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Area Forecast Discussion (AFD)

Issued by Denver/Boulder, CO (BOU)

FXUS65 KBOU 182020

Area Forecast Discussion
National Weather Service Denver/Boulder CO
220 PM MDT Sun Aug 18 2019

.SHORT TERM...(This evening through Monday)
Issued at 124 PM MDT Sun Aug 18 2019

A subtropical ridge is not going anywhere soon, and currently the
axis is right over our area. It shifts a bit east and intensifies,
reaching 594 dm by Monday afternoon. The ridge will continue to
suppress any hope of significant moisture return through Monday,
either in the mid levels or at the surface. PW values remain in in
the 0.3" range across the mountains to 0.5" across the I-25 
corridor, to 0.75" across the far northeast plains. With the 
dryness and subsidence indicated in QG fields, convective chances 
are pretty close to 0 the rest of today and tonight. Skies should 
remain mostly clear with lows in the 60s across the I-25 corridor,
and upper 50s to near 60 elsewhere across the plains.

On Monday more of the same but with the building ridge at 500 mb
just east of us and 700 mb temps around +18 to +19 degC, high 
temperatures should top out in the upper 90s across the plains. We
do not expect a slow start to the warming like this morning, 
because convection across the central plains will be nil this 
afternoon/evening, so there will not be a source of cool/moist 
low-level that could advect into our area later tonight (like
early this morning). It will also be hot in the mountains, with 
80s expected and even around 60 degrees at treeline. With 
significant 700-500 mb flow retreating north, there won't be as 
much wind in the mountains either. With very hot and dry 
conditions, despite weak winds, fire danger will be elevated 
tomorrow. Details in the fire wx discussion below.

.LONG TERM...(Monday night through Sunday)
Issued at 124 PM MDT Sun Aug 18 2019

Tuesday and Tuesday night, a dry and weak west to southwesterly 
flow aloft will remain over the northern CO. Some subtropical 
moisture does into the area late in the afternoon, primarily 
impacting the mountains east of the Continental Divide. It will 
remain hot and dry over the high valleys of Jackson and Grand 
counties. Across the plains, another hot day is expected but with
a gradual increase in low level moisture behind a frontal 
boundary that backs into the cwa late in the afternoon. This will
result in a better chance of showers and thunderstorms across the 
area late Tuesday afternoon and Tuesday night. Not as hot as 
Monday but still well above normal. Wednesday into Wednesday 
night, temperatures will be closer to seasonal normals, with a 
good chance of showers and thunderstorms across the region. Low 
level moisture will remain in place across the northeast plains 
with stationary front settled along the foothills and Palmer 
Divide. The flow aloft will be weak and northwesterly as the 
center of the upper ridge is centered closer to the Four Corners 
area. Layer Precipitable Water values range from 0.5 along the 
Front Range to 1.0 inch over the northeast plains Tuesday 
afternoon. Those values increase to 1.0 and 1.3 inches 
respectively for Wednesday afternoon. The trend of warmer and 
drier will develop the latter part of the week and into next 
weekend. There should still be a decent chance of thunderstorms 
over the region on Thursday, but the pops will be confined 
primarily to the higher terrain by the weekend with high 
temperatures back into the mid 90s by Saturday.


.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 124 PM MDT Sun Aug 18 2019

VFR conditions through Monday with almost zero chances of
convection impacting the airports. East to southeast flow should
continue through this evening before going to drainage. Light and
variable winds should occur mid morning on Monday, then go to 
northeast by midday and remain 8-12 kts or less. At this time we 
are not expecting any significant gust fronts via convection 
Monday afternoon and evening.


Issued at 124 PM MDT Sun Aug 18 2019

Winds in North and Middle Parks this afternoon are gusting to 25
mph with RH around 20 percent. Expect this to continue into the
early evening hours. On Monday, winds will be lighter pretty much
everywhere but it will be significantly hotter and a bit drier.
RH should get down around 10-12 percent across the mountain
valleys, foothills, and much of the plains. If winds were a bit
stronger we'd consider highlights for the afternoon, but they
should remain light. 

The fire danger will decrease a bit on Tuesday over the northeast
plains as low level moisture starts to increase from the 
east/northeast behind a weak frontal boundary in the afternoon. 
Dry conditions however will keep the fire danger elevated 
in the high valleys of North and Middle Parks Tuesday afternoon 
but with continued light winds.




SHORT TERM...Schlatter
LONG TERM...Cooper
FIRE WEATHER...Schlatter/Cooper