Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 181646

Area Forecast Discussion
National Weather Service Grand Junction CO
1046 AM MDT Thu Oct 18 2018

.SHORT TERM...(Today through Friday)
Issued at 435 AM MDT Thu Oct 18 2018

Showers continue to move northward this morning along the eastern
flanks of an upper level low that has made its way up into north-
central Utah. Bands of light to moderate rain/snow continue across
eastern Utah with rainfall amounts in excess of a half inch
reported by spotters and remote sensors over the past 24 hours.
Snow levels dropped to around 7k per spotters with light
accumulation, but bulk of the snowfall was above the 8500 foot
level. Remote SNOTEL sensors showing modest accumulations based
off snow water equivalent values (SWE), especially in the vicinity
of Camp Jackson, although temps only support ratios around 6:1 or
basically a slushy mess.

The upper level low responsible for this round of action will be
filling today and lifting east-northeast this afternoon, driving
showers eastward across western Colorado as the day progresses. is
expected to slowly fill and drag eastward day, sending more
showers across western Colorado by this afternoon with activity
likely lingering into the evening hours before shutting down. H7
temps running in the -1 to -4 C range today which keeps snow
levels in the 75 to 85k range. Could see another 2 to 5 inches
across the Abajos, La Sals and portions of the Bookcliffs north of
Interstate 70 and west of Thompson Springs. Impact zones in these
areas are minimal from a transportation standpoint and will hold
off on any winter highlights for now. Will re-evaluate these
areas once we can get some new ground truth reports later this
morning for any possible highlights. Otherwise, expect more
scattered coverage of showers with only light mountain
accumulations in western Colorado and generally at or just above
pass levels.

This system exits the area this evening with dry weather returning
for Friday. Temperatures will be running 10 degrees below normal
today with a 5 degree nudge closer to normal anticipated for

.LONG TERM...(Friday night through Wednesday)
Issued at 435 AM MDT Thu Oct 18 2018

Friday night through the weekend a ridge aloft builds across the
Pacific Northwest and northern Rockies. This will keep the
forecast area dry and with mild temperatures. Meanwhile the
expansive cut off low pressure over the CA and Baja coasts will
begin to lift northeastward in the wake of the ridge and ahead of
a strong trough digging over the Pacific Northwest. As it
approaches the Great Basin it begins to pull some moisture
northward from the Gulf and Eastern Pacific. By late Sunday the
moisture and forcing for ascent come together to produce
precipitation across the forecast area. The models are struggling
with how this low pressure gets absorbed into the main trough
tracking in from the northwest, so details are uncertain. The
other important factor is that the low will be comprised of
several pieces of energy and each model handles these vorticity
maximums differently. The southerly flow prior to the system will
bring in 700 mb temperatures that range from 0-5C so snow levels
should be relatively high. Given the current speed of the trough
and the potential for several rounds of forcing the precipitation
chances linger into at least Wednesday.


.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 1040 AM MDT Thu Oct 18 2018

Areas of precipitation and layered lower and mid clouds will
affect all TAF sites today through this evening with the most
impact expected at KVEL and KCNY. These two sites will experience
MVFR cigs and brief IFR CIGS in heavier showers. Mountains will be
frequently obscured and CIGS below ILS breakpoints will be common.
Conditions will improve from west to east after about 06z tonight.




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