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000
FXUS65 KBOU 180255
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
855 PM MDT Wed Apr 17 2024

.KEY MESSAGES...

- Breezy with a cold front and possible showers in the evening.

- Cooler, breezy and unsettled through Saturday with
  precipitation off and on. The best chances will be tonight into
  Thursday morning and again Friday afternoon into Saturday.

- Drier and warmer early next week.

&&

.UPDATE...
Issued at 845 PM MDT Wed Apr 17 2024

Radar shows light showers aloft mainly over the northeast corner
this evening. These showers will fill in north of I-70 as the
night progresses. High resolution model guidance is starting to
show more of a widespread band of showers extending from eastern
Grand County toward the CO/NE border by Julesburg. This seems
reasonable as forcing from an upper level jet moves across the
area. As a result, PoPs and QPF were raised overnight tonight.

Low clouds are expected to persist throughout the entire day
tomorrow across the plains and foothills. This will keep
temperatures well below normal and the forecast highs were
decreased 5-6 F to account for the cloudiness. There could be some
drizzle or flurries that fall from these clouds. There may be
slick spots on the roads primarily in the foothills were
temperatures will be cooler.

&&

.SHORT TERM /Through Thursday/...
Issued at 256 PM MDT Wed Apr 17 2024

Area radars are showing light rain showers over the northern border
of the CWA at this time. There are a few snow showers over the
higher peaks of the mountains north of I-70 as well.  There are
northerly surface winds over southern Wyoming and some portion of
western Nebraska, which could be the advertised incoming cold
front or outflow associated with the showers. Most of the models
don`t show that cold front to get into the northern border CWA
until 00Z or even later this evening.

Models continue to show fairly strong westerly jet level flow
overnight and Thursday.  The QG Omega fields have weak upward
vertical velocity over the CWA overnight into Thursday morning.
There is also decent upslope flow over the plains and foothills
tonight into early Thursday afternoon. However, moisture progs
continue to show pretty shallow moisture with this system. There is
a bit of CAPE around the northern half of the CWA early this
evening. There is also a tad progged over the southwestern CWA
Thursday afternoon. The QPF fields show limited measurable
precipitation for CWA overnight and Thursday as well. Will go with
"scattered" showers for the plains overnight and even lower pops
on Thursday. There could be a bit of snow mixed in over the plains
late this evening and overnight, but accumulations are not
expected. Will go with "likely" pops over the mountains and
foothills east of the divide overnight. Mostly snow is expected
but accumulations will be on the light side. Significant
precipitation is not expected with this system tonight or on
Thursday.

For temperatures, readings should cool down significantly behind
this evening`s cold front, with the plains dropping into the
lower to mid 30s for lows overnight. Thursday`s highs look to be
20 to 30 F cooler than today`s highs.

&&

.LONG TERM /Thursday night through Wednesday/...
Issued at 229 PM MDT Wed Apr 17 2024

Thursday night into Friday morning, a strong northwesterly flow
aloft will be over the forecast area. light rain/snow showers
primarily along the northern border and over the northeast plains
will linger as the under the left exit region of an upper level
jet max moving into the Midwest. Friday afternoon into Saturday,
another period of light to moderate precipitation will move
across the region. The next surge of northeasterly upslope will
develop along the Front Range starting around 00z Saturday,
continue overnight, then weaken and taper off Saturday morning.
Spatial cross-sections suggest the best chance of snow west of the
Continental Divide will occur Friday afternoon/evening, then the
focus will shift to the east slopes of the Front Range and
northeast plains Friday night into Saturday morning. Overall the
upslope is strongest Friday evening and confined from the surface
to 700 mb. The mid and upper level QG ascent will be weak through
midday, before weak subsidence moves across from the west. Based
off the 0-1km MLCAPE, the GFS20 suggests 300-500 j/kg of
instability especially in the mountains for Friday and Saturday
afternoons. Can`t rule it out for areas in and near the foothills
and Palmer Divide but those areas may be fighting better low level
stability. There will be a higher probability of showers vs
thunderstorms (10-20%).

A drier northwesterly flow will be over CO by Sunday with a warming
trends.  There will be enough moisture around to support a slight
chance of afternoon/early evening showers/thunderstorms. The ridge
axis will stay to the west of CO with a persistent northwest flow
aloft through Tuesday, then the ridge shifts over CO on Wednesday.
High temperatures by Sunday will warm to around 70, Sunday through
Tuesday, then back to near 80 by Wednesday.

&&

.AVIATION /00Z TAFS through 00Z Friday/...
Issued at 700 PM MDT Wed Apr 17 2024

A cold front has moved through the terminals this evening. Gusty
northeast winds have developed and they should persist for 2-3
more hours. Winds will decrease overnight tonight but will still
be out of the northeast. Recent high resolution model runs
continue to increase the chance for showers after midnight
tonight. There may need to be an amendment to include reduce
visibility down to 5 SM and ceilings down to 1,000 feet by 06Z.
There is even a chance of a thunderstorm occurring as well.

Low ceilings will be here to stay for a long time. Once they build
in tonight, ceilings between 500-3,000 feet will persist perhaps
into Friday. This is due to light upslope flow with a strong
inversion above the cloud layer. Therefore, there does not seem to
be too much hope in the ceilings breaking up during the day
tomorrow.

&&

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

&&

$$

UPDATE...Danielson
SHORT TERM.....Koop
LONG TERM......Coop
AVIATION...Danielson