Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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135
FXUS65 KBOU 191012 CCA
AFDBOU

Area Forecast Discussion...CORRECTED
National Weather Service Denver/Boulder CO
312 AM MST Sun Nov 19 2017

.SHORT TERM...(Today and tonight)
Issued at 240 AM MST Sun Nov 19 2017

Main concern over the next 24 hours will be the high wind
potential over the higher mountains and east slopes after midnight
tonight.

In the meantime for today, Colorado will be under a dry,
northwest flow pattern. Temperatures will be warmer today
as 700mb temperatures climb to around +0C by later today. This
will result in afternoon temperatures into the upper 50s and lower
60s across lower elevations with weak downslope flow. Some
increase in high level moisture today, but should have minimal
impact on temperatures.

For tonight, expect gusty west winds will increase over the
mountains after midnight. Cross sections show cross barrier flow
increasing to 40-50kt. There is a dry ripple in the flow aloft that
passes by around midnight with some weak subsidence with this
feature. Simulated WRF satellite water vapor imagery showing this
dry, subsident feature over the east slopes between 07z-11z before
passing off to the east. Could see some resultant wind gusts from
50 to close 70 mph but widespread 75 mph or more seems a stretch
so will not issue any high wind hilites at this time. Have
increased winds in the forecast for later tonight to account for
the winds.

.LONG TERM...(Monday through Saturday)
Issued at 240 AM MST Sun Nov 19 2017

Northwesterly flow aloft will increase Monday as a jet noses down
into the southern Great Plains. Cross sections show winds peaking
at 15z with 62 kts blowing perpendicular to the mountains. Some
downward QG vertical motion will help push these down the lee,
however there is not a good mean state critical layer set up to
really put the foothills and adjacent plains into a warning
criteria event. Believe we`ll see a few areas reach gusts of 65 to
70 mph, especially between sunrise and 10am, then should trend
downward. Winds will stay quite strong through the day over the
mountains, foothills and along the northern state border as the
jet finally peaks and moves off east Monday night. Speeds of 25 to
40 mph along with low humidity in the low teens will increase fire
danger - see fire discussion below.

Morning temperatures will be quite warm over the foothills and
urban corridor due to overnight downsloping winds. Since 700 mb
temperatures will also be warming 2-4 degrees, have increased
Monday`s expected max temperatures in these areas. Moisture in the
northwest flow will push into the mountains in the late
afternoon, with snow falling over the high country. Moisture isn`t
great, will likely see a quick 1-3 inches Monday night into
Tuesday morning. Moisture decreases, but just enough with
continued northwest flow will allow for light orographic snow to
continue through Tuesday.

Expect dry conditions across the area Tuesday through the weekend
as a ridge over the western and southwestern states moves east
slowly. A disturbance will produce weak cool down on Tuesday, back
to much warmer than average temperatures through Friday, before
another disturbance brings in another weak cooling for the
weekend.

&&

.FIRE WEATHER...
Issued at 240 AM MST Sun Nov 19 2017

The strong west-northwesterly winds expected Monday will push
across the northern plains with gusts of 25 to 40 mph possible.
Combined with humidity in the 12-16% range, critical fire weather
conditions may be possible. A Fire Weather Watch will be issued.

&&

.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 240 AM MST Sun Nov 19 2017

VFR with only some increase in high level moisture across
terminals today. General winds from the southerly direction today
and under 12kt. Expect some increase in winds tonight, especially
at BJC as mountain top flow increases and could see some gusts in
20-30KT range after 09z tonight.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Fire Weather Watch Monday late morning into early afternoon the
northern and northeastern plains, Fire Weather Zones
238...242...248...249... 250 and 251.

&&

$$

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



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