Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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671
FXUS65 KBOU 232036
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
236 PM MDT Mon Apr 23 2018

.SHORT TERM...(This evening through Tuesday)
Issued at 206 PM MDT Mon Apr 23 2018

Strong upper level trof moving east across Wyoming and associated
80kt jet moving into west central Wyoming this afternoon. Ahead
of the trof, isolated to scattered coverage of showers have
developed over our mountains. So far the strongest storms are over
Southern Wyoming with the best moisture and lift from the
disturbance. Surface cold front will move into northeast Colorado
near 00z and then sweep southward to cover all CWA plains by
midnight. Ahead of the front, there are brisk southeast winds up
to 30 mph with dewpoints on the plains in the upper 30s to mid
40s. This translates up to CAPE values from 500-900j/kg. Current
ACARS and supplemental soundings support these values. Given good
mid level flow could see gusts in the 40-50 mph range and some
small hail from the stronger storms.

Behind the cold front tonight, there will be shallow upslope flow
developing and with proximity of the jet will seen light to modest
amounts of upward ascent. This could lead to more uniform shower
activity after midnight and some mixing and changing to snow by
daybreak on Tuesday. Moisture depth becomes more shallow as the
day wears on which will limit the amount of shower coverage. Much
of the showers will shift south of Interstate 70 during the
morning/early afternoon hours as the jet core moves over Northern
Colorado. Looks like there will still be considerable cloudiness
for much of the day and will also result in much cooler
temperatures on the plains. Readings will only be in the 40s,
which will be a 25-30 degree drop in temperatures from today.

.LONG TERM...(Tuesday night through Monday)
Issued at 206 PM MDT Mon Apr 23 2018

By Tuesday night the system that brought a mixture of rain and snow
the region will have moved off to the NE over Nebraska. Some light
snow will still be possible late Tuesday over the foothills and
Palmer Divide as surface winds provided by a deepening surface
trough maintain a preferable upslope pattern from the NNE. Model
cross sections over the Denver area show a pretty dry low level so
expect little precipitation as you go east near I-25 with most of
the pop chances further west in the higher terrain. QG subsidence
will increase from the North helping to bring precip to an end by
midnight Tuesday into early Wednesday.

Wednesday will see clearing skies with increased upper level ridging
from the west. Temperatures will rebound slightly from Tuesday with
highs in the mid 60s on the plains and 40s in the mountains. The
next trough to impact the region will drop down from Canada on
Thursday. Models diverge slightly on the speed of the trough axis
with the EC ahead of the GFS and NAM. However, each have it moving
into northern Colorado by Thursday afternoon timeframe. Models have
the cold front associated with this system moving onto the plains
early Thursday. The cold air will push south by the afternoon
accompanied by minimal moisture. At this time precipitation looks to
be weak with just light QPF in the mountains. Temperatures however
will be cooler with the influx of cooler air with highs staying in
the 50s.

For Friday into the weekend upper level ridging will return with the
influence of the 551 low off the West coast. This ridge will
dominate the pattern through Saturday bringing temperatures into the
upper 70s all three days. At this time current 700mb temperatures
are flirting with 80...especially by Sunday. Models diverge greatly
on the speed and track of the closed low as it makes its way
onshore, however with increasing moisture ahead of this feature
there will be a slight chance of thunderstorms during the late
afternoon hours on Saturday.

&&

.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 206 PM MDT Mon Apr 23 2018

Showers are beginning to push off the foothills this afternoon
which should result in winds turning more back to the west and
north west. Main frontal boundary still expected around 03z at
KDEN as winds shift and increase northerly. Shallow upslope flow
will develop behind the front and could lead to a persistent
pattern of showers after midnight. Temperatures appear to be cold
enough for a mix of rain/snow towards midnight and finally all
snow before daybreak. However, by 11-12z time frame, airmass aloft
begins to dry out over Denver and also near the surface. If
moisture remains saturated in lowest levels, then possible
freezing drizzle could develop but confidence in that scenario is
quite low and will not mention.

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

$$

SHORT TERM...Entrekin
LONG TERM...Bowen
AVIATION...Entrekin



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