Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 222051

Area Forecast Discussion
National Weather Service Denver/Boulder CO
251 PM MDT MON AUG 22 2016

.SHORT TERM...(This afternoon through Tuesday)
Issued at 251 PM MDT Mon Aug 22 2016

Water vapor satellite imagery showing a circulation centered near
the four corners. Models show it weakening as it moves northeast.
Mid and upper levels of the airmass are on the moist side, but the
lower levels are dry with dew points in the 30s across parts of
the Front Range. Scattered thunderstorms have formed over the
mountains and northern foothills. The 12z model runs showed this
convection staying mainly over the higher terrain. However the
recent runs of the HRRR show some convection moving across the
Front Range and eastern plains despite the dry low levels. Expect
this convection to be high based and produce light to moderate
rain and gusty outflow winds. Southerly winds east of a surface
trough over the eastern plains is helping to transport low level
moisture into the area. The best chance for stronger storms will
be along and east of this trough where moisture and instability
will be greater. Will increase pops over the plains for this
evening because of the latest upward trends in convection from the
HRRR model.

With an increase in cloud cover Tuesday, expect high temperatures to
be cooler with most locations over northeast Colorado in the 80s.
There is a stronger wave embedded in the flow aloft that will affect
Colorado. Models in good agreement that scattered to numerous storms
will form over the mountains. However, only the GFS shows some
convection moving off the higher terrain and onto the Front Range.
Will keep low pops in the forecast for the Front Range and near by
plains. Since this system is suppose to be stronger, expect some
storms to move off the higher terrain, though this may occur during
the evening hours.

.LONG TERM...(Tuesday night through Sunday)
Issued at 251 PM MDT Mon Aug 22 2016

An upper level trough will stretch south past the four corners
region with a closed low over Canada. Models are showing
continued precipitation over the higher terrain with cooler and
more stable conditions on the plains with weak easterly flow
through the mid levels. This pattern will continue into Wednesday
with the upper trough bringing in moisture up from the south but
with a lee side trough over the plains the highest chances for
convection will be over the higher terrain...especially with
increasing easterly upslope flow. Temperatures will start the
extended cooler with highs in the upper 70s into Friday under this
cooler airmass.

For Thursday a diffuse upper trough will redevelop over the
western U.S through Saturday. Mid level flow will turn more SSW
bringing an influx of moisture into the region that will keep a
slight chance of storms...especially over the higher terrain
through saturday. Slightly drier air on the plains Thursday
afternoon will result in just a slight chance that convection will
form. If some storms do move off the plains the main threat will
be gusty winds due to drier air in the mid and lower levels.
Picture looks much the same for Friday with a slight chance of
afternoon storms mostly at higher elevations.

For the weekend the upper level trough will continue to dominate
over the western CONUS. Models indicate a weakened upper flow
moving into Saturday with a weak lee side trough that will bring
a slight chance of rain to the region by late Saturday. The trough
will grow to dominate the plains keeping rain in the higher
elevations on Sunday. Temperatures will finish out the week in the
mid to upper 80s.


.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 251 PM MDT Mon Aug 22 2016

Winds are expected to switch to the northwest by 22z as an
outflow boundary moves through. Isolated thunderstorms will be
possible through 03z. If a storm hits an airport, gusty winds to
40 knots and light to moderate rain will likely accompany the
storm. An additional outflow boundary or two may move through and
produce a sharp wind shift. Due to the dry low levels, ceilings
will remain above 6000 feet tonight and Tuesday. There will be
another round of thunderstorms Tuesday with the best chance being
after 22z.


.BOU Watches/Warnings/Advisories...


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