Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 121620
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1020 AM MDT Tue Sep 12 2017

.UPDATE...
Issued at 1015 AM MDT Tue Sep 12 2017

A north-south oriented streamer of mid-level moisture showing up
on GOES-16 H2O vapor satellite imagery over ern Colorado on the
way out. Drier, subsiding air rounding the bottom side of a
vigorous vort maxima spinning eastward over east central Wyoming
is now spreading down over nrn Colorado. In addition, a drier
boundary layer on the plains should result in noticeably fewer
t-storms today. Same goes for the high country, although still
expect to see scattered coverage mainly over the higher terrain
mid-afternoon thru early evening. Gusty winds and lightning more
likely than wetting rainfall from them today. Most of this falls
in line with the current forecast. So, few changes necessary at
this time.

&&

.SHORT TERM...(Today and tonight)
Issued at 358 AM MDT Tue Sep 12 2017

An upper level disturbance over Wyoming early this morning will
continue to weaken and move off to the east today. Behind this
feature, there is some short-lived drying noted by the GOES 16
low level water vapor channel. Upper level ridging and warming
will also occur through the day. The net result will be for a
little less convective activity today, although that`s not saying
much given the very dry conditions over the last 4 weeks.
Only look for isolated to scattered weak showers/storms over the
mountains this afternoon, with maybe a couple drifting onto the
nearby plains and forming along a weak convergence zone from the
Palmer Divide into the northeast corner of the state. Temperatures
will likely be a degree or two warmer than yesterday as temps
warm aloft. Highs on the most of the plains should be near or just
above 90F.

For tonight, isolated weak convection will come to an end this
evening with no synoptic forcing under the ridge. Then look for
clearing skies, but above normal temperatures.

.LONG TERM...(Wednesday through Monday)
Issued at 358 AM MDT Tue Sep 12 2017

Some moisture in WSW flow will traverse across the area on Wed and
allow for a chc of showers and tstms especially over the higher
terrain. Across the plains will keep in a slight chc of showers
and storms. As for highs, readings will remain well abv normal as
temps reach the upper 80s to mid 90s across the plains.

On Thu the flow aloft will become more swly as a weak upper level
low begins to move ene fm srn California. Subtropical moisture will
continue to move across the area ahead of this feature with another
chc of showers and storms over the higher terrain.  There also will
be a better chc of activity across portions of nern CO as well.
Temperatures will remain abv normal with readings in the upper 80s
to lower 90s across the plains.

For Thu night into early Fri the remnants of the upper level low
will move across the area bringing a chc of showers mainly across
the mtns.  Across the plains it will be mainly dry as a weak cool
fnt moves across in the morning.  Thus aftn highs over the plains
will drop into the lower to mid 80s.

By Fri night into Sat a stronger system will move across Wyoming and
will be accompanied by a decent cold front.  Based on current trends
appears best chc of pcpn with the upper level trough will stay north
of the area.  As for highs, readings will drop into the lower to mid
70s across nern CO.

For Sun into Mon the flow aloft will become more wsw with little
moisture shown by cross-sections.  Thus expect dry conditions both
days.  Temperatures will be near normal on Sunday and then rise to
slightly abv normal by Mon.

&&

.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1015 AM MDT Tue Sep 12 2017

VFR conditions likely in the Denver area for today and tonight.
Storm chances lower today as the atmosphere has become drier and
more stable. Winds should also remain light in speed, from a
south-southeast direction rest of this morning, then an east-
southeast direction this afternoon, then a west-northwest
direction by early this evening, then back to our typical south-
southwest drainage wind pattern later in the evening and
overnight. Speeds should generally remain under 13 kts.

&&

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

$$

UPDATE...Baker
SHORT TERM...Barjenbruch
LONG TERM...RPK
AVIATION...Baker



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