338 
FXUS65 KBOU 200358
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
858 PM MST Tue Feb 19 2019

.UPDATE...
Issued at 858 PM MST Tue Feb 19 2019

The areas of light snow which persisted through the afternoon and
early evening are on the decrease and moving eastward as the
main upper trough moves out over the Central Plains. Radar data
shows a few bands of heavier snow moving over central and eastern
Elbert County, with light snow extending across Lincoln and
Washington Counties. Cold temperatures and lower dew points are
moving in from the north and northwest. Areas of stratus are
evident over northern Weld County, but the latest HRRR shows that
this cloud cover should remain north of the Denver Metro area
overnight. Th emain changes to the evening forecast were removing
the snowfall from the plains areas except for the Palmer Divide
and up into Washington County. Palmer Divide locations may see
another inch or so of accumulation overnight, and Washington and
Lincoln Counties should see less than a half inch.  

&&

.SHORT TERM...(This evening through Wednesday)
Issued at 315 PM MST Tue Feb 19 2019

Current satellite IR picture shows moisture pulling up from the 
south and NE across the region. Another batch of moisture and CAA 
will move SE from Utah and into the central mountains by the evening 
hours. There will be a slight break over the mountains between the 
two disturbances but conditions are expected to remain mostly cloudy 
and cold. The next batch of energy is projected to impact the 
mountains around midnight with light to moderate snow. NAM model 
cross sections are showing 8-9 C/km lapse rates, which at first 
glance seems a tad high, but could indicate some instability in the 
mid levels that will increase snow intensity for a short period of 
time overnight. For the plains, a denver cyclone continues to spin, 
pulling in moisture from the SE and wrapping it around to the south 
keeping light snow across the region. Cyclone center remains just NE 
of the airport and is expected to break apart as increasing westerly 
flow moves in from the approaching system and a lee side low sets up 
over the northern foothills. This will aid in increasing westerly 
winds and dry out the low and mid levels over Denver, ending the 
snow. Accumulations into Wednesday evening will be 1 to 4 inches for 
the mountains with a trace to an inch across the plains, with the 
higher amounts east of a Sterling to limon line. Some gusting is 
possible over the higher northern foothills with increased 
subsidence during this time and some blowing snow may be possible 
early Wednesday morning with the low density snow. With the 
increased westerly winds by early Wednesday, conditions will 
partially clear out over the plains, minus the far eastern plains 
where some low level clouds may linger. Temperatures will drop into 
the low single digits overnight. 

For Wednesday, the upper trough will have moved out with increasing 
zonal flow aloft. There is enough moisture upstream ahead of the 
next upper level disturbance over Oregon to keep a slight chance of 
snow in the mountains through Wednesday, but amounts will be light 
and impact mainly the central and northern mountains. Highs on 
Wednesday will be slightly warmer in the 30s across the plains. 

.LONG TERM...(Wednesday night through Tuesday)
Issued at 315 PM MST Tue Feb 19 2019

A brief period of ridging will develop over Colorado Wednesday 
night which will allow for mainly dry conditions across the CWA. 
Strengthening southwesterly mid to upper level flow will increase 
the chance for snow showers in the mountains during the second 
half of Thursday. Temperatures Wednesday night into Thursday will 
be around 10 degrees below normal across the majority of the CWA.

By Thursday evening, the focus will shift to the trough digging
into the Desert Southwest. Models are now showing a weak shortwave
breaking off from the stronger trough and moving northeastward 
through Colorado early Friday morning. This will create a chance 
of snow showers in the mountains and foothills and northeastward 
across to the Cheyenne Ridge. In addition, a lee cyclone 
developing over east-central Colorado will likely develop low 
clouds over most of the South Platte River Valley. With shallow, 
low-level moisture in place, fog and perhaps freezing drizzle 
could develop but there remains considerable uncertainty with 
those developing so they were not included in the gridded 
forecast. 

The main portion of the trough will then eject onto the central
plains Friday night and into Saturday with a surface cyclone
developing over northeastern New Mexico. Models still produce
moderate to heavy snowfall over the northwest side of this cyclone
but overall guidance has shifted farther southeastward with this
system. Therefore, it looks less likely that the eastern plains
will receive moderate to heavy snowfall with this system unless
there is a major shift back northwestward. Instead, there is a 
good chance of light snow over the eastern plains Friday night and
Saturday with little impacts. 

Another system may affect Colorado Sunday night into Monday but
there is little agreement in the models on this system and low
confidence in the forecast. 

&&

.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 858 PM MST Tue Feb 19 2019

Lingering snow flurries over the Denver area airports should be
clearing out in the next hour or so. Drier air will be moving into 
the Denver area from the north and northwest through the night.
Winds should remain light. Some low cloud decks may hang around
through the early morning hours, but no ceilings below 2500 feet
AGL are expected. No impacts from ceiling or visibility are
expected tomorrow, but some gusty northwest winds may develop
during the late morning and afternoon hours. 

&&

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

$$

UPDATE...Dankers
SHORT TERM...Bowen
LONG TERM...Danielson
AVIATION...Dankers