Area Forecast Discussion
Issued by NWS Pueblo, CO

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FXUS65 KPUB 260500
AFDPUB

Area Forecast Discussion
National Weather Service Pueblo CO
1100 PM MDT Thu May 25 2017

.UPDATE...
Issued at 810 PM MDT Thu May 25 2017

Increased pops a little bit, into the scattered category, 04Z-
08Z, centered around 06Z (midnight). Several high res model runs
from the HRRR this evening have been ramping up convection during
that time around the Pikes Peak Region. Some have it centered more
over Pueblo County. Others have it farther north across Teller/El
Paso Counties. Taking a look at the experimental GOES-16 imagery
data this evening, there is clearly an area of lift to our west
coming this way. Couple this with the surface boundary that has
pushed through the region, visible in radar pushing south into Las
Animas County at this hour, and it seems plausible that we could
generate some nocturnal convection. Confidence is not real high
but high enough to raise pops into the scattered category.

&&

.SHORT TERM...(This evening through Friday)
Issued at 339 PM MDT Thu May 25 2017

...Severe weather threat ramping up into Friday...

Strong southwest flow aloft today has lead to gusty winds and low
humidities across all of southern CO this afternoon.  If fuels
weren`t moist/green from recent rains, this would have been a
critical fire weather day for all areas west of the dry line.
Meanwhile the cold front across northeast CO combined with upper
trof moving across the northern Rockies has sparked a round of
thunderstorms just north of the forecast area.  Latest HRRR drops
the front south of the Palmer Divide by 23z and through most of
southeast CO by 03z.  Some low level moistening behind the front
will allow for a window of one or two strong to severe thunderstorms
across northern portions of the southeast plains through this
evening, particularly northern El Paso and Kiowa counties.  Activity
should diminish overnight.

Trailing energy dropping southward out of Canada carves out an upper
low across ID which will move slowly eastward on Friday.  More
shortwave energy will eject eastward across CO interacting with the
frontal boundary and moisture hung up in eastern CO during the
afternoon.  Main challenge will be forecasting how far east low
level moisture will mix out during the afternoon. Have leaned
towards the NAM12 solution which maintains a more westward position
to the frontal boundary and puts best risk for severe thunderstorms
east of a line from roughly Falcon to La Junta to Kim.  Capes will
be running 1000-1800 J/kg east of this axis with deep layer shears
around 40 kts. Main threat will be hail and damaging winds with
supercell thunderstorms, however would think an isolated tornado
threat would be possible particularly where low level winds shift a
tad more easterly or where initial strong updrafts tap vorticity
along the surface boundary.  High res 4km NAM has isolated storms
developing across eastern Las Animas and southwest Otero counties
which move eastward across Bent, Prowers and Baca counties during
the afternoon. Another area of convection develops along/north of
the Palmer Divide where low level helicities should be a tad better.
So these will be the areas to watch for severe weather potential
tomorrow afternoon.

Farther to the west, thunderstorms will be more isolated and high
based with lightning and gusty winds the primary threats.
Temperatures tomorrow will be around 10 degrees cooler across the
southeast plains behind the front, to similar to a degree or two
cooler out west.  -KT

.LONG TERM...(Friday night through Thursday)
Issued at 339 PM MDT Thu May 25 2017

Unsettled meteorological conditions are anticipated during the
balance of the longer term with primary concerns being pops/qpf,
winds, temperatures and the potential for strong to severe
thunderstorms as well as locally heavy rainfall at times.

Recent longer term computer simulations, forecast model soundings
and PV analysis indicate that several upper disturbances will
interact with north-northeasterly surface surges over the forecast
district at times.

At this time, it appears that the highest potential for more
widespread locally heavy rainfall and stronger to possibly severe
thunderstorms should be noted Saturday and Monday(favoring eastern
sections), although the time-frame from Friday evening into next
Thursday has to potential to experience active conditions at
times over many locations(primarily during the afternoon and
evening hours).

Generally below seasonal later May maximum temperatures are
anticipated from Saturday into Tuesday, with maximum temperatures
then expected to run near to slightly above later May climatological
averages by next Wednesday and Thursday. In addition, minimum
temperatures are projected to hover near to slightly above later
May climatological averages during the duration of the longer
term.

Finally, the highest potential for stronger gradient winds over
the forecast district should be experienced Friday night.

&&

.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 1024 PM MDT Thu May 25 2017

Upper disturbances will track east across the flight area over the
next 24 hours. One disturbance will roll through tonight, bringing
isolated to scattered showers and a nocturnal thunderstorms to the
region. Another, more significant round of storms will develop
primarily over the plains Friday afternoon. There could still be a
few isolated cells over the mountains but the most widespread and
most intense activity will be out across the plains. Some of the
plains storms could reach severe limits. That would occur primarily
over the far eastern plains, east of the I-25 corridor. Storm
threats tonight include lightning and gusty winds. Threats on
Friday will also include hail and locally heavy rain, especially
across the plains east of the I-25 corridor.

The KCOS, KPUB and KALS TAF sites could each see a shower or
thunderstorm in the vicinity between now and about 9 or 10Z.
Friday, all 3 sites will probably remain VFR through the day.
There is a small chance, though, that something could develop in
the KCOS vicinity. The chance is too low to put in the TAF at this
time.

&&

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

$$

UPDATE...LW
AVIATION...LW



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