000
FXUS65 KBOU 181020
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
420 AM MDT Thu Apr 18 2024

.KEY MESSAGES...

- Colder with a few light showers today.

- Chance of accumulating snow Friday afternoon into Saturday
  morning.

- Drier and warmer early next week.

&&

.SHORT TERM /Through tonight/...
Issued at 420 AM MDT Thu Apr 18 2024

The shower band that brought a few hours of steady light snow to
areas north of Denver overnight is shrinking, fading, and moving
east now. There`s some very light precipitation, mostly snow, in
an area ahead of the band, including the Denver metro area. Some
lighter showers have developed over the Colorado/Wyoming border
area from Cheyenne westward, and there are a few light showers
coming into the central mountains from the west. Most of this is
being driven by little ripples in the mid/upper level winds,
though some flurries/drizzle may also be generated in the stratus
layer below the frontal inversion.

All of this will be shifting east this morning, with a general
decrease in the mid/upper level forcing and a little drying aloft.
Low levels probably won`t change much as east to northeast winds
will continue. This adds up to a decreasing chance of showers this
morning, but still a non-zero chance this afternoon and evening.
Right now it looks like the banded structures will be headed
mostly north and south of Denver. The shower chance should
decrease further late tonight as there starts to be some warming
and drying that will shrink the stratus layer and end the showers
aloft. We may start to see holes in the clouds later tonight.

We bumped up PoPs a bit in some places, but it`s for pretty light
amounts. Persistent showers from about I-70 south into Park county
and the gentle upslope into the east side of the Front Range are
the two areas most likely to see a little snow accumulation today.
Temperatures probably won`t climb much under the plains stratus.
The evening shift cut temperatures several degrees, and we cut a
few more. There still should be a little warming, but lower 40s
will likely be all we`ll get.

&&

.LONG TERM /Friday through Wednesday/...
Issued at 420 AM MDT Thu Apr 18 2024

The region will remain under zonal flow aloft Friday with weak
synoptic ascent with the main upper jet(exiting) to the north and
east. Expect light rain/snow showers in the morning along the
northern border areas and some snow showers in the mountains.
Temperatures will be warmer than Wednesday with some rebound in the
700mb temperatures. This bring highs in the 50s across the plains
and 30s/40s for most of the high country.

The next "wave" of precipitation will come late Fri afternoon
through Saturday. This will be supported by another embedded
shortwave trough in the flow aloft and the upward motion provided by
the right entrance region of a jet. A front will be the initiator as
it pushes across northeast Colorado from the north in the 20-00z
timeframe. This will bring a push of northeasterly upslope winds
behind it. Showers develop in the mountains first in the afternoon
with steepening lapse rates and increasing moisture. Once the front
is through by early evening and upslope is established,
precipitation chances increase across across the lower elevations as
well. Given the nature of the upslope flow, the higher chances will
be confined to the typical NE upslope favored areas (Palmer Divide,
south Denver metro, west I-25 corridor). Can`t rule out the
potential for some more organized shower banding with jet dynamics
in place.

Shower activity continues overnight into Saturday. With the help of
the cold air advection behind the front, temperatures generally drop
toward the freezing mark across the lower elevations. Rain will
begin to mix with and change over to snow Friday evening. There are
differences among model guidance in how cold the air is and how far
south and west it extends. This then results in uncertainty in snow
amounts and some variance from run to run. Overall snow
accumulations will follow the general upslope pattern favoring the
Front Range, Palmer Divide and areas adjacent with some bands
extending further onto the plains. Ensemble means keep totals on the
lighter side at the lower elevations (< 3"). Front Range
mountains/foothills could see moderate amounts at this point. We`ll
have more info on totals as this gets closer.

Synoptic subsidence works in Saturday afternoon/evening, gradually
decreasing showers on the plains. Residual moisture and afternoon
instability will support showers in the mountains. An upper level
ridge moves eastward into the region on Sunday drying out the plains
and bringing highs back into the 60s to near 70. A quick wave moves
to the north bringing showers to the high country. Similar story for
Monday with mainly dry conditions on the plains with mild
temperatures and another wave of afternoon showers in the mountains.
By Wednesday, highs across the plains rise well into the 70s.

&&

.AVIATION /12Z TAFS through 12Z Friday/...
Issued at 420 AM MDT Thu Apr 18 2024

MVFR conditions are expected through this evening. There will be
areas of IFR, mainly through 16z. Most shower activity is expected
to remain north of the Denver area, though some light rain
showers or drizzle are possible especially early this morning. The
low clouds will likely break up by 12z Friday.

&&

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

&&

$$

SHORT TERM...Gimmestad
LONG TERM...Mensch
AVIATION...Gimmestad