Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 091800

Area Forecast Discussion
National Weather Service GRAND JUNCTION CO
1200 PM MDT Wed Aug 9 2017

Updated aviation section

Issued at 948 AM MDT Wed Aug 9 2017

Updated chances of precipitation for this morning in seeing what
is materializing this morning. A weak disturbance early this
morning allowed for early development of showers and even a few
strikes of lightning across the Monticello area and into the
Paradox Valley. Upped chances of precip across this band of
vertically growing cloud tops and added a slight chance of precip
across the Four Corners to Pagosa Springs corridor anticipating
additional development as daytime heating increases. Also dropped
chances of precipitation across all of NW Colorado for the morning
hours with increasing chances of storms from west to east from NE
Utah into Moffat and Rio Blanco counties later this morning and
early afternoon. Anticipating mid afternoon will get busy across
NE Utah and the valleys of NW Colorado as another disturbance
passes through.


.SHORT TERM...(Today through Thursday)
Issued at 338 AM MDT Wed Aug 9 2017

The weather situation should remain relatively unchanged through
Thursday. High pressure will remain centered south of the Four
Corners with an old boundary running across its northern periphery
along which convection will be focused. PWATs remain high enough
that local, and mostly minor, flooding is a possibility in poor
drainage areas and if a few echoes train over and area.

.LONG TERM...(Thursday night through Tuesday)
Issued at 338 AM MDT Wed Aug 9 2017

As mentioned in the previous discussion, shallow ridging will
allow moisture levels to rise over southeast Utah and southwest
Colorado Friday. Expect this small shift in pattern will bring
about increased shower and thunderstorm coverage for those areas.
Interplay with the persistent 60 KT jet overhead may result in
some stronger cells and heavy rain. Coverage will be lesser to the
north where the airmass will be drier relatively speaking.

Expect flow to return to a westerly direction this weekend which
will allow the south to dry while the north remains largely
unchanged. Consequently, expect diurnal showers and thunderstorms
to redevelop each day much as it has over the past several days.
In addition, with the 50 to 60 KT jet still moving overhead,
cannot rule out some nocturnal moist convection.

The forecast for early next week remained in flux as GFS and
ECMWF were still not in very good agreement. EC solution featured
a deep closed low along the coast of the Pacific Northwest which
moves little from Monday into Tuesday. In contrast, the GFS
resolved a shallower trough over the Northwestern U.S. allowing
moderately moist Pacific air to continue flowing eastward across
the region. Southwest flow occurs with the EC solution which would
begin to tap into subtropical moisture yielding increased shower
and thunderstorm activity. Until model solutions come into
agreement will defer to the blended solution.

Expect zonal flow to bring about near normal temperatures during
the extended period.


.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 1200 AM MDT Wed Aug 9 2017

Storms are beginning to develop as afternoon heating increases.
Activity is expected to be relatively widespread across NE Utah
and NW Colorado today as a disturbance passes through from west to
east this afternoon. Conditions will likely remain VFR the next 24
hours, but ILS breakpoints may be reached at times.




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