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Area forecast discussion
National Weather Service Pueblo Colorado
336 PM MDT Tue Jul 16 2019

Short term...(this evening through wednesday)
issued at 309 PM MDT Tue Jul 16 2019

..warmer and breezy with fewer storms tomorrow...

Current water vapor imagery and upper air analysis is indicating
weak to moderate westerly flow aloft across the region, with the
center of the large mid level high in place across southwestern New
Mexico, as eastern Pacific energy continues to translate across the
Pacific northwest through the northern tier at this time. Water
vapor imagery is also indicating drier air across the Desert
Southwest working into the region, with blended total precipitable
water imagery indicating precipitable waters of 0.5 to to 0.7 inches across most
of Colorado, though precipitable waters are still running around 1 inch across the
far southeast plains. Regional radars are indicating scattered
showers and thunderstorms over the higher terrain, with a few storms
moving east across the immediate adjacent plains at this time.

Current models and forecast remain consistent with increasing
westerly flow aloft across the region through the day tomorrow, as
eastern Pacific energy continues to translate across the northern
tier and the upper high builds back into the Desert Southwest. This
will continue to bring in much drier air, noted in current water
vapor imagery across the southern Great Basin, into The Rockies.

For tonight, will continue to see a few storms pushing east across
the high valleys and I-25 corridor through the late afternoon and
evening, with the best coverage across the Pikes Peak/Palmer dvd and
the Raton Mesa. Latest high res models indicate that storms will
once again push east across the far southeast plains through the
evening hours, where best low level moisture and instability reside.
Latest models do indicate an embedded disturbance lifting out across
the Great Basin and into the northern rockies overnight, which could
keep a few showers and storms through the overnight hours across the
higher terrain along and west of the contdvd. Over night lows will
continue to be at or slightly above seasonal levels, in the mid 50s
to mid 60s across the plains, and mainly 40s and 50s across the
higher terrain.

For tomorrow, westerly flow increases with drier air embedded within
the flow leading to decreasing coverage of storms across the higher
terrain, with storms that do form being higher based, producing more
wind the wetting rains. Models also indicate induced Lee troughing
across the plains, with low level moisture mixing out across the I-
25 corridor through the afternoon. Models indicating a few storms
developing across the mts, the Palmer dvd and Raton Mesa early in
the afternoon, along with a few possible storms initiating along the
Lee trough across the far southeast plains. Storm threats tomorrow
will continue to be lightning and gusty outflow winds, with a few
stronger storms possible across the far southeast plains. With the
westerly downslope flow, should see temperatures pushing near record
levels with highs in the 90s to lower 100s across the lower
elevations, in the 70s and 80s across the higher terrain and mainly
50s and 60s at the peaks. Records for July 17th are 92f at als set
in 2005, 96f at cos set in 2010 and 105f at pub set in 2003. The
warm temperatures, drier air and breezy conditions will also lead to
near critical fire weather conditions across portions of the area
tomorrow afternoon.

Long term...(wednesday night through tuesday)
issued at 309 PM MDT Tue Jul 16 2019

Thursday - Friday...

A broad ridge will extend from Arizona to the southeast US coast,
with an upper jet and periodic disturbances over the far northern
US. Colorado will be oriented under the northwest portion of the
ridge, with weak westerly flow aloft. A feed of dry air will
continue over the state leading to slightly below normal tpw
values. Given lack of moisture and forcing, no precipitation is
expected across the forecast area. The main story will be the
heat, with temperatures across the plains expected to rise into
the 100 - 105 degree range, and those across the high valleys in
the mid 80s to mid 90s. The very warm temperatures and dry
conditions will drive surface relative humidity values down to 10-15%, or
critical levels, during each afternoon across the plains and
valleys. Despite deep vertical mixing, winds at the surface should
generally remain sub-critical considering weak flow aloft and a
lack of surface pressure gradient. Therefore, critical fire
weather conditions are not expected.

Saturday - Sunday...

The broad ridge remains in place over the southern half of the
US, with attention turning to a potentially potent shortwave
trough advancing east across the northern rockies in the Saturday
night through Sunday timeframe. There is considerable model
uncertainty with the evolution of this system that will influence
southern Colorado weather. The last couple days of GFS runs have
had a potent wave sending a surface cold front down the eastern
Colorado plains Saturday evening with Post-frontal surface winds
winds turning easterly. This would lead to a rapid increase in
moisture and considerable shower and thunderstorm coverage across
much of the County Warning Area by Sunday afternoon/evening, and much cooler
temperatures Sunday. The last couple of European model (ecmwf) runs have had a
weaker wave, a subtle northerly surge, a slower increase in
moisture, less precipitation on Sunday, and only slightly cooler
temperatures on Sunday. Forecast ensembles show considerable
spread with the evolution of the northern wave.

Regardless, it looks like most of Saturday will remain dry across
the forecast area, with afternoon temperatures similar to those
of Thursday and Friday. With or without the strong northern wave
and cold front, moisture aloft should start to creep up on Sunday
as the upper high begins to close off near the Colorado/nm border,
similar to last weeks orientation. This will lead to at least
isolated to scattered showers and thunderstorms over the high
terrain by Sunday afternoon and early evening.

Given all of this, forecast confidence is high that precipitation
coverage will begin to increase across the forecast area on
Sunday, but exact details, including related to temperature
trends, remain uncertain.

Monday - Tuesday...

The upper high pressure remains over Colorado, with its center
shifting north slightly to west-central Colorado by Tuesday
evening. This allows increased mid to upper level moisture to
continue to stream into Colorado. At the same time, low level flow
across the eastern plains should remain easterly to
southeasterly. This pattern will keep tpw near to slightly above
normal, yielding afternoon thunderstorm development over the high
terrain each day. Steering flow will be weak, so storm development
over the plains will again depend outflow boundaries emanating
from the western activity. Storm during this period have the
potential to produce heavy rainfall, so pose flash flood threat to
burn scars. Temperatures look to be near or slightly below to
start the work week.


Aviation...(for the 00z tafs through 00z Wednesday evening)
issued at 309 PM MDT Tue Jul 16 2019

Similar forecast as the last several days, with afternoon storms
over the higher terrain spreading east across the adjacent plains
through the early evening. With that said, VFR conditions remain
expected at cos, pub and als over the next 24 hours, with storms
possible at the terminals between thru 02z Wednesday. Storms will be
higher based, with gusty outflow winds up to 40kts expected to be
the main threat, though locally heavy rainfall and small hail will
still possible with the stronger storms. Less convection with breezy
afternoon westerly winds expected at the terminals tomorrow.


Pub watches/warnings/advisories...

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