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000
FXUS65 KBOU 191032
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
432 AM MDT Fri Apr 19 2024

.KEY MESSAGES...

- Springtime snow in the Rockies, with accumulations expected in
  most locations tonight through Saturday morning. Patchy
  drizzle/freezing drizzle to start the day

- Slick and hazardous travel in the foothills, and possibly onto
  the adjacent plains into Saturday morning

- Cold through Saturday, then drier and warmer for Sunday through
  much of next week.

&&

.SHORT TERM /Through tonight/...
Issued at 1257 AM MDT Fri Apr 19 2024

Plenty of low cloud cover in northeast Colorado this morning. Radar
shows a bit of a different picture than it did late last evening
with a fairly organized band of snow extending from the foothills of
Boulder County eastward onto the plains. There isn`t high certainty
on how long this band remains organized, but most model guidance
doesn`t keep it around too long this morning. A few showers will be
possible for the remainder of this morning across the east slope
and adjacent plains. Temperatures in the urban corridor are a
little above zero. If it were a tad colder at the surface,
freezing drizzle would be more of a threat this morning given the
low stratus. With light snow in parts of the foothills and cooler
temperatures overall, there may be some slick spots out there this
morning.

Plenty of small yet challenging elements in the forecast today
and tonight. Colorado will be under zonal flow aloft with a quick
shortwave trough moving across into Saturday. This morning, there
is a good amount of moisture in place with the low stratus to
prove it. The first question will be if and how long these low
clouds stick around. For most areas, it is becoming more likely
that the stratus sticks around today with some subtle thinning or
rising in the afternoon. Areas south of I-70 have a better chance
at some breaks in the deck. With that said, cloud cover and a
cooler airmass will keep highs cool today. Had to do some manual
adjusting to the highs as most guidance was too warm. Highs will
likely remain in the low 40s across the plains.

Late this afternoon through Saturday morning will be the most
"weather-active" timeframe. As the next wave approaches, better
ascent and moisture moves into the area. Snow showers develop in the
mountains this afternoon. A front will move across the plains in the
late afternoon-early evening timeframe bringing a push of NE upslope
winds and additional cold air advection. This will help develop
showers across the lower elevations. This will start as rain.
Early evening, as temperatures cool, snow will begin to mix in and
change to snow. Had to wrestle a bit with the snow levels to
paint the right picture. There is a low chance for some freezing
drizzle early PM on the plains. Moisture should be deep enough to
combat this however.

The jet will play a role in this event as it will support more
organized banding across the eastern slope mountains and plains
Friday night into Saturday. However, the downfall of bands is the
lower confidence in exact placement and more localized totals.
This isn`t looking like a high-impact event. Can`t rule out a few
localized bands with more moderate rates (0.5-1"/hour). Generally,
bands will move northward across the I-25 corridor, and east
slope overnight while also spreading eastward onto the plains.
Ensemble means are still consistent with moderate to high probabilities
40-80% for 1-3" for the adjacent plains. As you go further
eastward, confidence decreases in exact amounts and this is due to
the localized nature of the banding. The east slopes of the Front
Range and the foothills will be most favored with amounts in the
4-10 inch range. As a result, a Winter Weather Advisory has been
issued for the mentioned areas along the Front Range
mountains/foothills.


&&

.LONG TERM /Saturday through Thursday/...
Issued at 230 AM MDT Fri Apr 19 2024

Snow will be ongoing Saturday morning over much of the Front
Range Mountains, Foothills, and Plains. However, the best lift in
the form of the right entrance region of the upper jet, QG, and
mid level frontogenesis will be weakening. Thus, snow will start
to taper off once we hit mid morning with a further decrease in
most areas through the afternoon. Another inch or so of
accumulation is expected before tapering off in the mid to late
morning hours. There will be some convective redevelopment in and
near the mountains in the afternoon due to mid level instability,
but additional accumulation with those will be minimized by
daytime "heating". Heating is a loose term, as high temperatures
even on the plains will be struggling to reach the lower 40s
given some fresh snow on the ground, persistent low clouds, and
shallow upslope.

Now, if you`re looking for nice weather, you don`t have to look
any further than Sunday. Westerly flow develops which will lead to
warm advection, a return of sunshine, and downslope warming.
Thus, we expect high temperatures to push back into the mid to
upper 60s. Further warming is likely to occur Monday with good
ensemble agreement that we`ll reach the 70s across the plains,
although a cold front potentially reaches us earlier shaving a few
degrees off those numbers.

That late Monday cooling will last into Tuesday, but then warmer
temperatures will re-establish themselves for Wednesday into
Thursday in advance of the next storm system. That storm
system`s arrival is expected to bring a return of unsettled
weather toward Friday with scattered showers and storms, and some
mountain snowfall along with cooler temperatures.

&&

.AVIATION /06Z TAFS through 06Z Saturday/...
Issued at 1203 AM MDT Thu Apr 18 2024

Ceiling and weather impacts are expected to continue through the
TAF period.

Current radar shows areas of light drizzle across the terminals
with indications of it lifting northward. Can`t rule out
additional areas of drizzle or even a low chance of light snow
early this morning. Otherwise, BR should stay in place resulting
in visibilities and ceilings in the MVFR category. Later this
morning, soundings show some indication of small improvements in
ceilings into the higher end MVFR range. This isn`t high
confidence at this point as there is also the possibility that
these low ceilings stay socked limiting any improvement.

Another front moves across Colorado in the late afternoon-early
evening timeframe (20-00Z) followed by a push of northeast winds.
Showers develop around the terminals mid to late afternoon with
lowering ceilings. Early evening, rain showers will have changed
to snow. With light snow, conditions drop back into low MVFR to
IFR with lower visiblities and ceilings.

&&

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

&&

$$

SHORT TERM...Mensch
LONG TERM...Barjenbruch
AVIATION...Mensch