Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 170953

Area Forecast Discussion
National Weather Service Denver/Boulder CO
253 AM MST Wed Jan 17 2018

.SHORT TERM...(Today and tonight)
Issued at 219 AM MST Wed Jan 17 2018

Moderating temperatures today under increasing ridging and warm
air aloft. Strong surface inversions overnight have caused teens
along the base of the foothills with single digits over the
eastern plains while the higher foothills stay more mild in the
low 30s. Mostly clear skies will prevail through the morning
hours with just an upper level cirrus deck during the day. Upper
flow will turn NW by the afternoon with a branch of slightly
increased moisture moving over the region creating some additional
potential cloud cover over portions of the plains, but not enough
to impact the highs of upper 40s expected today. An increasing
lee side surface low will bring increased downsloping and highs in
the lower 50s for the Denver Metro.

Overnight lows will be more mild than in previous nights as warm
air advection increases with lows in the low to mid 20s. Areas
that traditionally are cooler near water sources and lower
elevations may see enough radiational cooling for lows dipping
into the teens and single digits at higher elevations.

.LONG TERM...(Thursday through Tuesday)
Issued at 219 AM MST Wed Jan 17 2018

Thursday and Friday will continue to see dry conditions with above
average high temperatures. Upper level ridging combined with dry
NW flow and increasing lee side lows will help bring highs into
the upper 60s by Friday.

This unseasonably warm weather will not last long as the next
system to impact Colorado will be over California by Friday night
with increasing moisture out ahead of it. This positively tilted
trough has decent consensus between the GFS, EC and Canadian with
the EC being slightly slower and deeper. Pre-frontal moisture and
lift provided by a 120kt jet will help to bring snow to the Park
and Gore region by Saturday mid-morning and will continue through
Sunday. As the upper trough moves into the desert SW strong SW
flow will move into NE Colorado increasing winds on the plains by
Saturday afternoon. Current model guidance timing has the cold
front entering from the North late Saturday. Upper air soundings
show a gradual cooling of the column with temperatures still warm
enough for rain or rain/snow mix before changing over to snow
by early Sunday morning. Confidence is low in any freezing
drizzle but this will need to be looked at as the event comes
closer. The upper trough will move through the region to the SE
and become negatively tilted as it makes its way into the Midwest.
Cold temperatures, snow and gusty winds will make for lower wind
chill readings for Sunday.

For the start of next week winds will continue to stay elevated
into Monday. Continued moisture and orographic influence will keep
light snow in the mountains through Monday. Highs will return
closer to seasonal normals into Tuesday.


.AVIATION...(For the 12Z TAFS through 12Z Thursday morning)
Issued at 219 AM MST Wed Jan 17 2018

VFR conditions are expected for the period. Winds will remain
southwesterly/drainage, with speeds generally below 10kts. The
light winds will remain into the afternoon with light and variable
conditions through 20z. At this point models are indicating a
counter-clockwise rotation to the NNE by 21z. The exception to
this is BJC which will most likely stay easterly through the
afternoon. Drainage is expected once again by 02z.




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