Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 160432
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
932 PM MST Fri Dec 15 2017

.UPDATE...
Issued at 930 PM MST Fri Dec 15 2017

Standing wave clouds continue to form and thicken over the
leeward slope of the Front Range with amplification of the mtn
wave and influx of mid and high-level moisture within a moderate
southwesterly flow aloft. This cloud formation is expected to
continue for the remainder of the night but remain concentrated
around the mtn wave. This wave cloud and downslope gradient
breezes will slow cooling esply in and near the foothills. This
could keep overnight min temps above the freezing mark in the
Boulder/Broomfield/Arvada/Golden area. In the high country, HiRes
models indicate a gradual increase in wind speeds through the
night up around timberline and east slope of the Front Range
Could see sustained westerly winds of 25-35 mph and peak gusts to
around 55 mph after midnight. Otherwise, current 1st period
forecast generally appears to be on track, However, will need to
add a bit more mid/high-level cloud coverage over the plains.


&&

.SHORT TERM...(This evening through Saturday)
Issued at 226 PM MST Fri Dec 15 2017

Winds will be lessening thought the afternoon and evening across
the region. Only slight changes made to the temperature for
tonight. Cold pools were left in the forecast due to clear skies
expected tonight allowing for radiational cooling. A dry cold
front is expected to move into northeast Colorado Saturday
morning. Highs for Saturday were lowered slightly to account for
the 10 to 15 degrees temperature drop behind the front.

.LONG TERM...(Saturday night through Friday)
Issued at 226 PM MST Fri Dec 15 2017

There is weak southwesterly flow aloft for the forecast area
Saturday night and Sunday. The upper trough axis moves across the
CWA Sunday evening, then northerly flow aloft moves in overnight
into Monday. For Monday afternoon and night, northwesterly flow
aloft is in place. There is weak upward synoptic scale energy for
the forecast area Saturday night into Sunday morning, then
downward energy is progged into Monday afternoon. After that there
is benign forcing in place. The boundary layer winds are
northeasterly Saturday night. A very weak pressure gradient and
wind field is progged on Sunday. Sunday night through Monday night
more normal diurnal wind patterns are in place. Looking at
moisture, there is some progged to increase Saturday night in the
upper levels and down at the lower levels of the plains and lower
foothills. The NAM deepens this moisture over the plains on
Sunday, the other models do not. What moisture there is decreases
somewhat Sunday night. All the models show some shallow alpine
moisture Monday and Monday night. Concerning pops, will keep the
thinking of the previous forecaster. The moisture is very shallow
Saturday night into Sunday morning and perhaps we will see another
minor freezing drizzle event for the western half of the plains.
Will need some minor pops in the high mountains Sunday afternoon
through Monday night. For temperatures, Sunday`s highs are 2-5 C
cooler than Saturday`s. Monday`s highs are 4-8 C warmer than
Sunday`s. For the later days, Tuesday through Friday, there will
be flat upper ridging over the CWA Tuesday and Wednesday. There is
strong southwesterly flow aloft Wednesday night and Thursday. An
upper trough moves into the CWA late Thursday and hangs around
over us through Friday well into next weekend. Models show
limited measurable precipitation on the QPF fields Thursday and
Thursday night. It does not look significant at this time.  A
fairly strong cold front moves across the CWA Wednesday night.
Thursday night/Friday morning`s temperatures may be the coldest so
far of this mild winter, but again, nothing significant.

&&

.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 930 PM MST Fri Dec 15 2017

VFR conditions will continue through 5 pm MST tomorrow. A weak dry
cold front is progged to slip south through the Denver Metro Area
between 8 AM and 930 AM MST tomorrow morning. Light west to
southwest winds prior to passage of this front are expected to
shift counter-clockwise to the northeast at 7-14 kts by late
morning. Then through the afternoon, winds will gradually shift to
an east-southeast direction at similar speeds. This shift in the
prevailing sfc wind will cause humidities to rise and clouds to
form along the Front Range. By late afternoon, could see a broken
7000-9300 ft cloud ceiling over the metro area, but no
precipitation as of yet.

&&

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

$$

UPDATE...Baker
SHORT TERM...Sullivan
LONG TERM....RJK
AVIATION...Baker


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