Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 171716
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1116 AM MDT Fri Aug 17 2018

.UPDATE...
Issued at 1115 AM MDT Fri Aug 17 2018

Moisture continues to slowly increase over the CWA this late
morning. Current ACARS soundings are showing the mid level cap
that was in place early is not as strong. There is pretty decent
CAPE progged over the central plains just east of the urban
corridor this afternoon. The wind field is pretty light and
variable over much of the CWA right now. The far east has
southerly winds up to 15 mph. There is not much in the way of any
significant boundaries visible on the radar right now. Satellite
and Radar pictures are showing some convection develop along the
divide at present. Will up pops a bit on the plains later this
afternoon and evening.

&&

.SHORT TERM...(Today and tonight)
Issued at 339 AM MDT Fri Aug 17 2018

Moisture will continue to gradually increase today, both at low
to mid levels creeping over the mountains from the southwest and
low level moisture in southerly flow over the plains. The air
aloft remain very warm, which will limit instability. The far
eastern plains are also potentially a little cooler. This will set
up an axis of maximum instability over the western part of the
plains, between Denver and Limon and southward from there. We
should see more shower/storm activity over the mountains, but
still mainly along and south of I-70. Intensity may be a bit
higher, but still generally weak storms. On the plains, there may
be a few storms further north, but again the most and strongest
storms will be along and south of I-70. CAPEs under 600 J/kg over
the mountains, and ranging from 600 J/kg up to about 1200 J/kg in
the most unstable area on the plains. This could produce a couple
of borderline severe storms, most likely east and southeast of
Denver, but elsewhere expecting garden variety storms.

There should still be enough sunshine to get temperatures in the
mid to upper 80s on the plains in line with forecast and guidance.

.LONG TERM...(Saturday through Thursday)
Issued at 339 AM MDT Fri Aug 17 2018

On Saturday, the models still show a potent trough dropping out of
the northern Rockies, and moving across northern Colorado in the
afternoon and evening. The airmass will become increasingly moist
and unstable across the northeast plains at that time. SPC has
most of eastern CO under marginal risk of severe thunderstorms.
NAM12 forecast soundings near Akron and Limon show fcst CAPEs in
the 2000-2500 j/kg range in the late afternoon with precipitable
water values over one inch. Increasing mid level ascent with the
approach of the trough should allow for scattered to numerous
thunderstorms in the afternoon and evening. In addition to heavy
rain, a few storms may also produce damaging wind and hail.
Greatest risk will be east of the I-25 corridor but cannot
completely rule out severe thunderstorms for the Denver area.
Showers and thunderstorms will likely persist over the northeast
plains Saturday night. On Sunday, a drier northwesterly flow
aloft will be over the western part of the cwa. Wrap around
moisture should allow for scattered showers and thunderstorms to
continue over the far northeast plains of CO as the trough exits
into the Central Plains. Cooler with gusty north to northwest
winds across the plains. Monday should be fairly quiet as an upper
level ridge and increasing subsidence over the area. Isolated
showers and tstms possible mainly over the mountains. On Tuesday,
the upper ridge will be centered over New Mexico with a
northwesterly flow aloft over the cwa. The models all show a weak
trough clipping northeast Colorado in the morning or early
afternoon, so could see isolated to scattered showers, with the highest
probability along the northern border. By the middle of the week,
temperatures will be closer to normal with the upper level ridge
near the Four Corners area. Still enough subtropical moisture
under the ridge for isolated to scattered thunderstorms each day.

&&

.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 1115 AM MDT Fri Aug 17 2018

Most of the models are showing weak east or southeasterly winds
at DIA from now into the evening, with normal type drainage
patterns after 03Z. Still not completely sure what the chances
are of a thunderstorms at the airport. Some of the models develop
the Denver convergence line just west of the airport so DIA may
see a storm later this afternoon. Will go with a TEMPO group in
the 18Z taf. Ceilings may get down to BKN070 if there is a storm.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

UPDATE...RJK
SHORT TERM...Gimmestad
LONG TERM...Cooper
AVIATION...RJK


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