Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 202256

Area Forecast Discussion
National Weather Service Grand Junction CO
356 PM MST Mon Feb 20 2017

.SHORT TERM...(Tonight through Tuesday night)
Issued at 355 PM MST Mon Feb 20 2017

Very mild February continues today with temperatures again
creeping above normal in many areas. In the Grand Valley after 2/3
of the month has gone by, we are experiencing the warmest February
ever. The next few days will help keep this top spot on track but
it may come under threat later in the week as the polar jet will
be sag into the Desert SW. Looking upstream anomalously wet
conditions are again creeping onto the left coast from a good
subtropical tap. PWAT is running near 200 percent from SoCal into
western AZ and southern NV. This moisture will be pulled into our
region tonight as ridging overhead is replaced by a backing and
increasing southwest flow aloft. This thickening cloud cover will
help keep things a bit mild overnight and should limit the amount
of dense fog across the region. There could be some light snow
showers develop over the high country as this moisture works
across. The only problem is there is a lack of focus or ascent
overnight in most areas so expect the coverage will be isolated as
the dendritic layer stays mainly unsaturated. The best focus will
be over the northern CO mountains toward just due to the fact they
will be closest in proximity to the upper jet. Clouds look to
inhibit warming some tomorrow but with increasing winds aloft do
expect some mixing as hinted at above we should end up well above
normal. By tomorrow evening the subtropical jet will be nosing
across the 4 Corners and pulling along elevated moisture to the
southern mountains. Not overly impressed with dynamics attm but
there should be some high country showers over the San Juans
through the early morning hours.

.LONG TERM...(Wednesday through Monday)
Issued at 355 PM MST Mon Feb 20 2017

More unsettled weather begins to creep into the West mid to late
week. The warm air that has been dominating the region looks to
get suppressed south and east as large scale troughing will be
dominating western NOAM. The storm pattern however looks to get
hung up mainly across the northern half of CO and UT through the
weekend. Wednesday into Thursday will be the most active of this
period. Showers will be increasing across the Northern Utah and
Colorado mountains Wednesday as the upper jet begins to dip
southward and focuses the last of the Pacific moisture up north. A
more organized wave approaches Wednesday night and moves along
the CO/WY line on Thursday. At the surface a front looks to dip
into our northern counties and provide low level ascent and focus
for heavier precipitation along with much colder temperatures. The
front will remain rather stationary due to the flow aloft and
should bring some decent precipitation rates up north...much in
the form of snow. The front will get a push southward by the
system moving along the state line Wednesday night and Thursday
will be much cooler across most areas with heavier snow likely
across the central and northern mountains and lighter showers to
the south. Lingering showers on Friday behind the system should
then lead to a downturn for the weekend as broad ridging sets up
ahead of the next Pacific storm arriving to the left coast.


.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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