666
FXUS65 KBOU 180151
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
751 PM MDT Mon Jun 17 2024

.KEY MESSAGES...

- Cooler Tuesday and Wednesday with a chance of showers and a few
  storms.

- Scattered thunderstorms Thursday into Friday.

- Hot and drier again by early next week.

&&

.UPDATE...
Issued at 751 PM MDT Mon Jun 17 2024

Going forecast on track with no changes planned. Airmass remains
very dry with only high-based cumulus clouds able to form. Cold
front located over central Wyoming will track southeast and push
across Colorado after midnight. This will usher in cooler air for
Tuesday.

&&

.SHORT TERM /Through Tuesday/...
Issued at 142 PM MDT Mon Jun 17 2024

Current surface observations show a notable N-S temperature/dewpoint
gradient across much of northeast Colorado early this afternoon.
Across areas such as the southern Foothills and east to Lincoln
County, SW winds have mixed down resulting in breezy conditions, low
relative humidity (< 15%), and hot temperatures (90F+). Locations
north of Denver have been slower to mix out. ACARS soundings still
show a weak stable layer along with persistent easterly flow
keeping temperatures cooler (80s) and dewpoints higher (50s). The
current trend is that gradually the environment will mix out
resulting in drying and warming from south to north for the
remainder of the afternoon. There is some uncertainty in how far
north things will mix/dry out. The main impact this will have is
on the fire weather conditions (Red Flag Warning). Most of this
uncertainty will be if conditions end up hitting criteria for in
spots. See fire weather discussion for more details.

There is a Slight Risk for the far northeast corner through
tonight for severe thunderstorms; however, this is still looking
like a low chance (<20%) given the capped environment. If
something initiates, a few severe storms with large hail, severe
wind, isolated tornado are possible given the environment.

A cold front moves across the region overnight with easterly upslope
winds setting up behind it across the plains for much of tomorrow.
This will bring much cooler temperatures for tomorrow with highs in
the 70s across the plains. Model soundings show a stable and fairly
dry environment for most of the region. An axis of marginal
instability over the higher terrain, mainly south of I-70 will
support a few high-based showers/storms in the afternoon.

&&

.LONG TERM /Tuesday night through Monday/...
Issued at 230 PM MDT Mon Jun 17 2024

Just enough mid level moisture and instability should be present
for a few showers and isolated thunderstorms Tuesday night. This
appears to be aided by the right entrance region of an upper level
jet streak, so showers could linger overnight. Overall, we could
see scattered coverage with the showers shifting slowly east
across the plains overnight with the departing speed max. However,
it all looks fairly weak at this point with rather meager low
level moisture.

For Wednesday, moisture values increase along/east of the
Continental Divide with a return flow of moisture in southeast low
level flow. Instability is still limited, but overall the
additional moisture should contribute to a little more intensity,
but still scattered coverage. Temperatures will remain on the
cooler side with a fair amount of clouds and cooler high pressure
locked in east of the Divide.

Thursday could see a threat of stronger thunderstorms due to a
combination of increased low level moisture and warmer
temperatures. There is reasonable agreement in the ensembles that
MLCAPE grows to 1000-1500 J/kg, although it`s a weakly sheared
environment so mainly pulse type storms expected. Convective
coverage should be about the best of the week ahead should the
moisture and instability come together as advertised. And the
same could be said for Friday as ensembles are pointing to a surge
of subtropical moisture arriving from the south and southwest.
That would support a deeper moisture profile more favorable for
locally heavy rainfall, so something to watch over the next couple
days to see if that plume remains consistent.

For next weekend into early next week, there is excellent
agreement between the GEFS and EPS that an upper level ridge will
be building over the Central Rockies. This would support a return
of hot and dry weather, with the hottest temperatures (mid to
upper 90s for the plains) likely returning by Monday.

&&

.AVIATION /00Z TAFS through 00Z Tuesday/...
Issued at 526 PM MDT Mon Jun 17 2024

Gusty southwest winds have finally moved through APA and DEN with
a cyclone located to the north of DEN. This will continue to
bring northwest winds to BJC. Because of the cyclone, believe
winds will turn west to northwest 00-01Z. By 04-06, winds will
become a southerly drainage direction as the cyclone dissipates.
The south winds will be short lived as a cold front pushes through
around 08Z bringing northwest winds at first. Winds quickly turn
north to northeast behind the front.

For Tuesday, easterly winds set in by 18Z with gusts to 25 knots.
Scattered showers are expected to form after 21Z. Don`t think the
showers will impact DEN much with ceilings stay above 6000 feet.

&&

.FIRE WEATHER...
Issued at 142 PM MDT Mon Jun 17 2024

Areas across the southern Foothills, Park County, Grand County,
Elbert and Lincoln counties have been approaching/hitting Red Flag
criteria this afternoon. Areas north such as Denver, Boulder,
northern Jefferson, Washington, Morgan counties still remain unmixed
resulting in dewpoints in the 50s. From south to north, this
"boundary" should slowly move northward with the environment mixing
down drier air and gusty SW winds. However, there is some question
on how "north" this boundary goes. Counties such as east Boulder,
Morgan, Washington counties may struggle to mix out quick enough
with peak heating keeping them out of RFW criteria.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning until 9 PM MDT this evening for COZ213-214-216-
239>241-244>247-249.

&&

$$

UPDATE...Meier
SHORT TERM...Mensch
LONG TERM...Barjenbruch
AVIATION...Meier
FIRE WEATHER...Mensch