Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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136
FXUS65 KBOU 231633
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1033 AM MDT Fri Sep 23 2016

.UPDATE...
Issued at 1019 AM MDT Fri Sep 23 2016

Strong upper low over north central Utah this morning will
continue to lift to the north and east into Wyoming through this
evening. Some winds gusts in the mountains already around 45 mph
above timberline...so have increased the winds there in the grids.
Rest of the forecast is ok for now. Showers associated with
baroclinic band over western CO will be moving into the north
central mountains with a better chance of showers and tstms this
afternoon. Stratus/fog north of Denver is dissipating at this time
and should start to see stronger winds mixing down to the surface.
the wind will be strongest in the mountains...along the Palmer
Divide south of Denver and the northeast plains of CO.

&&

.SHORT TERM...(Today and tonight)
Issued at 330 AM MDT Fri Sep 23 2016

Strong closed upper low now over the Nevada/Utah border area is
expected to lift out to the Northeast into Western Wyoming by
this evening. Ahead of the low there is a strong Southwest flow
aloft over Colorado and varying amounts of banded moisture.
Scattered showers have been developing over portions of Eastern
Colorado overnight and this trend will continue this morning and
afternoon. There is a threat of strong/marginal threat for severe
storms over far Eastern Colorado this afternoon where low level
moisture hangs on and results in CAPE values of 800-1200j/kg while
qg fields showing modest lift. biggest threat would be strong
winds given the strong flow aloft.

The strong southwest flow aloft will mix down to the surface
creating strong south to southwest surface winds this afternoon
over the Palmer Divide and Northward over the plains. Given the
strong flow could see some gusts in the 30-45 mph range. Once the
low lifts up into Wyoming....will see mountain top flow shift more
Westerly and looks like a decent swath of downslope West winds by
this evening and overnight. Current wind grids look good and
reflect this well. Expect some wrap around moisture in the
mountains by later tonight for continued showers.

.LONG TERM...(Saturday through Thursday)
Issued at 120 AM MDT Fri Sep 23 2016

The upper level low will be over Wyoming on Saturday with wrap
around moisture continuing to bring precipitation to the mountains
through Saturday afternoon. Temperatures will be cold enough to
bring a few inches of snow accumulation along Rabbit Ears
Pass...particularly the western slopes with snow spreading over
the Northern mountains by the late morning. Instability and
lingering moisture will keep a slight chance of precipitation
through Saturday evening for the higher mountains and adjacent
plains. Mountain wave energy that helped to bring increasing
downslope winds into Friday night will diminish by Saturday
morning but strong westerly flow aloft will continue to produce
wind gusts up to 40 mph at mountain top through the morning.
Elsewhere on the plains clouds will increase through the day with
cooler temperatures on continuing cold advection.

Both the GFS and EC show a piece of the energy associated with the
upper low breaking off and diving to the SW near the US and
Mexico border by Monday. Then for Sunday through the middle of
next week an upper ridge that was over the west coast will make
its way east helping to stabilize the airmass over CO. This will
bring a prolonged dry period but with continued cool temperatures.
Highs will be in the upper 60s to 70s into next week.

For the low to the south models are showing that the ridge will
move off to the east allowing for the now trough to move over CO
bringing another chance of precipitation to the region but under
slightly warmer temperatures then earlier in the week.

&&

.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 1019 AM MDT Fri Sep 23 2016

Southerly surface winds increasing at local terminals this
morning. Main concern will be the strong southerly winds expected
this afternoon at terminals with speeds in the 20-35kt range.
Looks too dry for any storms with this flow. Winds will shift more
westerly this evening as the big low over north central UT this
morning moves northeast into Wyoming.



&&

.FIRE WEATHER...
Issued at 330 AM MDT Fri Sep 23 2016

Critical fire weather concerns for this afternoon as strong
southerly winds mix down in approach of strong upper low over the
Great Basin. Humidity levels expected to drop into the teens by
afternoon. Have added fire weather zones 240 and 245 to the
current Red Flag warning as these areas as well will meet criteria
with the strong winds and low RH. Far eastern Lincoln county may
end up being more marginal as humidity levels will likely be a bit
higher and on the edge with the deeper moisture to the East.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning until 8 PM MDT this evening for COZ240-241-
245>247.

&&

$$

UPDATE...Cooper
SHORT TERM...Entrekin
LONG TERM...Bowen
AVIATION...Cooper
FIRE WEATHER...Entrekin



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