountains, gusts of 40-50 mph will be
possible. Doesn`t look like fire weather highlights will be needed
Monday as relative humidities will remain above critical levels.
Regardless, with all the wind, caution to avoid fire starts needs
to continue.

The high valleys, such as the San Luis Valley, the Upper Arkansas
Valley and the Wet Mountain valley could see maybe an inch of snow
from this system Monday and Monday night.  Western portions of the
San Luis Valley, closer to the San Juans, could do a little better,
possibly up to 2 inches.  The plains, particularly over the Pikes
Peak Region, could see some snow showers move across Monday night
into early Tuesday. However, any accumulations should be pretty
spotty and light, generally coming in well under an inch.

Another system could impact the region late in the week into the
weekend. However, the details of the system are pretty sketchy
right now as there is a lot of variability in the models.

&&

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 1031 AM MST Sun Feb 18 2018

Strong south to southwest winds will continue at KALS...and will
spread into KPUB and KCOS by 19-20z. Gusts to around 40 kts will
be possible at KALS...with gusts to around 30 kts at KCOS and
KPUB...though higher wind gusts will be possible closer to the
mountains. Threat for LLWS at KCOS should abate by 18z...as winds
increase and lower atmospheric layer mixes. Threat for the return
of LLWS looks low at this point, though certainly lots of
turbulence aloft with local llws near the mountains will be
possible through the day. Winds will decrease some this evening
but remain intermittently gusty from the southwest through the
night. Cold front will move into KCOS around 12z...and backdoor
into KPUB with northeast to east winds during the 13-14z time
frame. Low clouds may form behind the front during the
morning...and although models are reluctant to pick up on this.
Have introduced a SCT-BKN MVFR layer for both KCOS and KPUB based
on model performance with past fronts. Timing and height of these
CIGS will likely need refined as more simulations come in. -KT

&&

.PUB WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning until 6 PM MST this evening for COZ222-225>237.

High Wind Warning until noon MST today for COZ072>075-078>082-
084-085-087.

Winter Weather Advisory from 11 PM this evening to 8 AM MST
Tuesday for COZ058-060-061-065>067.

Winter Weather Advisory from 2 PM Monday to 8 AM MST Tuesday for
COZ073-075-082.

Winter Storm Warning from 11 PM this evening to 8 AM MST Tuesday
for COZ068.

&&

$$

UPDATE...KT
SHORT TERM...MOZLEY
LONG TERM...LW
AVIATION...KT



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