National Weather Service Raw Text Product

790 
FXUS65 KBOU 160214
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
714 PM MST Wed Dec 15 2021

.UPDATE...
Issued at 702 PM MST Wed Dec 15 2021

Winds have clamed down in most areas. However, satellite
data shows enhanced subsidence in the nrn foothills. This is
allowing for wind gusts in the 50 to 60 mph range in the normal 
windy areas. Cross-sections show gusty winds may last through the
night with a few gusts up to 70 mph possible in and down to the
base of the foothills. Can't rule out an isold higher gust or two, 
however, don't think these gusts will be widespread enough for
reissuing a high wind warning at this point.

Meanwhile, areas of light snow continue in some higher mtn areas 
with blowing snow. Doesn't appear to be that widespread so will 
let advisory expire at 8 pm.

&&

.SHORT TERM...(This evening through Thursday)
Issued at 108 PM MST Wed Dec 15 2021

GOES-16 Water Vapor shows the comma head moving across western 
Kansas. Broad and strong subsidence has taken over eastern
Colorado and will continue through this evening. The DEBRA dust 
satellite product shows the extent of the dust across SE CO and 
all of W. KS. There is a fair amount of dust across the northeast 
corner of Colorado, but with mid level clouds we can't see it on 
satellite but ASOS and trained spotters have been all over it. 
Will keep dust in the forecast through this evening across mainly 
the northeast corner. With the strong subsidence and departing 
short wave trough, the mountain wave is in the process of breaking
down, and by 3-5 PM winds in the foothills and west of I-25 will 
weaken significantly. Winds across the far eastern plains will 
remain up for a few more hours than that because those areas are 
more dependent on the surface pressure gradient, which will take 
longer to relax. Expect a few more hours of gusts to 80 mph in the
favored windy spots west of I-25, and gusts across the far 
eastern plains around 70 mph through 5-7 PM. Elsewhere, like much 
of central metro Denver north to Fort Collins and Greeley, should
see gusts 30-50 mph through 5 PM. The RFW will continue through 5
PM given the high winds and relatively low RH.

In the mountains, snow rates have come down this afternoon but
with upslope and moisture, light snow will continue through about
midnight with another 1-3" possible. With the wind and light snow,
roads have been slow to recover across the less traveled mountain
passes, so will keep the advisory going through 8 PM. Expect it 
to be seasonably cold across much of the area tonight with 
weakening winds, mostly clear skies, and snow cover in the 
mountain valleys. Lows tonight should be in the single digits in 
the mountain valleys, and teens across the plains other than the 
urban heat islands where lows should remain in the low 20s.

Southwest flow aloft is expected Thursday ahead of another trough
moving across the northern Rockies. Lapse rates improve
significantly above the mountains vs today, and combined with 
some moisture in the upslope flow, light snow is possible starting
late Thursday morning across the higher elevations. Very little 
accumulation is expected most areas though the higher totals 
should be for the Park Range where several inches look likely 
Thursday into Friday. 

Across the plains, southwest low-level flow combined with 
southwest flow aloft will result in a decent warm up. It will be 
very dry across the plains with RH dropping to 15-20 percent below
6,000 ft elevation. Elevated fire wx conditions are expected 
along and east of the Palmer Divide but winds may remain just 
below RFW criteria during the afternoon hours. It should be breezy
along and southeast of I-76 during the afternoon. Highs should be
in the low 50s across the plains, with 30s in the mountain 
valleys.

.LONG TERM...(Thursday night through Wednesday)
Issued at 108 PM MST Wed Dec 15 2021

Thursday night and Friday, an upper level trough will move across 
the Central and Northern Rockies. Increasing moisture combined with 
cold air advection and orographic lift will produce snow in the 
Mountains Thursday night and Friday. The best chance for 
accumulating snow should be before midnight due to a 100KT upper 
level jet over the area. Snowfall amounts are expected to range 
between 1 and 6 inches, heaviest over the Northern Gore and Park 
Ranges. Dry conditions are expected east of the mountains due to a 
downsloping flow. Cooler temperatures and breezy conditions 
(northern and eastern sections) of the plains are expected on Friday 
behind the passage of a weak cold front. 

Dry and warmer weather is expected on Saturday as an upper level 
ridge of high pressure builds over the Rocky Mountain Region. For 
Sunday through Tuesday, an upper level trough of low pressure is 
progged to develop just off the west coast of the U.S. with a dry 
west to southwesterly flow aloft over Colorado. This pattern should 
result in continued dry weather and above normal temperatures across 
the forecast area. 

On Wednesday, the mountains could see another round of snow as 
energy and moisture from the Pacific start to make its way into 
Western Colorado. 

&&

.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 702 PM MST Wed Dec 15 2021

Winds have been all over the place but have gone back to a more
westerly direction. HRRR has been all over the place with
directions this evening and overnight. Confidence in wind 
forecast overnight is low at best. Would think they would
eventually go more SSW in the 04z-06z timeframe. 

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 8 PM MST this evening for COZ031-
033-034.

&&

$$

UPDATE...RPK
SHORT TERM...Schlatter
LONG TERM...jk
AVIATION...RPK