Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service Pueblo Colorado
1205 PM MDT Tuesday Jul 29 2014

issued at 1205 PM MDT Tuesday Jul 29 2014

Threat for heavy rain continues this afternoon and evening. Like
the solutions given by the 4km arw...4km nmm and hrrr which
suggest a line of convection moving across the mountains during
the afternoon and reaching the Interstate 25 corridor in the early
evening. WV clearly shows a disturbance moving into southwest
Colorado. Some convection is already developing over northwest New
Mexico associated with the disturbance. Convection tends to weaken
during the evening as it moves onto the plains. With the amount
of moisture available...will still have to watch closely for
stronger storms on the plains this evening...with threat for
flash flooding.

During the evening...thetae ridge associated with southeast flow
remains mostly north of the County Warning Area...and models tend to develop an
mesoscale convective system over NE Colorado and southeast Wyoming. Another mesoscale convective system develops along
weak front where low level jet intersects the front over SW Kansas
and Oklahoma Panhandle. The heavier precipitation is most likely
to extend westward into Baca County and other counties near the
Kansas border. Like current day 1 wpc heavy rainfall outlook
which keeps region in slight risk...with moderate risk to the

On Wednesday...cold front passes in the morning with deep east to
northeast flow behind the front. BUFKIT soundings show a saturated
layer up to 400mb with precipitable waters over an inch. Lower
layers could become saturated with warm rain processes possible
enhancing precipitation. When see saturated lower layers with
1.5km deep easterly always concerned about flooding over
and close to the eastern mountains. Main challenge will be the
amount of instability. Current simulations suggest marginal
instability. --Pgw--


Short term...(today and tonight)
issued at 550 am MDT Tuesday Jul 29 2014

..flash flood potential this afternoon and tonight across all of
south central and southeast Colorado...

Monsoon plume over the area with embedded disturbances evident in WV
plume across the Great Basin and western Colorado. Models in good
agreement with overall synoptic details...with upper forcing
stronger today as wave over western Colorado rounds the upper ridge and across
Colorado. At the surface...easterly upslope flow will keep dew points in
the 50s and 60s...and even the valleys and mountains to the west
will maintain dew points in the 40s and lower 50s...quite moist for
these areas. Precipitation waters will be running around .65 to 1.0 across
the mts/valleys...and between 1.0 to slightly over 1.5 inches across
the southeast plains. So the classic ingredients are in place for
heavy rain/flash flooding...especially for the southeast mountains
and adjacent plains.

There are always challenges in the details...and model qpfs are not
all in agreement with where to put the heaviest amounts. The
general consensus if for thunderstorms to redevelop over the
mountains during the late morning...aided by afternoon heating and
upper lift with the disturbance moving through western Colorado.
Thunderstorms then spread eastward off the mountains in the adjacent
valleys/plains during the afternoon. Two broad areas of
precipitation maxima evolve during the evening and overnight hours.
One is associated with the disturbance coming across northern
Colorado...while a second maxima sets up across the southeast Colorado plains
into SW Kansas and Texas/OK where nose of upper level jet upglides over
warm front to the south. So overall...this suggests that northern
and eastern portions of the southeast plains may end up with the
heavier quantitative precipitation forecast amounts. This heightened concern area includes the Pikes
Peak region and Palmer Divide.

High res models seem to be suffering from convective feedback this have trimmed back probability of precipitation this morning from what the
consensus models suggested. But with all the moisture and
instability present...thunderstorms should expand in coverage over
the mountains during the late morning/early afternoon...then spread
off into the I-25 corridor during the late afternoon and evening.
Hrrr...nam12...and rap13 also develop thunderstorms over the Raton
Mesa region during the afternoon as southerly winds increase and low
level convergence sets up along this boundary. It takes a little
longer for thunderstorms to get going to the east of the I-25 and
corridor and north of the Raton Mesa region...with NSSL 4km WRF
holding this off until after 03z. Timing varies slightly with other
high res models...but overnight appears mesoscale convective system will take shape across
the far eastern counties into SW Kansas and Texas/OK which will drop to the
southeast during the overnight hours. Given the potential for heavy
rainfall to continue past midnight...extended the Flash Flood Watch
for the southeast mountains and plains through the overnight hours
into Wednesday.

Although majority of the concerns focus more on the heavy rainfall
and flash flood potential...will also have to watch for isolated
severe thunderstorms as well across the southeast plains this
afternoon. Cape values could achieve around 1000 j/kg with
sufficient heating this afternoon...and although deep layer shears
are not all that strong...we could see the potential for an isolated
severe hail/wind threat given the instability.

High precipitable waters and presence of forcing from the upper
level disturbance will also mean a heavy rain potential for the
mountains and valleys as well. Extended the Flash Flood Watch to
cover the San Luis valley for this afternoon and evening as reports
of stream flooding from heavy rainfall off the sangres occurred
tonight. Greatest threat may be more along the valley edges...but
really heavy rainfall with the stronger storms could occur anywhere
given the set up. -Kt

Long term...(wednesday through monday)
issued at 550 am MDT Tuesday Jul 29 2014

Localized areas of heavy rain...Hydro issues and temperatures are
primarily meteorological concerns during the longer term.

Longer term computer simulations and forecast model soundings keep
moist airmass in place over the majority of the forecast district
during the longer term.

By 12z of upper ridge shifts into southeastern
Arizona as an upper disturbance rotates across far eastern
Colorado...helping to enhance precipitation activity(including
storms with locally heavy rainfall) from later tonight into
Wednesday and have therefore issued/extended the Flash Flood Watch
over eastern sections of the County warning forecast area through Wednesday afternoon.

Then...additional rounds of showers and thunderstorms...some
capable of producing locally heavy rain and potential associated
Hydro/flash flooding concerns will be possible during the
remainder of the longer term...primarily favoring higher terrain
locations and area burn scars after projected
precipitable water values remaining in the 1.O to 1.5 inch range
interact with passing upper disturbances. Weather forecast office Pueblo will
continue to monitor closely and issue needed highlights...
advisories and warnings as needed.

Finally...generally below seasonal late July/early August maximum
temperatures are anticipated over the forecast district from
Wednesday into Saturday before warmer temperatures return by
Sunday and Monday as upper ridging shifts into northern new


Aviation...(for the 18z tafs through 18z Wednesday afternoon)
issued at 1205 PM MDT Tuesday Jul 29 2014

Thunderstorms scattered to numerous thunderstorms will develop at
the taf sites during the afternoon and continue into early
evening. A disturbance will move across the mountains during the
afternoon and reach the Interstate 25 corridor by early evening.
Behind the disturbance...scattered showers and thunderstorms can
continue into the evening. Coverage is not sufficient to put in
tafs. Winds will tend to be northerly at kcos tonight and limit
low cloud and fog development. Cold front may reach kcos by late
morning Wednesday for thunderstorms possible before 18z Wednesday.


issued at 550 am MDT Tuesday Jul 29 2014

Heavy rainfall the past couple days has lead to
saturated soils in many places...particularly across the southeast
mountains...I-25 corridor and southern portions of the southeast
plains. With forcing coming in later today...combined with high
precipitable waters...and upslope flow...we should see another round
of heavy rain producing thunderstorms develop over the mountains
then spread off into the adjacent plains. Most vulnerable
locations will be burn scars...steep terrain along the southeast
mountains...where upslope flow will focus thunderstorm development
with the potential for some training thunderstorms (particularly
across the Pikes Peak region). As moisture advection increases
tonight into the Front Range north of the warm front...soundings
suggest warm rain processes may occur...especially near the
mountains. This seems most focused across the Pikes Peak region
again. mesoscale convective system will develop across the southeast plains
to the east of I-25 which will continue into the overnight hours.
High stream flows and flash flooding of creeks and streams will be
possible as water from intense rainfall finds its way through the
drainages. Its possible we could see some flooding on area rivers
towards morning depending on how much and how quickly this water


Pub watches/warnings/advisories...
Flash Flood Watch through Wednesday afternoon for coz072>089-

Flash Flood Watch through this evening for coz058>071.




National Weather Service Glossary of Abbreviations