Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 280524
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
1124 PM MDT Mon Mar 27 2017

.SHORT TERM...(Tonight through Tuesday night)
Issued at 231 PM MDT Mon Mar 27 2017

An upper level trough continues to dig over the Great Basin this
afternoon. Despite mild air aloft, cloud cover has kept
temperatures in check this afternoon. Plenty of virga has been
noted on KGJX radar this afternoon - dry air below 600mb was evident
in both the morning observed and afternoon model soundings
throughout the region. Cloud cover has also helped to keep
instability down as well, with afternoon and evening thunder
appearing less likely ahead of the approaching trough. Still,
heavier precipitation on the nose of vorticity maximum is
expected to overspread the region this evening. Mesoscale models
are all in general agreement on this steadier stream of moisture
making it to the UT/CO border around 6pm, and as far east as
Craig/Eagle/Pagosa Springs by 9pm. Can not rule out a rumble of
thunder early in southeast Utah where skies have been a bit less
cloudy.

The previous forecast is still on track regarding the evolution of
the current storm system and minimal changes have been made in
this forecast package with regard to QPF and storm total snowfall.
Appears as though the best lift and dynamics will pass through
eastern Utah and western Colorado between this evening and 6am
Tuesday. Snow levels still appear to remain mostly above 8500
feet, with advisory-level snowfall totals in southern and central
Colorado above 9000 feet. Impacts to travel will be greatest
overnight and through the morning hours on Tuesday for those
travelling over the higher passes.

By sunrise Tuesday, guidance suggests the heaviest precipitation will
have come to an end across much of the western slope. As the
surface low develops over the southern high plains, southeasterly
flow will transport a stream of moisture northward into eastern
Colorado and southern Wyoming. This Gulf moisture will likely
result in lingering light to moderate precipitation across much
of northern Colorado west of the divide, as well as in
northeastern Utah. High-res short-term forecast models are zeroing
in on the region from the eastern Uinta Range, Roan and Tavaputs,
and Flat Tops for a secondary maximum in precipitation occurring
between around 9am and 3pm with continued east to northeasterly
flow. To the south of Interstate 70, more clearing in the morning
and early afternoon will result in the opportunity for afternoon
convective showers, given colder air aloft associated with the
upper-level low. Precipitation will wind down area-wide overnight
on Tuesday into Wednesday with the loss of surface heating. The
cutoff low pressure system will drift east through the morning
hours Wednesday with 500mb heights slowly rising as the day
progresses.

.LONG TERM...(Wednesday through Monday)
Issued at 231 PM MDT Mon Mar 27 2017

By Wed. evening the storm should be centered over the Panhandles with
moderate north to north-northwest flow aloft over the area. Most of
the moisture will be east of the area with just enough left over the
Continental Divide to provide isolated showers. Overnight  and Thu.
morning a transitory ridge moves over the area. In the GFS the ridge
is well east of the area by late afternoon with increasing SW flow
aloft ahead of the next Pacific system that will be moving through
the Great Basin.

Friday through Monday...the system closes over southern UT then
glides slowly south to NE Arizona Sat. morning. Throughout the day
Sat. and Sat. night the low center moves south to SE Arizona,
keeping wraparound moisture and TROWAL induced precip over much of
the area. By Sun. afternoon the low center will be well south of
the area and most of the moisture will be to the east. Monday
should be another in-between as a weak ridge will pass over the
area ahead of the next Pacific storm, that will be cruising
through the western Great Basin.

&&

.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 1119 PM MDT Mon Mar 27 2017

Significant impacts expected to continue across much of eastern
Utah and western Colorado through Tuesday evening as widespread
showers persist. Mountains will be frequently obscured with ILS
CIGS expected at all sites. Areas of IFR and MVFR conditions will
occur at KTEX, KASE and possibly KEGE with brief MVFR conditions
possible at the lower terminal sites. Confidence remains high
through this forecast period.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...
CO...Winter Weather Advisory until noon MDT Wednesday for COZ009-010-
     012-013-018-019.

UT...Winter Weather Advisory until 9 AM MDT Wednesday for UTZ023-028.

&&

$$

SHORT TERM...MAC
LONG TERM...CC
AVIATION...JDC


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