Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 140359
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
959 PM MDT Fri Apr 13 2018

.UPDATE...
Issued at 955 PM MDT Fri Apr 13 2018

Winter weather advisory was allowed to expire earlier this evening
as snowfall continues to decline in the high country. The High
Wind Warning and the Blizzard Warning will remain in expect even
though wind speeds were on the decrease as well las snowfall
rates. Many roads remain either closed or restricted on the
plains roughly east of a Ft. Morgan to Strasburg to Limon line due
to strong winds, drifting and poor visibilities. No indication
from CDOT when these roads will open, however weather conditions
should gradually improve overnight as the potent storm that
produce this severe winter weather slowly moves away from
Colorado. Otherwise made only minor changes to ongoing forecast.
Changes include reducing snow totals in the Sterling area as
little snow fell in this area, adjusting sky cover to account for
the clearing already underway over northern portions of the I-25
urban corridor, and sped up the reduction in wind speeds in most
areas.

&&

.SHORT TERM...(This evening through Saturday)
Issued at 403 PM MDT Fri Apr 13 2018

Howling blizzard continue across the northeast corner of Colorado
this afternoon, through warm temperatures have limited the impact.
Places like Sterling and Limon have been warm enough that not much
snow has accumulated, while places a couple degrees cooler such as
much of Washington county have had more snow and ferocious blowing
and drifting. Meanwhile the winds further west have not
disappointed. We`ve received a lot of reports of minor wind damage
and there are lots of power outages in the eastern portions of the
plains.

Current thinking is that the main snow band will sit where it is
through mid evening, then start to creep eastward. There is a bit
of lift and better moisture rotating around further west toward
Denver, which has started to produce some shower bands. Our midday
update raised PoPs and allowed for some minor accumulations with
this, but we don`t expect anything more than that. With warm
roads, there shouldn`t be any travel impact for the Front Range
cities. Big question of the day has been the west fringe of the
blizzard warning. Sterling has been warm and the little snow that
fell there melted, but this will fill in again and they should get
a couple inches overnight. It gets much worse outside of the South
Platte valley. Expect Fort Morgan to be a little drier than that,
probably some light accumulation. Limon and the Palmer Divide will
get the benefit of the upslope wind, but in a still rather dry
airmass. They may have steady snow, but not heavy. The colder
parts could get a couple inches of snow and have some drifting,
but we don`t expect blizzard conditions.

As for the winds, the best pressure gradient is probably now
through early evening as the pressure falls in the trough axis
slide to the east. Winds will probably drop below warning criteria
after midnight but will still be close, and then come up a bit
with mixing during the day Saturday. Enough of a threat to keep
the warning going into Saturday afternoon, though zone 41 may be
questionable and we may be able to drop that later this evening.

Mountain snow was in a lull at midday, but convective showers are
breaking out, so we will hang on to the advisory through mid
evening. No changes for Saturday, clearing but windy and warmer.

.LONG TERM...(Saturday night through Friday)
Issued at 403 PM MDT Fri Apr 13 2018

Saturday night a deep upper level low pressure system will be over
the Midwest, with an upper level ridge of high pressure over the
western U.S. Colorado will lie between these two systems under a
strong northwesterly flow aloft. This pattern should result in dry
weather east of the mountains with breezy conditions across the
far northeast plains. There will be enough moisture combined with
orographic lift to produce scattered snow showers in the
mountains.

Warmer, drier and less windy weather is expected on Monday as the
upper level ridge of high pressure moves over the Rocky Mountain
Region. Temperatures on the plains should be 10 to 15 degrees above
normal with the exception of the far northeastern corner due to
lingering snow cover and wet ground. The warm weather weather
combined with low relative humidity and some wind may result in
elevated fire weather conditions from South Park eastward across the
southern foothills and Palmer Divide.

On Tuesday, a quick moving storm system will move across the central
and northern Rockies. This system should bring increasing wind to
north central and northeastern Colorado, especially across the
plains behind the passage of a cold front. The gusty winds
combined with low relative humidity may result in another day with
elevated fire danger mainly across southern sections of the CWA.
The mountains should see some light snow during the day with the
possibility of some locally heavier snow after the trough passage
due to cold air advection, greater instability and better
orographics.

Upper level high pressure forecasted to build over the Rocky Mountain
Region Wednesday and Thursday should lead to dry weather across
all of the CWA. This pattern would suggest much above normal
temperatures. However, east to southeasterly flow at the surface
due to the gradient between surface high pressure over the
northern plains states and lower pressure over Colorado will keep
temperatures on the plains at or slightly above normal values.

By end of the work week, a deep upper level low pressure system is
forecasted to move into Colorado from the west. The models have been
consistently showing this pattern over the past few days. This storm
has the potential to produce significant weather across north
central and northeastern Colorado starting on Friday with much needed
precipitation, heavy snow in some areas and even some severe weather
not out of the question. It all depends on the track and speed of
the system. We will need to keep a close eye on this system over the
next several days.

&&

.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 955 PM MDT Fri Apr 13 2018

Conditions will continue to improve in the Denver metro area rest
of tonight as drier air spreads dry from the north. Winds
overnight should not be as strong as they were during the day, but
still remain gusty from the north-northwest at 15-30 kts. VFR CIGS
can be expected overnight at KDEN and KBJC, while low CIGS
(2500-4000ft AGL) are expected to linger until a least 06z at
KAPA. After which time, CIGS at KAPA should gradually lift above
6000 ft AGL. There is also a chance of light snow at KAPA until
around 06z, but no new snow accumulation is anticipated.


&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Blizzard Warning until 6 AM MDT Saturday for COZ048>051.

High Wind Warning until midnight MDT tonight for COZ042>045.

High Wind Warning until 3 PM MDT Saturday for COZ041-046-047.

&&

$$

UPDATE...Baker
SHORT TERM...Gimmestad
LONG TERM...Kalina
AVIATION...Baker



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