661
FXUS65 KPUB 212158
AFDPUB

Area Forecast Discussion
National Weather Service Pueblo CO
358 PM MDT Sat Sep 21 2024

.KEY MESSAGES...

- Widespread showers/scattered thunderstorms across most of
  southern Colorado this evening and overnight, then
  precipitation intensity/coverage begin to fade early Sunday
  morning.

- Snow levels drop down to around 9000 feet early Sunday
  morning, though most accumulating snow (5-10 inches) will stay
  across the higher peaks at/above 10kft.

- Below average temperatures throughout the majority of the
  week, returning to normal by the end of the week.

- Dry conditions are expected throughout the week.

&&

.SHORT TERM /THROUGH SUNDAY/...
Issued at 352 PM MDT Sat Sep 21 2024

Currently, upper low over nern AZ at mid-afternoon, with expanding
area of showers and thunderstorms over much of the region as upward
vertical motion increases across srn CO. Strongest storms so far
today have been over the San Luis Valley, where weak instability
(CAPE around 500 J/KG) and strong wind shear/upward motion were
generating some fast moving convection. Hail threat with these
storms will be limited by weak instability, but will need to watch
for at least a low end severe wind threat across the Valley through
00z given storm motions of 50-60 mph.

For the remainder of the afternoon into the evening, shower and
thunderstorm coverage will expand across the area as low approaches,
with HRRR suggesting a rather robust band of thunderstorms crossing
the mountains 23z-03z, then impacting the I-25 corridor and eastern
plains 02z-07z. Will continue with high pops and a mention of
thunderstorms all areas, as strong forcing will overcome weak
instability and keep tsra chance going until at least midnight. Snow
levels hangs out between 9-10k feet through the evening, though
wouldn`t be surprised to see stronger convection drive it lower
toward 8k feet at least briefly, though accums should remain mainly
over the peaks. After midnight, low passes overhead with vertical
motion gradually diminishing from sw to ne as main deformation zone
shifts into nrn CO. Overnight QPF, starting at 00z, will range from
a half inch to slightly over an inch over much of the higher
terrain, while valleys and I-25 corridor see numbers around a half
inch. Plains should see a quarter to half inch overnight, perhaps a
little heavier far southeast corner if stronger convection over ern
NM/wrn TX can hold together as it comes north this evening. Overall,
made only a few minor changes to ongoing forecast, as previous set of
grids appear to have a good handle on things.

Sunday, upper low gradually shifts out of Colorado into nwrn KS by
late afternoon, though moisture and instability will linger across
the area. Still a good deal of showers early in the morning over the
eastern mountains and plains, with most activity then weakening/
ending by noon. A few showers/weak storms could re-fire over mainly
the mountains in the afternoon as mid-level lapse rates remain
rather steep, though not expecting anything particularly strong or
widespread. It will definitely fell like fall across all the area
temperature-wise, with max temps only in the 50s/60s at lower
elevations, 40s/50s mountains.

&&

.LONG TERM /SUNDAY NIGHT THROUGH SATURDAY/...
Issued at 352 PM MDT Sat Sep 21 2024

The closed that has been impacting the short term forecast continues
its journey towards the northeast, but a lingering trough will still
be overhead at the beginning of the long term forecast period, which
will bring some light rain below 12kft and light snow above 12kft
over the easter San Juan Mountains. The strong low pressure system
brought cold air over the region and that will continue during the
overnight where low temperatures will be in the 30s and 40s over the
mountain valleys and the plains. Currently it doesn`t seem that any
frost products will be needed, but it is close, so we`ll need to
keep monitoring.

Below average temperatures are expected throughout the majority of
the week over the plains and mountain valleys. On Monday the high
temperatures will be in the upper 60s to low 70s over the plains and
mountain valleys. A weak shortwaves will begin to pass over
Colorado, once again bringing light snow over 12kft and rain below
12kft over the eastern San Juan Mountains. Otherwise dry conditions
and light winds everywhere else.

Tuesday through Saturday:

The rest of the will have some influence from a tropical system that
will be impacting the U.S. South, therefore there is some uncertain,
depending on the tropical system`s path. Overall, the flow over
Colorado is expected to be fairly weak with ridging aloft
developing over the western half of Colorado with northerly
winds over the eastern half. There isn`t precipitation being
resolved for the rest of the forecast period, just dry
conditions with temperatures reaching closer to seasonal by the
end of the week.

&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 1133 AM MDT Sat Sep 21 2024

Upper level low across nrn Arizona at midday will move north
and east across south central Colorado through the evening,
then continue into northeastern Colorado on Sunday. This system
will develop widespread precipitation, with showers and
thunderstorms spreading north and east across the central
Rockies through tonight.

At the taf sites, lowering VFR cigs and vcsh 18z-20z, then more
widespread showers and areas of MVFR cigs/vis from 20z until at
least 08z. Risk of tsra this afternoon at KALS and will carry a
20z-24z tempo, while at KPUB and KCOS, tsra threat is later in
the period generally in the 00z to 04z timeframe. After 08z,
precip trends back toward vcsh, though with plentiful moisture
and weakening winds, prevailing MVFR cigs are likely at all
sites, with a risk of IFR 10z-18z, especially at KALS if
significant precip occurs Sat evening.

&&

.PUB WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until noon MDT Sunday for COZ058-060-
082.

&&

$$

SHORT TERM...PETERSEN
LONG TERM...SKELLY
AVIATION...