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Area forecast discussion 
National Weather Service Grand Junction Colorado
527 PM MDT Monday Oct 20 2014

Short term...(this evening through Tuesday night)
issued at 330 PM MDT Monday Oct 20 2014

The forecast area remained sandwiched within an area of split
flow between a ridge over the northern plains and a low over
southeast New Mexico. Moisture has increased over the area which
has fueled isolated showers over the mountains and at least one
thunderstorm over the San Juan Mountains.

As the evening progresses...expect a downturn in shower activity
as the atmosphere cools. However...a vorticity center over east-central
Arizona will become entrained in the southerly flow ahead of a
deep Pacific trough providing lift over east-central Utah and
west-central Colorado and renewed shower activity later tonight.

Showers and thunderstorms will increase Tuesday as the trough
swings inland across the Great Basin and lifts to the northeast.
Decent large scale ascent and moderate moisture expected to bring
widespread precipitation to most mountains and a strong chance for
rain in the valleys. Snow levels will begin near 11000
not expecting impactful snowfall over the passes.

The trough axis will pass east of the area around midnight so
anticipate that precipitation will continue into the evening...
lingering across The Divide mountains during the night as
orographic lift wrings residual moisture from the airmass. Snow
levels will fall to near 10000 feet by morning so light
accumulations on the northern and Central Mountain passes likely
to slow traffic a bit by Wednesday morning.

Long term...(wednesday through monday)
issued at 330 PM MDT Monday Oct 20 2014

Latest models show decent subsidence moving into the forecast
area on Wednesday...however some lingering instability is expected
to produce isolated showers from west to east in the early
morning hours through the afternoon. These showers will dissipate
throughout the afternoon into the evening as the atmosphere
stablizes from west to east. By late Wednesday...high pressure
will be building into the region and will produce dry and
unseasonably warm temperatures through the end of the workweek.

A deep trough will move onshore the Pacific northwest states on Saturday
increasing the pressure gradient between the ridge over the area.
Southwest winds will increase throughout the day Saturday ahead of
this feature as the ridge gradually moves east. Long term models
are in agreement that this trough/cold front will move through the
northern part of the forecast area on Sunday...bringing
winds...precipitation...and cold air with it. Since this storm
system is still quite far out in the future...the timing and
strength of it may change so we will continue to monitor it for
its forecast development over the next week.


Aviation...(for the 00z tafs through 00z Tuesday evening)
issued at 524 PM MDT Monday Oct 20 2014

Expect VFR conditions to continue at taf sites through the next 12
to 18 hours. However...there will be isolated showers and a few
thunderstorms over the central and southern mountains this
evening. This activity will result in localized mountain
obscuration and gusty outflow winds. There is a 20 to 30 percent
chance that this activity could impact taf sites through 04z this
evening...though flight rules should remain visual. After 15z
Tuesday...a cold front will push across the region...bringing more
widespread showers and isolated thunderstorms. Ceilings will be
dropping with areas of MVFR conds expected...mainly over the


Gjt watches/warnings/advisories...


Short layers
long term...jam

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