Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 231005
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
405 AM MDT Sun Apr 23 2017

.SHORT TERM...(Today and tonight)
Issued at 355 AM MDT Sun Apr 23 2017

High pressure ridge aloft will shift across Colorado today and
then into central plains tonight. Airmass will initially be dry
but there will be increasing high level cloudiness during the day
ahead of next Pacific weather system. Lower elevations will see
temperatures climb well into the 70s with the warm advection and
building high pressure.

Fast moving weather system will move across northern Colorado
tonight with showers developing in the mountains between 03-06z
and then continuing overnight. There will be increasing westerly
flow at mountain top level and improved orographics and some qg
ascent. Could see a quick few inches of snow over northern
mountains with this system. Expect winds to also increase as cross
sections showing increasing 40-50kt of cross barrier flow after
midnight tonight.

.LONG TERM...(Monday through Saturday)
Issued at 355 AM MDT Sun Apr 23 2017

Gusty winds will likely continue into mid morning over the high
terrain according to spatial cross-sections. This makes sense with
the departing surface low and continued westerly flow aloft. A jet
will push into the state later in the afternoon and evening to
increase upward QG motion and increase rain and snow over the
mountains as well as over the northern plains. Enough instability
will allow for the slight chance of afternoon thunder over the
high terrain before the showers spread over the plains that
evening. Westerly flow at midlevels and higher will likely
downslope the urban corridor. Snow levels are expected to drop to
around 7500 feet that night, with the higher mountains seeing 2
to 6 inches possible overnight. A cold front will push south
across the plains after midnight to increase the chance of showers
south.

A deeper upper trough is expected to move over the state Tuesday
night while high surface pressure will create upslope conditions
by the afternoon. Look for showers to increase during the day,
becoming numerous in upslope areas, with a slight chance of seeing
thunder.  Snow levels will stay rise slightly to around 8500
feet, with the eastern slopes of the Front Range and foothills
seeing additional snow fall, potentially another 3 to 6 inches or
more. Temperatures will be about 10 degrees cooler than Monday.

The progressive pattern will continue Wednesday and into early Thursday
as moisture riding in on west to northwesterly flow aloft. Expect
cooling temperatures along with at least a chance of showers and
possible thunder as well.

Models have trended toward a slightly more common solution later
in the week, with GFS and ECMWF delaying the main lobe of energy
to affect the area Friday and Saturday, digging the upper low
toward the Four Corners area by late Friday, lifting across the
state Saturday. The GEM is more progressive with the pattern,
keeping it an open trough and pushing it east of the state by
Friday night. Will have the better chances for widespread
precipitation Friday and Saturday, with cooling temperatures below
the average for this time of year and perhaps seeing a chance of
snow mixing in down at lower elevations over the plains,
especially the Palmer and Cheyenne ridges Friday night and
Saturday morning. As the system lifts east into the Great Plains,
PoPs will decrease Sunday with temperatures slow to make a rebound
with northwesterly flow aloft expected.

&&

.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 355 AM MDT Sun Apr 23 2017

VFR with varying amounts of high level cloudiness through the day.
Healthy southerly winds overnight will turn more southeast during
the afternoon. Could see a brief push of westerly winds late
afternoon as airmass mixes out. Weak cold front will turn winds
more northerly later tonight but speeds generally under 20kt.

&&

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

$$

SHORT TERM...Entrekin
LONG TERM...Kriederman
AVIATION...Entrekin



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