Area Forecast Discussion
Issued by NWS Pueblo, CO

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477
FXUS65 KPUB 211158
AFDPUB

Area Forecast Discussion
National Weather Service Pueblo CO
458 AM MST Sat Jan 21 2017

.SHORT TERM...(Today and tonight)
Issued at 457 AM MST Sat Jan 21 2017

...Dense Fog along the Arkansas River Valley this Morning...

A long stretch of dense, pea soup fog has formed along the lower
Arkansas River Valley this morning.  Most recent visibilities are
currently 1/4 mile at the Pueblo, La Junta and Lamar Airports.
According to the high res models, the fog could persist into the mid
or even late morning hours.  Conditions are near saturation and
winds are light so see no reason for it too kick out earlier.
So a Dense Fog Advisory will remain in effect for the lower Arkansas
River Valley, including Pueblo, Crowley, Otero, Kiowa, Bent and
Prowers Counties until 11 am.  This is primarily for the low lying
areas nearest the river.  The fog is likely to be less the farther
north or south you go from the river.

Otherwise, snow is ramping up along the Continental Divide this
morning, mainly over the southwest mountains so far.  Snow will
continue to increase along the Divide this morning and continue
through most of the day into the evening before winding down
overnight.  The existing Warnings and Advisories for the mountains
are on track and will remain in effect until 03z.  Elsewhere, some
spotty snow or rain showers possible over the next 24 hours.  For
the mountains and valleys west of I-25 the primary window for this
would be today with decreasing chances tonight.  For the plains, the
threat for any precip will persist until around midnight or possibly
later over the far southeast plains where the system is last to
depart.  According to the GFS, it is possible that the far southeast
plains, particularly Baca and Prowers Counties, could pickup a more
organized period of light snow and gusty winds this evening.
However, confidence is low as other models are not really showing
this. Something to keep an eye on though.

Another concern is the potential for some patchy fog along the lower
Arkansas River Valley again tonight.  Surface flow looks westerly
behind departing system which should help to preclude fog formation
but some of the statistical guidance at both LHX and LAA suggests it
is possible.  Not in the forecast now but may have to be added in
later. The San Luis Valley may also need fog added for tonight
pending precipitation today.

.LONG TERM...(Sunday through Friday)
Issued at 457 AM MST Sat Jan 21 2017

Fairly active weather pattern continues through the extended period,
with significant new snow for the mountains expected.

Sunday...A quick-moving upper ridge moves across the region, with
the ridge axis passing east across Colorado during the aftn. Expect
dry conditions through the first half of the day, then isolated
showers moving back into the Continental Divide through the late
aftn and eve. Max temps are forecast to be in the 30s for the high
valleys, and 40s to around 50F for the e plains. The showers moving
into western CO in the aftn are on the leading edge of the next
incoming weather feature, an upper low sitting off the Pacific NW
coast.

Monday through Wednesday...The upper low pressure system moves
onshore across the PAcific NW Monday morning, with a longwave trough
extending back across the West Coast down into southern CA. This
system sweeps across the Pacific NW and Great Basin on Mon, then the
Rockies on Tue and reaching the midsection of the country late Tue.
Snow is expected to be restricted to the mts through Mon, then as
the upper low crosses the Rockies winds will shift to a more
northerly direction and get gusty for the e plains. This will bring
isolated to low end scattered pcpn chances to the plains on Tue. By
Wed the system will be exiting the area, with showers lingering the
longest over the central mts under lighter northwest flow aloft. The
mts will likely need some sort of highlight for Mon, but will hold
off for the time being to avoid confusion since there are existing
highlights for the same area. As for temps, Mon will be the warmest
day of the extended with max temps in the 30s and 40s for the high
valleys, and 50s for the plains. As the upper low passes to the
north on Tue, more cloud cover and cold northerly flow will keep max
temps in the 20s and 30s for the high valleys and 40s for the
plains. The coldest day will be Weds, with max temps in the 20s and
30s for all areas.

Thursday and Friday...Extended models are still shaky on what
happens closer to the weekend, but indicate that light northwest
flow aloft will keep a few showers in place for the central mts Thu
morning. Otherwise, dry conditions with slowly warming temps into
the 40s for the e plains, and a cold 20s to mid 30s for the high
valleys. Moore

&&

.AVIATION...(For the 12Z TAFS through 12Z Sunday morning)
Issued at 457 AM MST Sat Jan 21 2017

Areas of LIFR dense fog will persist along the lower Arkansas River
Valley from the Pueblo area east to Kansas until 16-18Z. Conditions
frequently less than 1/4SM FZFG and CIGS VV001 at the KPUB, KLHX and
KLAA airports until fog lifts later this morning.

Fog has lifted across El Paso County and is no longer expected to be
widespread or dense although patches will remain possible at
KCOS until around 16z.

Snow showers are currently impacting KALS.  Currently MVFR CIGS and
VSBYS there. Conditions may go down briefly to IFR or even LIFR as
snow showers move across the terminal through the day.  Snow showers
should wind down overnight but then dense fog will become a concern
following the recent precipitation.

Otherwise, periods of snow will continue along the Continental
Divide through this evening, with snow winding down overnight.
Frequent IFR to LIFR expected in snow across the Divide.  For the
mountain ranges farther east and plains, mainly scattered
precipitation expected next 24 hours with areas of MVFR to briefly
LIFR conditions expected in showers.  The far southeast plains
around Baca and Prowers Counties, could see more widespread
reductions in flight conditions for a period this evening as a
potentially more organized area of snow moves through primarily
between 22z and 04z.

&&

.PUB WATCHES/WARNINGS/ADVISORIES...
Dense Fog Advisory until 11 AM MST this morning for COZ086-089-
093-095>098.

Winter Weather Advisory until 8 PM MST this evening for COZ058-
060-073-075-082.

Winter Storm Warning until 8 PM MST this evening for COZ066-068.

&&

$$

SHORT TERM...LW
LONG TERM...MOORE
AVIATION...LW



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