Area Forecast Discussion
Issued by NWS Pueblo, CO

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FXUS65 KPUB 152056
AFDPUB

Area Forecast Discussion
National Weather Service Pueblo CO
256 PM MDT Tue May 15 2018

.SHORT TERM...(This evening through Wednesday)
Issued at 251 PM MDT Tue May 15 2018

...May Thunderstorms are Here...

Well, the weather finally looks like May... afternoon and evening
thunderstorms are here.  High res model trends today initiate
convection in primarily two areas before it heads eastward.  One
area of convection is already underway over western Las Animas and
Huerfano Counties.  This convection will continue to develop and
expand as it heads eastward across Las Animas County and the rest of
the far eastern plains during the afternoon into the evening hours.
This is the area of greatest severe threat today.  CAPEs are in the
1,000-1,500 J/kg range and the shear is around 35 knots. Also, while
mixed surface dewpoints are only in the upper 40s now, southeast
winds are advecting higher dewpoint air into the region as we speak.
This should bring dews up into the 50s as we move through the
afternoon. This will increase the prospects for strong to severe
convection.  Primary threats at this point look like quarter-size
hail, 60 mph winds, locally heavy rain and lightning.

The other area of focused convection this evening looks like the
Pikes Peak Region.  While the prospects for severe convection look
lower in this area, a few storms could be little on the strong side.
Surface dew points are a low right now, generally only in the mid
to upper 30s. It will be hard to get strong convection going with
that. However, high res models show convection initiating north
of the Palmer Divide after 4 pm that sends a boundary, and likely
higher dew points, south into El Paso County. The boundary and
higher dew point air looks to act as a focus for convection
across the Pikes Peak Region into the evening hours. Maybe, with
CAPEs progged around 1,000 J/kg and forcing from the boundary, a
few storms could produce some half inch hail and wind gusts to
around 50 mph along with some locally heavy rain and lightning.

Elsewhere, isolated storms will be possible this evening with
primary threats of lighting and winds to around 50 mph.

Tomorrow, upper level high pressure builds in over the region.  This
appears to be placing a pretty good cap over the area as any of the
models are having a hard time breaking out precipitation anywhere.
We`ll have to keep an eye on the dry line over the far eastern
plains but we may get through the day too capped to pop vigorous
convection.

.LONG TERM...(Wednesday night through Tuesday)
Issued at 251 PM MDT Tue May 15 2018

Wed night thru Fri an upper level trof will be over the western
U.S., and slowly working its way eastward.  This will keep south to
southwest flow aloft over southern CO during this period. Wed
evening, the NAM has some showers/tstms over the sern corner of CO
that dissipates after the loss of heating, while the GFS has more
widespread precip chances over the southeast plains that continues
into the late night hours and maybe into Thu morning.

On Thu it looks like the chances for precip will be more limited.
The NAM and GFS show precip mainly in the evening, and over areas
near the KS border, and maybe over the Palmer Dvd. There could even
be some strong to severe storms over the far southeast plains. The
main concern for Thu is the potential for critical fire weather
conditions.  It looks breezy to windy over much of the area Thu
afternoon and evening. However, much of the southeast CO plains are
expected to have RH values that are too high to issue a fire weather
highlight. At this time, the areas of highest concern include the
southwest mtns, the San Luis Valley, portions of the Sangre de
Cristo mtns, and a good portion of Las Animas county. The latest
fuels report for the San Luis Valley, still indicates that the fuels
are not critical, so will not issue a fire weather highlight for
that area.

Fri there may be more fire weather concerns, mainly over the
southeast corner of the state where low humidities, gusty winds and
dry fuels may combine to create the high fire danger.  However, it`s
too early to issue a highlight for Fri.  It looks like most of the
forecast area will remain dry on Fri, with mainly just the
central mtns, Teller and El Paso counties, expected to see chances
for precip as an upper level disturbance moves acrs nrn CO. Fri
night and Sat, the weakened upper low/trough is expected to move
acrs nrn CO/srn WY. Late Fri night, a front is expected to move
south thru the area, bringing gusty northerly winds. Later in the
day Sat, the forecast models show the potential for precip
increasing, especially over the mtns. Higher humidities on Sat
will mean lower fire danger.

Sun, the combination of an upper disturbance and increased mstr ovr
the area is expected to lead to a good chance for precip over the
mtns and high valleys, and maybe some of the southeast plains.  The
models continue showing moist conditions and precip potential for
much of the area on Mon.  The GFS shows an upper ridge over the area
for Tue, with drier conditions, but the ECMWF has an upper low over
western AZ with widespread precip chances over southern CO.

&&

.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 251 PM MDT Tue May 15 2018

Afternoon high resolution model runs continue to indicate two
primary areas of convection will track across the area the remainder
of the afternoon through the evening. The first area has already
initiated over western Las Animas and Huerfano Counties.  It will
expand and track east across the plains through the remainder of the
afternoon into the evening.  The second area of convection is
expected to initiate along the Palmer Divide late in the afternoon
and then spread south across the immediate Pikes Peak Region during
the evening. Storms in these two areas of convection could produce
half inch to quarter size hail, 50-60 mph winds, locally heavy rain
and lightning. Isolated thunderstorms will be possible elsewhere
across the flight area this evening with primary threats of
lightning and wind gusts to around 50 mph.  Wednesday currently
looks capped with little or no convection currently expected through
the day.

KCOS could see some thunderstorm activity late this afternoon and
this evening. KPUB and KALS will probably stay clear of storms
this evening.

&&

.PUB WATCHES/WARNINGS/ADVISORIES...
Fire Weather Watch from Thursday afternoon through Thursday
evening for COZ223-225-230-233.

&&

$$

SHORT TERM...LW
LONG TERM...28
AVIATION...LW



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