Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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526
FXUS65 KBOU 212122
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
222 PM MST Sun Jan 21 2018

.SHORT TERM...(This evening through Monday)
Issued at 215 PM MST Sun Jan 21 2018

The upper low is currently over southeastern Colorado with
continued diffluence aloft over eastern Colorado helping to bring
heavier snowfall over those areas. Snowfall rates of 2 inches per
hour have been reported under this heavier band. Northerly winds
are increasing with gusts up to 40 mph already, and these will be
increasing through the rest of the afternoon and into the evening.
Heaviest snowfall band is moving east of the forecast area, which
may limit the visibility reduction for Blizzard Warning criteria.
However, with the increasing winds and what snow has fallen
already, expect to see some stations still hit 1/4 mile or less,
will allow the Blizzard Warning to continue. Further west, snow is
winding down over the mountains as well as the northern urban
corridor with the increase in northerly winds downsloping off the
Cheyenne Ridge. The warnings expire at 2pm over the northern urban
corridor and over the mountains at 3pm, though lighter snow will
continue - especially over the mountains.

Snow will continue to taper off through the evening from west to
east, though some snow will likely still occur east of a line from
Sterling to Limon into the early morning hours. Expect another 1
to 4 inches over the mountains and east of a line from Denver to
Sterling, with less than an inch elsewhere. Skies will clear
allowing for minimum temperatures to drop into the single digits
to below zero over the mountains. The exception will be along the
east slopes down into the foothills as westerly downslope winds
increase overnight in response to the system pulling further away
east. Look for minimums in the teens there and down across most of
the plains.

Northerly flow will turn northwesterly Monday with mostly clear
skies over the the plains, while clouds and isolated orographic
snow showers will be over mountains. Temperatures will likely stay
in the low 30s over most of the eastern plains, especially where
the higher snow amounts are found, while along the urban corridor
it should reach into the 40s with the help of the west-northwesterly
winds.

.LONG TERM...(Monday night through Sunday)
Issued at 215 PM MST Sun Jan 21 2018

There will be a moderate northwest flow aloft over Colorado Monday
night through Tuesday night. A weak disturbance will brush
northern Colorado on Monday night and early Tuesday with scattered
snow showers in the mountains. Moisture depth not all that deep
so any snowfall accumulations will be minimal. Cross sections show
some gusty winds over mountains and east slopes through this
period with potential gusts in the 30-45kt range, especially
Monday night and Wednesday.

High pressure ridge aloft will be over Colorado on Wednesday with
dry and warmer conditions then flow aloft will shift southwest on
Thursday in response to next Pacific storm system moving inland
over Great Basin.

Long range models still showing next system to sweep across
Colorado Thursday night and Friday but is rather progressive with
the brunt of the energy shifting north over Wyoming and the
panhandle of Nebraska on Friday. Downslope flow will likely limit
precip chances over the Front range so best chance of snow will be
over the mountains and far northeast corner of the state. Certainly
temperatures will be colder over all of Northern Colorado on
Friday and Saturday.

&&

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 215 PM MST Sun Jan 21 2018

IFR to LIFR conditions should prevail through about 23z this
afternoon before they begin improving in the evening, becoming VFR
by 03-06z. Snowfall intensities will be decreasing, less than 1/4
inch per hour. North winds continue to increase this afternoon,
gusts of 25 to 40 mph this afternoon could cause periods of
blowing and drifting snow. The storm will be moving out of the
state tonight with drier air moving in from the west by midnight.
Total snow accumulations at the area airports are expected to be 6
to 9 inches by this evening. Winds will become westerly overnight
as skies clear, then return to northwest Monday under VFR
conditions.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Blizzard Warning until midnight MST tonight for COZ046>051.

Winter Storm Warning until 3 PM MST this afternoon for COZ031-
033>036.

Winter Storm Warning until 5 PM MST this afternoon for
COZ039>042-044-045.

&&

$$

SHORT TERM...Kriederman
LONG TERM...Entrekin
AVIATION...Kriederman



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