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fxus65 kbou 172057 
afdbou

Area forecast discussion
National Weather Service Denver/Boulder Colorado
257 PM MDT Tue Sep 17 2019

Short term...(this evening through wednesday)
issued at 200 PM MDT Tue Sep 17 2019

The showers and storms have produced strong to severe wind gusts
across western Colorado this afternoon. Meeker saw a 63 mph gust
while Craig saw a 59 mph gust. Showers haven't produced as strong
of gusts in our County Warning Area but they could reach 50 mph across higher
elevation under the stronger showers this afternoon. Clouds have
struggled to develop vertically over the foothills and plains
this afternoon likely due to the dry air aloft and lack of
instability. The thinking is still that showers stay confined to
the far northern plains which is closer to the shortwave moving
through Wyoming.

A cold front pushes through this evening bringing in slightly
cooler temperatures. Lows will be roughly 5-10 degrees cooler than
last night but will still be above normal.

Southwesterly flow aloft will continue through the day Wednesday
with weak qg descent over the County Warning Area. Model soundings show a dry
inversion around 500 mb persisting through the afternoon with dry
air in place throughout the troposphere. The 18z model runs have
been slightly more bullish than the 12z runs on showers
developing over the mountains and foothills during the afternoon.
I think the drier solutions will prevail but there still could be
a stray shower mainly over the I-70 corridor mountains and
foothills. Much like the lows, wednesday's highs will be cooler
but above normal.

Long term...(wednesday night through tuesday)
issued at 1201 PM MDT Tue Sep 17 2019

Minimum temperatures Wednesday night will be slightly warmer due
to continued warm advection in the southwest flow aloft, as well
as some cloud cover and some downsloping winds over the higher
terrain and into the urban corridor.

On Thursday, the upper trough over the Pacific northwest will drop
into the Great Basin, increasing southwesterly flow into the
state, as well as midlevel moisture and lift. Showers and
thunderstorms will increase over the high terrain early afternoon
then spread east into the plains. As the upper trough moves closer
through Thursday night and into Friday, showers and possible
thunderstorms will likely continue overnight over the high
terrain. Minimum temperatures will likely be even warmer over the
plains Thursday night due to the warm advection, cloud cover and
winds, but should be similar or perhaps cooler as the upper level
trough moves its cooler air into western Colorado and the
mountains.

The upper trough will move north-northeast across the northern rockies Friday,
with stronger southerly winds and dry air across the eastern
Colorado plains. This may increase fire weather concerns there
before the cold front is expected later in the evening. Showers
and thunderstorms will continue in the mountains with less
coverage over the plains, focusing more over the northern plains
in the evening closer to the upper trough passage. Lows overnight
will be about 10 degrees colder behind the front.

Models diverge on a secondary shortwave trough on the backside of
the main trough. The GFS being the quickest leaving Saturday a
dry and cool day. However the Canadian and European model (ecmwf) are lagging
behind which would keep some lift over the area and allow for more
showers Saturday. As the recent European model (ecmwf) has sped up its previous
solution, will trend the forecast toward the GFS. Will keep the
mountains dry, but will keep a chance of showers and thunder over
the far northeastern corner to account for this uncertainty in
timing. High temperatures will be about 5 to 10 degrees cooler
this weekend, back toward average for this time of year. Sunday
will warm a couple degrees as upper ridging builds in with a dry
day in store with the stability of the ridge overhead. Even though
temperatures will be cooler, drier air will move in from the west.
Stronger southwesterly winds may increase fire weather concerns
this time over the mountains, specifically the high valleys.

A stronger upper low will drop south along the western US coast
Sunday into Monday. Models significantly diverge on the evolution
and speed of this system, with some holding it off the southern
californian coast through Wednesday, some digging down into
Arizona and some bringing it across the northern rockies again.
Subtropical moisture will likely be pulled up by this low, so
depending upon the actual track, we could be completely dry or
quite wet/stormy. Needless to say, forecast confidence past this
weekend is quite low. Will vary only slightly from sunday's
temperature forecast into Monday and Tuesday with an introduction
of slight chance of storms for Monday and Tuesday.



&&

Aviation...(for the 18z tafs through 18z Wednesday afternoon)
issued at 230 PM MDT Tue Sep 17 2019

VFR conditions will continue through Wednesday afternoon. Clouds
are struggling to grow in height this afternoon and are
dissipating as they move onto the plains. It appears any showers
that develop will miss the terminals this afternoon. Gusty
westerly winds will develop late this afternoon but there is low
confidence in the timing of when they will develop. The most
likely time will be around or slightly before 00 but they could
develop as early as 22z. Drainage winds tonight will turn
southeasterly tomorrow morning.

&&

Bou watches/warnings/advisories...
none.
&&

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