Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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402
FXUS65 KBOU 182222
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
322 PM MST Sat Feb 18 2017

.SHORT TERM...(This evening through Sunday)
Issued at 320 PM MST Sat Feb 18 2017

Area radars are still showing no precipitation over the CWA at
this time. There is still plenty of high level cloudiness over the
CWA currently. Models have the center of the upper low over the
northern Gulf of California at 00Z this afternoon. Models show
this feature weakening somewhat as it moves northeastward into
the northwestern quarter of Colorado by 00z Sunday late day. There
is fairly strong southwesterly flow aloft over the CWA overnight
into Sunday afternoon, then it decreases as the upper trough/
closed low moves our way. There is benign synoptic scale energy
progged for the CWA tonight, but there is some upward energy
expected on Sunday. The boundary layer keeps a southerly component
to it for most of the CWA tonight and Sunday. For moisture, there
is not a lot in the immediate upstream on the satellite pictures.
The upper low is moving slow and much of the more significant
moisture with it is moving nearly due north, staying to our west.
Models agree with this and do not bring deeper moisture into the
western CWA until Sunday afternoon and over the plains until
around 00Z late Sunday afternoon. Boundary layer dew points over
the plains are progged in the 30s F on Sunday. The QPF fields show
limited measurable precipitation over the western CWA Sunday
afternoon. The SPC Convective Outlook, Day 2, shows the northeast
quarter of Colorado in general thunderstorms. There is some
limited CAPE over the plains, but it mostly Sunday evening and
over the far eastern border. Soundings do show minor instability
by afternoon. There is already "isolated" storms mentioned in the
GFE grids. Will let them in, but after 21Z. For pops elsewhere,
will go 0-10%s tonight and Sunday morning in the mountains only.
Will go with 30-60%s Sunday afternoon in the mountains because of
the moisture and the upward energy associated with the nearing
upper closed low. There will be no orographic help Sunday
afternoon concerning snowfall/precipitation in the high country.
For temperatures, Sunday`s highs are 0-1 C warmer than this
afternoon`s.

.LONG TERM...(Sunday night through Saturday)
Issued at 1248 PM MST Sat Feb 18 2017

By 00Z Monday, the upper trough will be over southwest CO/nwrn New
MX, it will then shift east into southeast CO around 06z, then
lifts northeast into central NB/nwrn KS by 18z Monday. Weak to
moderate qg ascent will pass across CO Sunday evening, with the
strongest lift across srn CO. The qg ascent will be decreasing
overnight. In the mountains, minimal orographic component in the
evening, but the best moisture/instby will be at that time. After
06Z Monday, strong northwest winds around 40 kts at ridgetop but
decreasing moisture late Sunday night/Monday morning. Some blowing
snow above timberline and higher east facing slopes 06z-12z
Monday.  Generally light snowfall in the high country, around 3
inches overnight. Across the northeast plains, marginal profile
for tstms but will keep slgt chc in the grids until 03z. High
based with gusty winds the main by product of the storms. On
Monday, increasing stability as a ridge of high pressure aloft
moves over the state. Generally westerly winds, some lingering
showers in the west facing slopes. Dry and warmer for the
northeast plains with highs back in the 60s. Gusty northwest winds
across the plains Monday aftn. Spatial cross-sections show
overrunning moisture deepening in the mountains late Monday
night/Tuesday morning so some light snow psbl west of the
Continental Divide at that time. Dry, windy and warm across the
northeast plains. The flow aloft increases fm the southwest
Tuesday night through Wednesday night, ahead of the next
approaching trough. Generally dry, windy and continue mild for
Wednesday. Fire danger will be elevated each aftn, Monday through
Wednesday, see the fire weather discussion below. The next trough
will bring cooler temperatures and a chance of snow to the
mountains Thursday and Friday, with a chance of showers over the
northeast plains, highest pops will be over the northeast corner
of the state.

&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 320 PM MST Sat Feb 18 2017

The models were pretty good with the wind directions this
afternoon ans DIA, but the speeds were to light compared to
current reality. South-southwesterly winds can be expected after
02Z and they will likely continue on Sunday. There should be no
ceiling issues at DIA until at least 18Z Sunday afternoon.

&&

.FIRE WEATHER...
Issued at 1248 PM MST Sat Feb 18 2017

Monday through Wednesday, low relative humidities, above normal
temperatures and gusty winds will elevate the fire danger at times
across the northeast plains each aftn. Temperatures will be well
above normal in the mid 60s to lower 70s, warmest on Tuesday.

&&

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

$$

SHORT TERM...RJK
LONG TERM...Cooper
AVIATION...RJK
FIRE WEATHER...Cooper



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