Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 251717
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1017 AM MST Sun Feb 25 2018

.UPDATE...
Issued at 1015 AM MST Sun Feb 25 2018

Westerly winds are widespread from the divide eastwards across
the foothills and all of the plains right now. There are gusts as
high as 35 knots. Models keep this flow going until around sunset.
GFE grids have a decent handle of this. Will do a little fixing
to the sky cover grids. Otherwise the forecast is in good order.

&&

.SHORT TERM...(Today and tonight)
Issued at 433 AM MST Sun Feb 25 2018

Mountain cameras show light snow falling in most of the higher
mountains early this morning. Snow amounts have been rather
limited (about 1/2 - 2 inches) so far. The light amounts are most
likely due to the marginal amounts of available precitable water,
as orographics and instability would support more significant
snowfall. Nonetheless, we do expect light snow to continue through
most of the morning as the weakening short wave moves across
Colorado, and then decrease to just a few showers this afternoon
behind the disturbance. We look for another 1-2 inches over the
higher slopes generally above 9500 feet this morning, with a
dusting to one half inch in valley locations. Breezy conditions
will redevelop down to valley floors in the well mixed atmosphere
today. High temperatures will only make it into the teens for the
skie areas, with breezy conditions making it feel quite a bit
colder than that. Some blowing snow will also occur over exposed
mountain ridges and areas above timberline.

On the plains, overall temperature profile behind yesterday`s
short wave to today`s is quite similar. There`s maybe just a
degree or two of warming seen in most model fields, so highs
should be able to make it into the mid 30s to lower 40s. The lower
atmosphere will once again become well mixed late this morning
into the afternoon with breezy conditions developing. Today`s
gusts in the lower elevations should generally peak at 25-35 mph,
with the stronger gusts near the foothills and Wyoming border.
Nearly full sunshine expected in the dry and subsident airmass.

For tonight, winds decrease early this evening in all but the
Front Range Mountains and Foothills. There is little mountain wave
amplification but 35-40 knots of cross mountain flow keeping
things breezy there with gusts reaching 60 mph in wind prone areas.
Mostly clear skies should prevail with only scattered high
clouds.

.LONG TERM...(Monday through Saturday)
Issued at 433 AM MST Sun Feb 25 2018

The upper flow pattern over the western United States is forecast
to be somewhat transitional through the upcoming week as a cutoff
low develops over southern California early in the week and then
ejects eastward in the middle of the week. Each of the medium
range forecast models have similar solutions for the western U.S.
through about 132 hours, which is Friday morning. During that time
period, the upper trough that is over British Columbia today dives
southward over the western U.S. as a strong upper jet feeds cold
air into the trough. This trough will then become a cutoff low
over the Los Angeles area Tuesday morning. During that time,
Colorado will be under increasing southwest flow aloft that will
be drier than what we have had over the past week. Temperatures
will undergo a gradual warming trend with snow ending in the
mountains and the plains continuing dry. The strongest flow aloft
will be over Arizona and New Mexico while Colorado comes under a
benign weather pattern.

The cutoff low over California is being forecast to move eastward
Tuesday night through Wednesday with a track across southern
Arizona and southern New Mexico. Colorado will be under the col to
the north of the ejecting low. This will be a region of decreasing
winds aloft and a continued lack of moisture. The central
mountains may pick up a little snowfall on Wednesday, if the
northern fringe of moisture with the passing disturbance drifts a
little northward. By Thursday, dry weather returns across the
forecast area as an upper ridge builds over the state.

For next weekend, the GFS, Canadian and ECMWF all have quite a bit
of troughing over the western U.S. with differences concerning
whether the lowest heights will be offshore or inland over the
northern Rockies. This deeper system will have a better chance of
moving moisture back into the Colorado mountains through the
weekend. For now, will only mention the chance of snow in the
mountains.

&&

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 1014 AM MST Sun Feb 25 2018

The west-southwesterly winds should continue at DIA through about
01Z. Models kick in drainage flow by 03Z this evening which seems
reasonable.  There will be no ceiling issues.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

UPDATE...RJK
SHORT TERM...Barjenbruch
LONG TERM...Dankers
AVIATION...RJK


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