Area Forecast Discussion
Issued by NWS Pueblo, CO

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FXUS65 KPUB 240939
AFDPUB

Area Forecast Discussion
National Weather Service Pueblo CO
339 AM MDT Thu May 24 2018

.SHORT TERM...(Today and tonight)
Issued at 338 AM MDT Thu May 24 2018

...Isolated Thunderstorms Possible Parts of the Eastern Plains...

By and large, upper high pressure will build in over the area today,
resulting in hot and dry weather.  It will be a hot one by late May
standards with afternoon highs topping out around 10 degrees above
average.

There are, however, a couple areas to watch for potential t-storm
development during the afternoon and evening hours.  A very weak
upper level disturbance will move across northern Colorado during
the afternoon.  This disturbance may trigger some convection along
the natural moisture boundary that tends to align with the Palmer
Divide in light, diurnal wind situations.  Models have a narrow axis
of CAPE, instability and low level moisture convergence aligned
along the Palmer at 00z that shifts slowly southward into Kiowa
County through 03z.  If the upper disturbance can provide enough
lift, a few late day storms could generate along the Palmer from
northern El Paso County southeast into Kiowa County. This is a
pretty low confidence scenario but certainly possible. Will carry
some low, isolated pops for these areas this afternoon and evening
to reflect this possibility.  If storms are able to develop, the
primary threats would appear to be lightning, 60 mph winds and
possibly hail up to the size of quarters, particularly in Kiowa
County.  SPC has this area in the marginal risk for severe weather
today and that seems about right. For the rest of the area, the
airmass looks a little too dry for convection today.

.LONG TERM...(Friday through Wednesday)
Issued at 338 AM MDT Thu May 24 2018


An upper level ridge continues to affect southern Colorado through
Sunday afternoon. An upper level low will propagate northeasterly
over the intermountain west, starting over central California
(Friday Night) and will end up over the Dakotas (Tuesday evening).
The thunderstorm threat through Saturday will remain over the
mountains, but if any storms form, they will likely be extremely
isolated and weak. There are fire concerns from Saturday through
Monday. The upper level pattern become more zonal on Tuesday and
Wednesday, but added moisture to the atmosphere will result in
daily thunderstorm potential over the mountains.

Friday:

A ridge of high pressure settles over Colorado to start the forecast
period, bringing oppressive temperatures that are well above normal
for this time of year. Expect temperatures surpassing the 90s over
the plains, 80s in the SLV and lower Upper Arkansas River Valley,
and 70s in Lake County. The risk for thunderstorms will remain over
the mountains, but the lack of moisture will likely inhibit any from
from forming. Fire concerns will be minimal as surface flow will be
weak.

Saturday and Sunday:

An upper level ridge will continue to affect southern Colorado over
the weekend. Temperatures will be the warmest on Saturday, with some
locations likely passing 100F over the eastern plains. The main
concern for Saturday and Sunday is critical fire weather conditions.

The limiting factor for critical fire conditions on Saturday in
previous discussions was the temporal criteria of the Red Flag
Warning. The latest models resolves conditions being met for greater
than 3 hours, meaning a Fire Weather Watch is possible. The SLV and
the eastern plains meet Red Flag Criteria, but Otero, eastern Las
Animas, and Baca county`s fuel are too moist for a Red Flag warning,
so expect them to be excluded from any products that are issued. The
surface flow will be from the south on Saturday, with sustained
magnitudes up to 15 to 20 mph possible and gusts up to 25 to 30 mph.
RH values will be in the single digits over the SLV and the adjacent
plains, whereas the far eastern plains be in the low teens.

Sunday will also be critical fire weather day for southern Colorado.
Once again, Otero, eastern Las Animas, and Baca county will be left
out of the critical fire concerns due to moist fuels. Winds are
expected to stronger on Sunday, as the upper low encroaches near
Colorado.  Across the plains, winds are expected to be from the
south, sustained values around 20 to 25 mph; gusting up to 30 to
35 mph. RH values will be around 15 percent over the far eastern
plains and in the single digits for the SLV and adjacent plains.
In addition to critical fire weather concerns, there is the
possibility for thunderstorms over the for eastern plains during
the early afternoon hours. A dryline is forecast to tighten over
the Colorado and Kansas border and a shortwave trough embedded in
the upper flow may spark a few thunderstorms. CAPE values, as
analyzed by the GFS, are much below 1000 j/kg, so at this point,
do not expect any thunderstorms to become severe. Of course, there
is uncertainty of where the dry line sets up. If it sets up
further west, there will be more instability in the atmosphere,
resulting in stronger storms.

Monday through Wednesday:

The upper low is expected to propagate past Colorado on Monday, with
its associated cold front moving over southern Colorado as well. The
exact timing is still uncertain, but as of right now, expect it to
pass in the evening hours on Monday. The cold front will bring
the chance of precipitation over all of the plains. Fire concerns
continue into Monday over the far eastern plains. The upper
pattern will become more zonal on Tuesday and Wednesday, with the
chance of daytime thunderstorms over the mountains and a chance of
isolated thunderstorms over the plains. -Skelly

&&

.AVIATION...(For the 12Z TAFS through 12Z Friday morning)
Issued at 338 AM MDT Thu May 24 2018

VFR expected for most of southern Colorado over the next 24 hours.
This includes the KCOS, KPUB and KALS terminals.  Some isolated
thunderstorms could develop from the Palmer Divide down into Kiowa
County during the late afternoon and evening hours.  It currently
looks like this convection will remain north of KCOS.  However,
there is a low chance that it could make it as far south as KCOS
between 22 and 02 UTC.  If this happens, primary concerns at the
terminal would include convective wind gusts to around 50 mph and
lightning.  KALS and KPUB should be deep enough into the dry air for
no thunderstorms today.&&

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

$$

SHORT TERM...LW
LONG TERM...SKELLY
AVIATION...LW


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