Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 212130
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
330 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 Sunday 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 package.

.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 18Z TAFS through 18Z Sunday afternoon)
Issued at 1145 AM MDT Sat Apr 21 2018

Heavier cloud cover and low CIGs will continue to lift this
afternoon as the low pressure system moves well to our east. By
00Z widespread VFR conditions will return to the area as high
pressure gradually builds in from the west. Isolated snow showers
are possible over the San Juans after 15Z Wednesday.


&&

.GJT WATCHES/WARNINGS/ADVISORIES...
CO...None.
UT...None.
&&

$$

SHORT TERM...MAC
LONG TERM...MAC
AVIATION...MMS


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