Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 221009

Area Forecast Discussion
National Weather Service Denver/Boulder CO
409 AM MDT Sun Oct 22 2017

.SHORT TERM...(Today and tonight)
Issued at 400 AM MDT Sun Oct 22 2017

Short wave ridging in the northwest flow aloft will usher in
warmer and continued dry air. Skies will be mostly sunny to partly
cloudy. High clouds are expected to increase later today as
Pacific moisture makes its way into the region. Highs are expected
to top out in the mid 60s to lower 70s over northeast Colorado.
Windy conditions are expected at times in the mountains, foothills,
and near the Wyoming border. These windy conditions are expected to
persist into the nighttime hours.

High clouds and a warmer airmass will help keep temperatures
warmer tonight. There will also be some wind to help mix the
airmass especially in the foothills where gusts to 50 mph will be
possible. Moisture and clouds will increase late tonight over the
north central mountains. Could end up with enough moisture for a
few flurries towards sunrise Monday morning.

.LONG TERM...(Monday through Saturday)
Issued at 400 AM MDT Sun Oct 22 2017

On Monday, a weak mid-level shortwave trough quickly swing out over
the northern Great Plains, and as it does a weak cold front will
slip south acrs nern Colorado during the morning hours. May see a
few snow showers early in the nrn mtns with weak QG forcing
generated by the passing trough, but no precip on the plains with
the passing front. A modest N-NE wind behind the front will lower
max temps by 5-8 deg f. See little change in temperature for Tuesday
with the CWA sandwiched between a high amplitude upper ridge to the
west, a deep upper trough to the east and a rather strong north-
northwest flow aloft. It will continue to be dry on Wednesday with
flow aloft weakening as it transitions to a west-northwesterly
component with the upper ridge expanding eastward over the state.
Look for daytime temperatures to be as much as 10-15 deg f above
those on Tuesday.

Wednesday night into Thursday, the western ridge quickly breaks down
as a potent jet maxima and upper trough swing down from the Pacific
Northwest. By Thursday morning, models show a well organized trough
packing plenty of cold air and moisture racing across Wyoming, and a
leading cold front pushing south acrs northeast Colorado. Do not see
any precip with the front itself, however should see scattered snow
showers breaking out over the nrn mtns by late morning. In addition,
could see northerly winds on the plains gusting 30-40kts for a
couple hours following frontal passage. Models show winds turning
nely up to around 700 mbs by early afternoon and precip quickly
after that happens. Greatest chance for measurable precip will be
over and near the Front Range during the afternoon and early evening
hours. Should see wetbulb zero heights quickly fall through the
afternoon, sufficiently low enough for at least a rain-snow mix
within the I-25 corridor after 23Z/Thu. Although the ECMWF would
have us believe the change over may occur sooner than that. At
elevation above 6000 feet, precip should be all snow during the
afternoon with a quick shot of QG lift with a passing upper air
disturbance. East facing slopes of the Front Range could see a quick
3-6 inches of snow by evening, and possibly up to 2 inches of wet
snow on the nearby plains roughly above 5300 feet. It now appears
that the bulk of this precip will move south of the fcst area by
06z/Friday. Clearing skies after midnight will allow temps on the
plains to fall into the upper teens and lower 20s. Friday looks dry
overall but still quite chilly as the upper trough and its bundle of
cold air aloft will still be impacting the region. Friday also looks
windy with gusty north-northwest winds for much of the day.

For the weekend...the region remains under the influence of a fairly
strong north-northwest flow aloft. Small bundles of moisture and
instability slipping down from Wyoming will possibly produce short
periods of light snowfall in the high country. Do not see much
warming both days with temps predicted to remain below average.
See no reason to argue with that.


.AVIATION...(For the 12Z TAFS through 12Z Monday morning)
Issued at 400 AM MDT Sun Oct 22 2017

VFR conditions will prevail with high clouds streaming over the area
at times. At KBJC, gusty west winds to 40 knots will be possible
through 15Z. Otherwise, winds will generally be light, less than 20
knots. South-southwest winds at KDEN and KAPA will turn west to
northwest after 18z and return south-southwest around 03Z Monday.




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