FXUS65 KBOU 161021

Area Forecast Discussion
National Weather Service Denver/Boulder CO
421 AM MDT Sun Jun 16 2019

.SHORT TERM...(Today and tonight)
Issued at 421 AM MDT Sun Jun 16 2019

Today is another day of subtle changes that will influence
thunderstorm possibilities. The lift associated with the low over
Texas and Oklahoma should be out of the picture today, so events
will be dominated by low level features. Over the western part of
our area conditions are similar to yesterday, except for a bit
more wind aloft. Over the eastern parts of the plains there will
be a bit more moisture, along with south winds developing during
the day. There is also a boundary coming out of the overnight
convection over northern Wyoming. This will likely stall somewhere
near the northern Colorado border, and probably retreat northward
a bit. Convection should then focus on this boundary in the
afternoon and send a new outflow boundary south into Colorado in
the late afternoon or early evening.

Once again, the initial air over the plains will be a little cool
for surface based convection, though it should get warm enough
late in the afternoon over the eastern portions. The big question
is how buoyant the air behind the boundary dropping southward
will be. If this is richer in moisture without being too cool, it
could support some evening storms over much of the area. This
would be the case if it's not fresh outflow winds but just the
more moist air dropping southward after being heated in the
afternoon. This might be more likely closer to the mountains where
the afternoon convection in Wyoming might be weaker/less
widespread. Further east we're more likely to have a cool outflow
boundary moving into slightly buoyant southerly flow. Either way
brings a chance of storms late in the day and into the evening.
CAPEs look to be around 500 J/kg in the initial air over the
northeast, but could be up to 1000 J/kg on the eastern border, or
behind the boundary along the northern border if it's not cooled
much. These areas have a chance for a marginally severe storm or
two. Over the mountains, a fairly high coverage of relatively weak
convection is expected again. There still could be some heavy
rain as the moisture hasn't changed much, but faster storm motions
will limit accumulation. There could be a bit more of a heavy
rain threat over the northeast corner where there may be some
backbuilding or training along the boundary if it stalls. Again,
this depends on how cold the outflow air is, but if strong
convection develops it should send the boundary southward, so the
training scenario shouldn't last for more than an hour or two.

Main changes at this time were to refine the timing of the
convection. A similar pattern to yesterday's mountain convection
is expected, at fist fizzling as the storms try to move east in
the early afternoon, but having better success later in the day
along with storms developing along the plains boundary and at
least isolated convection further south. We did lower PoPs on the
plains for the afternoon thinking that most of the activity will
be in the early evening. Forecast highs for today are a little
above guidance but seem alright as there should be sun for much of
the day on the plains.

.LONG TERM...(Monday through Saturday)
Issued at 421 AM MDT Sun Jun 16 2019

On Monday, there will be a period of weak QG ascent in the mid
levels as an upper level disturbance moves across northern
Colorado. Forecast soundings indicate the greatest instability in
the early part of the afternoon, before the mid and upper
portions of the sounding saturates. Forecast CAPES 1300-2300 j/kg
generated by the NAM12 in the 18-21z time frame. Better
directional shear in the lower levels at that time. The Storm
Prediction Center has most of eastern CO in the marginal risk for
severe thunderstorms Monday afternoon as this looks reasonable.
Only issue that may limit this is the cooler afternoon
temperatures. Precipitable water values close one inch as well,
so the threat of locally heavy rainfall also exists. On Tuesday,
more of the same with a cool and unsettled weather pattern. Best
instability Tuesday afternoon will be east of the urban corridor
with CAPES of 1000-1500 j/kg at that time. CAPES only around 500
j/kg in Denver. The sounding will be saturated with continued high
precipitable water values. The storms may not be as intense but
could still produce locally heavy rain and hail. Overall forecast
for the middle and latter part of the week does not change with a
warmer and drier trend for Wednesday through Friday. By Saturday
however, another potential trough may move across northern CO,
producing cooler temperatures and a better chance of showers and


.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 421 AM MDT Sun Jun 16 2019

VFR conditions will prevail through tonight. Scattered
thunderstorms are expected in the Denver area between 21z and 03z.
Localized MVFR visibilities are expected, along with areas of
ceilings below 6000 ft during this time. A couple of wind shifts
with gusts to 30 knots can also be expected.




SHORT TERM...Gimmestad
LONG TERM...Cooper
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