Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 231024

Area Forecast Discussion
National Weather Service Denver/Boulder CO
424 AM MDT Wed Aug 23 2017

.SHORT TERM...(Today and tonight)
Issued at 424 AM MDT Wed Aug 23 2017

Upper level ridge axis and light westerly flow aloft will remain
over the forecast area today. There is some mid/upper level
moisture in place per latest satellite imagery, but low levels are
drying out and will continue to do so today as airmass mixes in
westerly flow aloft. The exception will be farther east on the
plains where low level moisture should hold in place east of the
lee trough.

Scattered thunderstorms will first develop over the mountains and
then attempt to move east onto the plains. The storms will be
high based with large T/Td spreads around 45F during peak heating
and mixing along the Front Range I-25 Corridor, so gusty winds
and only light rainfall expected. Those storms will likely send
outflow boundaries eastward onto the eastern plains, and should
interact with the richer low level air and CAPES near 1000-1500
J/kg. At this time, expect a better chance of late
afternoon/evening storms roughly along/east of a Sterling to Akron
to Deer Trail line. Some of those storms may be stronger with
brief heavy rain, small hail, and gusty winds to around 50 mph.

Convection should dissipate rather quickly this evening with the
loss of daytime heating and lack of upper level support. Exception
would be over the far eastern plains and a few light showers
possibly lingering til midnight in the mountains.

High temperatures today will be a few degrees warmer on most of
the plains and cooler easterly flow is replaced by warmer
south/southwest flow. Should see most of the plains approach 90F.
Lows tonight will be a couple degrees above normal.

.LONG TERM...(Thursday through Tuesday)
Issued at 424 AM MDT Wed Aug 23 2017

Short to medium range models indicate that Thursday will have a
decent amount of subtropical moisture in place over the state as
an upper disturbance crosses over the region. NAM Model soundings
on the plains Thursday afternoon show CAPE values between 1500
and 2000 j/kg with precipitable water values around 0.95 inches.
This should make for an active afternoon as thunderstorms develop
over the mountains by early afternoon and then propagate onto the
plains. Hail, gusty winds and locally heavy rain will be the main
threats from the thunderstorm activity. Temperatures will be
slightly cooler due to the increased cloud cover by mid-afternoon
cutting off the afternoon warming.

From Friday through the first part of next week, a drying and
warming trend will develop as a strong upper ridge builds over the
Great Basin. Colorado will come under drier and more subsident
northwesterly flow aloft, downstream from the upper ridge axis.
Afternoon highs on the plains will peak in the upper 80s each day,
about 5 degrees warmer than seasonal normals.


.AVIATION...(For the 12Z TAFS through 12Z Thursday morning)
Issued at 424 AM MDT Wed Aug 23 2017

VFR conditions will persist through the period. Main concern will
be high based convection, which is most likely 21Z-01Z. There
should be enough convection in the area to produce variable and
gusty winds to around 35 knots, so will keep tempo gusty winds in
the forecast for that period. Chance of thunder and rainfall is
less and closer to 20-30% at any given airport. Outside of
convection, fairly normal and light diurnal wind patterns should
persist with speeds 5-12 knots.




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