Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 221700

Area Forecast Discussion
National Weather Service Grand Junction CO
1100 AM MDT Sun Apr 22 2018

.SHORT TERM...(Today through Monday)
Issued at 302 AM MDT Sun Apr 22 2018

A low amplitude ridge will pass over the area today and tonight
bringing dry conditions, but a weak disturbance will ride through
the ridge tonight. This feature will bring isolated showers to the
northern and central CO mountains.

On Monday a strong trough will move through the northern Rockies
and affect mostly northern UT and CO. West to southwest winds will
increase Monday as the low closes off at 500 mb over northern WY.
The NAM12 is strongest with this storm, while the GFS and ECMWF
bring less moisture into the area with it. The EC in particular
bring very little moisture west of the Continental Divide Monday.

.LONG TERM...(Monday night through Saturday)
Issued at 302 AM MDT Sun Apr 22 2018

It appears favorable upper jet location and a sagging cold front
may keep showers going across portions of the northern and central
CWA early Tuesday. There will be a narrow band of moisture
feeding into the ascent as the jet shifts overhead during this
time. There could be enough focus for some precipitation to reach
lower elevations but the northern and central Colorado mountains
will again be favored. Showers will likely linger late into the
evening Tuesday energy in the back end of this trough rotates
through. With this cold front temperatures look to drop off some
7 to 12 degrees on Tuesday compared to Monday. Kind of an
interesting pattern developing for the mid week period. What this
really means is the models are throwing out a solution that is not
a well recognized pattern so confidence is not very high. A
plethora of things seem to be happening concurrently in the West.
A transitory ridge moving in behind the early week trof will be
dropping into the Northern Rockies which will slow the progression
of a moist subtropical wave lifting across the Baja into the
Southwest. Problem one arrives with solutions for the trough
following the northern stream ridge. The digging trough of the
Euro draws in some of this moisture and brings better precip to
the southern divide and eastern Colorado by late Thursday. The GFS
sweeps the trough well to the Northeast and leaves this moisture
to linger over our CWA and leads to some weaker showers Thursday.
All the while as this is happening during the week a cutoff low is
slowly churning toward the Left Coast. Models are really not
handling the arrival of this system to the landmass very well and
will not go into great detail...except if you want a wetter
outcome cheer on the GFS. Temperature generally above normal
beyond Tuesday.


.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 1100 AM MDT Sun Apr 22 2018

VFR conditions will prevail at all TAF sites for the next 24
hours. A minor disturbance will bring scattered showers mainly to
the higher terrain along the Continental Divide after 21z and
diminish by 06z. Local mountains obscurations are expected.




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