678 
FXUS65 KBOU 051735
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1135 AM MDT Sat Jun 5 2021

.UPDATE...
Issued at 944 AM MDT Sat Jun 5 2021

Morning stratocumulus has dissipated from the plains, while still
some weak convective activity in the mountains. Radar picking up a
few light showers along and mainly west of the Park and Gore
ranges. With this update have blended in some HRRR pops late this
morning to push back onset of precipitation, although have kept
some slight chances along the higher terrain mentioned above.
Looks like we'll hit convective temperature right around noon,
with pops coming up into chance category after that. Still expect
scattered coverage, and lighter precipitation amounts with
inverted V sounding and evaporation in the low levels. Could see
some wind gusts to 35-40 mph from collapsing storms, and lightning
is a threat no matter what. If you're hiking today be headed
downhill by noon.

For temps, little change there. Adjusted hourly temperatures to
current trends, and blended in the latest bias corrected max temp.
Only affected highs a degree or two.

&&

.SHORT TERM...(Today and tonight)
Issued at 425 AM MDT Sat Jun 5 2021

Another warm day is in store across northeast Colorado today. 
Weak flow aloft will continue today under a ridge axis, which is 
currently wedged between a cutoff low in Texas and a larger-scale 
trough axis over the Pacific Northwest. A little bit of moisture 
and synoptic scale lift will be around the area today, which 
should help initiate scattered thunderstorms over the higher 
terrain during the early afternoon hours. With the nearly non-
existent flow aloft (cloud layer mean wind < 10kt) storms should 
stay over the higher terrain through much of the day. The main 
threats from any storms this afternoon would be lightning and some
light rain showers. Some high-resolution guidance does hint at a 
few storms making it into the I-25 corridor during the evening, 
but confidence in these solutions is low. Forecast soundings 
continue to show an inverted-V profile extending to about 500mb, 
which suggests that any storms over the plains would likely 
produce virga and some gusty winds as they collapse. Convection 
should decrease in coverage through the evening hours with mild 
conditions overnight tonight.

Temperatures will be similar if not a few degrees warmer compared
to yesterday. Highs for Denver look to make it to 90F, with lower
90s across most of the plains. Over the foothills and mountains, 
temperatures should warm up into the upper 70s to low 80s. 
Overnight lows will remain in the upper 50s for most of the 
plains, with 40s to 50s expected for the higher terrain.

.LONG TERM...(Sunday through Friday)
Issued at 425 AM MDT Sat Jun 5 2021

Only subtle changes in our weather for the coming week. The
current batch of mid level moisture over the mountains, which is
largely residual clouds from a couple days of afternoon
convection, will be drifting slowly east on Sunday and Monday and
be enhanced both days be renewed afternoon mountain convection. As
light west to southwest flow picks up a bit ahead of the deepening
trough off the west coast, this moisture should drift out over the
plains eventually. Right now, the model consensus is just a little
eastward drift on Sunday with more afternoon and evening clouds
near the mountains, then a wholesale drifting east across the 
plains late Monday. Whether this enhances or hurts convection
depends on the timing and whether there is cloud cover Monday
morning. Meanwhile, we should keep a moist but slightly capped
airmass over the eastern border areas, with somewhat drier air
over and just east of the mountains. There will be a front hanging
out north of Colorado that could potentially surge southward,
especially if there would be convection along it, and if that
happened the moisture and low level convergence could shift back
into northeastern Colorado. This appears unlikely in the
Sunday/Monday time frame but isn't out of the question, and we'll
have some low overnight PoPs in the northeast corner for this. 

There's some mid level drying behind a shortwave Tuesday. This
should lead to an overall drying trend, but could set up a Day 2
scenario for Wednesday with moisture coming further westward. If
this happens though it would likely be slightly cooler as well and
weakly capped. Models are showing another shortwave in SW flow
that is stronger in some runs. Depending on timing and cloud
cover, this could bring a hotter and breezy day. Friday will then
be another attempt at the Day 2 scenario, perhaps with a better
chance given the stronger shortwave the day before. If we are able
to generate convection in the moist air, there will be some shear
to work with as well so this day could be a better chance of
severe weather after a long string of days without much shear. Of
course, we could still have a moist but weakly capped boundary
layer.

Our model blend is sufficient for all of this since all these
little details are uncertain. This gives us a week of mostly dry
days with a low level of diurnal mountain convection and some
slight chances of nocturnal storms out on the eastern plains, with
highs sticking around 90 degrees.

&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 1132 AM MDT Sat Jun 5 2021

VFR through the period. Outside chance that showers and
thunderstorms that develop in the mountains and foothills move
onto the plains this evening. Left the VCTS in the forecast at
KBJC but chances too low at KDEN and KAPA to include. Northeast
wind much of the day will switch back around to NW in the 23-24z
timeframe. Wind speeds will increase with the direction change,
and included gusts to 20-25 kts after 00z. Wind will settle down
to SW overnight.

&&

.HYDROLOGY...
Issued at 425 AM MDT Sat Jun 5 2021

A limited flash flood potential threat is anticipated for today
across the burn areas. Scattered showers and thunderstorms should
develop by the early afternoon over the higher terrain with
relatively slow storm motions. However, dry air in the lower
atmosphere should limit heavy rainfall potential. Thunderstorm
activity will decrease by the late evening.

There will be a low level of thunderstorm activity over the coming
week. Storms will tend to be slow moving on Sunday and Monday so
there is a low chance of flooding for the new burn areas but a
rather dry air mass will limit the threat. For Tuesday through
Thursday storm motion will be a bit faster, so the threat is very
low. There may be some increase in moisture Friday but that is
uncertain.

&&

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

$$

UPDATE...Hanson
SHORT TERM...Hiris
LONG TERM...Gimmestad
AVIATION...Hanson
HYDROLOGY...Gimmestad/Hiris