Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 210323

Area Forecast Discussion
National Weather Service GRAND JUNCTION CO
923 PM MDT Thu Apr 20 2017

Issued at 920 PM MDT Thu Apr 20 2017

Updated the forecast through midnight tonight. Cold front will
continue moving through western CO this evening with a nice
vort max in the flow traveling just north of Grand Junction and
should track over Rifle and Eagle.

UPDATE Issued at 819 PM MDT Thu
Apr 20 2017

Winds have been dropping steadily in the zones impacted by the Red
Flag Warnings with relative humidity values climbing back up and
above 15 percent. With weather conditions improving in regards to
fire weather conditions, have allowed the Red Flag Warning to
expire for Colorado Fire Weather Zones 207 and 290. Now we turn
out attention to the increasing showers and isolated thunderstorms
across our central and northern zones. Expect snow levels to
slowly drop through the overnight period with light to moderate
snowfall accumulations across the northern and central mountains
above 9000 feet. Current Winter Weather Advisories remain on track
with the heaviest snowfall expected across the Park Range near
Steamboat Springs and over the Flat Tops. HRRR run has nudged
snowfall up a bit, but still within advisory criteria. Rabbit Ears
Pass and Vail Pass will be impacted by this passing system.


.SHORT TERM...(Tonight through Friday night)
Issued at 333 PM MDT Thu Apr 20 2017

Isolated to scattered showers popping as expected in the
warm...highly mixed atmosphere this afternoon. Dry air really
infiltrating from the southwest is keeping most of the activity
limited to the central and northeast zones with a few strikes of
lightning in the mix. The warm temperatures and instability is
also helping mix winds down with Red Flag conditions being met
across SW.Colorado and the occasional strong gusts near showers.
The upstream system digging out of the PacNW has trended northward
the past 24 hours with the slower fropa of the GFS also
verifying better today. This front will be the focus for
organized precipitation moving across the northern half of the CWA
this evening with the large scale dynamics and orographic flow
keeping precipitation focused on the portions of the central and
northern Colorado mountains through Friday evening. The northward
trends of the models will not have a huge impact on the forecast
with the best accumulating snow favored over the higher terrain
from the Park to the Elk Ranges. Some snow likely to fall in the
upper Yampa...Colorado and Eagle Basins but temperatures do not
appear favorable for accums on the roadways at this time. The
pattern in the central CONUS takes on a mini-Rex pattern as the
negatively tilted trough over the Rockies undercuts the ridge of
high pressure it will be replacing. This allows a back edge energy
to rotate across the northern mountains to front range early
Saturday and may keep some snow showers going across the divide.
Temperatures on Friday can be expected to be some 10 to 15
degrees cooler than today behind the front with lows dipping in
into the mid to lower 30s in some of the western lower valleys.

.LONG TERM...(Saturday through Thursday)
Issued at 333 PM MDT Thu Apr 20 2017

A gradual warmup begins Saturday with warm and breezy conditions
setting up for Sunday as we get transitory short wave ridging
setting up over the Rockies. A pattern change does look to be on
the horizon after this as more amplified ridging in forecast to
develop in the northern Atlantic and central Pacific. This will
force the jet stream farther south leading to a general and
prolonged trough pattern over the West. As a result cooler and
more active weather will be impacting our region. Details still
fuzzy but appears a brush by system is likely Monday followed by a
more significant storm system by midweek. Downstream blocking
will allow this system to organize and wrap up farther west than
the past several storms. Temperatures stay seasonable up until
this possible scenario then would cool significantly to end the


.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 540 PM MDT Thu Apr 20 2017

Scattered showers and thunderstorms will continue through this
evening with showers becoming more widespread along and north of
Interstate 70 after 09Z tonight. Rain or a rain/snow mix will
changeover to all snow in the mountains overnight, favoring the
northern and central CO mountains for moderate to locally heavy
snowfall rates through Friday morning. CIGS will gradually lower
this evening with widespread MVFR to IFR CIGS/VSBYS over northern
and central CO mountains, through about 18Z Friday.


CO...Winter Weather Advisory until 6 PM MDT Friday for COZ004-010-013.



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