Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 201751

Area Forecast Discussion
National Weather Service Grand Junction CO
1051 AM MST Mon Feb 20 2017

Issued at 904 AM MST Mon Feb 20 2017

Visibilities are improving across the Central and Upper Yampa
River Basins as the dense fog has mixed out. Fog remains patchy
and thin in some localized areas but the threat for dense fog has
ended so the Dense Fog Advisory was allowed to expire.

UPDATE Issued at 724 AM MST Mon Feb 20 2017

Went ahead and hoisted a quick dense fog advisory for both the
Central and Upper Yampa River Basins. Current webcams show fog
lingering in these areas where visibilities will frequently be
reduced to 1/4 mile or less. These conditions will persist through
midmorning before conditions improve shortly after.


.SHORT TERM...(Today through Tuesday)
Issued at 334 AM MST Mon Feb 20 2017

Low clouds and scattered morning showers will gradually give way
to clearing conditions by this afternoon. The clearing will be
short-lived as we see more mid and high level clouds spread back
over the region with fast WSW flow setting up aloft. The upper jet
aligned to bring another prolonger atmospheric river event to
portions of the western U.S. with bulk of deep moisture sliding to
our north with the jet aligned from northern California NE to
eastern Wyoming by Tuesday. What does this all mean for us? Looks
like mild conditions will continue for a few more days with
isolated to scattered showers favoring the high country through
midweek. The jet eventually drops far enough south to drive better
forcing into our area just outside of this short-term packaged.
Temperatures will be 5 to 10 degrees above seasonal normals today
and Tuesday with mild overnight lows expected with increasing
blanket of mid/high level cloud cover.

.LONG TERM...(Tuesday night through Sunday)
Issued at 334 AM MST Mon Feb 20 2017

An increasingly moist zonal flow will develop as a weak baroclinic
zone sets up across the northern half of the forecast area on
Tuesday night and Wednesday. This feature has grown stronger with
each successive run and could see some light to moderate
accumulations Tuesday night through Wednesday, especially over the
northern mountains. After a brief lull, a colder and more active
weather pattern sets up for the region. A better organized
shortwave will drop into the Great Basin on Wednesday night and
move across the area on Thursday bringing another round of snow to
the mountains and rain/snow to the lower elevations Wednesday
night into Friday. Moist zonal flow will keep mountain snow shower
activity continuing on Saturday as another wave moves across the
Great Basin and brings another round of precipitation on Saturday
night into Sunday, with the best focus over the southern half of
the forecast area. After seasonable temperatures on Wednesday,
expect seasonably cold temperatures Thursday through the weekend.


.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 1050 AM MST Mon Feb 20 2017

Generally dry conditions are expected for W CO and E UT through
the next 24 hours as weak ridging builds in overhead. Mid and high
clouds will increase this evening and tomorrow as moisture
increases. This will also result in isolated to scattered showers
returning over the northern and central mountains after 18Z.
Another round of patchy valley fog is possible again tonight,
possibly impacting KVEL east to KSBS.




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