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520
FXUS65 KBOU 230156
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
756 PM MDT Thu Sep 22 2016

.UPDATE...
Issued at 744 PM MDT Thu Sep 22 2016

With dewpoints in the upper 50s across much of northeast
Colorado along with brisk ene winds...along with the rich rh
forecasts from HRRR...will add patchy fog to forecast for much of
the area from shortly after midnight to shortly after sunrise.
Also touched up the winds...do not see as much southerly flow
overnight...but early tomorrow developing southerly flow will
cause the erosion of the fog from the south. the rest of the
forecast looks good.

&&

.SHORT TERM...(This evening through Friday)
Issued at 337 PM MDT Thu Sep 22 2016

Stratus cloud cover that lingered over the northeast plains held
temperatures cooler through this afternoon. At the same time,
increasing southwest flow aloft over the mountains has been
generating some thunderstorms. Scattered showers should continue
for a few more hours. Not much shower activity is expected on the
plains due to the stability of the airmass.

On Friday...southwesterly flow aloft over Colorado will be
increasing ahead of the deep upper low moving into the Great
Basin. Mid level moisture and a southerly upper jet will increase
the threat of shower activity over the mountain zones. On the
plains, increasing winds will bring warmer and drier condtions.
Temperatures will reach well into the 80s with humidity levels
dropping to 20 percent or less. Fire danger levels will be
elevated, mainly on the Palmer Divide.

.LONG TERM...(Friday night through Thursday)
Issued at 337 PM MDT Thu Sep 22 2016

Deep upper level low for this time of year will shift northeast
across Wyoming Friday night. The majority of the scattered showers
and thunderstorms will lift north to near the Wyoming border early
in the evening with the main instability area. CAPES only near 500
J/kg so threat of any severe weather seems limited as moisture
scours out rather quickly to the northeast.

Behind that action, look for strong downslope to develop along
the Front Range during the evening. Through midnight, there is
potential for a mean state critical layer with almost pure
southerly flow aloft ahead of the trough axis. Meanwhile, mountain
top flow turns nearly due westerly and increases to 30-35 knots.
The combination of these may allow for brief development of strong
winds along the Front Range Mountains and Foothills as mountain
wave energy would be deflected down the Front Range, so have
increased winds significantly in downslope wind prone areas Friday
evening. In the mountains, moisture increases as well so should
see snow develop with the arrival of wrap around moisture during
the overnight hours into Saturday. Could see a couple inches of
snow accumulation in the mountains near Rabbit Ears Pass, with
some lighter snow spreading toward the Front Range mountains and
Rocky Mountain National Park area.

Temperatures will be much cooler in all areas by Saturday with
continued cold advection. Could still see a few showers mainly
in/near the mountains and adjacent plains due to cold air aloft,
instability, and potential for shallow anticyclonic upslope flow.

By Sunday, latest models are still diverging on solutions but
appears some splitting of energy is expected to drop into the
southern Rockies. There may be just enough moisture to keep a low
chance of showers in the forecast, but overall looks like the
ridge building over the top of the energy will begin to influence
our weather with mainly dry but continued cool conditions.
Overnight lows Sunday night will likely drop into the 30s/lower
40s on the plains with frost possible in some areas if skies clear
sufficiently.

Monday through Thursday, its becoming more confident that Colorado
will reside under the blocking ridge. This ridge builds in
between the upper low in the Great Lakes region and the upper low
dropping to the U.S./Mexico border. As a result, will have mainly
dry conditions and a gradual warming trend for this period.

&&

.AVIATION...(For the 00Z TAFS through 00Z Friday afternoon)
Issued at 755 PM MDT Thu Sep 22 2016

believe earlier taf was too strong with downslope flow overnight.
as a result fog may develop rather close to dia overnight. it will
be a close call if the fog makes it to the airport...but 03z taf
will carry fcvg from 07z to 12z. strong southerly winds are still
expected to develop on friday.

&&

.FIRE WEATHER...
Issued at 337 PM MDT Thu Sep 22 2016

Increasing southerly flow across the state tomorrow is going to
bring warmer temperatures...lower humidities and gusty south to
southwest winds over the Palmer Divide. High temperatures in the
lower 80s and humidities dropping to the upper teens will raise
the fire danger levels...especially on the plains where grasses
have cured out due to the recent dry weather. Will issue Red Flag
Warning for zones 241...246 and 247 where the combination of gusty
winds...warm temperatures and low humidities will make to most
volatile conditions. The warning will run from noon through 8 PM.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning from noon to 8 PM MDT Friday for COZ241-246-247.

&&

$$

UPDATE...RTG
SHORT TERM...Dankers
LONG TERM...Barjenbruch
AVIATION...RTG
FIRE WEATHER...Dankers