Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 201238
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
538 AM MST Mon Nov 20 2017

.UPDATE...
Issued at 534 AM MST Mon Nov 20 2017

Updated for Red Flag warning for fire weather zone 238 this
morning. See fire weather discussion below.

&&

.SHORT TERM...(Today and tonight)
Issued at 343 AM MST Mon Nov 20 2017

Main concerns today will be strong winds in the mountains and
foothills along with elevated fire danger over portions of the
northern plains this afternoon.

Current observations showing wind gusts in the mountains and
foothills mainly in the 25-45 mph range with a few higher gusts of
50 to 65 mph over Berthoud Pass and wind prone areas of the
northern foothills. Radar showing some increase in wave
enhancement of the winds in the past hour and would expect that to
continue through daybreak. Latest model data continues to keep
the higher winds below 70 mph so will not issue any wind hilites,
especially given approach of upper jet and increased shear
profile, and lack of any strong subsidence today.

Temperatures will be a little warmer today but will go a few
degrees below MOS guidance given quite a bit of cloud cover
upstream which will continue to spread over the area. Still
readings into the 60s, well above seasonal normals for this time
of year.

For tonight, moisture depth increases in the mountains with
approach of upper wave/jet max with brunt of snowfall expected
after 06z. Decent orographic flow but lapse rates only in the
3-6C/KM range so will keep accumulations in the 1-4 inch range
tonight. May see a few rain showers on the eastern plains as
strong jet max aloft moves over the area. Main change to the
mountain forecast was to delay chances of snow until mainly later
this evening and overnight.

.LONG TERM...(Tuesday through Sunday)
Issued at 343 AM MST Mon Nov 20 2017

Snow in the mountains will be decreasing Tuesday morning as the jet
max over the forecast pushes southeast. The energy may produce a
few showers over the plains as a cold front pushes down as well.
Maximum temperatures will be similar to todays readings in the
mountains, but about 10 degrees colder behind the front over the
plains. The Jet core will push east of the area Tuesday evening
with the upper ridge over the western states to push closer. A
surface lee trough will develop overnight to keep minimum
temperatures moderated in and against the foothills.

Some light moisture rounding the top of the ridge will push into
the mountains in the favored northwest flow Wednesday for isolated
to scattered light snow showers. Otherwise, global models are in
agreement with having a dry and unseasonably warm period Wednesday
through the weekend as the ridge dominates. High temperatures
will generally be 10-20 degrees warmer than climatologically
average for late November. Readings will be in the 60s, and even
70s on Thursday and Friday over the plains. The mountains will see
highs in the 40s and 50s. Models then diverge with the breakdown
of the western US upper ridge for the beginning of next work week.

&&

.AVIATION...(For the 12Z TAFS through 12Z Tuesday morning)
Issued at 343 AM MST Mon Nov 20 2017

Mountain wave conditions expected today with main impact over BJC
with potential of some gusts in the 30-45kt range this morning.
Strong surface gradient in place so may also see some gusty winds
surfacing up to 25kt at KDEN later this am and afternoon. Varying
amounts of middle and high level cloudiness today. Weak
disturbance will move across later tonight but any showers look to
remain east of the local terminals.


&&

.FIRE WEATHER...
Issued at 534 AM MST Mon Nov 20 2017

Fire zone zone 238 is already experiencing red flag conditions
so will start the warning now with low humidities and gusty
winds.

For the rest of the area, have upgraded the fire weather watch to
red flag warnings for portions of the northeast plains,
especially near the northern border areas with Wyoming and
Nebraska. Expect low humidity values and enough mixing to result
in gusty winds to 30 mph by late this morning. will not have a
red flag warning over the foothills as modest amounts of qpf
occurred a few days ago and land managers have deemed the southern
foothills not dry enough for rapid fire growth.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning from 11 AM this morning to 5 PM MST this
afternoon for COZ242-248>251.

Red Flag Warning until 5 PM MST this afternoon for COZ238.

&&

$$

UPDATE...Entrekin
SHORT TERM...Entrekin
LONG TERM...Kriederman
AVIATION...Entrekin
FIRE WEATHER...Entrekin



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