Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 161822
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1222 PM MDT Sat Sep 16 2017

.UPDATE...
Issued at 1222 PM MDT Sat Sep 16 2017

Stratus is thinning but a little slow, and temperatures are
lagging a few degrees, so we are adjusting the forecast for a
little slower clearing and a couple degrees cooler today. Still
some hints of some light showers developing on the plains east of
Denver overnight, but it looks like the moisture is pretty
marginal. Will keep some low PoPs but trim them back a bit.

&&

.SHORT TERM...(Today and tonight)
Issued at 404 AM MDT Sat Sep 16 2017

Cold front with gusty winds pushed across the plains last night,
and now much cooler air and areas of stratus are settling over
the forecast area. GOES 16 mid level water vapor imagery shows one
more wave of moisture moving across western Colorado, and this
should promote one last batch of showers for the mountains and
portions of the plains this morning. Grand Junction radar showing
returns increasing in the last hour. Snow levels will dip to
around 9000-10000 feet this morning with some cold advection, but
any accumulation should be near timberline or higher with a couple
spots possibly picking up a quick inch if heavier showers develop.
On the plains, looks like showers could spread about as far south
as the I-76 corridor, as they will be driven by the right rear
entrance region of the upper jet departing to our north this
morning. Then a moderately subsident airmass will bring a return
of sunshine to the mountains, and likely more to the plains as
the afternoon wears on. Hard to say how fast stratus will break
up, but some southeasterly component across the Palmer Divide
should help. Still a sufficient low level easterly upslope
component to the north however may slow the erosion. That would
also keep temperatures a few degrees cooler than forecast.

For tonight, most models continue the idea of generating some
light showers over the Palmer Divide area. This appears to be
driven by weak Q-G lift in warm advection pattern. Normally this
pattern will bring a few showers but east of the I-25 Corridor.
Forecast handles this well. May see some development of a mid
level stratus deck in the 3000-5000 foot range.

.LONG TERM...(Sunday through Friday)
Issued at 404 AM MDT Sat Sep 16 2017

WSW flow aloft will be across the area on Sun with possibly a weak
disturbance embedded in the flow.  This feature would move across
late in the day or at night.  Meanwhile sfc high pres will move into
the cntrl plains with sely low lvl flow across nern CO.  Thus may
see a Denver Cyclone developing by aftn with a convergence zone near
the urban corridor.  Overall if the weak disturbance mentioned abv
is real then would see a slight chc of aftn storms over the higher
terrain and over the front range urban corridor.  These storms would
then move northeast across the plains Sun night.  With a favorable
shear profile could see a few stronger storms across portions of the
plains with an isold svr storm possible.  As for highs, readings
will range fm the lower 70s over far nern CO with mid to upper 70s
over the urban corridor.

By Mon dry wsw flow aloft will be over nrn CO as a sfc lee trough
develops over nern CO.  This will allow for warmer temps as readings
rise into the lower to mid 80s across the plains.  For Tue into Tue
night an upper level trough will move across the nrn Rockies with
increasing wsw flow aloft. Overall there will not be much
moisture around although there could be a few showers in the mtns
nr the WY border. Meanwhile temperatures will remain abv normal
with highs in the 80s across nern CO.

On Wed an upper level trough will develop over the nwrn US with dry
wsw flow aloft across nrn CO.  A weak fnt will move across nern CO
Tue night into early Wed so highs will drop back to seasonal
normals.  For Thu a broad upper level trough will be ove the wrn US
with sw flow aloft over the area.  Overall it still looks rather dry
except for a slight chc of showers over the higher terrain nr the WY
border.  As for highs temps may wrm back into the lower to mid 80s
across the plains as swly low lvl flow develops.

By Fri the upper level trough is supposed to move a bit further east
with some increase in moisture across the mtns.  Thus may see a
better chc of showers over the higher terrain.  Over nern CO a fnt
may move across during the day bringing cooler temps and possibly a
chc of showers.

&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 1222 PM MDT Sat Sep 16 2017

Low clouds are thinning but a little slower than expected.
Ceilings are expected to dissipate between 19z and 21z. Some
clouds will likely redevelop with ceilings between 4000-7000 feet
AGL overnight.

&&

.FIRE WEATHER...
Issued at 404 AM MDT Sat Sep 16 2017

Fire Danger will increase from Monday into Tuesday across the
higher terrain and plains due to above normal temperatures, low
humidities and increasing wind.

&&

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

$$

UPDATE...Gimmestad
SHORT TERM...Barjenbruch
LONG TERM...RPK
AVIATION...Gimmestad
FIRE WEATHER...RPK


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