Area Forecast Discussion
Issued by NWS Pueblo, CO

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FXUS65 KPUB 222120

Area Forecast Discussion
National Weather Service Pueblo CO
320 PM MDT Tue Aug 22 2017

.SHORT TERM...(This evening through Wednesday)
Issued at 319 PM MDT Tue Aug 22 2017

Thunderstorms developing over the mountains and along the Raton
Mesa at mid-afternoon, with very slow n-ne drift to most convection.
Air mass over the plains is moderately unstable, but soundings
suggest a rather stout cap will continue to suppress convection,
especially east of I-25. HRRR occasionally suggests a few storms may
drift eastward across the I-25 corridor and along the NM border
later this the evening, so will keep some low pops in place along
and west of the interstate. Models suggest best coverage of
convection will be across the central mountains late this afternoon,
with perhaps some southward development into the nrn San Luis Valley
during the evening. Given slow storm motions and weak shear, main
storm threats will continue to be flash flooding, especially over
recent burn scars. Convection fades away overnight, with just some
sprinkles lingering over the peaks by early Wed morning.

On Wed, a little less in the way of convection over the mountains as
air mass dries slightly, though still enough moisture for isolated
to low end scattered pops most areas. Cap looks weaker on the
plains, with both NAM and GFS developing some isolated storms along
and east of I-25 from very late afternoon into the evening. Again,
flash flooding will be the main storm threat, though swly steering
currents do increase as weak upper jet migrates eastward across CO,
which should lead to slightly faster storm motions versus the past
few days. Max temps will climb back toward seasonal values, with 3-6
degf of warming at many locations.

.LONG TERM...(Wednesday night through Tuesday)
Issued at 319 PM MDT Tue Aug 22 2017

Wed night an upper level ridge will be over the area with enough
moisture over the area for isold to sct showers/tstms.  The GFS has
better chances for pcpn Wed night than the NAM.  On Thu an upper
level disturbance moves acrs CO, aiding in the development of pcpn
acrs southern CO.  The forecast models are still showing better pcpn
chances for the southeast plains Thu night as that disturbance moves
acrs the area, with the potential for areas of heavy rain. There
could also be a few severe storms over the eastern plains.

The upper ridge rebuilds over the area on Fri behind that upper
wave, and Fri looks drier, although there should still be isold to
sct pcpn mainly over the higher trrn.

On Sat the upper ridge will be centered over the Great Basin, with
north to northwest flow aloft over southern CO.  A weather
disturbance is forecast to move through eastern CO in that northwest
flow in the afternoon and evening, and it looks like fairly
widespread pcpn could occur over the southeast plains.  The upper
ridge remain centered over the western states on Sun.  The best
chances for pcpn on Sun are expected to be over the mtns, but a
disturbance may brush the far eastern portions of CO Sun night,
bringing increased pcpn chances to areas near the KS border.

The northerly flow aloft continues on Mon, with yet another
disturbance making its way south acrs the area to help increase pcpn
chances through Tue morning.  A sfc fronts moves into southeast CO
Tue.  After the morning hours, the plains may dry out but the mtns
and adjacent areas should see pcpn in the afternoon and evening.


.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 319 PM MDT Tue Aug 22 2017

TSRA will continue over the mountains this afternoon and evening,
and will include a VCTS mention at KALS as a few storms may drift
across the San Luis Valley. Also a low chance of a TSRA at KCOS
this evening as storms move away from the mountains, though for
now will monitor radar trends and keep any mention out of the TAF
until storm coverage increases. Convection slowly decreases
overnight with VFR conditions most areas by Wed morning. Cycle
continues Wed afternoon with storms developing over the mountains
after 18z, then drifting toward lower elevations beginning 20z.
Terminals will have a low chance of storms after 20z, though storm
coverage will remain fairly isolated at lower elevations.




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