Area Forecast Discussion
Issued by NWS Pueblo, CO
FXUS65 KPUB 231754
Area Forecast Discussion
National Weather Service Pueblo CO
1154 AM MDT FRI SEP 23 2016
Issued at 940 AM MDT Fri Sep 23 2016
Timing of the trof axis crossing the mountains seems a tad slower
in latest set of model runs...which would suggest a westward shift
of the dry line position this afternoon. This would mean a slight
shift westward in the severe potential and a potential trimming
of the eastward extent of the Red Flag warning for this
afternoon...with the position of the dry line late this afternoon
and evening over western portions of Crowley...Otero...and
central Las Animas counties. Overall the difference is not
significant enough to warrant changing fire weather headlines at
this time...but will watch for thunderstorm generation to occur
slightly farther west this afternoon than the original POP grids
portrayed. Modified POP grids to account for this.
Otherwise...majority of forecast package looks on track. -KT
.SHORT TERM...(Today and tonight)
Issued at 337 AM MDT Fri Sep 23 2016
...High Fire Danger and Severe Weather Possible Today...
Currently...a strengthening upper level low is located over the
Great Basin with broad southwesterly flow increasing across
Colorado. Weak embedded energy has kept isolated showers and
thunderstorms going over the mountains, east into the I-25 corridor
early this morning. Models have precipitation over the eastern
mountains into the plains dissipating through sunrise. Gusty
southwest winds have kept temperatures warm with upper 60s to mid
70s over the lower elevations.
Today...there are two main concerns for today, dangerous fire
weather conditions for the I-25 corridor, and the potential for
severe weather over our far eastern counties. The upper level low
is forecast to move across Utah into southwest Wyoming through the
day. As it does, it will spread strong southwesterly winds across
Colorado, along with sending a strong vort max across the region.
Severe weather...the primary focus will be a dryline that develops
by mid afternoon over the plains. Models are in good agreement with
later development, generally by 21-22z this afternoon. Shear will
not be an issue with 40 kts expected across the area, along with
good directional shear through the lower to mid levels. Model
dewpoints east of the dryline are expected to remain in the lower
50s. That should allow for CAPE values to run around 1000 j/kg by
this afternoon. Expect thunderstorms to develop by 22z, east of a
Fowler to Branson line, and shift east through the late afternoon
and early evening. Soundings indicate strong winds will be the
primary threat given the high cloud bases. Gusts in excess of 60
mph are possible. Updraft rotation should also allow for a few
cells to rotate with hail to around one inch in diameter possible.
Fire weather...strong mixing is expected in the lee of the eastern
mountains as southwesterly flow increases across the region. These
strong winds should mix down to the surface and help reduce humidity
values by mid afternoon. Southwest winds gusting to near 40 mph are
expected along with humidity values in the 10 to 15 percent range
west of the dryline, including the I-25 corridor. Outdoor burning,
including grilling, is highly discouraged this afternoon and
Models also keeping isolated to scattered showers and thunderstorms
over the mountains through much of the day, lifting northeast into
the Palmer divide this afternoon. Afternoon highs will once again
be warm with upper 80s to lower 90s across the plains.
Tonight...the upper level low will continue to lift northeast into
northern Wyoming with strong energy continuing east across Colorado.
The dryline will transition east into western Kansas through 06z. As
it does so, the strong to severe thunderstorms will track east into
western Kansas, with the plains dry after 06z. Over the mountains,
most shower and thunderstorm activity will end this evening as flow
aloft turns northwesterly around the upper low. The exception will
be the central mountains, where isolated showers will likely
continue into Saturday morning. In addition, light snowfall will be
possible over the peaks with an inch or so possible by morning.
Overnight lows will be cooler, with the plains in the mid to upper
40s. A freeze watch is in effect for the San Luis Valley where
overnight lows will fall into the mid to upper 20s. Mozley
.LONG TERM...(Saturday through Thursday)
Issued at 337 AM MDT Fri Sep 23 2016
Latest model trends are splitting the large upper low pressure into
2 main parts, keeping 1 well to the north and taking the other well
to the south. That leaves southern Colorado in between, likely to
see some good cooling but not a whole lot of precipitation.
Cooler temperatures will move in Saturday as the atmosphere cools in
response to the upper trough moving through the northern Rockies.
Readings over the mountains will cool by just a few degrees compared
to Friday since cooling had already started in that area. However,
readings over the plains will cool 10-15 degrees compared to Friday.
This will take temperatures down below average in most areas. The
chances for precipitation are not looking as good as they once did.
With much of the energy staying well north or well south of the
area, looks like just some isolated to scattered showers or
thunderstorms, primarily over and near the mountains. With the
airmass being cooler, could be some snow showers down to about
10,000 feet or so with maybe a local wet accumulation of an inch or
2 here and there from some of the more intense showers.
Looks like the strongest push of cool air will move in Saturday
night, resulting in Sunday being the coolest day of the next
several. Could have some more freezing temperatures in the mountains
and high valleys Sunday morning. Sunday looks dry and cool, with
highs around 10 degrees below average across the area.
Monday through Wednesday...temperatures will gradually warm back to
average levels although nights will remain cool under mostly clear
skies and light winds, especially Monday morning.
The next chance for precipitation could move in Wednesday night and
Thursday as forecast models have a system moving up from the
southwest at that time. However, this is still almost a week
away so confidence is low at this point.
.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 1130 AM MDT Fri Sep 23 2016
Gusty south to southwest winds will continue to increase across
the area this afternoon with a cold front expected to bring a wind
shift out of the west at all three terminals between 22Z and 00Z.
Wind gusts to 40-45 kts will be possible during the late afternoon
and evening hours as this front moves through. Showers will
continue along the CONTDVD with periodic mountain top obscurations
in -TSRASN. A line of thunderstorms will develop across the
southeast plains to the east of KCOS and KPUB late this afternoon
and evening. These could produce localized wind gusts to 55 kts
along with GR around 1 inch in diameter. Thunderstorms will move
northeastward through the evening hours and out of the southeast
plains by 06Z. Some MVFR to IFR CIGS will persist along the
continental divide through the overnight hours. -KT
Red Flag Warning until 8 PM MDT this evening for COZ226>233.
Freeze Watch from late tonight through Saturday morning for