Area Forecast Discussion
Issued by NWS Pueblo, CO

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FXUS65 KPUB 212132

Area Forecast Discussion
National Weather Service Pueblo CO
332 PM MDT WED SEP 21 2016

.SHORT TERM...(This evening through Thursday)
Issued at 255 PM MDT Wed Sep 21 2016

...A Warm and Breezy Thursday...

Current water vapor imagery and upper air analysis is indicating
moist southwest flow aloft across the state, as remnant moisture
from tropical system Paine continues to lift out across the region.
Water vapor imagery is also indicating drier air embedded within the
flow across the Desert Southwest moving into western New Mexico and
western Colorado, ahead of an upper trough digging across the West
Coast at this time. Regional radars indicating isolated to scattered
showers lifting north and east across the region, with a few
thunderstorms across northwestern New Mexico at this time.

Tonight and tomorrow...Latest models remain in fairly good agreement
with southwest flow aloft slowly increasing across the region
through the day tomorrow, as digging upper trough across the West
Coast carves out an upper low across the Great Basin tomorrow

With that said, should continue to see showers with a few embedded
thunderstorms moving across the area through the rest of the
afternoon and into the early evening, with HRRR remaining consistent
with the best coverage of storms being across the Pikes Peak region
and the Raton Mesa region into Baca County. Showers and storms to
diminish through the late evening, with loss of solar heating.
However, could see some showers developing across the ContDvd and
especially the southwest mountains, into early tomorrow morning,
with increasing orographic flow. Overnight lows to be at or above
seasonal average, especially across the eastern plains, where lee
troughing will keep breezy southerly winds across the far se plains

Will see more sun across the area early tomorrow, and with the
increasing flow aloft and lee troughing across the plains, should
see breezy southerly winds mixing across the area through the late
morning and afternoon. Mid and upper level moisture slowly increases
across the area again ahead of the Great Basin system, along with
southerly low level winds across the plains keeping low level
moisture in place, owning to another round of isolated to scattered
afternoon showers and storms, with the best coverage over and near
the higher terrain. Models continue to suggest near record high
temperatures in the 80s to lower 90s across the plains for tomorrow,
with highs in the 60s and 70s across the higher terrain and mainly
40s and 50s at the peaks. Current records for tomorrow are 85F at
ALS...88F at COS and 93F at PUB.

.LONG TERM...(Thursday night through Wednesday)
Issued at 255 PM MDT Wed Sep 21 2016

...Critical Fire Weather conditions I-25 corridor...Severe
thunderstorm potential eastern plains...and snow possible higher
mountains Friday...

Western U.S. upper low will move across the Great Basin Thursday
night before lifting northeastward into WY and MT Friday and
Friday night. Deep southerly flow across the plains will advect 50
dewpoints northward into the southeast plains Thurs night into
Friday morning. Initially will see some showers confined to the
mountains Thurs night and Fri with snow levels down to around
12kft at times along the continental divide. Dry air moves in
Friday afternoon as the trof axis moves across...which shallows out
the moisture along the continental divide. By this time...westerly
winds will be spreading eastward into the plains...sharpening up a
dry line just east of the I-25 corridor. All areas will see gusty
west to southwest winds west of the dry line...and gusty southerly
winds to the east of the dry line. CAPE values could be up to
around 1000 J/kg (according to the NAM12) with deep layer shears
around 30-40 kts. This will lead to a potential for severe
thunderstorms across the eastern counties including...Kiowa...
Bent...Prowers and Baca. Severe wind gusts and large hail will be
the primary storm threats.

To the west...RHs dropping to around 15 percent...and
the dry fuels will combine with gusty winds up to 40 mph to
create the potential for critical fire weather conditions Friday
afternoon and evening along the I-25 corridor. There are still
some questions as to the position of the dry line and how low
surface dew points will drop...however NAM12 seems too moist which
is its bias...and have leaned grids towards the drier GFS and EC
solutions for locations west of the dry line. For now have
restricted the Fire Weather Watch to the southern I-25 corridor
and a couple counties bordering to the east...but its possible
that the watch may need to be expanded northward and eastward a
bit more. Will let later shifts make any needed adjustments.

As the trof axis lifts out to the north Friday night...should see
drying conditions from west to east overnight. Any snowfall into
the mountains looks brief and relatively light...with spotty
amounts of an inch or two possible above 12kft.  The San Luis
Valley could see a fairly widespread hard freeze Friday night.

While the main upper low lifts off to the northeast...more energy
digging into the base of the trof across CO will keep generally
unsettled weather over the region through the weekend. A cold
front will drop through the region on Saturday with another surge
of colder air for Saturday night. Models keep majority of
precipitation across the southeast mountains and adjacent plains
where H7 temperatures dropping to 0 to -2C could drive snow levels
down to 9kft or a tad lower Sat night and again Sunday night. EC
and GFS differ with QPF during these periods...with EC on the
wetter side. Hard to say at this point how much snow will fall
across the southeast mountains...but at this point a few inches
of wet snow across the higher elevations look possible as GFS has
trended back towards a wetter solution.

Models shift the upper low eastward into the plains early next
week...though differ with the track as GFS keeps the upper low
center to the north across the Dakotas through Wed...while ECs
track is farther south. Either way...CO is on the back side of the
system with drier but cooler northerly flow. This will keep below
normal temperatures across the region through the longer ranges.


.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 255 PM MDT Wed Sep 21 2016

VFR conditions expected to persist at COS, PUB and ALS over the next
24 hours. Monsoonal moisture embedded within the west to southwest
flow aloft will keep scattered showers and thunderstorms in the
forecast across the higher terrain with more isolated storms
possible across the lower elevations through the evening, though
probability of storms affecting terminals too low to include in
TAFs. Breezy south to southwest winds of 15-20kts expected at
terminals through the evening. Less cloud cover expected tomorrow
morning, with breezy south to southwest winds and isolated
afternoon showers and storms again possible at the terminals.


.PUB Watches/Warnings/Advisories...
Fire Weather Watch from Friday afternoon through Friday evening
for COZ227>232.



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