Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 142129

Area Forecast Discussion
National Weather Service Denver/Boulder CO
229 PM MST Thu Dec 14 2017

.SHORT TERM...(This evening through Friday)
Issued at 230 PM MST Thu Dec 14 2017

Currently there are some light showers pushing south-
southeastward in the northerly flow aloft. Models have strong
northerly flow for the CWA tonight into Friday morning. The flow
aloft becomes more northwesterly and decreases considerable on
Friday afternoon as an upper ridge moves in from the southwest.
Weak downward synoptic scale energy is progged for the CWA tonight
and Friday. The boundary layer winds will be a mix of normal
diurnal patterns and downsloping both tonight and Friday. Speeds
will be up a bit over the eastern plains this evening, and also in
and alos near the divide and eastward overnight as a bit of
mountains wave set-up develops. There is limited moisture on the
cross section tonight and Friday. There is no measurable
precipitation on the QPF fields tonight and Friday. No pops. For
temperatures, Friday`s highs warm up 6-12 C from this afternoon`s

.LONG TERM...(Friday night through Thursday)
Issued at 135 PM MST Thu Dec 14 2017

A flat upper ridge will rebuild back into the SW CONUS Friday
night into Saturday ahead of an upper trough. Westerly flow will
increase during this period before turning SW as the upper trough
enters the west coast of CA. Saturday will start with a downslope
component with the help of a lee side low. The low will shift
south as a cold front drops south out of WY by the afternoon
lowering temperatures. This means the warmer portions of the day
will be early before the temps drop around 18z Saturday. By
Saturday night the models have the elongated trough over Nevada
with a separate closed low over Mexico. This will split the energy
and pull it mostly to our south. By early Sunday mountains may
start to see some light snow with the foothills following suite by
the morning hours on Sunday. EC lost some of its strength this
last run and came more in line with the GFS and Canadian so will
lean toward the drier pattern compared to the NAM. Have amounts 4
to 8 inches in the mountains with just a trace to 2 inches on the
plains with the higher amounts over the higher foothills where
upslope will be more favorable.

Temperatures through the weekend will be cooler Sunday behind the
front with highs in the 30s and overnight lows in the low 20s. As
the trough moves to the SE upper ridging will return and slowly
increase temperatures back to above normal with upper 50s by
Wednesday. There is another system possible toward the end of the
week but details still need to be worked out.


.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 230 PM MST Thu Dec 14 2017

Models still show normal drainage winds tonight, perhaps with a
bit of southwesterly downsloping mixed in. On Friday, weak
downsloping is progged all day. If there are any ceiling issues,
they should be done by 00Z this early evening. Precipitation is
not expected tonight or Friday.




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