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193
FXUS65 KBOU 222118
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
318 PM MDT Fri Sep 22 2017

.SHORT TERM...(This evening through Saturday)
Issued at 318 PM MDT Fri Sep 22 2017

An upper level trough spinning over the Great Basin and Northern
Rockies will slowly shift eastward tonight and Saturday. Airmass
has becomes unstable over the mountains and nearby plains this
afternoon ahead of the upper level trough. Expect isolated to
scattered showers and storms to move across the higher terrain
through early evening. These storms will be quick moving due to
the strong flow aloft. Brief heavy rain, small hail, and wind
gusts to 50 mph will be possible with the thunderstorms. A cold
front will drop south across the eastern plains late this
afternoon and evening. Moisture will increase behind it. Expect a
few showers and storms to move onto the plains late this
afternoon and evening.

A moist east to southeast low level flow will bring cool and
cloudy conditions Saturday. Models show an area of rain over the
eastern plains during the late morning and afternoon associated
with the right entrance region of the jet. Will have 60-80 pops in
this area. Expect lighter precipitation for the higher terrain
and Front Range. Models have a large difference with temperatures
for Saturday. The NAM is showing upper 40s and lower 50s while the
GFS shows 60s for northeast Colorado. Will lean towards the
cooler NAM because of the expected cloud cover, but will not go as
cold.

.LONG TERM...(Saturday night through Friday)
Issued at 145 PM MDT Fri Sep 22 2017

The upper low will bottom out over Southern Utah by early Sunday
morning providing moderate QG ascent over much of Northern
Colorado. Will have likely pops for much of the area Saturday
night and Sunday with the highest pops over the Eastern plains.
The moisture further west is more shallow as mid levels are
rather dry with the strong southwest flow aloft. Some light snow
expected over higher elevations in the mountains, mainly above
9500 feet.  The low will then begin to slowly weaken and lift out
into Wyoming on Monday. However more troughiness will drop back
into the mean trof position through much of next week. Temperatures
will remain below normal for much of next week with a continued
chance of showers.

&&

.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 318 PM MDT Fri Sep 22 2017

Isolated high based showers will slowly spread east through this
evening. Just a slight chance for a thunderstorm, not a large
enough chance to mention in the TAFs at this time. West to
northwest surface winds are expected to prevail at the Denver
airports behind a surface low over eastern Colorado.

Clouds will increase tonight. By 12Z, low clouds are expected to
form with ceilings falling to 2000 to 4000 feet by 18Z. Rain
showers will be likely Saturday afternoon, with a slight chance
for thunderstorms.

&&

.FIRE WEATHER...
Issued at 318 PM MDT Fri Sep 22 2017

Will let the Red Flag Warning continue through early evening.
Winds are gusting to 40 mph will relative humidities in the teens
along the Palmer Divide and near by plains. Relative humidities
are just above the 15 percent criteria for Red Flag Warnings in
many places, however since winds are well above threshold and
humidities are very close to threshold will leave the warning in
effect.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning until 7 PM MDT this evening for COZ241-244>247-
249.

&&

$$

SHORT TERM...Meier
LONG TERM...Entrekin
AVIATION...Meier
FIRE WEATHER...Meier