Area Forecast Discussion
Issued by NWS Pueblo, CO

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FXUS65 KPUB 162130

Area Forecast Discussion
National Weather Service Pueblo CO
330 PM MDT Wed Aug 16 2017

.SHORT TERM...(This evening through Thursday)
Issued at 310 PM MDT Wed Aug 16 2017

Limited CAPE (ML CAPE around 500 J/kg or less) and less forcing has
resulted in lower storm coverage and strength across the forecast
area today.  Best coverage will be across the Pikes Peak region
through this evening where high res models have been consistent in
spreading showers and thunderstorms eastward off the mountains. Most
showers and thunderstorms will diminish during the evening with the
loss of heating...however several HRRR runs have been generating
another round of showers across northern portions of the southeast
plains towards morning.  Will maintain some isolated pops across the
area to account.  Otherwise...most areas will be dry and low
temperatures will be on the cool side.

Tomorrow will be a more active day for thunderstorms as de-amplifying
upper trof moves across the area in the afternoon.  Return southerly
flow will advect upper 50 dew points back northward into the far
southeast plains while passing trof helps mix out low level moisture
again and sharpens up a dry line across the far southeast plains.
Shear will be stronger...around 30-40 kts...and ingredients come
together best across the far southeast corner of the state including
Las Animas, Baca, Prowers, and Bent counties.  One or two severe
storms will be possible in this area with large hail and damaging
winds the primary threats. Temperatures will return to closer to
normal. -KT

.LONG TERM...(Thursday night through Wednesday)
Issued at 310 PM MDT Wed Aug 16 2017

Storms that will have developed along the shortwave trough axis
earlier in the day Thursday will continue to propagate easterly, and
once the storms move over the Colorado - Kansas border, the
environment will be favorable for rotating supercells. Forecast
BUFKIT sounding over Lamar, CO indicate CAPE values exceeding 2000
J/Kg and 6 km bulk shear values near 40 knots. The main threat from
the storms that strengthen over eastern Colorado will be strong
thunderstorm winds and large hail. The low level shear is not all
that impressive, so the tornado threat is small, but still possible.
SPC is in agreement with our severe weather forecast, they upgraded
the day 2 outlook over extreme southeastern Colorado to a slight
risk this morning, whereas the rest of the southeastern plains are
under a marginal risk. The complex of thunderstorms should exit
Colorado by midnight, Friday.

Moving onto Friday now, the shortwave trough will have passed and
lower dew point values fill the region. The GFS20 has storms
developing later in the day over the Upper Arkansas River Valley and
over Pikes Peak, in response to weak easterly upslope flow, whereas
the NAM12 does not have thunderstorms developing, suggesting that
there will be westerly flow at the surface. Some uncertainty does
exist for Friday, but for the time being, a chance of thunderstorms
is included in our forecast grids over the mountains, Palmer Divide,
and Raton Mesa.

The synoptics over the weekend and into next week include an upper-
level low developing over southern California and a broad upper-
level ridge building over the southern contiguous United States. The
response from the previously mentioned synoptic set-up will be a
monsoonal surge of moisture impacting southeastern Colorado. The
common daily theme will be thunderstorms initiating over the
mountains, followed by the upper-level steering flow propagating the
storms over the plains. The intensity of the thunderstorms and showers
will be dependent on how much moisture exists and how strong the
upslope component of the wind is. According to the GFS20, the
precipitable water amounts trend higher as the next week
progresses. On Tuesday, models suggest that a cold front will
pass, which may spark some showers over the plains in the early
morning hours and will lead to moist upslope flow for Wednesday


.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 310 PM MDT Wed Aug 16 2017

TAF sites will predominantly see VFR conditions with
KCOS seeing the best chance for a stray thunderstorm in the vicinity
of the TAF site.  Gusty winds up to 40 kts and brief VFR cigs will
be the primary impacts.  Thunderstorms will diminish during the
evening with light winds expected overnight.  Thursday will see
another round of thunderstorms develop over the mountains and move
off into the adjacent plains.  These should remain pretty isolated
for the TAF sites with VCTS most likely for KCOS.  -KT




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