Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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654
FXUS65 KBOU 240347
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
947 PM MDT Fri Sep 23 2016

.UPDATE...
Issued at 939 PM MDT Fri Sep 23 2016

Updated earlier this evening for higher PoPs over the mountains
and northern border areas. Main precip shield is now shifting
toward Larimer county and will continue to pivot northeastward
through the middle of the night. Some questions about the
magnitude of the snow in the advisory area later tonight as there
appears to be a little dry area before the moisture comes back in.
Still should be a round of orographic snow around Rabbit Ears pass
later tonight into Saturday morning. Also probably some light
accumulations from Rocky Mountain National Park northward this
evening, but that should be fading as the northwesterly flow
strengthens overnight. Below 8000 feet too warm and also undercut
by drier air in the downslope.

Only minor adjustments now for current conditions.

&&

.SHORT TERM...(This evening through Saturday)
Issued at 311 PM MDT Fri Sep 23 2016

A strong upper level low was over northern UT this aftn with
moderate QG ascent over CO at this time. A strong southerly flow
associated with a 100+kt jet overhead. This features will shift
over eastern CO this evening then lift northeast into Nebraska
Saturday morning. Good lift coupled with aftn instability has
allowed for a mix of rain showers...snow showers and thunderstorms
in the mountains this aftn. Precipitation will increase in the
mountains this evening. Mid level winds will be south/southwesterly
tonight...then west/northwesterly on Saturday. No much qg support
for snow in the mountains late tonight but good orographics. Have
gone ahead and issued a winter weather advisory for snow/blowing
snow for zone 31 from midnight to 10 am saturday morning. low
vsbys in exposed areas above timberline tonight and saturday
morning in snow/blowing snow. Across the northeast plains...gusty
southerly winds will transition to northerly this evening. Red
Flag Warning continues for areas east and south of Denver until 8
pm this evening. Isolated thunderstorms this evening but the best
chc will be along the northern border. one or two could produce
very strong winds toward Wyoming and Nebraska. As the upper low
moves into central Wy tonight...then wrap around moisture may
allow for another round of showers/tstms along the northern border
overnight. Cooler on Saturday and generally dry across the
northeast plains. Best chc of any showers on Saturday will be
near the foothills and palmer divide. A mix bag of rain and snow
showers in the high country saturday aftn.

.LONG TERM...(Saturday night through Friday)
Issued at 311 PM 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 06Z TAFS through 06Z Saturday night)
Issued at 939 PM MDT Fri Sep 23 2016

Chaotic wind pattern around Denver this evening. Initial cold
front washed out and winds returned to WSW across the area. Expect
another surge of northerly winds with lighter speeds sometime
around 06z, then rotating around through east and back to south by
morning. This process will likely be repeated through the midday
and afternoon hours with winds going north-east-south during the
afternoon. Still a chance of showers or at least ceilings low
enough to require instrument approaches to KDEN during the night,
but this is looking less likely. VFR conditions expected on
Saturday.

&&

.FIRE WEATHER...
Issued at 939 PM MDT Fri Sep 23 2016

Colder temperatures and higher humidities behind the cold front so
Red Flag conditions have ended. Gusty winds will continue over the
eastern border counties until around 11 PM, with gusts to 55 mph
possible with thunderstorms.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 10 AM MDT Saturday for COZ031.

&&

$$

UPDATE...Gimmestad
SHORT TERM...Cooper
LONG TERM...Dankers
AVIATION...Gimmestad
FIRE WEATHER...Gimmestad



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