Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 101641

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1041 AM MDT Thu Aug 10 2017

Issued at 1030 AM MDT Thu Aug 10 2017

Northeasterly push currently seen in observations and on satellite
over the northeast corner of the state. This will help provide
lift early this afternoon for storms that fire off the high
terrain. Ample sunshine over the rest of the plains will allow for
surface heating to help increase CAPE values this afternoon.
Several models continue to show 1000-1500 J/kg over the plains,
with areas over 2000 J/kg down over Lincoln County. Bulk shear of
upwards of 50-60 kts will provide storms an environment to become
strong to severe strength. Environment will be suitable for large
hail, up to golf balls with the strongest storms, heavy rain, and
strong damaging outflow winds near 60 mph. An isolated tornado
can`t be completely ruled out due to the shear. The best area for
the strongest storms will be over far eastern Elbert and Lincoln
counties. Other areas over the plains could see smaller hail and
gusty winds this afternoon.


.SHORT TERM...(Today and tonight)
Issued at 255 AM MDT Thu Aug 10 2017

A disturbance embedded in the westerly flow aloft is expected to
keep isolated/showers and thunderstorms going through mid morning.
Expect a lull in activity late this morning before convection
reforms this afternoon due to day time heating. A cold front will
push south across northeast Colorado early this afternoon.
Northeast upslope flow behind it will help produce lift and
trigger storms. Thunderstorms development is expected to spread
from north to south through the afternoon and early evening hours.
Chances for severe weather should be limited to the plains south
of I-70. Later arrival of the cold front will allow for more
heating and a little better instability. Hail up to one inch in
diameter and wind gusts to 60 mph will be the main severe threats.
High temperatures today are expected to be cooler due to cloud
cover and a cooler airmass moving in behind the cold front.

Convection is expected to end early to mid evening as the best
lift sinks into southern Colorado. Will have the mention of
showers and storms through most of the evening, then dry after
midnight. Clearing skies and a moist layer of air near the surface
should produce low clouds and patchy fog across northeast
Colorado tonight and into Friday morning.

.LONG TERM...(Friday through Wednesday)
Issued at 255 AM MDT Thu Aug 10 2017

The airmass over north central and northeast Colorado will remain
moist on Friday. In the morning, there will be a fair amount of
low clouds or fog backed up against the Front Range through the
mid morning hours. A moderate west to northwesterly flow aloft
will be in place over the state, with an east/southeasterly flow
at the surface. NAM12 forecast soundings still advertise high
CAPE values in the afternoon, 1500-1800 J/kg. Precipitable Water
values still around one inch. SPC has most of the northeast plains
of Colorado in a marginal risk for severe and this looks
reasonable at this time with large hail and damaging winds the
primary threat. However, plenty of cloud cover around could
hinder the heating which may limit the severe thunderstorm threat.
Storms will likely initiate off the higher terrain than spread
into the adjacent plains. The pattern will remain unsettled on
Saturday and Sunday. The lower levels are progged to dry out
across the Urban Corridor but deeper moisture still present
further east. The flow aloft will remain northwesterly through
Sunday, so will continue to keep sct pops in the grids for most of
the cwa in the aftn and evening hours. Lesser pops along the
urban corridor where it will be drier in the lower levels. The
ridge aloft is still progged to build some for early next week,
with the axis shifting over the state. Warmer temperatures with
more subsidence in the mid levels should help limit the
thunderstorm development to some degree in the aftn and evening.
For now will continue with the trend of warmer and drier next
week. In spite of the warming trend, the temperatures overall will
continue to run below average.


.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 1030 AM MDT Thu Aug 10 2017

Mid and high clouds will stream across the area with ceilings
above 6000 feet. A front will cause winds to turn northeasterly
around 20Z. There will be a good chance for thunderstorms across
the Denver area from 19Z to 01Z. Added a tempo for the expected
thunderstorms. Ceilings could approach MVFR in stronger storms.
Low clouds and fog will form over northeast Colorado after 06Z
Friday. Ceilings are expected to drop below 1000 feet with a good
chance for fog and visibility of a quarter mile or less for Friday




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