Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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176
FXUS65 KBOU 201637
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1037 AM MDT Tue Jun 20 2017

.UPDATE...
Issued at 1037 AM MDT Tue Jun 20 2017

Well on our way to a very warm/hot day. Temperatures already 88 at
KDEN and will likely hit 90 by 11AM. Record high is 97 degrees and
may be broken. Based on satellite, reduced cloud cover a little
for this morning. Models continue to show isolated convection
over the higher terrain this afternoon and evening. Will have low
pops over the higher terrain for this. The 12Z GFS has a little
more over the northern parts of the area and will increase pops
into the 10-20 percent range. Any rainfall is expected to be
light. Main feature with the convection will be gusty outflow
winds to 40 mph, which may spread out a long ways from the initial
convection.

&&

.SHORT TERM...(Today and tonight)
Issued at 222 AM MDT Tue Jun 20 2017

Warmer mid level temperatures will be drifting around the ridge
over eastern Colorado today. This will bring near record
temperatures. There is some high cloudiness wrapping around the
ridge, but this should mainly be thin so not too much impact. It
could be enough to keep the hottest places below 100 and hold
Denver just below the record of 97. Expect some convective clouds
to develop over the mountains and shift east in the late
afternoon and evening. Probably not much in the way of rainfall
with a deep dry subcloud layer and CAPES below 500 J/kg, but could
be some sprinkles and gusty winds. Expect coverage to be limited,
so the current low PoPs are fine. No change to the hot
temperatures, just a little more cloud cover for this morning`s
forecast package.

.LONG TERM...(Wednesday through Monday)
Issued at 222 AM MDT Tue Jun 20 2017

On Wednesday, the ridge will be centered over Arizona/New Mexico
with a light to moderate northwesterly flow over the cwa. The
models show a surface trough over eastern Colorado as well. NAM12
forecast soundings show little change in the 700 mb temperatures
from Tuesday aftn, so highs in the mid 90s again expected. The
winds for Denver at the sfc and aloft are northwesterly. Boundary
layer CAPES pretty low across the northeast plains in the 50-300
mb range, and around 300 j/kg over the mountains. Will keep
10-20 percent coverage mainly over the elevated terrain in the
aftn and evening. Fire danger will be elevated, but lack of
significant wind keeps the overall threat in the marginal
category. On Thursday the ridge flattens a bit as an embedded
system passes to the north of CO. The models still shows a weak
front backing into the cwa from the northeast in the afternoon
after 21z. High based thunderstorms develop over the mountains.
Better low level moisture over the eastern plains will allow for
stronger thunderstorms in the aftn and evening, with boundary
layer computed CAPES ranging fm 800-1500 j/kg. Enough instability
to produce a slight risk of severe storms especially along the
northern border and far eastern plains Thursday afternoon and
evening. Temperatures on Thursday will drop a bit with highs
around 90. The trend of decreasing temperatures continues Friday
into Saturday. A strong surge of cold air pushes into the cwa from
the northeast in the afternoon on Friday. the airmass becomes
increasingly stable across the plains behind the front, but along
and ahead of the cold front, there should be a better chance of
thunderstorms. The cooler airmass remains in place across the
northeast plains of Colorado through the weekend. Best chc of
thunderstorms will be over the elevated terrain through this time
frame. The ridge remains in check until Tuesday of next week, when
it starts to rebuild over the west and the warmer temperatures
return.

&&

.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1037 AM MDT Tue Jun 20 2017

VFR Conditions will prevail through Wednesday. Light diurnal winds
are expected through the next 24 hours. Isolated showers and
storms may form over the higher terrain west and south of Denver.
Outflow winds may produce a wind shift or two at the Denver
airports, otherwise no other impacts are expected from the
convection.

&&

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

$$

UPDATE...Meier
SHORT TERM...Gimmestad
LONG TERM...Cooper
AVIATION...Meier



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