-- Discussion containing changed information from previous version are highlighted. --
901
FXUS65 KBOU 290017
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
617 PM MDT Sun Apr 28 2024

.KEY MESSAGES...

- Warmer and drier conditions to start the week.

- Turning to cooler and possibly wetter Wednesday and Thursday.

&&

.SHORT TERM /Through Monday/...
Issued at 255 PM MDT Sun Apr 28 2024

Convection is slow to develop this afternoon.  It isn`t very warm
after all.  The winds are pretty weak over much of the CWA.  The
eastern third of the plains do have some northwesterlies gusting to
20-25 mph.  There is pretty decent snow shower coverage in the high
mountains at this time, especially north of I-70.

Models have moderately strong northwesterly flow aloft tonight,
becoming zonal on Monday at 50-60 knots at jet level.  Models do not
have much low level moisture for the CWA; just a bit in the
mountains this evening.  I will lower pops a tad over the plains for
early evening based on current development, current temperatures and
model MLCAPE prongs. Little to no pops on Monday, maybe just 10%s
over high mountains by afternoon.

For Monday`s highs, thickness grids point to a 3-6 C warm-up over
today`s readings.

&&

.LONG TERM /Monday night through Sunday/...
Issued at 232 PM MDT Sun Apr 28 2024

The focus for the extended forecast period looks to reside to our
north. With multiple disturbances embedded within the upper-level
flow stemming from the PNW through the week. Models are consistent
with solutions for the beginning of the week, then quickly diverge
come mid week.

As the weak ridging shifts east out of the region Monday afternoon,
northern CO will be on the outskirts of the main QG forcings
associated with an upper level low passing through Montana. A
strengthening westerly jet at the base of the shortwave trough will
dig southward enough to be a source of lift for the northern border
of CO. A cold front associated with this system will also move into
northern CO overnight, these forcings will be plentiful enough to
bring some rain and snow showers to the northern Colorado Rockies
into early morning Tuesday. Accumulations are expected to be light
with minimal impacts.

Tuesday will be drier and slightly warmer than Monday as westerly
flow aloft brings downsloping conditions to the lee side of the
Rockies. With an 85-95 kt jet overhead, expect windy conditions in
the typical wind prone areas in the mountains and foothills as well
as the Cheyenne Ridge. Forecast soundings depict inverted V
solutions with DCAPE values reaching as high as 1030 J/kg for the
afternoon hours, which could bring some dry microburst potential
across the plains. High temperatures will be a few degrees above
normal reaching the low 70s across the plains. Overnight low temps
will be similar to Monday`s, albeit slightly warmer at the base of
the foothills. As the upper level low shifts east across Montana
through the day Tuesday, another will begin to push inland into the
PNW behind it. It is with this approaching system that models begin
to diverge.

From a deterministic perspective, the GFS shows the upper level
low digging far more southward than the ECMWF and Canadian
solutions. This would place the main QG forcings directly over the
forecast area bringing more impactful weather to the area. This
contradicts previous runs that had the ECMWF being the deeper
trough solution. With continued uncertainties remaining, we will
have to see how the models resolve future runs to have a clearer
picture for the latter half of the week. For now, we should expect
high temperatures in the 70s on Wednesday with increasing chances
for rain showers through the day. Thursday will likely bring
cooler high temperatures and some more widespread precipitation.

Ensembles show a wide spread with regards to QPF between 6 PM
Wednesday and 6 PM Friday. The GFS (wettest of the bunch) shows up
to an inch of QPF for some mountain locations and .75 inches for
areas across the plains. The Canadian and EC are slightly more
aligned, however, the Canadian is the driest showing .3 inches for
the mountains and .15 inches for the plains.

After the system moves through in the Wednesday-Friday timeframe,
ridging looks to build behind its exit bringing warmer and drier
conditions for the weekend with a chance for Denver to see the upper
70s on Sunday.

&&

.AVIATION /00Z TAFS through 00Z Monday/...
-- Changed Discussion --
Issued at 555 PM MDT Sun Apr 28 2024

VFR conditions are expected through the TAF period.

Expected scattered showers, virga and a few storms around the
terminals early this evening. Some of the more organized
showers/storms nearby may result in variable outflow gusts up to
30 kts for brief periods as they move generally from NW to SE.
Shower/storm activity diminishes by 03/04Z. Winds return to
southerly drainage at APA and DEN by midnight. Light winds
expected Monday morning becoming light and variable around 15-16Z.
W/WNW winds for the afternoon at 05-10 kts.
-- End Changed Discussion --

&&

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

&&

$$

SHORT TERM...RJK
LONG TERM....Bonner
AVIATION...Mensch