Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 202110

Area Forecast Discussion
National Weather Service Grand Junction CO
310 PM MDT Mon Mar 20 2017

.SHORT TERM...(Tonight through Tuesday night)
Issued at 310 PM MDT Mon Mar 20 2017

Mid and high level cloud cover and mild temperatures will continue
through Tuesday in southwest flow, as a couple of weak shortwaves
pass through the region. Some isolated to scattered high-based
showers are developing across mainly northern portions of the area
but due to the dry low levels, not expecting much precipitation
to reach the ground with virga being detected further upstream.
Winds will be breezy both today and Tuesday afternoon as well due
to the milder temps and in vicinity of any virga showers.
Temperatures are still above normal but afternoon highs are
expected to be a few degrees cooler than this past weekend due to
increased cloud cover with overnight lows being a bit milder.

.LONG TERM...(Wednesday through Monday)
Issued at 310 PM MDT Mon Mar 20 2017

Southwest flow will increase on Wednesday afternoon and evening
ahead of a Pacific trough moving inland over the western states as
a 110 kt jet noses into the Four Corners by Wednesday evening, with
H7 winds of 40 to 50 kts ahead of this system. Forecast models
are in better agreement on the timing and placement of this system
impacting the area Wednesday evening through Friday morning.
Showers may develop in the southwest flow ahead of this system by
late Wednesday afternoon over the higher terrain, but the better
chances for precipitation will come Wednesday night into Thursday.
Abundant moisture is available as Precipitable Water (PW) values
increase to between 0.4 and 0.6 inches Wednesday evening into
Thursday, with specific humidity values in the 4 to 5 g/kg range.
This is well above the normal values for this time of year. Warmer
temperatures also mean high snow levels to start, with snow
levels mainly between 8000 and 9000 ft MSL during the day on
Thursday. The cold front looks to move through later than earlier
forecast model runs indicated, with current timing sometime
Thursday afternoon and evening. H7 temps will lower to -5C to -3C
post-frontal Thursday night into Friday morning, with snow levels
lowering to around 6000 to 7000 ft MSL. Potential exists for 5 to
10 inches of snow in the mountains and rain in the lower
elevations at this time. The best chance for the lower valleys to
see snowfall will be after midnight Thursday night into Friday
morning as the colder air moves in with some mixing of
precipitation, but accumulations look limited. Decent rainfall
amounts however are possible in the valleys on Thursday with
potential for thunderstorms as well given the steep lapse rates,
instability and convective nature of this storm. The southern and
central mountains look favored for best snowfall accumulations
given the proximity of the low. Some wraparound moisture is
evident Thursday afternoon and evening on the north side of the
low with Q vector convergence over the central mountains, as well
as a TROWAL signature by Thursday evening in that wraparound

This system will move across our southern border as a closed low,
with the low strengthening and becoming vertically stacked by
Friday morning over the western OK panhandle and SE Colorado
border. This will take most of the energy to our east over the
Plains and Front Range by Friday morning with a drying trend
Friday afternoon from west to east. Some snowfall will linger
through Friday morning over the western Colorado divide mountains
with north-facing slopes being favored as the flow shifts from
the west-southwest Thursday afternoon towards northerly by
Thursday evening. This setup looks prime for the Uncompahgre
Gorge in the NW San Juans to see the potential for enhanced
snowfall Thursday night into Friday morning, so something to keep
an eye on. Will continue the Special Weather Statement and update
wording to reflect this potential. Still a little too early for
any winter weather highlites but this will be something for later
shifts to consider as details come into greater focus on snow
levels and amounts.

Models are in good agreement in showing a shortwave ridge of high
pressure building back into the region by Friday afternoon through
Saturday for mostly dry weather. Clouds and southwest flow will
increase on Saturday ahead of yet another storm system set to move
through the region on Sunday. The weather pattern looks unsettled
into next week as a series of systems move through the region
bringing potential for more precipitation.


.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 1136 AM MDT Mon Mar 20 2017

Some mid to high clouds and gusty winds are expected over the
region today - afternoon virga enhancing that chance of gusty
winds at all TAF sites. Isolated to scattered showers and
thunderstorms will develop over higher terrain this afternoon and
evening but are not expected to impact TAF sites except for the
occasional erratic wind from outflow. VFR conditions are expected
to persist at all TAF sites over the next 24 hours.


Issued at 310 PM MDT Mon Mar 20 2017

Well above normal high temperatures and dry weather will continue
today. Relative humidities are again expected to drop into the 15
to 25 percent range this afternoon. The gustiest winds will occur
after 3 pm with wind gusts of 20-25 mph at lower elevations. The
gusty winds combined with warm temperatures, low humidity and
still dormant or dry vegetation will require a heightened fire
weather awareness. Check the latest forecast before attempting any
burning through as conditions can change rapidly. The potential
for near critical fire weather conditions will be greatest for
elevations below 8000 feet.




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