Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 250914

Area Forecast Discussion
National Weather Service GRAND JUNCTION CO
314 AM MDT Sun Jun 25 2017

.SHORT TERM...(Today through Monday)
Issued at 300 AM MDT Sun Jun 25 2017

An approaching area of low pressure off the California coast will
cause the ridge axis to become more oriented from north to south
as opposed to northwest to southeast. In the grand scheme of
things, this won`t make much of a change for our weather.
Afternoon convection looks possible over the San Juans though the
short-range models all agree that the best chances look to be to
our south and east. Even so, marginal CAPE and some modest
instability may lend itself to a few showers or storms so forecast
captures this thinking. No mention of smoke this afternoon for
southern areas though depending on upper level winds it may need
to be added later on today. Temperatures will inch up a few
degrees from those seen yesterday but aside from that, another
warm, sunny day on tap.

By Monday, the low pressure will become a low amplitude trough and
will continue shifting the ridge axis east eventually causing our
windflow to become more zonal in nature. A bit more convective
build up is possible over the higher terrain on Monday but any
precipitation looks to be very minimal in nature with the San
Juans again favored. Temperatures will remain on their upward
trend with high temperatures flirting with triple digits for some
valleys. All in all, minimal change from day to day.

.LONG TERM...(Monday night through Saturday)
Issued at 300 AM MDT Sun Jun 25 2017

Southwesterly flow will increase on Tuesday and again on Wednesday
as a broad upper level trough digs into the western CONUS. A jet
maxima at the 250mb level will be ejected ahead of the trough during
this timeframe which will result in stronger winds mixing down to
the surface. Given the continued dry state of the atmosphere ahead
of this trough (as evident by the previously situated ridge as well
as low precipitable water values of 0.25 to 0.35 inches), relative
humidities will be quite low. Marginal to critical fire weather
conditions keep looking more likely for Tuesday and Wednesday.

The trough will push through the forecast area the latter half of
the week with temperatures cooling closer to seasonal norms in
response to the colder air mass behind the passage of the trough.
The latest GFS run now appears to be on board with the Euro`s
solution for the weekend by bringing yet another trough into the
Great Basin by Saturday.


.AVIATION...(For the 12Z TAFS through 12Z Monday morning)
Issued at 300 AM MDT Sun Jun 25 2017

Continued VFR conditions under high pressure. Some hazy conditions
possible for southeastern Utah and southwestern Colorado thanks to
the Brian Head Fire. A brief shower or storm is possible over the
San Juans but will not affect any TAF sites.





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