Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 072328

Area Forecast Discussion
National Weather Service Grand Junction CO
428 PM MST Wed Dec 7 2016

.SHORT TERM...(Tonight through Thursday night)
Issued at 302 PM MST Wed Dec 7 2016

Radar and satellite imagery is showing the convective nature to
the precipitation this afternoon with cold air shifting overhead.
Do expect much of this to dissipate over the next few hours though
some orographic showers are likely to hang on near the divide
through mid evening. A cold night on tap with very dry air in
place and we will start the evening under mainly clear skies as
the convection wanes. However, we will be seeing some higher
clouds begin to invade from the southwest by late evening and it
could be a race between how far the temperatures drops before this
blanket arrives. Did lower the Yampa River Valley and Gunnison
Valley where this thicker cloud cover will arrive later to these
cold sinks. Most of the warm advective cloud cover will not
produce much snow through tomorrow afternoon but definitely could
be some isolated showers along the higher mountain tops. Warm air
aloft and cloud cover is leading to shaky confidence for
temperatures and warming today has been better than expected.
Guidance is warming things up a few degrees and did lean that
way, probably a regretful decision. Moisture, fed by a robust
subtropical tap, will be increasing by Thursday evening as PWAT
begins to push back above normal. The first of many passing waves
in this moist persistent flow is coming across late Thursday into
Friday with support aloft from a passing jet. The northern and
part of the central mountains, the Park and Flat Tops, look
favored for the heaviest snow and there could be some 4 to 8
inches near near Vail to Rabbit Ears passes by the end of this
wave. The precipitation and cloud cover will limit radiational
cooling and warmer temperatures expected.

.LONG TERM...(Friday through Wednesday)
Issued at 302 PM MST Wed Dec 7 2016

Snow. Probably lots of snow. The moist westerly flow does not
abate through much of the upcoming week which means there will a
prolonged period of at least light snow falling somewhere across
the mountains and even some valleys at times. The tap of moisture
from the Pacific weakens a bit but still keeps our PWAT near to
above normal through the middle of next week. Basically there will
be a large gyre of low pressure circling the northern latitudes of
central and eastern NOAM which will help supply cold air and
transitory upper jet to bring periods of heavier snow to the
intermountain west including our mountains. There will be peaks
and lulls during this time as the upper and lower atmosphere gel
with favorable orographic flow. Timing of these waves are
difficult at best with confidence at this time pointing to early
to mid Saturday for the next passing disturbance. This flow will
help mixing and many of the valley inversions should be washed out
meaning rain could fall at lower elevations at times. By this
time next week, the big winners should be the northern and
central mountains where totals will be measured in feet. The
southern mountains will not be left out totally but this pattern
is not as favorable overall. However, expect the northern San
Juans should see some decent snowfall at times if the jet is able
to dip far enough southward. Stay tuned. Otherwise temperatures
stay near to below normal as cold air is ushered in behind waves
and lifts out ahead of the next.


.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 421 PM MST Wed Dec 7 2016

A few mid level broken ceilings are being reported at this hour
over KEGE...KVEL...KASE and KRIL. These will lift very shortly
though so do not expect much of a threat, if any, for aviation
concerns. VFR will set up overnight and persist through tomorrow
afternoon. Clouds will increase late Thursday afternoon into the
evening hours ahead of the next system.




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