Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 212333

Area Forecast Discussion
National Weather Service Grand Junction CO
533 PM MDT Sat Apr 21 2018

.SHORT TERM...(Tonight through Sunday night)
Issued at 300 PM MDT Sat Apr 21 2018

Light northerly flow remains over the mountains of western
Colorado this Saturday afternoon. Lingering lower cloud cover
will generally dissipate through the evening and overnight hours
as dry air in the lower levels continues to work in from the west.
On Sunday, our next trough will dive into the northern Rockies. A
few afternoon thunderstorms will develop in the higher terrain of
the central Rockies as a bit of moisture return sneaks in through
the mid-levels. With the loss of daytime heating, this activity
should diminish quickly after dark. Temperatures will warm on
Sunday, ending up around 5 degrees or so above average. No major
changes have been made to the short term forecast in today`s

.LONG TERM...(Monday through Saturday)
Issued at 300 PM MDT Sat Apr 21 2018

Winds will increase during the day on Monday especially to the
north of Interstate 70. A small but notable jet aloft will
accompany the trough that will pass to the north of the forecast
region. In addition, showers and possibly even a thunderstorm or
two will pass through the central and northern portions of
Colorado. This trough quickly passes east of the divide by early
Tuesday morning, however a stream of moisture aloft appears to
hang up in the mountains. This could allow for a few additional
showers in the central and southern mountains on Tuesday...however
guidance has not been very consistent with this solution. The NAM
and the ECMWF show a drier outcome on Tuesday, and the current
forecast package follows these trends.

Beyond Tuesday, forecast guidance is in generally good agreement
showing a dry and warm forecast west of the Continental Divide
through Thursday. After Thursday however, differences emerge. The
GFS hints at moisture return from the Gulf leading to clouds and
shower activity, increasing in coverage from Thursday through
Saturday. The ECMWF is vastly different, showing a trough passing
just east of the area on Thursday evening and ridging/dry weather
from Friday through Saturday. Ensemble guidance both from the GEFS
and EPS favors ridging and a drier weather for the end of the
week and early next weekend, adding confidence to the forecast
currently shown by today`s deterministic ECMWF.


.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 519 PM MDT Sat Apr 21 2018

VFR conditions are expected at all sites through Sunday afternoon.
However, local CIGS near ILS breakpoints will persist through 03Z
this evening east of a line from KCAG to KGUC with CIGS gradually
scattering out after sunset. Scattered light mountain showers are
expected to develop after 18Z/SUN with no impact anticipated at
TAF sites.




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