Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 230555

Area Forecast Discussion
National Weather Service GRAND JUNCTION CO
1155 PM MDT Thu Mar 22 2018

.SHORT TERM...(Tonight through Friday night)
Issued at 340 PM MDT Thu Mar 22 2018

In looking at sounding climatology at GJT against forecast model
soundings, the atmospheric river event reaching the UT/CO border
today will likely exceed record precipitable water values across the
region over the next 24 hours. Showers this evening will be
scattered and mainly over the higher terrain (generally above 8000
ft), with clouds and virga for most valleys of eastern UT and
western CO. The system still looks on track from previous forecasts,
with a vort max rolling through in the early morning hours which
means that precipitation coverage will increase across the region by
sunrise Friday. Strong warm air advection ahead of the cold front
associated with this system will keep temperatures mild and snow
level high on Saturday before cooler air advects into the region.
The winter weather advisories for significant accumulating snow at
locations above 9500 feet still look accurate, though snow will be
possible as low as 8000 ft by late Friday morning. Decided to add
zone 10 (southern Gore Mtns/Maroon Bells) to advisory above 9500 ft,
as winds will shift early Friday morning to a favorable flow for
this high peaks. As this weather system moves eastward on Friday
morning, precipitation will clear out of eastern Utah before noon
and roll eastward out of western Colorado to the Continental Divide
by noon. A few additional isolated showers may pop up Friday
afternoon over the mountains after the main line of precipitation
moves through.

.LONG TERM...(Saturday through Thursday)
Issued at 340 PM MDT Thu Mar 22 2018

A large trough rolls into the Pacific NW on Saturday, which will
house a -35C cold core at 500mb. This is a rather cold system for
late March, but it will lose some "oomph" before it reaches the
Great Basin. While this trough moves onshore, winds will remain
slightly elevated across eastern UT/western CO in being between
the cold air mass situated with the trough and ridging over the
southern US and conditions will remain dry (late Fri through
Sun). The closed low associated with this western US trough is
expected to drop south into Arizona then retrograde eastward
midweek south of the Four Corners. This system will bring
unsettled weather to the region from Monday through Tuesday, but
there hasn`t been excellent consistency between models so my
forecast confidence is low on how this will play out. After this
closed low feature moves through the southwestern US, forecast
models do diverge on features late next week. At this time,
confidence is moderate that northwesterly flow will stick around
for a few days late next week with the potential for some light
precipitation over the northcentral Colorado mountains.


.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 1155 PM MDT Thu Mar 22 2018

Broken mid and high level clouds will become scattered early this
morning as drier air works in ahead of a cold front set to move
through the area after between 12Z and 18Z Friday. Some occasional
light showers will occur ahead of the front with heavier
precipitation and isolated thunderstorms expected along the cold
front as it moves quickly through the area, with a brief reduction
to MVFR and possibly IFR conditions. ILS breakpoints look to be
met at most TAF sites under these heavier showers as the front
moves through. Expect rain at most TAF sites with some snow
possible at KTEX and higher elevations above 10,000 feet MSL.
Conditions will improve with rising ceilings and clouds becoming
scattered by early Friday afternoon into the evening with some
lingering isolated showers possible. Winds will gust into the 20s
and possibly 30s as the front and trough move through late Friday
morning into the early afternoon.


CO...Winter Weather Advisory until 6 PM MDT Friday for COZ004-009-012-

     Winter Weather Advisory from 6 AM to 6 PM MDT Friday for COZ010.



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