Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 211655

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1055 AM MDT SAT MAY 21 2016

Issued at 1055 AM MDT Sat May 21 2016

No big changes to the forecast at this time. The latest runs of
the HRRR and RAP models are now showing the afternoon convection
occurring in western Kansas, keeping northeast Colorado dry. A
model sounding from the northeast corner of Colorado shows that
the afternoon airmass will remain capped. Will still hold on to
the isolated showers that are already in the forecast. The showers
that do develop will have the potential to be strong, but they
should be east of our forecas tarea. Have also held on to the
isolated showers that are expected to develop over the northern
Front Range foothills.

Temperatures have been warming about as expected and some
increasing southwest winds have been noted over Douglas County and
the Palmer Divide. This was all expected as southwest flow aloft
will be increasing statewide through the afternoon.


.SHORT TERM...(Today and tonight)
Issued at 450 AM MDT Sat May 21 2016

Plume of low level moisture has moved across northeastern Colorado
with drier air near the foothills. Low clouds and areas of drizzle
out there, but it appears that there is enough mixing for the
clouds to mainly be off the ground so only limited fog. Expect the
current wind pattern to continue with the exception of a bit more
development of a Denver cyclone circulation this morning. This
will help some of the moisture get wrapped back along the
foothills by midday, at least toward Fort Collins and Boulder. By
this afternoon increasing southerly winds should redevelop a
dryline from the Denver area toward Limon with drier air coming
off the mountains of southern Colorado. There may be a sweet spot
between the colder air to the northeast and drier air to the
southwest where it gets warm enough to generate thunderstorms
before the drying moves in. Washington county looks most likely,
with any storms that would develop moving NNE and posing a severe
weather threat. With temps around 80 and dew points still around
50, CAPES would be around 2000 j/kg and with 15 knot east winds as
in the HRRR helicities would be 100-200 m2/s2. Not the sharpest
low level turning but a good supercell environment if it gets
warm/moist enough. However the air aloft is pretty warm so there
is a chance that this will not happen at all, with the better
threat further southeast in western Kansas where there will be
more moisture and thus less capping.

Further west only isolated weak convection is expected, possibly
nothing at all over the central mountains and Palmer Divide areas.

For tonight any diurnal thunderstorm activity should be moving
quickly northeast with the weaker activity over the west
dissipating. There will be some cooling aloft and moisture moving
into the mountains later tonight, so there may still be a slight
chance of light showers there. Meanwhile, the moisture plume will
continue to flow over the northeast corner with a chance of
stratus/drizzle/fog in the late night hours.

.LONG TERM...(Sunday through Friday)
Issued at 450 AM MDT Sat May 21 2016

On Sunday...a strong southwesterly flow aloft will be over CO
with an embedded disturbance moving across the cwa. The models
lift the surface trough to northeast CO by 12z Sunday morning.
Weak westerly winds in the morning will transition to gusty
southerly winds in the aftn. There is some weak mid level qg
ascent during the day. NAM12 capes around 300-400 j/kg at Denver
and 600-700 j/kg over far northeastern CO. Tstms will be high
based with the lower levels drying out as the drier southwesterly
winds aloft mix down to the this likely the main
threat with the storms. The best lift/mstr will be in the best coverage will be there. Sunday night into
Monday...the mdls show stronger mid level qg descent. The
southwesterly flow aloft will be a little weaker...with cooler
north/northwesterly winds at the surface following the passage of
a cold front Monday morning. The best chance of tstms Monday will
again be in the high country with lesser chance across the
northeast plains with stronger subsidence there. On Tuesday...the
upper trough to the west will stretch from central CA into MT with
a moderate to strong southwesterly flow aloft over CO. The best
chc of tstms will be over the northeast corner of the state with
some potential for severe with a better shear profile present with
a there along with deeper low level moisture. Sely winds on Tue
may help produce a Denver Cyclone which could help produce some
strong/severe storms in the aftn. For late Thu into Fri the
GFS/ECMWF and Canadian all eject the trough fm southern CA at 00Z
Thu into swrn CO by 00Z Fri. The best chc of pcpn for the cwa may
be Thu night into Fri if these solutions pan out.


.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 1055 AM MDT Sat May 21 2016

An area of fog approached the airport from the north this morning,
but mid-morning warming helped it dissipate before causing any
operational impacts. Southerly winds are expected to continue
through this afternoon as high level clouds gradually increase.
Aviation impacts at Denver area airports should be minimal today
and tonight.


.BOU Watches/Warnings/Advisories...


SHORT TERM...Gimmestad
LONG TERM...Cooper
AVIATION...Dankers is the U.S. government's official web portal to all federal, state and local government web resources and services.