Area Forecast Discussion
Issued by NWS Pueblo, CO

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FXUS65 KPUB 231813
AFDPUB

Area Forecast Discussion
National Weather Service Pueblo CO
1213 PM MDT Thu Mar 23 2017

.SHORT TERM...(Today and tonight)
Issued at 358 AM MDT Thu Mar 23 2017

...Strong Spring Storm to impact the region today into Friday...

Upper low over the Great Basin early this morning will track
eastward into the srn Rockies today, then deepen as it ejects
eastward into the plains tonight. Will see multiple weather
hazards over srn CO today and tonight, with red flag warning and
high fire danger over the I-25 corridor and plains, the potential
for thunderstorms over the mountains and near the KS border, and
snow plus strong winds spreading across the higher terrain today
and across the Palmer Divide late tonight. Made no changes to the
Red Flag Warning on the plains, as surface low will deepen through
the day, leading to increasing S-SW winds most locations along
with very low RH by this afternoon. Severe threat looks fairly
minimal as dryline mixes to the KS border today, but will keep a
low chance for tsra over the far east late this afternoon and
evening, with also a chance for a few storms over the mountains as
lapse rates steepen under the approaching low. Have added a
Winter Wx Advisory to high mountain zones along the Continental
Divide for late this afternoon and overnight, as combination of
snow and wind should create some difficult travel conditions over
high mountain passes by this evening.

Cold front will then drop quickly south through the plains this
evening as surface low deepens over far sern CO, with howling north
winds developing along and east of I-25 after midnight. Should see
rain and snow fill in quickly behind the front as dynamic lift
increases, with potential for heavy snow and strong winds to create
blizzard conditions over the Palmer Divide as snow level falls
toward 6k feet by early Fri morning. Teller county/Pikes Peak
should see heavy snow as well, though winds here will be less than
on the plains and will keep the Winter Storm Watch for these
areas unchanged. Biggest question mark will be amount of snow over
the Sangres/Wets, along with snow level along the southern I-25
corridor and across the Raton Mesa. Somewhat concerned that window
for heavy snow will be brief across the mountains, as low moves
east and flow becomes NW by early Fri morning. Will keep Winter
Storm Watch intact for the higher peaks for now, but won`t upgrade
or expand yet. Southern I-25 corridor and lower mountain zones
will likely see a mix or change over to snow early Fri morning
with a few slushy inches possible by sunrise, and perhaps the
north slope of the Raton Mesa and ern portions of Las Animas
county could see some heavier snow if surface temps can fall quick
enough.

.LONG TERM...(Friday through Wednesday)
Issued at 358 AM MDT Thu Mar 23 2017

...Three Springtime Storms to Affect the Region During This Period...

3 storm systems will affect the forecast area during this period
bringing much needed precip to the area along with significant
impacts. The first will affect the region Friday, the second on
Sunday and the third during the middle of the week. The 1st and 3rd
storm systems appear to be most significant.

STORM #1

The first storm will be ongoing at the beginning of this period. I
am very confident that this storm will bring strong winds to the
plains on Friday, with relative high certainty that the winds will
reach high wind criteria.

Certainty is also high that snow will fall across Northern El Paso
county ("Palmer Divide") and Teller county. Confidence is also
relatively high that the heaviest and most persistent snow will fall
across northeastern sections of Northern El Paso county. Confidence
is a bit less regarding snowfall amounts across the Monument Hill
region. Models all indicate it will snow across all of northern El
Paso, but the amounts (and duration) vary from model to model. Based
on the snowfall amounts that are possible, and the winds, and with
coordination with NWS Boulder, the Winter Storm Watch will be changed
to a Blizzard Watch for northern El Paso county.

Snow across the Pikes Peak region will likely dissipate by early
afternoon Friday, with the winds slowly decreasing.

Another concern is how much snow will fall across the southern mtns
(Wet mtns/Sangres mtns?Wet mtn valley). Models are not is good
agreement with this. Euro has the best potential for heavier snow
while the NAM and GFS show less potential. Additionally, the
guidance is hinting that the best chance of heavy snow
development may be along and just east of the I-25 corridor.

Rain, with some mixed snow above ~4500-5000 feet, will be likely
over all of the plains. N Pueblo county and S EL Paso county will
likely be "shadowed" due to the strong downslope winds, However I do
expect a band of heavy precip to move through and last ~1-2 hours or
so before it shuts down due to the strong downslope.

The Raton Mesa region will likely see a QPF bullseye across this
region. However, expect the precip to be a mix of rain and snow,
with not too much accumulation due to the warm ground and relatively
warm air temperatures. The heaviest precip will likely fall across
eastern Las Animas county.

As for winds, high wind warning criteria will likely occur across
all of the plains. The only concern is down near KTAD where winds
may not reach warning criteria. For now, we have decided to keep the
area under a high wind watch, and let later shifts refine
timing/intensity of winds across the plains.

The interior mtns/valleys will not see much in the way of any
significant sensible weather with this first system as most of the
forcing will be east of this region by 12 UTC Friday.

Storm #2

This storm appears to be the weakest of the three, although the
models do wrap this system up a bit once it gets east of the
rockies. This system will also be relatively warm, but not as warm
as the storm #1. Snow will likely develop over the contdvd Saturday
night with the precip moving onto the plains on Sunday. HIghest QPF
this this system will be dependent on how much the storm actually
wraps up, but the guidance for now is showing there will be snow on
the divides and east slopes of the s mtns.

Storm #3

This appears to be the stronger  of the three storms on all of the
guidance, but there is noticeable disagreement on the track of this
3rd storm. The EC is the most favorable track for us as it moves is
along (roughly) the CO and NM border as a large closed circulation.
It also moves it relatively slowly across the region. during the TUE-
THU time frame. The GFS on the other hand has a large circulation,
but moves it a bit too far south to bring beneficial widespread rain
to the region (It does bring precip to the southern 1/2 of the fcst
area). For now, leaned towards the EC solution based on this models
overall  performance and climatology, but decreased POPs somewhat
across the plains.

Given the active storm track during this long term forecast period,
temperatures will be more closer to seasonable values for this
time of the year, but will be on warmer side of climo.

The long range guidance shows a 4th weather system affecting the
area beyond this long range forecast time period (next weekend).
/Hodanish

&&

.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 1206 PM MDT Thu Mar 23 2017

VFR conditions at all taf sites today, with gusty S-SW winds
developing through the afternoon. Cold front then drops south
through KCOS and KPUB this evening, with strong N winds
developing, and both sites could see some gusts to near 50 kts
from 12z into midday Fri. Should see -SHRA develop at KALS after
22z this afternoon, with a switch to snow this evening and
overnight before precip ends by 12z Fri. -SHRA will fill in
behind the cold front at KPUB and KCOS 03z-06z and rain will
likely mix with or change to snow at KCOS 06z-09z and possibly
KPUB for short spell 09z-12z, though with surface air temps at or
slightly above freezing, accumulations will be slushy and mainly
on grassy, non paved surfaces. Over the mountains, SCT TSRA
possible this afternoon, with numerous -SHRA/-SHSN late afternoon
and overnight, leading to widespread IFR or LIFR conditions after
00z.

&&

.PUB WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning until 8 PM MDT this evening for COZ226>237.

High Wind Watch from late tonight through Friday afternoon for
COZ085>089-093>099.

Winter Storm Watch from 8 PM MDT this evening through Friday
morning for COZ073-075.

Winter Weather Advisory until 9 AM MDT Friday for COZ058-060-066-
068.

Winter Storm Watch from midnight MDT tonight through Friday
morning for COZ080>082.

Blizzard Watch from midnight MDT tonight through Friday morning
for COZ084.

&&

$$

SHORT TERM...PETERSEN
LONG TERM...HODANISH
AVIATION...LW



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