Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

Home | Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS65 KBOU 180426
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
926 PM MST Fri Feb 17 2017

.UPDATE...
Issued at 920 PM MST Fri Feb 17 2017

Clouds spreading and lowering over the western half of Colorado
at this time are the product of weak QG ascent, orographic forcing
and marginally unstable lapse rates associated with a weakly
organized mid-level weather disturbance. The Front edge of this
cloud shield...made up of mostly cirrus...is now reaching the
I-25 corridor according to satellite imagery. Clear skies up to
now have allowed temperatures on the plains to quickly fall into
the 30s and lower 40s with wind speeds on the decline. With high
clouds increasing over the plains tonight...this cool down should
slow. Have already hit the predicted low at many locales including
DIA. So have lowered mins at least a few more degrees.

Next...the mid-level disturbance presently over eastern Utah
is projected to slowly lift northeast over western Colorado
overnight. Both the NAM and GFS show light precip breaking out
over the nrn mtn ranges including the Park, Gore and Ten Mile
ranges in the next couple of hours...and over remaining mtn areas
of our CWA after midnight. The snow level will start out high say
up around 10500 feet, and then lower to the high valley floors
before morning. Precip amounts are predicted to be light...
although parts of the Park Range could see snow accums of 2-4
inches by morning. East of the mtns, the surface high in wrn
Nebraska responsible for the 12-22kt east-southeast winds for
most of the afternoon continues to move away from Colorado. This
has caused speeds to drop and become more southerly in direction
this evening.

Changes to tonight`s forecast include accelerating cloud
coverage starting out west and making minor adjustments to high
country precip and snow amounts. Also loaded new wind and temp
data into the fcst grids based of the 00z model guidance.

&&

.SHORT TERM...(This evening through Saturday)
Issued at 302 PM MST Fri Feb 17 2017

A decent surge of upslope is moving southeastward across the
plains of northeast Colorado. The airmass behind it is not colder
but a bit more moist. Dewpoints have come a bit, about 3-10 F.
The satellite pictures are showing associated cloudiness with the
next upper level trough just getting into western Colorado at
this time. The models have weak westerly flow aloft this evening
and it becomes south-southwesterly by Saturday afternoon and
increases in speed as an upper trough/closed low moves into the
desert southwest by 00Z Sunday. The QG Omega fields have weak
upward motion in the synoptic scale tonight and Saturday. The
boundary layer winds look to become normal range later this
evening. Over the far east, southeasterlies hang on much of the
night. On Saturday south-southeasterly winds seem to dominate in
most place, so the Metro area will likely see a Denver Cyclone
develop by early afternoon. For moisture, it increases overnight
and is fairly pretty deep over the mountains on Saturday. The
plains will mostly have upper level moisture around. The QPF
fields show limited measurable precipitation over the western CWA
tonight and Saturday. The orographic enhancement for mountain
snowfall is poor. Winds speeds are weak and directions are not
good for the north central Colorado mountains. For pops, will go
with "chance"s in the high mountains from about 06Z tonight
through Saturday. No pops for the plains. For temperatures,
Saturday highs are close to today`s highs, perhaps a tad cooler.

.LONG TERM...(Saturday night through Friday)
Issued at 302 PM MST Fri Feb 17 2017

Focus continues to be on one system moving over the forecast are
Sunday evening and then another one in the middle of next week.
Between those two systems, ridging over the area will bring
periods of dry and warm weather.

The first weather disturbance now appears like it will be a
negatively tilted trough lifting over the state from the south
Sunday and Sunday night. Ahead of it, southerly flow will
transport warm and moist air over the state. Snow levels will
begin high, but quickly drop due to evaporative effects of the
falling precipitation. This trough will lift out quickly and be
leaving the state by Monday morning. Mountain areas should pick
up a few inches of snow overnight. Plains locations should see a
round of evening showers which could be rain that changes to snow
as the storm moves out.

Ridging over the state will quickly develop Monday and Tuesday
with dry and warmer temperatures through Wednesday. During the
latter half of the week, the flow pattern across the country will
undergo a transition to more zonal flow as a longwave trough
carves out over the western United States. By Thursday afternoon
the first part of the trough is forecast to be over Colorado with
much cooler temperatures and more unsettled weather. This is still
nearly a week away, so we will watch how later model runs handle
the evolving pattern. For now, cooler and a chance of showers
across the forecast area will suffice.

&&

.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 920 PM MST Fri Feb 17 2017

South-southeast winds of 8-14 kts presently on the south and
east side of the denver metro area will gradually turn to a
south-southwest direction of 6-12 kts after 06z tonight. On
the west side of the metro area...winds will remain generally
light and variable overnight. Overnight...skies will gradually
fill with high clouds/generally at or above 20,000 ft agl in
advance of a weak weather disturbance moving over western
Colorado. No precipitation in the Denver area tonight or
tomorrow as the lower atmosphere east of the mtns will remain
quite dry.

&&

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

$$

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


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.