Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 210944

Area Forecast Discussion
National Weather Service Grand Junction CO
344 AM MDT Fri Sep 21 2018

.SHORT TERM...(Today through Saturday)
Issued at 157 AM MDT Fri Sep 21 2018

Much drier air flowed across the forecast area from the west
beneath a low amplitude ridge of high pressure during the night.
The latest surface observations reported dew point values which
were down by 20 to 30 degrees as compared to 24 hours earlier.
In fact, KCNY was down by 32 degrees with the dew point at 08Z at
just 15 degrees. Under completely clear skies, the dry air has
been very efficient in radiating away surface warmth and
temperatures were 10 to 20 degrees cooler across the north early
this morning, and from 5 to 10 degrees cooler elsewhere. KCAG was
at 34 degrees at 09Z and will very likely to fall below freezing
before sunrise justifying the Freeze Warning hoisted Thursday

Though drier for most locations today, models suggest a backdoor
surge of moisture into the San Luis Valley working up the eastern
San Juans will fuel isolated afternoon/early evening thunderstorms
over the higher ridges of the western San Juan Mountains. Expect
this activity to be high based, producing more wind than rain.
Elsewhere, sunny skies and slightly warmer afternoon highs are
expected, with most areas around 5 degrees above normal.

Winds will shift to the southwest on Saturday as a low pressure
trough moves to the coast of the Pacific Northwest. Meanwhile,
height packing aloft increases and will generate breezy afternoon
winds across the northwestern portion of the forecast area during
the afternoon and evening. Aside from the shift in winds,
conditions will be very similar to those forecast for today with
sunny/mostly sunny skies helping to sustain above normal warmth.
Meanwhile, lingering moisture in the San Juans is expected to
bring a few thunderstorms during the afternoon.

.LONG TERM...(Saturday night through Thursday)
Issued at 157 AM MDT Fri Sep 21 2018

Saturday and most of Sunday will continue to bring sunny skies
and warmer than average temperatures as they run about 5 degrees
above normal. The jet will remain to our north but this changes
during the day Sunday into Monday morning as a strong portion of
the jet starts to drop down from the Gulf of Alaska. This jet will
cause a trough to form which will support a weak surface cold
front. Previous runs really downplayed this system but latest runs
are now increasing precip amounts across the area. Despite that,
amounts still look to range from .1 to .25 inches as the front
moves through. Clouds will increase from the northwest towards
sunset. The front will move through early Monday morning and will
reach the San Juans by noon, give or take. Wouldn`t be surprised
for the higher elevations (above 12 to 13K) to see a skiff of
snow. Once the front moves through, northwesterly flow will usher
in cooler temperatures and these temps look to hang around for the
rest of the work week. Once the front moves through, a
progressive pattern sets up for the central states as systems drop
down from Canada and bring precipitation to those areas. We`ll be
sandwiched between a deep trough to the east and very weak
ridging over the Desert Southwest. Unfortunately, doesn`t look
like any precipitation for us though we`ll see some clouds from
time to time.


.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 1140 PM MDT Thu Sep 20 2018

Clear skies overnight will give way to a few high clouds tomorrow.
Some afternoon breezes are possible and may reach 20kts from time
to time. VFR conditions will remain in place.


Issued at 157 AM MDT Fri Sep 21 2018

Expect southwest winds to increase over northwest Colorado this
weekend ahead of an approaching Pacific trough. Vegetation remains
very dry across the region so gusty southwest winds combined with
above normal temperatures and low relative humidity could result
in critical fire weather conditions.



CO...Fire Weather Watch from Saturday afternoon through Saturday
     evening for COZ200.

     Fire Weather Watch from Sunday afternoon through Sunday evening
     for COZ200.

     Freeze Warning until 9 AM MDT this morning for COZ002-005.




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