284 
FXUS65 KBOU 110938
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
338 AM MDT Thu Apr 11 2019

.SHORT TERM...(Today and tonight)
Issued at 338 AM MDT Thu Apr 11 2019

Water vapor satellite imagery showing the center of the strong 
winter storm over southern Nebraska. The low will continue to move
northeast and take the snowfall with it. Snow will end from west 
to east through the early morning hours. By 6am, expect the back 
edge of the snowfall to be just east of the Denver area. Will keep
the Blizzard Warning in effect for the plains north of I-70 and 
east of Sterling to Limon. Where an additional 2 inches of snow 
will be possible this morning. Wind gusts here may reach to 40 to 
50 mph. To the west of this, where snowfall is lighter or ended 
but windy conditions continue will downgrade the Blizzard Warning 
to a Winter Weather Advisory. For the Urban Corridor, snow should 
end around 6am and winds are expected to be less than 30 mph, so 
plan on canceling the Winter Weather Advisory.

For the mountains, web cameras show most roads are snow covered 
with areas of snowfall. Moist northwest flow behind the exiting 
system is expected to keep snow showers going through the day. 
Will keep the Winter Storm Warning going through the morning 
hours. Additional snowfall of up to 4 inches will be possible 
today. 

Northerly winds are expected to turn northeasterly this afternoon
over the Denver area and to the southwest. This combined with 
steep low level lapse rates may produce a few snow showers. Some 
models show snowfall late this afternoon and early evening. If 
snow occurs, up to an inch will be possible. In the mountains, the
moist northwest flow aloft will persist through tonight. Expect 
the snow showers to continue through most of the night. New 
snowfall tonight of up to 3 inches will be possible for the 
mountains. 

.LONG TERM...(Friday through Wednesday)
Issued at 338 AM MDT Thu Apr 11 2019

The trough associated with Wednesday's strong storm will move 
northeastward toward the upper Great Lakes region on Friday as a 
weaker trough builds in over the Four Corners region. This
secondary trough will have very cold mid to upper level air
associated with it as 500 mb temperatures are forecast to be
around -26 degrees Friday evening which is below the 10 percent 
moving average for DNR soundings on the SPC sounding climatology 
page. With sunny skies expected over much of the CWA Friday
morning, the heating at the surface will allow for steep lapse
rates especially across the southern foothills and the Palmer
Divide. A NAM sounding in Jefferson County at 21Z Friday showed
mid level lapse rates around 8.5 C/KM and surface to 3 KM lapse 
rates of 9.7 C/KM. Those low level lapse rates seem a bit unrealistic
and they are likely a contributing factor in the unrealistic QPF 
values in the same area. The NAM, NAM nest, and GFS all have over 
an inch of QPF along or near the Palmer Divide and southern 
foothills Friday night which leads me to believe these models are 
struggling with convective feedback. The Euro has snow showers in 
the same general areas as the aforementioned models but much lower
QPF amounts. Therefore, I decreased the QPF and snowfall values in
this area but increased the POPs Friday night. This system is 
worth keeping an eye on though as the weak mean flow and 
instability may allow for moderate to heavy snow showers to 
develop and sit over one location. Areas under the heaviest bands 
of snow along the southern foothills and Palmer Divide could pick 
up 3 to 5 inches by Saturday morning but most snowfall amounts 
will likely end up in the 1 to 4 inch range. 

With cold air aloft lingering over the area Saturday afternoon,
there could be a few snow showers that develop in the mountains 
but these will be light. Mid to upper level ridging will build in
over Colorado Sunday and Monday keeping things dry. A trough will
move through southern Colorado late Tuesday into Wednesday
bringing the next chance of precipitation. The Pacific moisture
associated with this system will likely allow for light to
moderate snowfall in the mountains and rain changing to snow
across the plains. Models begin to differ after Wednesday but they
indicate a substantial ridge may build over the western US to end
next week. 

&&

.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 338 AM MDT Thu Apr 11 2019

Conditions will slowly improve through 12-13Z when snow is 
expected to end. Additional snowfall for the Denver airports 
should be less than an inch. North winds gusting to 25 to 30 knots
may produce blowing snow at KDEN and KAPA through early 
afternoon. Ceilings continue to rise and should range from 5000 to
10000 feet today. Snow showers will continue in the mountains 
through the day. There is a slight chance a couple snow showers 
will move across the Denver area after 21Z. Any new snowfall later
today is expected to be light and less than an inch.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Blizzard Warning until noon MDT today for COZ046-048>051.

Winter Storm Warning until noon MDT today for COZ031-033-034.

Winter Weather Advisory until noon MDT today for COZ041-042-044-
045.

High Wind Warning until noon MDT today for COZ047.

&&

$$

SHORT TERM...Meier
LONG TERM...Danielson
AVIATION...Meier