Area Forecast Discussion
Issued by NWS Pueblo, CO

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FXUS65 KPUB 191025

Area Forecast Discussion
National Weather Service Pueblo CO
425 AM MDT Tue Jun 19 2018

.SHORT TERM...(Today and tonight)
Issued at 341 AM MDT Tue Jun 19 2018

Currently...Outflow from convection across the northern portions of
the state has helped push a cold front south into southern Colorado
early this morning, with northerly winds gusting up to 35 to 40 mph
at times. There has been some patchy fog over Monument Hill
overnight, but the rest of the forecast area has been mostly clear.
Temps have dropped into the 40s and 50s for the high valleys as of 4
am, while the plains were still in the 60s to lower 70s.

Today and Tonight...The upper low over ID and MT early this morning
will slowly edge to the east over the next 24 hrs, sweeping the
trough axis across Colorado. A favorable combination of llvl
moisture, shear, and dynamics as provided by the nose of an upper
jet all point towards thunderstorm activity this aftn and eve, with
the potential for some of those storms to become severe. SPC has
painted much of the plains in the Marginal category, and has Slight
over El Paso, Crowley, Otero, Kiowa, Bent and Prowers Counties.
These storms will be capable of producing hail up to an inch and a
half in diameter, 60 mph wind gusts, frequent cloud to ground
lightning, periods of moderate to heavy rain and possibly a tornado.
Look for max temps in the 80s for the high valleys, and 80s to
around 90F for the plains. Activity is then expected to diminish
after midnight, with temps dropping into the 40s for the high
valleys and 50s for the plains. Moore

.LONG TERM...(Wednesday through Monday)
Issued at 341 AM MDT Tue Jun 19 2018

Conceptual Day 2 post frontal upslope pattern will be over the
eastern plains of the forecast area for Wednesday. Limiting
factor however appears to be low level moisture as both GFS and
NAM12 are drying out surface dew points during the afternoon with
values dropping into the 40s. So in spite of good deep layer
shear resulting from NW flow aloft and easterly surface flow, CAPE
appears to be limited to a couple hundred to near 800 J/kg at the
best according to NAM12. This really appears to limit the severe
thunderstorm threat for Wednesday. However with sufficient
heating, the southeast mountains/adjacent plains should still see
some isolated to low end scattered thunderstorms develop late in
the afternoon and push eastward into the evening. Overall,
Wednesday looks like convection will be much more sparse.
Meanwhile, western mountains will continue hot and dry.

Upper ridge to the southwest builds in over the area for Thursday.
Temperatures will heat up even more across the mountains as
heights rise aloft. Meanwhile, upslope flow will continue across
the plains with temperatures warming a bit over Wed. Still appear
to be lacking a good tap of low level moisture so CAPE still looks
rather limited in spite of relatively good deep layer shears.
Generally isolated thunderstorms will be possible across the
eastern mountains.

A shortwave will move across the area late Friday in NW flow aloft
signaling another potential uptick in thunderstorms for portions
of the southeast mountains and plains. It will all depend on how
quickly the front moves in Friday and timing of moisture return
behind it. Meanwhile...gusty west winds will spread across the
mountains raising concerns for critical fire weather conditions.
This will need to be watched closely as this period ticks up into
the shorter range as fire weather watches may become necessary.

Forecast confidence drops for next weekend into early next week.
Extended models take another closed low from the Pacific northwest
across the northern or central U.S. Rockies, with GFS
considerably farther south than ECMWF. Saturday could be a
potential day 2 severe thunderstorm day across the plains in post
frontal upslope flow...however neither GFS nor EC look
particularly moist with surface dew points and atmosphere could be
capped near the KS border. Its too soon to say. Will maintain
isolated pops across the southeast mountains and plains for now.
Meanwhile, the western mountains and interior valleys will stay
hot and dry. Sunday the upper low passes by to the north. This
should cool temps everywhere, and potentially increase pops for
the southeast mountains and plains. Central mountains may also see
some shower/thunderstorm activity depending on the track of the
upper system. Meanwhile, dry westerly flow would suggest another
potential critical fire weather day for the southwest mountains
and San Luis Valley. Given the storm track differences, confidence
is low at this point. Monday could be wet again for the plains
and cooler but still relatively dry out west. -KT


.AVIATION...(For the 12Z TAFS through 12Z Wednesday morning)
Issued at 341 AM MDT Tue Jun 19 2018

KALS: VFR conditions expected over the next 24 hrs. West winds
increasing up to 15 to 20 mph after 21z.

KCOS and KPUB: MVFR to IFR conditions over the Palmer
Divide/Monument Hill this morning until around 15z due to low cigs
and patchy fog. Otherwise, VFR conditions for the plains including
TAF sites of KCOS and KPUB through 21z. After 21z, thunderstorms are
forecast to develop across the plains with some becoming severe.
Lowering cigs, periods of moderate to heavy rain as well as hail,
and gusty outflow winds will lower conditions to MVFR to IFR at
times until 06z. Improving conditions after 06z, though depending on
pcpn amounts, patchy fog may develop and introduce more
restrictions. Moore




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