Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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215
FXUS65 KBOU 220953
AFDBOU

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

.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.
a chance of showers
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 06Z TAFS through 06Z Sunday night)
Issued at 353 AM MDT Sun Apr 22 2018

Latest satellite/metar obs this morning indicates stratus/fog
north and east of Denver at this time. Cannot rule it out of the
terminals, and could see MVFR vsbys with tempo cigs aob 010 ft
agl, primarily in the 10-15z period. A weak Denver cyclone
appears to be developing based off the metar wind plot. For now
will delay the lower clouds/vsbys until 10-11z. Once the airmass
mixes out this morning, after 15z, then VFR and generally light
east/northeast winds blo 10 kts through early this evening.

&&

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

$$

SHORT TERM...Cooper
LONG TERM...Gimmestad
AVIATION...Cooper



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