Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 270326
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
826 PM MST Thu Nov 26 2020

.UPDATE...
Issued at 825 PM MST Thu Nov 26 2020

There has been some light snow in the northern mountains and
foothills and flurries on the adjacent plains this evening with a
band of low clouds moving southeast through the area. Light
accumulations in the mountains and foothills may cause areas of
slick roads. We added areas of flurries to the urban corridor and
nearby plains over the next few hours, and still expect all
precipitation from these clouds to be done by midnight. Skies are
clear behind the band and it doesn`t look like there is anything
upstream in the synoptic flow to reach our area tonight. The upper
trough is currently closing off a cutoff low to southwest and
will continue this process overnight without impacts for our area.
The forecast is on track without significant changes this
evening.

&&

.SHORT TERM...(This evening through Friday)
Issued at 233 PM MST Thu Nov 26 2020

A return to dry weather in the short term. The elongated positively
tilted trough will split apart, with passage of northern stream
trough into the upper Midwest. On the southern end, a low will close
off off over Arizona and slowly moving east into New Mexico on
Friday. Colorado will be in the col region between the two with weak
QG descent.

Lingering snow showers in the mountains this afternoon will be
coming to an end by midnight. The band of mid level moisture that
has accompanied the elongated trough before it splits in two will be
replaced by drier air from the north. Model sounding time series
show moisture drying in the mountains after midnight, and toward
sunrise further east on the central plains. Clouds in place over the
higher terrain will be on the decrease late tonight into Friday.
Temps tonight near normal on the plains with radiational cooling and
cool northerly flow. In the mountains clearing skies and a fresh
dusting of snow will allow temperatures to radiate into single
digits, a few degrees below normal. Near normal Friday with mainly
clear skies and light winds.

.LONG TERM...(Friday night through Thursday)
Issued at 233 PM MST Thu Nov 26 2020

Friday night into Saturday a closed upper level low will track from
southern New Mexico into the Texas Panhandle, with a weak west to
northwesterly flow aloft over Colorado. This pattern will bring dry
weather and above normal temperatures to north central and
northeastern Colorado. With 700 MB temps between +1 & 2 degrees C
and some downslope flow, have decided to raise Saturday`s max temps
a few degrees across the Front Range Corridor.

On Sunday, an upper level shortwave moving across the Northern and
Central Plains States will push a dry cool front across Northeastern
Colorado.  As a result, high temperatures east of the mountains
should be around 10 degrees cooler than Friday`s readings. Above
normal temperatures are expected to return on Monday as upper level
high pressure builds over the Rocky mountain region.

Colder unsettled weather is expected Tuesday and Wednesday as an
upper level trough of low pressure dives south out of the Northern
Rockies and Great Plains into Colorado. At this time, there is quite
a bit of uncertainty due to the discrepancy between the models. On
Tuesday, the GFS and ECMWF are in pretty good agreement with the
upper trough moving across Colorado, while the GEM forms a large
cutoff low over southern Nevada. The GFS and ECMWF solutions would
produce light accumulating snow across the northern mountains on
Tuesday, while the GEM solution would result in a continuation of
dry weather across the area.

By 12Z Wednesday, the ECMWF and GFS begin to diverge with the ECMWF
showing a 500 MB closed low over southwestern Kansas, while the GFS
has two centers, one over central Utah and a stronger center over
south central Kansas. Both solutions suggests the potential for some
light snow across the plains and Palmer Divide along with gusty
north to northeasterly winds over the far northeastern Plains. On
the other hand, the GEM has the upper low digging into southern
Arizona by Wednesday evening with an upper level shortwave and
associated dry cold front moving into northeastern Colorado, This
pattern would bring dry and cooler weather to the CWA with the
possibility of gusty northerly winds across the far northeastern
plains. For now have decided only to raise pops slightly due to all
the uncertainty and inconsistencies between the models.

&&

.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 825 PM MST Thu Nov 26 2020

A band of clouds with a roughly 8 kft deck is moving southeast
across the area this evening and bringing flurries to the urban
corridor. No snow accumulation or visibility impacts are expected
for any terminals. Skies are clear behind the band and should
remain clear overnight. Winds are northerly under the band but
will turn to drainage behind it tonight. Expect rather light winds
under 10 kts through most of the day tomorrow before drainage
winds again tomorrow evening and night, with VFR conditions
through the TAF period.

&&

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

$$

UPDATE...Direnzo
SHORT TERM...Hanson
LONG TERM...jk
AVIATION...Direnzo



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