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000
FXUS65 KBOU 231741
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1141 AM MDT Tue Apr 23 2024

.KEY MESSAGES...

- Cooler today with a few showers/isolated storms, but then above
  normal temperatures again for Wednesday and Thursday.

- Stormier weather pattern in the works, starting late Thursday
  and peaking next weekend, with accumulating snowfall in the
  mountains.

- Stronger storms possible northeast plains Thursday
  afternoon/evening.

&&

.UPDATE...
Issued at 1137 AM MDT Tue Apr 23 2024

Only minor changes at this time. It looks a slightly warmer/drier
for this afternoon. A few light showers drifting off the mountains
late afternoon/early evening still looks good. With an inversion
persisting over the plains, this will be elevated weak showers
that should decay as they move east this evening.

&&

.SHORT TERM /Through tonight/...
Issued at 311 AM MDT Tue Apr 23 2024

Surface cold front pushed across northeast Colorado in these wee
morning hours, with cooler air filtering in. The airmass is
gradually drying behind the front, so despite the developing
upslope component this morning it will be hard to develop much if
any stratus. Farther west over the mountains and stretching into
northern Utah, there was a modest amount of mid level moisture,
cloudiness, and isolated light showers. Those may continue this
morning with weak QG lift noted, and a few of these are now
spreading onto the adjacent plains. There could be a little more
sun this morning, and just enough to help us warm a couple
degrees more than earlier anticipated - but that`s still a good
10-15 degrees cooler than yesterday. That puts most of the plains
and I-25 Corridor at near normal temperatures with highs mostly in
the lower 60s. Over the mountains and high valleys, the airmass
is relatively unchanged since yesterday, outside of the increase
in moisture, so mild temperatures will continue until clouds and
evaporative cooling become more widespread later in the day.

With daytime heating and destabilization, we expect scattered
showers to develop over the high country by early afternoon,
gradually spreading eastward onto the I-25 Corridor and northeast
plains late this afternoon and evening. They will be relatively
high based, but can`t rule out a couple rumbles of thunder in/near
the mountains this afternoon with MLCAPE near 200 J/kg.

There is weak QG forcing noted through the night, while the best
mid level frontogenesis lifts northeastward overnight. Those
features would favor the higher PoPs transitioning from the
mountains this afternoon to the northern border area and northeast
corner of the state later this evening into the early morning
hours. Gradual clearing will occur after that, with low
temperatures near or slightly above normal.

&&

.LONG TERM /Wednesday through Monday/...
Issued at 311 AM MDT Tue Apr 23 2024

A ridge of high pressure will bring warmer temperatures back to
the region on Wednesday. The flow aloft will be westerly Wednesday,
then southwesterly Wednesday night as the ridge axis shift to the
east. 700 mb temperatures will warm up to 8C on Wednesday, with
breezy southerly winds across the plains. Max temperatures will
range from the mid to upper 70s. Higher dewpoints in the low 40s
will be possible over the far northeast plains. Model surface
based CAPES of 200-400 j/kg support a slight chance of
thunderstorms in the afternoon/evening mainly along the northern
border. On Thursday, the flow aloft increases from the southwest
with a next short wave trough expected to move across northeast CO
either Thursday afternoon or Thursday evening as light to
moderate mid/upper level QG ascent spreads across the forecast
area. GFS surface based CAPES over the northeast plains are
progged to be in 500-900 j/kg range which could produce one or two
strong thunderstorms.  Another warm day with highs again in the
70s. Southeasterly winds over the plains will help advect higher
dewpoints into the northeast plains in the afternoon, which should
result in a better chance of thunderstorms especially to the
north and east of Denver. In the mountains, there will be fairly
deep layer of moisture around with the passage of the trough with
west/northwest ridge tops winds of 35 kts with the snow level
dropping to around 8500 feet Thursday night. The moisture does
appear to decrease overnight. The best chance of snow in the
mountains appears to be late Thursday afternoon and Thursday
night. There could a brief window of elevated fire weather
conditions for eastern Elbert and Lincoln counties Thursday
afternoon with min rh around 15 percent and wind gusts to 30 mph.

By midday Friday, the trough will shift into central NE and
a short wave ridge will move into central CO. While there will
still be snow showers in the high country, it should be lighter
and primarily orographic with decreasing west/northwest ridgetop
winds. Across the plains, shower activity will persist especially
over the northeast plains where wrap around moisture associated
with the exiting trough still impacting that area. A colder
airmass with north/northeast post frontal winds will allow for
showers to continue and develop further west near the
foothills/Palmer Divide Friday afternoon/Friday night. Mid/upper
level moisture will be increasing from the west ahead of the
another approaching trough. Basically the models are still leaning
towards a cool and unsettled period, with snow showers in the
mountains, and rain showers across the plains. The most active day
would appear to be Friday night and Saturday for the entire
forecast area. By Sunday afternoon, maybe another period of
lighter orographic snowfall in the mountains, with wrap around
moisture impacting the northeast plains, as the next trough lifts
to the northeast of CO. The best window for accumulating snowfall
in the mountains will be from Friday Night into Sunday morning
where maybe a Winter Weather Advisory may be necessary at some
point. By Monday it appears to be drier and warmer as another
synoptic scale ridge spreads across CO.

&&

.AVIATION /18Z TAFS through 18Z Wednesday/...
Issued at 1137 AM MDT Tue Apr 23 2024

VFR through tonight. Scattered light showers are expected in the
Denver area about 22z-04z, but ceilings should stay above 6000
feet. There`s a chance (30%) of a wind shift with variable winds
to 20 knots from the showers. Otherwise, east winds becoming
normal S/W drainage winds by 06z with speeds around 10 knots.

&&

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

&&

$$

UPDATE...Gimmestad
SHORT TERM...DB
LONG TERM...Cooper
AVIATION...Gimmestad