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000
FXUS65 KBOU 171031
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
431 AM MDT Wed Apr 17 2024

.KEY MESSAGES...

- Warm and breezy today with a cold front and possible showers in
  the evening.

- Cooler, breezy and unsettled tonight through Saturday with
  precipitation off and on. The best chances will be tonight into
  Thursday morning and again Friday afternoon into Saturday.

- Drier and warmer by early next week.

&&

.SHORT TERM /Through tonight/...
Issued at 431 AM MDT Wed Apr 17 2024

Main changes for today and tonight are to increase cloud cover,
and decrease PoPs for tonight.

A Front Range wave cloud has developed already as moisture
increases ahead of the jet streak/shortwave/cold front that will
pass by us tonight. This should continue to expand into a high
cloud shield over the whole area this morning. There will still be
enough wind for decent mixing to warm us up today, but the
increased clouds will take a few degrees off today`s highs.

The cold front will move through in the late afternoon (north?)
to early evening (south) with a few hours of gusty north winds.
There will be a sharp temperature drop, from near 70 to 50 or so
in a couple of hours. There will be a little moisture/instability
in the mid levels just ahead and behind the front for a chance of
light showers. A thunderstorm isn`t out of the question, but model
soundings are just showing about 300-500 J/kg of CAPE so it`s a
stretch. Later tonight, low level moisture increases with a
stratus layer in the frontal inversion, but by that time it`s
likely drying above that layer. Our PoPs for later tonight may be
too high and we backed off some. There`s low level moisture and
convergence, but it`s in/under the inversion and the moisture
layer is shallow. If there are some showers from an elevated
source, it would probably be just cold enough for a little snow,
but the layer at the frontal boundary isn`t cold enough and could
produce a little drizzle/freezing drizzle if there`s enough lift
and thickness to it. More likely, it`s just cool with a stratus
layer overnight. With a bit stronger cold advection in the
guidance tonight, we lowered the lows a couple of degrees to near
or a little below freezing across the plains.

&&

.LONG TERM /Thursday through Tuesday/...
Issued at 431 AM MDT Wed Apr 17 2024

By early Thursday morning, the cold front will have pushed across
Colorado accompanied by northeasterly upslope flow across the
plains. This upslope flow will remain on the shallow side (750mb).
An upper level jet will be just to the north putting us in more of a
neutral environment, then leaning slightly more subsident
(descent) toward the afternoon. There is sufficient moisture in
the mid- levels, but it is drier near-surface. Model soundings
hint at the possibility for some freezing drizzle in the AM, but
there might not be deep enough moisture in the mid-levels for
that. Kept shower chances low (<30%) across the plains/I-25
corridor. Can`t rule out snow mixing in any showers early Thursday
morning as well. The mountains will have a better shot at showers
with mainly light accumulations (< 6") favoring the northern
mountains and parts of Front Range mountains. It will be cooler in
the post-front airmass with highs in the upper 40s to low 50s
across the lower elevations.

Above normal moisture remains in place over Colorado in the fairly
zonal flow aloft on Friday and Saturday. Another weak wave or two
will bring periodic chances for showers. Ensemble guidance is in
general agreement with this, although some differences in QPF are
notable still. Position of the upper level jet will put Colorado
under large scale ascent with more support for organized/banded
showers. A front comes through Friday, providing another reinforcing
push of NE upslope flow. Together, this will support higher chances
for showers starting in the late afternoon/early evening timeframe.
Shower chances continue overnight into Saturday. During this time,
mountains will have snow showers with light accumulations.

Saturday night, conditions begin to gradually dry out as a weak
ridge moves in from the west. This will keep the plains dry with
afternoon snow showers in the mountains through early next week.
With ridging aloft, temperatures rebound Sunday and early next week
into the 60s to around 70 for the lower elevations.

&&

.AVIATION /12Z TAFS through 12Z Thursday/...
Issued at 431 AM MDT Wed Apr 17 2024

VFR today, with west winds at 10 to 20 knots developing around
18z. A cold front will move through 21z-02z with north winds
gusting to 30 knots behind it for a few hours. Scattered rain
showers are expected behind the front, with areas of MVFR
ceilings. Instrument approaches to KDEN will likely be needed
starting sometime between 01z and 04z.

&&

.FIRE WEATHER...
Issued at 431 AM MDT Wed Apr 17 2024

Warm, dry, and breezy conditions are expected this afternoon ahead
of a cold front. Critical fire weather conditions are possible
this afternoon along the foothills and on the plains south of
Interstate 70, but we expect them to be short lived. A couple
hours of strong north winds and colder temperatures are expected
behind a cold front reaching the northern border in the late
afternoon and south through the Denver area in the early evening.
Winds will diminish with scattered showers overnight.

&&

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

&&

$$

SHORT TERM...Gimmestad
LONG TERM...Mensch
AVIATION...Danielson
FIRE WEATHER...Gimmestad