Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 191844

Area Forecast Discussion
National Weather Service GRAND JUNCTION CO
1244 PM MDT Mon Mar 19 2018

Issued at 1242 PM MDT Mon Mar 19 2018

Isolated to scattered snow showers will continue over the
mountains through this afternoon. See some patchy low clouds as
well developing down into the valleys, so made some adjustment to
the sky grids for this afternoon. Cloud cover should dissipate
rather quickly this evening as we lose the low level instability.
No other changes at this time.


.SHORT TERM...(Today through Tuesday)
Issued at 422 AM MDT Mon Mar 19 2018

The storm system which brought snow to the area over the past
twenty-four hours continued to shift eastward across the southern
Plains early this morning. Meanwhile, snow persisted over the
northern, and portions of the central Colorado mountains early
this morning despite the absence of large scale dynamic forcing.
Regardless, the combination of steep lapse rates and orographic
lift provided by moderate northwest flow were sufficient to
sustain snowfall over the northern and central Colorado mountains.
Though snowfall rates will decrease this morning, models
indicated moisture and orographic forcing will continue to
generate snowfall well into the morning before snowfall becomes
more scattered this afternoon. Therefore, will keep the Winter
Weather Advisories going over the Elkhead, Park, Gore, and Elk
Mountains through midday. However, will drop advisories a couple
of hours early for the Grand Mesa, West Elk and Sawatch Mountains
with this package as snowfall had become light and scattered over
those ranges. Except for the lower elevations east of a KCAG to
KRIL to KASE line this morning, expect dry conditions today with
partly cloudy to mostly sunny skies.

Instability showers were indicated to linger over the northern
Colorado mountains tonight, though coverage and intensity will
continue to decrease. GFS maintains this activity through Tuesday
afternoon while the NAM and ECMWF finally bring an end to
convective showers Tuesday morning. Given model differences, held
onto slight chances of snow for the higher terrain of northeast
Utah and northwest Colorado through Tuesday afternoon. Elsewhere,
dry weather will continue.

Expect temperatures to remain cool today and tonight, running
from 5 to 10 degrees below seasonal norms. Temperatures trend
upward Tuesday with highs approaching normal for most locations
during the afternoon.

.LONG TERM...(Tuesday night through Sunday)
Issued at 422 AM MDT Mon Mar 19 2018

A weak ridge will allow for steady warming through the middle
portion of the week over the western slope. As the ridge axis
passes on Wednesday afternoon, guidance suggests enough
saturation in the mid and upper levels to possibly squeeze out a
few orographic showers in the highest terrain of the central and
northern mountains. Flow turns southwesterly on Thursday as a
notable atmospheric river event comes ashore along the California
Coast. Moisture from this event spills into the Four Corners
region by late in the day on Thursday. Temperatures will be quite
warm ahead of this system, as is typical for these kind of
events, with highs in the mid-60s in the lower elevations and
700mb temperatures in the +2 to +5C range throughout most of the
mountains as precipitation begins. Precipitable Water normalized
anomalies climb to 4 to 5 Sigma by Thursday evening, and remain
in this general range through Friday afternoon. The 0z GFS has
come in a bit wetter as far as surface QPF is concerned, in
comparison to the past several deterministic runs. This appears to
be due to a slight southward shift to the overall AR plume. These
kinds of swings will likely continue over the next few days of
model cycles and will ultimately determine what ranges see the
most liquid out of this event. Guidance suggests this system will
exit by Friday evening with ridging moving in for Saturday and a
dry start to this coming weekend, before another storm of Pacific
origins skirts the central and northern mountains on Sunday.


.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 1118 AM MDT Mon Mar 19 2018

A few light snow showers will linger over the northern mountains
in western Colorado this afternoon. This will result in local
mountain obscuration and brief MVFR CIGS. CIGS may briefly drop
below ILS breakpoints this afternoon at KHDN, KEGE and KASE,
otherwise VFR conditions are expected through Tuesday afternoon.




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