531
FXUS65 KBOU 081119
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
519 AM MDT Wed May 8 2024

.KEY MESSAGES...

- Freeze warning for the Palmer Divide...and a Frost Advisory most
  of the plains and I-25 corridor early this morning.

- Continued light snowfall in the mountains with some blowing snow
  over the higher passes.

- Cool and unsettled weather Thursday through Friday.

- Warming Saturday through Tuesday with late day showers and
  limited thunderstorms.

&&

.SHORT TERM /Through tonight/...
Issued at 346 AM MDT Wed May 8 2024

The upper level low will be over the central High Plains today with
a continuation of WNW flow aloft.  Overall, the flow will gradually
decrease thru the day so wind speeds won`t be as high as the last
few days.  However, for this morning, there will be at least a minor
mtn wave which will combine with cross-barrier flow in the 35-40 kt
range to produce of period of gusty winds in and near the foothills.
At this point, gusts should stay below 60 mph. By midday, winds
should gradually decrease as mtn wave breaks down and cross-
barrier flow decreases. In the mtns, cross-sections still show
enough moisture combined with favorable orographics to produce
periods of light snow mainly north of I-70. Across the plains, it
will be dry, although with improving lapse rates by aftn can`t
rule out a slight chc of showers near the WY-NE border area. As
far as highs, readings this aftn will be in the upper 50s to lower
60s over nern CO.

For tonight, the upper level low will gradually elongate and split
apart as one piece of energy moves WSW into wrn CO by 12z Thu.
Meanwhile, a cold front will move across nern CO overnight with
upslope flow developing.  May see a gradual increase in shower
development in the nrn foothills and nrn portions of the I-25
Corridor after midnight which will spread southward into the srn
foothills and the rest of the I-25 Corridor by 12z Thu. In the
mtns, best chc of additional snow will be on east facing slopes
overnight.

Finally, as far as frost/freeze winds have been stg enough to keep
temps well above freezing in most areas.  However, near sunrise may
still see an hour or two where readings may drop to near freezing,
so will keep highlights in place.

&&

.LONG TERM /Thursday through Tuesday/...
Issued at 306 AM MDT Wed May 8 2024

Models have an east-west oriented upper trough across the CWA on
Thursday. By late Thursday night, an upper closed low is over the
Great Basin and Utah with weak troughing over us. This pattern
stays that way all day Friday into the evening, then the upper
circulation moves a bit east and is over southern Utah by 12Z
Saturday morning. There is weak downward vertical velocity over
much of the CWA concerning the synoptic scale energy Thursday and
Thursday night. Weak upward vertical velocity is progged Friday
afternoon through Friday night. The low level pressure and wind
fields have upslope in place for the plains Thursday and Thursday
evening. Normal diurnal wind patterns should be in place Friday
and Friday night.

Looking at moisture, it is pretty deep on Thursday, especially over
the western half of the forecast area.  Moisture stays pretty deep
over the western half of the CWA Thursday night well into Friday
night. The eastern CWA is fairly moist Thursday into Friday mid
day. The QPF fields show limited measurable precipitation for much
of the CWA Thursday, with just the far east to stay mostly dry.
Precipitation is progged over the alpine areas through Thursday
night, Friday and most of Friday night. There could be some snow
mixed in over the plains above 5,500 feet with the heavier
precipitation areas Thursday. Expected snowfall amounts in the high
country do not look significant through Friday night.

Looking at temperatures, Thursday still looks to be the coolest day,
with highs up to 20 F below seasonal normals over the plains. Friday
warms up 3-6 C with most of the plains to make it into the lower
60s F.

For the later days, Saturday through Tuesday, models continue to
show the pinched off upper closed low to move across Utah and get
into Colorado Saturday night. Upper ridging gets into our state by
Sunday night. There is weak northwesterly flow aloft on Monday and
weak to moderate zonal flow aloft on Tuesday. Most of the models
point to late day convection each day with the best chance of
precipitation to be over the mountains and foothills. The
insatiability is not great, so the thunderstorm coverage will be
minor. Temperatures warm slowly each day with readings to be a bit
above seasonal normals Sunday. Monday and Tuesday.

&&

.AVIATION /12Z TAFS through 12Z Thursday/...
Issued at 514 AM MDT Wed May 8 2024

Once again winds have remained gusty overnight from the west.
However, they have become more WSW in the last hour. By 15z,
they should go back to more WNW with gusts up to 25 mph thru
20z. After 20Z, they will go more NW but decrease in speed.
By 01z, expect a north direction which will switch more to
the NE by 03z. Overnight they will become SE by 07z. VFR
conditions for today but will see ceilings drop to around 9000
ft early this evening.  Late tonight, will likely see MVFR
ceilings by 12z Thu.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Frost Advisory until 8 AM MDT this morning for COZ038>040-
042>047-049.

Freeze Warning until 8 AM MDT this morning for COZ041.

&&

$$

SHORT TERM...RPK
LONG TERM....RJK
AVIATION...RPK