Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 230237
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
837 PM MDT Fri Mar 22 2024

.KEY MESSAGES...

- A weather system will affect the area Sunday through Monday
  morning. This system may bring heavier snowfall to portions of
  the mountains, southern foothills and Palmer Divide Sunday
  night. However, confidence in exact details remain low at this
  time.

- Snow shower activity will continue in the mountains Tuesday and
  Wednesday with mainly dry conditions over the plains.

&&

.UPDATE...
Issued at 837 PM MDT Fri Mar 22 2024

Pretty quiet evening again with partly cloudy skies and relatively
mild temperatures. There is some low level cooling noted over the
northeast plains and moisture advection overnight, which could
lead to stratus late tonight and early Saturday morning.
Elsewhere, we`re only looking at mid/upper level moisture, and
the mid level moisture looks rather scant per satellite and
observations to our west. Therefore, don`t think we`ll see more
than isolated to scattered light snow showers in the mountains
later tonight. Better chance later Saturday afternoon in the high
country but even that looks limited and little or no accumulation.
There`s good agreement will be a few degrees warmer Saturday,
with highs into the mid to upper 60s over most of the plains.

&&

.SHORT TERM...(This evening through Saturday)
Issued at 300 PM MDT Fri Mar 22 2024

Current satellite imagery shows clear skies and sunshine continue
across the forecast area this afternoon. Temperatures have made
it to the mid 50s and should continue to climb with additional
radiational heating. Enough Pacific moisture will move into the
high country tonight to allow for some scattered late night snow
showers. Accumulations will be minor. Strong winds will develop
over the highest elevations early Saturday morning with gusts
reaching 45kts. 35kt gusts are possible across parts of the plains
east of DIA throughout the day. West/southwesterly flow will help
temperatures reach the mid to upper 60s across the foothills and
plains Saturday, which will bring max temperatures to roughly 10
degrees above normal. Saturday will also see increasing chances
for rain showers to develop throughout the afternoon. Forecast
soundings are unstable but show dry low levels, therefore anything
that may form will likely become virga and have trouble reaching
the ground.

.LONG TERM...(Saturday night through Friday)
Issued at 350 PM MDT Fri Mar 22 2024

A jet stream will move eastward into Colorado Saturday night with
our forecast area being under a diffluent, left exit region of the
jet. This will provide lift and with some weak instability across
the northeast plains, there will be showers and thunderstorms that
will continue through the evening into the overnight hours. These
will mainly be to the north and east of DIA. Despite this lift,
there will not be much mid to low level moisture in the mountains so
light snowfall is expected to fall from the occasional snow
showers.

On Sunday, a shortwave trough will move from Arizona towards
southeast Colorado. Meanwhile, there will be strong lee cyclogenesis
over southeast Colorado. With limited moisture in the morning, there
will be mostly dry conditions before noon. By the afternoon, a cold
front will move southward out of Wyoming. This will bring additional
moisture behind it initially and will shift winds out of the north
with strong gusts up to 50 mph by Sunday evening. A combination of
factors including, moisture behind the trough, lift from the cold
front, and instability due to steep mid level lapse rates, will
create showers and thunderstorms across the plains. The most likely
area of thunderstorm initiation will be along the Palmer Divide
and eastward to southern Washington County. Some models are
showing most unstable CAPE upwards of 1,000 j/kg in Washington
County and storms that form there will likely have hail associated
with them. This hail should stay below severe limits but it is
possible a storm or two produce 1 inch hail.

By Sunday night, the entire system will strengthen as the
shortwave trough deepens over the CO/NE and CO/KS borders. The
700 mb trough will deepen as well and this will help to create
strong northerly winds across all of the plains. Convective
showers will begin to turn into more stratiform precipitation as
the evening progresses. The aforementioned cold front will
decrease temperatures below freezing across the plains as rain
switches to snow. The timing of this precipitation type switch
will determine how much snow the plains receive. If the front
comes through quicker, snow may begin closer to sunset. However,
if the cold front is slow, the transition to snow may not occur
until late in the evening. Given the northerly flow, the Palmer
Ridge will receive the heaviest snow amounts. Ensembles would
suggest values in the 4-10 inch range there. The west suburbs of
Denver will receive more snowfall than the east suburbs with
generally 2-8 inches expected. Areas from DIA northward towards
Greeley and Fort Collins may not see much snowfall at all from
this system. The Front Range mountains and foothills are expected
to pick up moderate amounts of snow as the precipitation type
issue is less of a concern there. There was consideration for
highlights for these areas but since the worst impacts will not be
until Sunday afternoon, it was decided that we will hold off. The
area that may have the most uncertainty of all is the far
northeast corner of Colorado. Depending on where the storm tracks,
it could rapidly develop in far western Nebraska or Kansas. If
this were to be the case, significant snowfall amounts could fall
on the northwest side with areas like Holyoke and Julesburg
receiving double digit snowfall totals. However, the more likely
scenario is that the storm intensifies farther to the east leaving
eastern Colorado much drier. Due to this uncertainty, the 90th
percentile snow grids were increase substantially over the far
northeast corner of Colorado.

Very cold air aloft will continue to be overhead on Tuesday and
Wednesday. While there are no intense shortwave troughs to provide
lift, there will be enough instability in the mountains and
foothills for afternoon snow showers to form. Some of these snow
showers may drift onto the plains but little, if any, accumulation
is expected.

Conditions will be much warmer Thursday and Friday as ridging will
build in aloft. The mountains will likely get another shot of snow
on Friday and into the weekend as Pacific moisture along with
strong westerly flow will arrive.

&&

.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 544 PM MDT Fri Mar 22 2024

VFR conditions will persist through Saturday. A little westerly
push occurred late this afternoon into the northern Denver area
TAF sites including KBJC and KDEN, but that appears to be shearing
out at the present time, so southerlies are expected to spread
back northward and then become enhanced with deep southerly flow
and drainage winds combining. Sustained winds of at least 15 knots
with gusts to 25 knots at KDEN and KAPA are expected to develop
03Z-06Z, and persist through about 09Z before weakening. There`s
moderate confidence in the wind for later tonight and tomorrow
retaining a southerly component. However there is a chance of
west/southwest winds gusting to near 20 knots after 20-22Z
tomorrow if sufficient heating and mixing occur.

&&

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

$$

UPDATE...Barjenbruch
SHORT TERM...Bonner
LONG TERM...Danielson
AVIATION...Barjenbruch


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