Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 220009

Area Forecast Discussion
National Weather Service GRAND JUNCTION CO
609 PM MDT Mon Aug 21 2017

Updated aviation section

.SHORT TERM...(Tonight through Tuesday night)
Issued at 325 PM MDT Mon Aug 21 2017

The sky cooperated relatively well late this morning and made for a
nice viewing of the total solar eclipse for much of the forecast
area under mostly to partly sunny skies. Further south in the Four
Corners and southwest Colorado scattered clouds persisted where
the better midlevel moisture remained. As expected, another round
of diurnal showers and thunderstorms developed over the higher
terrain and as has been the trend over the past several days, most
convection should end after sunset with the loss of daytime
heating. Overnight lows tonight will remain slightly above normal
for this time of year.

The axis of the upper level ridge attempts to build across the
length of the Rockies on Tuesday as the SoCal low remains planted
just off the California coast. A shortwave trough associated with
this low will be ejected through our southern forecast area Tuesday
afternoon which will enhance the coverage and intensity of showers
and thunderstorms over the southern and central mountains.
Elsewhere, expect typical pop-and-drop summer convection to fire
off over the rest of the higher terrain as a result of daytime
heating and residual moisture. Skies should clear pretty quickly
behind the aforementioned shortwave trough which will cool
overnight lows Tuesday night by several degrees across much of the

.LONG TERM...(Wednesday through Monday)
Issued at 325 PM MDT Mon Aug 21 2017

The deep upper level low dropping in from the Gulf of Alaska that
we`ve been watching over the past several days will migrate south on
Wednesday. As it digs into the Pacific Northwest throughout the day
the SoCal low will be ushered inland. Models had previously
projected the low to become an open wave and trek through the Great
Basin but latest guidance now suggests it will dive further south
into Baja. Even so, the monsoonal tap should still set up as the
ridge of high pressure shifts, allowing moisture to advect
northward. Additionally, another piece of energy from the SoCal
low will traverse across our region throughout the day, so
Thursday still looks to be the most active day in terms of
precipitation coverage for our CWA this week.

Northwesterly flow aloft will begin to set up late Friday and into
the weekend as high pressure rebuilds over the Great Basin. While
lingering moisture should allow for at least isolated orographic
storms to fire off each afternoon, generally drier and warmer
conditions will persist through the beginning of the new week under
the benign weather pattern.


.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 609 PM MDT Mon Aug 21 2017

Showers and thunderstorms will continue over the San Juans and
Four Corners valleys over the next few hours and potentially a bit
overnight. These will reinitiate late morning and spread northward
throughout the day. ILS breakpoints will be reached at times and
and gusty outflow winds will develop around 18z.




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