Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 210440
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
1040 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 flow.

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 06Z TAFS through 06Z Tuesday night)
Issued at 1040 PM MDT Mon Mar 20 2017

Showers associated with a weak disturbance are expected to
diminish during the early morning hours. Latest radar indicated
activity over the northern mountains and the San Juan mountains
was decreasing in coverage and intensity late this evening. It`s
unlikely that showers will impact TAF sites through 18Z, therefore
expect VFR conditions and CIGS above ILS breakpoints through
midday Tuesday. Light drainage winds will prevail tonight through
Tuesday morning. However, showers and isolated thunderstorms are
expected to redevelop over the mountains after 18Z, but are
unlikely to bring rain to TAF sites. CIGS will stay above ILS
breakpoints and VFR conditions will continue. Outflow winds from
showers or thunderstorms are possible at KASE and KTEX due to
their close proximity to the mountains.

&&

.FIRE WEATHER...
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 to 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.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

CO...None.
UT...None.

&&

$$

SHORT TERM...MDA
LONG TERM...MDA
AVIATION...NL
FIRE WEATHER...TGJT



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