Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 221518
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
918 AM MDT Sun Apr 22 2018

.UPDATE...
Issued at 910 AM MDT Sun Apr 22 2018

Still some patchy/areas of fog over the northeast plains, mainly
over the Fort Collins to Greeley area, and further east over
Lincoln county. Fog and low stratus should dissipate over much of
the area by 11 am leading to mostly sunny skies for the afternoon.
Temperatures will warm nicely into the upper 50s/lower 60s as weak
upper ridge moves over the area. Dropped temperatures a few
degrees based on latest observations.

Across the mountains, still some low clouds over Jackson and Grand
counties. With the lingering moisture there expect scattered
rain/snow showers this afternoon.

&&

.SHORT TERM...(Today and tonight)
Issued at 353 AM MDT Sun Apr 22 2018

An upper level ridge axis will move over central Colorado today.
The northerly flow aloft this morning will be replaced by a
weaker westerly flow this afternoon. The airmass will be drier
today, with 700 mb temperatures warming from around -4C yesterday
to +2C this aftn. This will allow for high temperatures in the
mid 60s for Denver which would be near normal. There will be
enough mid level moisture trapped in the mountains this aftn to
produce isolated to scattered rain/snow showers. Across the
northeast plains this morning, GOES-16 showing areas of fog
primarily east of the Urban Corridor, but some of this could slip
into the Denver area primarily in the 10-14z period. Will go with
patchy coverage along the I-25 corridor until around 15z, with
areas of fog to the north and east of Denver. The models indicate
the gusty winds in the mountains will decrease significantly by
the afternoon. For tonight, the ridge axis shifts to the east with
a stronger westerly flow aloft developing. Overall just isolated
showers in the mountains overnight, dry and stable conditions over
the northeast plains. Spatial cross-sections to show some shallow
moisture across the eastern plains towards 12z Monday, with the
potential for patchy fog late. Will leave it out of the grids at
this time.

.LONG TERM...(Monday through Saturday)
Issued at 353 AM MDT Sun Apr 22 2018

A shortwave trough will become sheared as it moves across the
northern Rockies Monday and Tuesday. This will bring moisture into
the northern mountains by Monday afternoon, with colder air,
moisture and instability sagging southward with the tail of the
trough Monday night and Tuesday. This should bring a round of
mainly light showers with the snow level dropping from near 10
thousand feet Monday afternoon down to somewhere around 5-6
thousand feet by Tuesday morning. Warm temperatures should limit
the impact to the higher mountains again. It will be fairly windy
on the plains behind the front Monday night and Tuesday.

For the rest of the period the theme will be longwave ridging
ahead of a low coming onto the west coast. A northern stream
shortwave will pass into the northern plains about Thursday. The
operational EC is stronger with this, enough for some moisture
and a little cooling, while the GFS would have little impact.
The operational EC appears to be on the stronger side of its
ensemble though. Behind this system, we will be under the ridge
axis. GFS has some moisture trapped in the ridge while the EC has
a stronger, drier ridge. This week may be the first with our warm
season diurnal convection pattern starting about Thursday. How
much shower/storm activity each day will depend on the details
mentioned above. For now we`ll plan on low grade diurnal
convection, mainly over the mountains. There does not appear to be
any particular excess of moisture or instability through this
period. Saturday could be a warm/dry/breezy day on the plains
ahead of more moisture being drawn up from the Gulf of Mexico
ahead of the approaching trough.

&&

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 910 AM MDT Sun Apr 22 2018

VFR with no impacts expected today. Dissipating fog/stratus this
am remains well north of the terminals. Surface winds will shift
to the north and northeast this afternoon but overall speeds under
10kt.

&&

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

$$

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


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