Area Forecast Discussion
Issued by NWS Pueblo, CO

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FXUS65 KPUB 240532

Area Forecast Discussion
National Weather Service Pueblo CO
1132 PM MDT Mon Apr 23 2018

.SHORT TERM...(This evening through Tuesday)
Issued at 257 PM MDT Mon Apr 23 2018

...Cold Front on the Way...

A large upper low pressure area is slowly dropping south into
northern Wyoming this afternoon.  A shortwave is rotating through
the southeast quadrant of the storm through eastern Wyoming,
triggering showers and thunderstorms north of Cheyenne.  The whole
system will make it`s way south through Wyoming tonight.  On
Tuesday, the upper jet on the south side of the system will track
across northern Colorado, placing southern Colorado in the right
rear entrance region of the jet during the afternoon.

This evening, LIs will range from 0 to -2 and CAPEs will run 200-500
J/kg.  Combined with maybe a little bit of forcing from the
approaching disturbance, this should be enough for a few spotty
evening showers or storms around the area, primarily over and the
near the mountains and out along the Palmer Divide.  The main threat
from any storm will be lightning.  Additionally, snow showers above
10,000 feet over the central mountains could produce local snowfall
amounts of 1 to 3 inches and some areas of reduced visibility
through the mountain passes.

Late this evening and through the overnight hours, a cold front will
push south through the plains. Gusty north winds will develop over
northern El Paso County toward late evening and then spread south
across the rest of the plains overnight into Tuesday morning.  Gusts
to around 40 mph will be possible behind the front.  Snow showers
will continue in the central mountains overnight.  Some snow showers
may also develop across Teller and northern El Paso Counties late
tonight into early Tuesday as the result of the front.  Local light
accumulations, mainly on grassy areas, will be possible around the
time of the morning commute Tuesday.

The best forcing and the best chance for precipitation with this
system doesn`t really move in until Tuesday afternoon when the right
rear entrance region of the upper jet passes overhead.  Models have
the upper jet developing a west to east oriented band of
precipitation somewhere in the vicinity of the US50 corridor in the
afternoon, allowing it to develop and sink slowly southward into
Tuesday evening.  Exactly where the band or bands will form is a big
question because model runs have varied on this over the past couple
of days.  But at least the models are generating enough lift to
develop precipitation.  Hopefully, those who need it most will get

The airmass behind the front is pretty chilly.  It should drop
temperatures over the plains by around 25 degrees Tuesday.  It will
also be cold enough to lower snow levels down to about 6,000 feet by
Tuesday morning and keep it there through the day Tuesday.  It could
even go a little lower under the heavier precipitation.  In any
event, any accumulations should be pretty light, mainly on grassy
areas and confined mostly to elevations above 6,000 feet.

.LONG TERM...(Tuesday night through Monday)
Issued at 257 PM MDT Mon Apr 23 2018

Operational models in slightly better agreement through the
extended period this forecast cycle and ensembles spreads are a
bit smaller heading into the weekend. So, there is a bit higher
confidence in the extend period compared to yesterday.

Tuesday upper level disturbance will drop south across
the Eastern Plains Tuesday night. Models in good agreement with a
band of precipitation dropping south with the disturbance. Expect
ongoing showers over the Palmer Divide during the evening hours,
clearing south into New Mexico by Wednesday morning. Snow will be
possible over the Palmer Divide, and the Eastern Mountains, down
to about 6500 feet. Minor accumulations are possible over the
Eastern mountains with generally 2 to 4 inches. Palmer Divide
areas will maybe see half an inch on grassy surfaces during the
evening hours.

Wednesday...the upper disturbance will shift southeast of the area
Wednesday morning with broad northwest flow across Colorado.
Expect dry conditions across the area. Temperatures will warm into
the 50s and 60s across the lower elevations.

Thursday...models in much better agreement with an upper
disturbance dropping south out of the Northern Plains and into
Kansas. This will send a strong cold front south across our
Eastern Plains by Thursday morning. Given how far east the
disturbance will drop, the latest guidance has come in pretty dry
for southern Colorado during the day. There will likely be a few
showers over the Eastern Mountains, with little if any
precipitation expected over the Plains. Snowfall totals over the
Eastern Mountains will once again only be an inch or two.
Temperatures will remain mild across the lower elevations with 50s
and 60s for highs.

Friday through upper level storm system off the west
coast will move onshore with increasing southwesterly flow across
the area. Increased moisture and instability will likely bring a
few diurnally driven showers and thunderstorms to the mountains
Friday and Saturday. Temperatures across the Plains will start to
warm through the 70s and into the 80s. The main question is how
far north the disturbance passes. The GFS is further north and
would bring elevated fire weather concerns to the area both Sunday
and Monday. The ECMWF is further south with better chances for a
few showers across the area and not as high of fire danger across
the area.  Mozley


.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 1124 PM MDT Mon Apr 23 2018

A cold front will continue dropping south through southeast CO
tonight. It has already moved thru KCOS, bringing strong north
winds that will continue into Tue morning. The strong north winds
will be moving into KPUB around 07Z. Wind gusts of around 35 kts
are expected to continue thru at least 12Z, then decreasing, with
gusts around 25 kts into midday Tue, then decreasing even more
toward evening. Some showers will continue in the vicinity of
KCOS thru maybe 08Z, and then will be possible again after 12Z.
KCOS should see low clouds develop and remain in the area thru
Tue. KPUB will also see increasing clouds with a lower ceiling,
but it may remain VFR, or lower into the MVFR category after 12Z,
when some showers may move into the area. Another round of showers
will be possible Tue evening. KALS is expected to have VFR
conditions thru Tue afternoon, and may see westerly winds with
gusts of 20-25 kts in the afternoon. Tue evening, winds are
expected to become easterly, with ceilings lowering and the
potential for showers developing.




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