Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 121202

Area Forecast Discussion
National Weather Service Denver/Boulder CO
502 AM MST Wed Dec 12 2018

.SHORT TERM...(Today and tonight)
Issued at 502 AM MST Wed Dec 12 2018

A strong trough now over Idaho and Nevada will move quickly across
Colorado this afternoon and evening. The main feature will be the
sharp pressure rises with cold advection behind the trough. Winds
will become northwesterly and increase sharply in the late
afternoon, trending more northerly on the plains this evening as
a surface low deepens over the southern Great Plains. Meanwhile,
the flow aloft will increase a bit in the mountains today, before
becoming more northerly for less wave amplification this evening.
Conditions are not highly favorable for amplification, but with
40-50 knot winds near mountaintop, windier spots above timberline
will likely have gusts to 70 mph with 50 mph plus gusts getting
into the higher lee slope areas. The strong alpine winds should
decrease a bit overnight, but there is another brief window where
there could be wave amplification around sunrise. With a more
northerly direction, this would primarily hit the US 285 corridor
in South Park and higher parts of Clear Creek county. Plains wind
forecast looks good. The usual model biases are there with GFS MOS
a bit higher than NAM. I did blend in the NAM MOS for higher winds
in the mountains, but this just added a few mph on the plains.
Near high wind criteria in Lincoln county for a few hours this
evening, but it doesn`t look like it`s quite there.

As far as precipitation goes, moisture is not that great. There is
an area of weak instability that will translate across in the
afternoon and evening, but for the most part the moisture is not
deep and the instability is limited. Moderate QG forcing will last
about 8 hours, in the afternoon and evening for our mountains, and
that should be the main period of light to moderate snowfall.
Previous forecast snow amounts of 2 to 5 inches look good. There
could be some impact at the height of the snowfall, perhaps around
sunset for I-70. For the plains, low levels will stay dry with the
downslope winds. There`s an outside chance the strongest showers
could reach the ground, but the odds of any significant
accumulation seem very low.

.LONG TERM...(Thursday through Tuesday)
Issued at 502 AM MST Wed Dec 12 2018

On Thursday, high pressure at the surface and aloft will bring dry
and cool conditions to the region. Gusty northerly winds will
continue over the northeast plains through 15z, then the surface
pressure gradient starts weakens from north to south as the
surface low drops into northeast TX. Temperatures will only warm
to around 40 degrees for Denver. Thursday night through Friday
night, a ridge of high pressure will to bring dry and mostly clear
weather to the cwa. The flow aloft will transition to westerly by
Friday night as the ridge axis shifts to the east. A weak upper
level disturbance will brush northern Colorado on Saturday as it
passes through Wyoming. This system will produce some gusty winds
over the northern mountains but no precipitation. Temperatures on
Saturday will be mild with highs in the mid 50s. The outlook
Sunday into Tuesday will remain mostly dry as weak storm systems
split with any beneficial precipitation passing to the south and
north of the region.


.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 502 AM MST Wed Dec 12 2018

VFR through tonight. Winds will increase from the west 16z-20z
with 20-25 knot gusts, then stronger northwest winds after 21z becoming
more northerly in the evening with 30-40 knot gusts for a few
hours. The winds will then gradually diminish overnight. Isolated
snow showers 22z-02z are not expected to impact Denver terminals.




SHORT TERM...Gimmestad
LONG TERM...Cooper
AVIATION...Gimmestad is the U.S. government's official web portal to all federal, state and local government web resources and services.