Area Forecast Discussion
Issued by NWS Pueblo, CO

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189
FXUS65 KPUB 201727
AFDPUB

Area Forecast Discussion
National Weather Service Pueblo CO
1127 AM MDT Sun May 20 2018

.SHORT TERM...(Today and tonight)
Issued at 440 AM MDT Sun May 20 2018

Currently...

Low clouds were noted over a good part of the fcst area, and they
were banked up as far west as the Sawatch range and Sangre De
Cristo range. West of this region it was mostly clear.

Temps at 4 am were in the 40s across a majority of the plains with
30s and 40s in the valleys. 20s were noted in the mtns.

Today...

Low clouds over the lower elevations are likely to remain over most
of the plains until at least mid morning. Along the mtns/plains
interface, the clouds may not clear until early afternoon,
especially across the south facing slopes of the Palmer Divide.

By mid afternoon, showers and thunderstorms will develop over the
higher terrain, with the brunt of the activity over the central mtn
region. Some of this activity will move east off the mtns, but is
not expected to get too far onto the plains due to the stable
airmass that will be in place.

Temp-wise, it is going to be a very nice day, with highs in the 60s
to around 70 across the valleys and plains and 50s in the mtns.

Tonight...

Isold/sctd Showers and tsra over the higher terrain and along the
I- 25 corridor will quickly dissipate early this evening, with
most activity ending by 9 pm. It will be cool once again tonight
with lows in the 40s to around 50F valleys and plains and 20s and
30s in the mtns.

.LONG TERM...(Monday through Saturday)
Issued at 440 AM MDT Sun May 20 2018

Monday through Tuesday...An upper low centered over central
California at the beginning of the period is forecast to slowly
drift east into the Great Basin. This will lead to south/southwest
flow aloft over Colorado with periodic embedded disturbances and a
decent fetch of moisture from the south/southeast from the surface
to 700 mb. These factors along with intense daytime heating will
allow thunderstorms to develop each day over the mountains, with a
few storms advancing east onto the plains and mountain valleys.
Coverage over the plains will be isolated considering a lack of
upper level forcing and the potential for convective inhibition.
Further, instability and deep layer sheer will not be all that
impressive, so severe storms are not likely, though some may be
strong. Surface winds will pick up each afternoon across the
plains to 15-25 mph sustained, gusting to around 30 mph. However,
atmospheric moisture content will be adequate enough to preclude
the development of critical fire weather conditions. High
temperatures will be in the mid 80s across the plains, and mid to
upper 70s across the high valleys and Colorado Springs.

Wednesday through Thursday...Models agree to lift the upper low to
the northeast on Wednesday and then east well north of Colorado on
Thursday. The fetch of favorable moisture to Colorado gets cut off,
and drier southwest US air advects over Colorado and mixes to the
surface each day. RH values will dip to critical levels during the
afternoons, but wind speeds look to be weaker than on previous
days, and recent rainfall across the region should mitigate the
fire danger. Thunderstorm activity will be less during these days
given decreased moisture and a continued lack of forcing.
Temperatures will be even warmer, with highs in the low 90s across
the plains, mid 80s in Colorado Springs, and upper 70s to low 80s
in the high valleys.

Friday through Saturday...Compared to yesterday, models are in
slightly better agreement during this period. An upper low is
forecast to advance east to just off the central-to-northern
California coast by Friday as a ridge builds over the western US,
increasing disturbed westerly to northwest flow over Colorado. The
models advance the low very slowly east toward the coast during this
period. The GFS continues to be a little slower than the ECMWF
moving the low to the east, causing the ridge axis to be positioned
further west, and leading to better northwest flow over Colorado and
increased precip chances. The low position in the GEFS is also
displaying considerable spread. Regardless, it appears that precip
chances are likely to increase again during this period.

&&

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 1119 AM MDT Sun May 20 2018

Persistent southeast upslope flow keeping IFR to even LIFR
conditions across KCOS with conditions expected to persist through
19z before cigs start to lift into the MVFR category. Given latest
satellite trends have hung on to MVFR conditions through at least
21z...but will have to monitor this for possible extension
depending on latest trends. KPUB will remain MVFR before improving
to VFR by 20z. Scattered showers and thunderstorms will develop
across the mountains and move eastward through the afternoon.
Stable air across the plains should keep thunderstorms from
progressing too far off into the plains...though a weakening storm
or two along portions of the I-25 corridor will be possible late
this afternoon and evening and have VCSH in the KCOS taf to
account for this. Also have VCTS in the ALS TAF as satellite
shows some moderate development on the western side of the San
Luis valley. Showers and thunderstorms will diminish this evening
with clearing skies overnight. Not expecting stratus redevelopment
overnight across the terminals as flow aloft becomes more
southwesterly. -KT


&&

.PUB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...HODANISH
LONG TERM...LINE
AVIATION...KT



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