849
FXUS65 KBOU 102340
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
540 PM MDT Mon Jun 10 2024

.KEY MESSAGES...

- Scattered thunderstorms this afternoon. A few strong to severe
  storms along with a risk of heavy rain, localized flooding with
  some storms.

- Snowmelt producing minor impacts from high streams, mainly in
  Grand County.

- Hot and mainly dry weather is expected Wednesday and Thursday.
  There is potential for a Heat Advisory on Thursday depending on
  the timing of the cold front.

- Cooler conditions will arrive Friday and Saturday with scattered
  showers and storms. Some of these storms could be strong to
  severe with heavy rain.

&&

.SHORT TERM /Through Tuesday/...
Issued at 201 PM MDT Mon Jun 10 2024

Airmass is unstable again this afternoon with MLCAPE of 700-1500
J/kg. Sounding out of Fort Collins shows a capped airmass until
temperatures reach the mid 80s. An upper level trough moving
across the Northern and Central Rockies will provide lift for
thunderstorm develop and help overcome the cap in places. Models
generally agree a broken line of storms move across the Front
Range and nearby plains. As this line progresses eastward into the
more moist and unstable air, the line of storms fills in. Threat
for severe storms is low today because of the lack of shear.
However, a few brief severe storms will be possible with hail
slightly larger than 1 inch in diameter. Heavy rain could cause
localized flooding, where storms reform or remain stationary. The
stronger storms are expected to be east of the area by mid evening
with a few weaker storms lingering to around midnight.

Weak cold front drops south across the area after midnight. The
slightly cooling with the cold front will keep highs in the 80s
over northeast Colorado. The airmass dries with precipitable water
falling a little below an inch and dew points dropping into the
upper 40s to lower 50s. Airmass remains unstable with MLCAPE
climbing to 500-1500 J/kg. An upper level ridge begins to build
over Colorado Tuesday, bringing warmer air aloft. Even though the
airmass will be moist and unstable, the warming aloft will cap
convective development for most places. Storms may be able to
break through the cap over/near the Palmer Divide. If storms are
able to form, they`ll drift east-southeast across Lincoln County.
Can`t rule out a brief severe store with one inch hail, but the
lack of shear will keep most storms sub severe.

&&

.LONG TERM /Tuesday night through Monday/...
Issued at 201 PM MDT Mon Jun 10 2024

Colorado will be under the right exit region of a mid to upper
level jet on Wednesday with strong subsidence creating hot and
dry conditions. Ensemble guidance has locked in on highs in the
mid 90s across the I-25 corridor. The NBM 50th percentile and
ECMWF ensemble MOS 50th percentile both have a high of 95 F in
Denver so the forecast is exactly that. A high of 95 F would be
only 2 degrees from the record daily high of 97 F in Denver set
in 1952. With such strong subsidence, some of the CAMs are showing
no rain at all. It can`t be ruled out that a couple light showers
form, however.

The axis of a strong ridge aloft will be over Colorado on Thursday
with 500 mb heights of 2 standard deviations above normal.
Meanwhile, there will be a shortwave trough that will move over
Lake Superior during Thursday afternoon. There is a cold front
associated with this trough that will move through northeast
Colorado during the day on Thursday. Recent model runs have been
slightly more progressive with this front and have it moving
through Denver in the early afternoon. Some ensemble members are
starting to show highs in the 80s on Thursday which would be the
cool scenario. However, the majority of the ensemble members
still have a high in the mid to upper 90s in Denver and the rest
of the plains. Given the majority of ensemble runs have such warm
conditions and there will be very warm air aloft, the forecast
high in Denver was left at 97 F. There is still a chance that
Denver reaches close to 100 F which would require a Heat Advisory
given the early season heat. There is still not enough certainty
to issue a Heat Advisory so no highlights are in effect.
Otherwise, the steep lapse rates will allow for some showers and
perhaps a storm to form. There will be more wind than rain with
these showers and storms.

A decently strong shortwave trough for mid June will move through
Colorado Friday afternoon. At the surface, there will be lee
cyclogenesis over eastern Colorado with southeast surface winds.
These winds will draw in moisture and there will be moderate
instability. With moderate southwest winds aloft and southeast
winds at the surface, there will be moderate deep layer shear.
All of the parameters seem to be coming together for an active
severe weather day. Large hail and damaging wind gusts will be the
primary threats.

Thunderstorms will again be possible on Saturday but there will be
lower coverage than Friday. Ridging will build in on Sunday with
southwesterly flow throughout the atmosphere. Given the downslope
flow and plenty of sunshine, ensembles have locked in a very hot
day for Sunday. Highs could reach the upper 90s across the plains.

&&

.AVIATION /00Z TAFS through 00Z Tuesday/...
Issued at 534 PM MDT Mon Jun 10 2024

Threat of storms at DIA appears to be diminishing as outflow
boundary is moving across with a westerly wind shift.  Winds
by 01z may trend back to more SW or SSW unless outflow boundary
from convection to the northeast moves across with a NE wind
shift. Not confident on winds by mid to late evening as they
could just transition to drainage. On Tue, light and variable
winds in the morning will become light east by 19z. Otherwise VFR
conditions thru the period.

&&

.HYDROLOGY...
Issued at 201 PM MDT Mon Jun 10 2024

Winds aloft remain weak today, leading to slow storm motions, but
a bit faster than Sunday. Heavy rain from slow moving storms
could produce localized flooding.

Elevated flows continue across the upper Colorado River basin.
Remain cognizant of the dangers of these cold flows, and be aware
of any Flood Advisories and Warnings. Flow may increase mid to
late week as warmer temperatures return to the area.

&&

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

&&

$$

SHORT TERM...Meier
LONG TERM...Danielson
AVIATION...RPK
HYDROLOGY...Meier