000
FXUS65 KPUB 232027
AFDPUB

Area Forecast Discussion
National Weather Service Pueblo CO
227 PM MDT Fri Jul 23 2021

.SHORT TERM...(This evening through Saturday)
Issued at 225 PM MDT Fri Jul 23 2021


Tonight... Starting the short term period, an active period of
weather is expected. Synoptically, an upper level low pressure
system will begin trekking westward just to the south of the Pueblo
CWA. As the low pressure system moves closer to southern Colorado,
pockets of positive vorticity advection (PVA), will begin
influencing the area and will aid in increased synoptic level
ascent. Also, winds aloft will begin to shift more easterly in
response to this low pressure system just to the south of the area.
This upper level low will also begin advecting low and mid level
moisture around the eastern periphery into the region. With
orographic forcing increasing overnight, the support of the PVA,
increasing moisture, and mixed-layer CAPE (ML CAPE) values around
200-500 j/kg, rain showers and thunderstorms will persist into the
overnight hours, particularly over the mountains and mountain
valleys. With CAPE values beginning to decrease by late overnight
and into early morning, rain showers and thunderstorms will begin to
dissipate in coverage. Elsewhere over the Pueblo CWA, isolated
thunderstorms will be possible over the I25 corridor this evening,
but will dissipate by around 12 am, and otherwise expect dry
conditions overnight east of the I25 corridor. Lows will hover just
above normal, with the plains falling into the low/mid 60s, the
valleys dropping into the mid 40 and low 50s, and the mountains
cooling to the low/mid 40s.

Saturday... Continuing into the short term period, the
aforementioned upper level low will continue to influence the
region. Winds throughout the column will maintain a easterly
component, and will maintain a steady state throughout the day. Low
and mid level moisture will continue to be advected around the
eastern side of the low pressure system and into the area. With
persistent easterly winds aloft, inducing orographic lift, decent
mid level moisture, and ML CAPE values 500+ j/kg over the region,
rain showers and thunderstorms will initiate over the mountains
throughout the afternoon. Given moisture pooling along the eastern
mountains, especially within the upper Arkansas River Valley, which
will increase CAPE values, the most vigorous thunderstorms will
likely be along the northern parts of the I25 corridor. Despite
having decent moisture streaming into the region, large temperature
and dewpoint spreads will increase DCAPE values over the region.
With bulk shear values only around 10-15 kts over the Pueblo CWA,
minimal organization of convection is expected. The main hazards
with these thunderstorms will then be heavy rain and gusty outflow
winds to around 50 mph. Over the eastern plains, unless a parcel
reaches the convective temperature, which will be possible, expect
no thunderstorms as a weak CAP and the lack of a lifting mechanism
inhibit any sustained updraft development. High temperatures
tomorrow will hover at or just below normal highs. The plains will
warm into the mid 80s and mid 90s, the valleys rising into the low
70s and low 80s, and the mountains reaching into the low 50s and
upper 60s.

.LONG TERM...(Saturday night through Friday)
Issued at 225 PM MDT Fri Jul 23 2021

...Better chance for convection on the plains Sunday and Monday...
...Drying trend next week...

.Sunday...As the main ridge axis temporarily builds over the
Great Basin, the jet stream may dip far enough south to get some
northwest flow aloft over the region. A weak disturbance will
move across Wyoming and into the high plains during the day. GFS
and NAM12 suggest an MCS may develop to our north and east during
the afternoon and into the evening. The weak northwest flow
would allow for the potential for storms to move off of the
mountains during the afternoon and into the evening. The best
chances for storms over the plains will be northeast Colorado.
Precipitable waters decrease over the mountains, but they still
are modestly above average. The threat for flash flooding will be
reduced, but slow storm motions can still result in some flash
flooding.

.Monday...The MCS from Sunday may push a boundary across the
eastern plains. In addition, a weak disturbance will move
westward across New mexico. This pattern could result in an
increase in convection on the plains Monday. The models suggest
the best chances for storms on the plains will be south of US 50.
The NBM PoPs continue to show higher PoPs along the Raton Mesa.
Will have to wait and see how the specifics develop with the
amount of moisture on the plains, but there could be an enhanced
risk for stronger storms with locally heavy rain along the
southern border.

.Tuesday through Thursday...Upper high gradually builds to the
north and wanders to the east. Amount of convection will depend on
minor details, but the overall trend is for a warming and drying.
The best chances for storms will be over the Continental Divide
region with PoPs decreasing towards the east. Near the Kansas
border, only have silent PoPs

.Friday...The ensemble means indicate a stronger trough will move
into the midwest. This could send a cold front through the region
at the end of the week. The potential increase in low level
moisture along with northwest flow aloft increases the chances for
convection to move onto the plains. --PGW--



&&

.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 225 PM MDT Fri Jul 23 2021


KCOS: VFR conditions are expected over the next 24 hours. Widely
scattered rain showers and thunderstorms are expected this afternoon
and evening. The main impacts from the precipitation will be brief
heavy downpours and erratic outflow winds. While precipitation
should stay scattered in nature, the TAF site could still experience
gusty outflow winds away from any precipitation. Precipitation will
dissipate late this evening. Rain showers and thunderstorms will
also be likely tomorrow afternoon and be scattered in nature.
Tonight, winds will become light and clouds will begin to thin.

KALS: VFR conditions are expected over the next 24 hours. Isolated
to widely scattered rain showers and thunderstorms are expected this
afternoon and into overnight. The main impacts from the
precipitation will be brief heavy downpours and erratic outflow
winds. Rain will be the primary concern overnight, but thunder can
not be ruled out. Precipitation will begin to dissipate by early
morning hours. Isolated thunderstorms will again be possible
tomorrow afternoon.

KPUB: VFR conditions are expected over the next 24 hours. Isolated
to widely scattered rain showers and thunderstorms are expected this
afternoon and early evening. The main impacts from the precipitation
will be brief heavy downpours and erratic outflow winds. While
precipitation should stay scattered and to the northwest of the TAF
site, KPUB could still experience gusty outflow winds away from any
precipitation. Precipitation will dissipate late this evening, but
isolated thunderstorms will again be possible tomorrow afternoon.

&&

.PUB WATCHES/WARNINGS/ADVISORIES...
Flash Flood Watch until midnight MDT tonight for COZ058-060-061-
064>068-072-073.

&&

$$

SHORT TERM...SIMCOE
LONG TERM...PGW
AVIATION...SIMCOE

NWS PUB Office Area Forecast Discussion