281 
FXUS65 KBOU 150342
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
942 PM MDT Thu Jul 14 2022

.UPDATE...
Issued at 942 PM MDT Thu Jul 14 2022

There is still some convection around, but it is slowly ending. The
best rainfall is occurring in the mountains but rates are fairly
low. Cell movement remains slow, under 10 mph. High resolution
models show the convection to be over by 06Z later this evening.
Will adjust some of the sky, pop, and wind GFE grids this update
with actual data in mind.
&&

.SHORT TERM...(This afternoon through Friday)
Issued at 317 PM MDT Thu Jul 14 2022

Key Messages

1. Increased threat for flash flooding over the burn areas tomorrow 
afternoon/early evening with a few stronger storms possible

2. Warm high temperatures tomorrow afternoon with mid-upper 90s 
over the lower elevations 

Showers and thunderstorms continue to develop this afternoon 
spreading eastward onto the plains. SPC mesoanalysis shows PW 
values increasing up to 0.9" across the plains and up to 0.7-0.8" 
over the higher terrain. Main concerns for the remainder of the 
afternoon/early evening will be gusty outflow winds, lightning 
with storms (up to 40-50 mph) and a threat for flash flooding over
the burn areas. 

Tomorrow remains to be a fairly active day weather-wise. An upper 
level ridge stays positioned over the region with a plume of richer 
moisture wrapping around through the Desert SW, extending into Utah 
and Colorado. Moisture in place will be above normal with PW values 
ranging 120-170% of normal shown by ensemble guidance. HREF 
guidance shows ensemble means with PW values around 1.2" over the
plains and 0.7- 0.9" for the higher terrain. A fairly strong 
shortwave trough moves over the north portion of the ridge through
the north Colorado border with QG ascent ahead of it. Instability
will be in sufficient amounts with MLCAPE 500-1000 J/kg over most
areas and strong lapse rates. This will support higher coverage 
showers and thunderstorms, first initiating over the higher 
terrain early afternoon, spreading eastward onto the plains into 
the early evening. 

The main concern for tomorrow will be the threat for flash flooding 
over the burn areas (See Hydrology section for more details). As a 
result, a Flood Watch has been issued for a good portion of the high 
country where the burn areas reside. In regards to severe storm 
potential, it will be limited. Shear appears to be on the weaker 
side with 0-6km bulk shear 20-25kts. Given the other indices in 
decent ranges, couldn't rule out a stronger storm or two. Soundings 
take on the inverted-V profile, indicating the main threat to be 
gusty outflow winds up to 60 mph. 

.LONG TERM...(Friday night through Wednesday)
Issued at 1010 AM MDT Thu Jul 14 2022

...EXTENDED PERIOD OF ABOVE NORMAL TEMPERATURES BUT A FEW EPISODES
OF MONSOONAL MOISTURE TO PROVIDE A LITTLE RELIEF...

A dominating ridge of high pressure will be centered near the Four
Corners for the vast majority of this forecast period. The result
will be a continuation of above normal temperatures and summer
heat, with a few bouts of monsoonal moisture and increased
thunderstorm activity to help offset the daytime heat.  

The main bout of thunderstorms that originates on Friday will be
shifting east across the plains during the evening, likely
organizing into a complex or mesoscale convective system with
support from a southeast low level jet and low/mid level theta-e
axis. We'll have the highest evening PoPs there. While the
mountains and I-25 Corridor airmass should generally be worked
over by tomorrow afternoon's convection, we expected to see at 
least scattered showers and thunderstorms continue due to upper 
level support from a short wave riding northeast across the top of
the ridge. Locally heavy rain will still be possible into the
evening hours given the proximity of this feature and precipitable
water values near 150% of normal (and near the max moving average
of sounding climatology). Some of those showers and storms may 
very well linger through the night and into Saturday morning with 
a continuation of weak upper level support. 

On Saturday, there is relatively low confidence in the forecast as
we'll be trying to get into a more subsident airmass and mid level
stabilization. However, lingering moisture may allow for more
instability and a chance of thunderstorms. Shear will also be
increasing so if we can break through the cap with sufficient
instability (MLCAPE 1000-1500 J/kg), a few severe storms would be
possible. At this point, the main threat appears to be shaping up
for the Palmer Divide area where cap would be the weakest and
perhaps some lingering upper level support depending on timing of
the upper level wave. Saturday should be the "coolest" day of the
upcoming seven day forecast with highs on the plains in the lower
90s.  

Sunday is still shaping up to be the driest day of the week as
northerly flow and drier air works into the forecast area as the
ridge retrogrades slightly and amplifies near the Four Corners.
The plains should be effectively capped off and/or too dry to
support any storm development, while we'll keep lower chances in
the high country. 

On Monday, a shortwave trough will move across the Northern
Rockies, while temperatures warm aloft over Colorado. The
increased westerly flow will result in downsloping conditions and
most likely the hottest day in this forecast cycle. Ensemble 
means show a high averaging at or just above 100F. As long as this
flow becomes more zonal by Monday, wedon't see any reason we 
wouldn't get to 100F or more across the I-25 Corridor. A Heat
Advisory may very well be needed for this time frame especially
since nighttime lows will stay well above normal as well. There
could be some relief late in the day, however, as mid level 
moisture advects into the region leading to scattered afternoon
convection. Denver's record high for July 18 is 99F, set in 2020,
2019, and 1998. 

Confidence in the forecast still starts to decrease by Tuesday,  
but it could another day of higher storm coverage behind a weak
cold front/additional low level moisture. However, these haven't
been panning out too well this year since were so warm and
generally stable aloft. Above normal temperatures will continue
through the latter half of next week, and ensembles are pointing
to less convective activity. That said, the mountains will still
likely see scattered storms each day, with lower coverage on the
plains. 

&&

.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 942 PM MDT Thu Jul 14 2022

There are still a few showers lingering around at DIA, but it
looks like the precipitation is over. Models show the drainage 
winds to kick in by 05Z, which seems reasonable. There could still
be a FEW-SCT050-070 cloud deck around through about 05Z, then 
ceiling issues are not expected. 

&&

.HYDROLOGY...
Issued at 230 PM MDT Thu Jul 14 2022

Another round of afternoon and evening thunderstorms will occur 
today. Moisture and instability will greater than yesterday so 
expect an increase in the number of storms and also an increase in 
intensity. The stronger storms will be capable of producing up to 
inch before they move on. This will lead to a slightly greater 
threat for flashing flooding and debris flows over the burn areas.

Abnormally high moisture will lead to widespread coverage of
storms on Friday. These storms will be strong and slow moving so
there is an elevated risk of flash flooding over the burn areas.
Locally heavy rain and minor flooding threat will even be possible
on the eastern plains due to slow movement and storms taking
advantage of an increasing southeasterly low level jet. That would
give some organization and threat of up to 2 inches or more of
rain from isolated stronger/training storms. 

The flash flood threat for the burn areas decreases on Saturday 
to limited as moisture and the coverage of storms lowers, at least
for the burn areas. Areas farther south toward the Palmer Divide
and Southern Front Range Foothills could still see locally heavy 
rain. Sunday will see a near zero threat for flooding but it 
can't be completely ruled out. There is a low/limited threat of 
flooding in burn areas most days next week. 

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Flash Flood Watch from Friday morning through Friday evening for 
COZ032>035.

&&

$$

UPDATE.......RJK
SHORT TERM...Mensch
LONG TERM....Barjenbruch
AVIATION.....RJK
HYDROLOGY....Mensch/Barjenbruch