Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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602
FXUS65 KBOU 221002
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
302 AM MST Wed Nov 22 2017

.SHORT TERM...(Today and tonight)
Issued at 255 AM MST Wed Nov 22 2017

An upper ridge over the western states and an upper trough from
the Great Lakes to the Gulf of Mexico will keep Colorado under
north-northwesterly flow. The speeds have significantly come down
over 24 hours ago, and will continue to slowly decrease today.
Some moisture in the flow will continue to bring light orographic
snow to the high country today, with accumulations less than an
inch. Wind gusts of 25 to 40 mph may still cause some isolated
blowing snow problems, but much improved over yesterday. Warm
advection will push into the forecast area today with 700 mb
temperatures warming 6 to 7 degrees Celsius over yesterday. High
clouds today may inhibit the full warming, but still looking for
highs in the 60s across the plains, 40s and 50s over the
mountains. A disturbance moving over the ridge will deepen the
surface trough over the plains and move it out east. Northwesterly
winds of 30-45 mph in the high country will become a little more
widespread. Then northwesterly winds will push across the
plains with the strongest found over the northern and
northeastern plains.

With the warm advection in place, some high clouds remaining
overnight and a slight gusty downslope wind pattern overnight,
minimum temperatures will likely be above freezing across the
plains. Colder temperatures in the mountains will result from
clear skies and lower winds.



.LONG TERM...(Thursday through Tuesday)
Issued at 255 AM MST Wed Nov 22 2017

The high pressure center over the Pacific will deepen slightly and
continue to bring strong NW flow over the region. For Thursday a
surface lee-side low will form bringing winds down the foothills and
downslope along the base of the foothills and into portions of the
western plains. This will aid in the slight increase of temperatures
over the Metro bringing highs into the low 70s. Current record for
the day stands at 74 degrees with the current record Thanksgiving at
73. Stuck with 72 at this time...which was a slight increase from
model output to count for the downsloping effects. There is a chance
however that one or both of these records could be broken with
leeway only being 1-2 degrees.

By Friday the upper ridge flattens ahead of a quick moving elongated
upper trough that clips the northern mountains Friday afternoon and
evening. A surface cold front will accompany this system with the
frontal passage moving south over the plains by Friday afternoon.
Ahead of the front in the early morning hours on Friday expect an
increase in winds in the mountains and plains. For the higher
terrain gusts to 60 mph will be possible with 30-35 mph on the
plains. A mixture of rain and snow will be possible in the
mountains...especially NW favored areas of Park range and northern
mountains Tuesday with the plains staying dry.

For the weekend...we continue to have dry and unseasonably warm
temperatures. Highs will range in the upper 60s to low 70s under
mostly sunny skies. By Monday the ridge breaks down and moves
eastward with an incoming upper trough that models have digging
toward the four corners region by early Tuesday morning. Both the
GFS and EC show strong jet influence that could result in decent
snow for the higher terrain and bora type cold winds for the plains.
700 mb temperatures show a 15 degree drop behind the strong frontal
passage Tuesday morning. Will keep an eye on this system to see how
it evolves.

&&

.AVIATION...(For the 12Z TAFS through 12Z Thursday morning)
Issued at 255 AM MST Wed Nov 22 2017

VFR conditions will prevail through Thursday morning. Light
drainage winds continue to mix with a more westerly direction off
the foothills. Forecasting the wind direction through the rest of
the day will be tricky. The northwesterly winds may mix down and
blow across all airports, or as only the HRRR and RAP show, they
may anticyclone off the Cheyenne Ridge, which would bring them
into the airports from the northeast. Will keep the winds from
the west/northwest...which may gust to 25 knots for a few hours
during the middle of the day. However, they many end up in the
anticyclone pattern with much lighter speeds.

&&

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

$$

SHORT TERM...Kriederman
LONG TERM...Bowen
AVIATION...Kriederman



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