Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 191214
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
514 AM MST Tue Feb 19 2019

.SHORT TERM...(Today and tonight)
Issued at 514 AM MST Tue Feb 19 2019

Area of weak lift will move across eastern Colorado this morning.
Moisture appears to marginal for generating accumulating snow
though, but there are widespread flurries. Still expecting a few
shallow bands to produce some accumulation, most likely over the
mountains and east and south of Denver through mid morning. There
is a paradoxical break in the moisture in the trough axis around
midday, then slight cold advection and gentle northerly flow aloft
kick in by the end of the day which should provide another
increase in the light snow for a few hours this evening. The idea
of some convective showers over the mountains does look good, but
there`s not much instability and the moisture content above the
boundary layer is starting to dry. This will likely combine with
the broader increase in showers from the slight cooling behind the
trough by the end of the afternoon. We raised the PoPs for this
period, but we don`t expect any heavy showers, just a better
chance of getting light accumulations from late afternoon through
the evening. Drying continues overnight with the subsidence
inversion/warming aloft arriving by morning along with increasing
low level westerly flow that should be eroding the low clouds
around sunrise.

.LONG TERM...(Wednesday through Monday)
Issued at 514 AM MST Tue Feb 19 2019

Wednesday and Wednesday night, a dry and more subsident
northwesterly flow aloft will be over the region as a short wave
ridge of high pressure moves over the cwa.  Main question on
Wednesday morning will be how fast the stratus and/or fog shifts to
the east of Denver.  The models may be attempting to kick it by 12z
Wednesday morning, but may not be until 15z.  By the midday
Wednesday however, mid and upper level subsidence with a low level
westerly wind component will allow for mostly sunny conditions from
the Front Range foothills eastward. There is the potential for some
lingering light orographic snow showers over the northwest facing
slopes in the morning, but all snow should be done by the afternoon.
Sunny skies and mid level warm air advection will allow for high
temperatures to climb back into the 30s.

Thursday and Thursday night, the ridge axis will shift to the
northeast of the state with the flow aloft transitioning from zonal
flow Thursday morning to a southwesterly flow Thursday afternoon and
Thursday night.  This will be ahead of another storm system which
will be over the Great Basin region by Thursday afternoon.  The
models indicate increasing mid and upper qg ascent developing over
Colorado at that time.  Snow will likely redevelop in the high
country Thursday afternoon with the mid level southwesterly flow
favoring zones 31 and 33.  The flow aloft will remain southwesterly
Thursday night as the system does not make much eastward progress
through 12z Friday.  Across the northeast plains, the models show
low level moisture advecting north and west across the cwa in the
evening.  East to southeast winds north of a surface low located
over southeastern CO, will help usher in colder temperatures with
the fog/stratus Thursday night into Friday morning.  Some concern
of freezing drizzle developing as well along and east of the
front as it settles along the Front Range urban corridor.

On Friday, if the shallow cold and moist airmass remains in place
then temperatures will be several degrees colder than those in
the max temp grids for Friday afternoon. Main adjustment will be
to lower the afternoon temperatures, especially for areas north
and northeast of Denver. Mid and upper levels will moisten up
Friday night into Saturday. The models show an open mid level
trough near the Four Corners region by 06z Friday night, closing
up as it moves into the TX/OK panhandles by 12z Saturday morning.
Light to moderate snowfall in the mountains Friday afternoon into
Saturday. Best chance of snow in the high country would appear to
be south of Interstate 70. Trajectory of this system still a big
question mark. At this time, there appears to be the potential of
snow in the 1 to 4 inch range over the northeast plains/urban
corridor from 00Z Saturday to 00Z Sunday. Overall confidence in
these amounts is still low as this is still in days 4 and 5.

Another short wave ridge on Sunday with a zonal flow aloft over
the state with warmer temperatures. The models show the flow
aloft shifting to the southwest Sunday night into Monday, ahead
of another trough moving across the northern Rockies/Pacific
Northwest.

&&

.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 514 AM MST Tue Feb 19 2019

MVFR ceilings and visibilities will continue in light snow over
the Denver area, with the snow diminishing by late morning. Only a
slight increase in the ceilings is expected during the middle of
the day. Light snow is expected to redevelop in the late afternoon
and continue through the evening, with MVFR conditions continuing
to prevail. The snow is expected to end between 04z and 08z
tonight with clearing skies around 12z.

&&

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

$$

SHORT TERM...Gimmestad
LONG TERM...Cooper
AVIATION...Gimmestad


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