Area Forecast Discussion
Issued by NWS Pueblo, CO

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FXUS65 KPUB 222117

Area Forecast Discussion
National Weather Service Pueblo CO
317 PM MDT Tue May 22 2018

.SHORT TERM...(This evening through Wednesday)
Issued at 317 PM MDT Tue May 22 2018

...Critical Fire Weather Conditions expected across the San Luis
Valley Wednesday...

Isolated thunderstorms will continue to develop across the area
through this evening though coverage has been more sparse than past
couple days.  HRRR continues to advertise a line of showers and
thunderstorms developing down around Walsenburg and expanding and
moving northeastward towards Fowler along convergent boundary within
surface trof axis through the late afternoon. Main threat with
thunderstorms through the evening will be plentiful amounts of small
hail and wind gusts to around 50 mph, as it is supported by around
1000 j/kg of CAPE but deep layer shears more in the 20-30 kt range.
This activity lifts off to the northeast with some redevelopment
across the southern border counties of the southeast plains during
the overnight hours. Some iterations of the high res models keep
this activity to the south...across the New Mexico/Ok Panhandle
region. But with some lift possible due to strengthening low level
jet have opted to maintain some isolated pops out that way.
Otherwise...convection over the mountains should decrease during the
evening hours and diminish for most areas by midnight.

Western U.S upper low opens up and lifts out on Wednesday with main
circulation center lifting northeastward into the northern U.S.
Rockies.  Main effect for our area will be a warming and drying
trend as a dry air mass helps to knock back dew points across the
mountains and valleys.  Given increasing flow aloft, winds in
soundings look sufficiently strong to support a Red Flag Warning for
the San Luis Valley where RHs are expected to drop low enough for
long enough to meet the 3 hour duration.  Across the plains, dryline
will be mixing eastward during the afternoon with northern portions
of the I-25 corridor across El Paso and Pueblo counties and
potentially portions of Crowley and Otero counties seeing dew points
fall into the upper 20s and 30s.  Could see an hour or two of
critical fire weather conditions for these areas as well, but not
quite getting the areal coverage and duration of RH below 15 percent
to justify a Red Flag Warning. To the east of the dryline, CAPE
values will be running in the 1000-1500 j/kg range.  Unidirectional
nature of the winds are not yielding very high deep layer shear
values though, so threat for widespread severe looks limited.  With
decent CAPE however, can`t rule out a marginal near severe storm or
two across the plains. Will maintain isolated pops across the
eastern counties. Main threat would be gusty winds and hail.  -KT

.LONG TERM...(Wednesday night through Tuesday)
Issued at 317 PM MDT Tue May 22 2018

Wednesday night-Thursday...Southwest flow aloft across the region
Wednesday afternoon moderates Wednesday night and becomes more
westerly through the day Thursday, as a broad upper trough
translates north and west across the Northern Rockies and upper
level ridging builds into the Great Basin. Models still hinting at
the potential for a few stronger storms along a dryline across the
far Southeast Plains and western Kansas border late Wednesday
afternoon with the potential continuing through the evening with
models developing a low level jet along the Kansas border. Drier and
warmer air within the westerly flow aloft will help to keep
convection at bay on Thursday, however, still can`t rule out an
isolated high based late afternoon storm over the higher terrain and
possible across the far Southeast Plains, where best low level
moisture resides. Temperatures on Thursday look to remain above
seasonal levels, with highs in the 80s to lower 90s expected across
the lower elevations, 60s and 70s across the higher terrain and 40
and 50s at the peaks.

Friday-Saturday...Upper level ridging builds across the Rockies into
the early part of the holiday weekend, as Eastern Pacific energy
digs across the West Coast and into the Great Basin. Pattern
supports warm and mainly dry weather, with temperatures expected to
remain above late spring norms, as highs warm into the mid 80s to
mid 90s across the lower elevations, and mainly in the 60s and 70s
across the higher terrain. As for precipitation, can`t totally rule
out some high based convection in the afternoon and early evening
hours over the higher terrain, though soundings support mainly virga
and gusty winds.

Sunday-Tuesday...Models fairly consistent of increasing southwest
flow aloft across the region as developing upper low across the
Great Basin slowly weakens as it ejects north and west across the
Northern Rockies through early next week. Again, pattern would
suggest mainly dry, warm and breezy conditions across the area with
increasing fire danger and the potential for critical fire weather
conditions across portions of the South Central and Southeast
Colorado, along with the potential for strong to severe convection
across the far Southeast Plains into early next week with possible
dryline interaction.


.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 317 PM MDT Tue May 22 2018

Isolated thunderstorms will develop across the area through this
evening, producing VFR cigs/vis along with the potential for some
small hail, and erratic gusty winds up to 45 kts.  Likelihood of
these impacting the terminals is small, with KALS and KPUB seeing
the best chance for VCTS and erratic gusty winds.  Otherwise,
activity will diminish this evening with clearing skies.  KALS could
see a return of patchy ground overnight which could result in IFR to
LIFR conditions for a 3 hour window around/shortly after sunrise.
Otherwise, TAF sites will see increasing southwest winds on
Wednesday with gusts in the 25-30 kt range.  Thunderstorms will be
less likely for the TAF sites as drier and warmer air works in.  -KT


Red Flag Warning from noon to 8 PM MDT Wednesday for COZ224.



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