Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 241011

Area Forecast Discussion
National Weather Service GRAND JUNCTION CO
311 AM MST Fri Nov 24 2017

.SHORT TERM...(Today through Saturday)
Issued at 203 AM MST Fri Nov 24 2017

Mid and high clouds streamed eastward over the forecast area early
this morning ahead of an approaching disturbance over Oregon.
This fast moving short wave trough will push across the northern
Great Basin this morning before brushing northeast Utah and
northwest Colorado this afternoon. Dynamic lift combined with
steepening lapse rates beneath the transient 5H cold pool is
likely to bring showers to the Elkhead, Park, Gore and Flat Top
Mountains this afternoon. Mild temperatures will limit snowfall to
areas above 9000 feet. Meanwhile, unimpressive moisture surge
combined with the short duration of this event will result in only
light accumulations of up to 2 inches above the tree line.

The pressure gradient over the area tightens ahead of the cold
front accompanying the short wave resulting in breezy west winds,
most notable across the mountains and northern valleys this
afternoon. Expect afternoon highs to dip across northwest Colorado
as the front moves in this afternoon, though highs will still be
well above normal. To the south, temperatures should be pretty
similar to those experienced yesterday.

Ridging returns tonight as a trough deepens over the eastern
Pacific. This will result in fewer clouds and dry conditions
across the region overnight. The ridge amplifies on Saturday
which ensures that above normal warmth and dry weather will
continue across the area.

.LONG TERM...(Saturday night through Thursday)
Issued at 203 AM MST Fri Nov 24 2017

Good model consensus with a strong upper level ridge over the
region Saturday night into early Monday will maintain dry and
well-above to near record level warm temperatures. A long wave
upper level trough over the eastern Pacific will move rapidly
inland Monday which will increase southwesterly aloft over our
region. Long range models agree on the initial path and the idea
of closing a low center off over the lower Great Basin, near Las
Vegas by Monday evening. Thereafter, timing and path differences
begin to take shape with the GFS and Canadian models quicker and
farther south taking the center over the Four Corners east out
over the Southern Plains. The ECMWF brings a nearly cut-off low
over the Four Corners then lifts it northeast over south central
CO and out over the Central Plains. While the details will still
need to be resolved, the trend is for greater chances of
precipitation for the southern two-thirds of the area Monday night
and Tuesday as dynamics ahead of the low, then a deformation zone
axis of precipitation move over the region. Have introduced low
precip chances for lower valley areas which will likely need to be
raised if this wetter trend continues. Still dealing with an
initially warm airmass until the colder air associated with the
core of the trough moves overhead, so expect snow levels to start
out high and storm total snow amounts to be on the underwhelming
side of the spectrum.

After this excitement, another upper level trough follows quickly
on its heels, affecting the region Wed night into early Thursday.
Moisture with this system will be lighter and there is still quite
a bit of uncertainty with how this evolves, so chances of precip
in the forecast are currently very low for this period. It does
appear more likely that temperatures will cool off for the last
half of next week - close to or only a few degrees above normal.


.AVIATION...(For the 12Z TAFS through 12Z Saturday morning)
Issued at 203 AM MST Fri Nov 24 2017

Expect VFR conditions and CIGS above ILS breakpoints through the
next 24 hours. A passing disturbance will bring mountain showers
to the northern Colorado ranges this afternoon, though this
activity will not impact TAF sites. Breezy west winds will
accompany the passage of the disturbance resulting in modest
mechanical turbulence at TAF sites.






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