FXUS65 KSLC 261000
Area Forecast Discussion
National Weather Service Salt Lake City UT
400 AM MDT Wed Sep 26 2018
.SYNOPSIS...A dry and stable northwest flow aloft will remain over
the area through Thursday. The flow aloft will turn more westerly
by Friday and bring warmer but still quite dry air across the
region heading into the weekend.
.SHORT TERM (Until 00z Sunday)...The deep upper level trough
across the upper Midwest/Great Lakes with a blocking pattern
across the eastern Pacific will leave the Great Basin in a dry
and quite stable northwest flow aloft through Thursday night.
Temperatures will run at to a little below late-September norms
the next couple of days.
The mean layer flow aloft will turn to the west Friday, then
back around to the southwest heading into the weekend. This west
then southwest flow will bring increasingly warm, but still dry
air to the forecast area. Temperatures Friday and Saturday should
come in above to well above normal with no real possibility for
.LONG TERM (After 00Z Sunday)...A longwave trough off the Pacific
coast will eject a shortwave trough northeast across the southern
PACNW into the Northern Rockies Saturday. This disturbance will
increase southwest winds and bring unseasonably warm temperatures to
much of the CWA. This trough will kick a secondary shortwave out on
Sunday prolonging the strong southwest flow across the region
although temperatures are expected to be down a few degrees.
The global models diverge on the evolution of this longwave trough
with the EC cutting the trough off by late Monday off the northern
California coast and tapping the moisture from hurricane Rosa and
bringing it northward across the Great Basin. The GFS keeps the
longwave trough progressive and although it taps moisture from
hurricane Rosa, the brunt of the moisture reaches only southern and
eastern Utah before being swept eastward. This latest GFS run is
somewhat of a flip flop from previous runs and will be taken with a
grain of salt. Have increased the PoPs for Monday night into
Tuesday, especially across the south and east but probably underdone
at this time.
An eye will need to kept on this evolving system as large amounts of
rain could bring problems to the recent burn scars in Utah county.
Rain amounts of up to 2 inches are possible according to the EC and
GFS from Utah County southward, but exactly where or if that ends up
occurring is yet to be determined.
.FIRE WEATHER...A weak disturbance moving SE across Wyoming will
increase winds some across NE Utah today, otherwise dry with
seasonable temperatures. Another disturbance could cause winds to
approach critical levels across far northern Wasatch mountains
Thursday. A trough developing along the West Coast will cause SW
winds to increase across most of the area Saturday and Sunday
along with low RH and unseasonably warm temperatures. The moisture
from Hurricane Rosa is now looking more likely to be tapped and
brought northward across most of Utah on Tuesday. However, the
amount of rain and duration are questionable as the models diverge
on their forecast solutions after Tuesday.
.AVIATION...Southeast winds at the SLC terminal will shift to
northwest about 17Z today and then back to southeast at 03Z tonight.
VFR conditions will prevail.
WY...Red Flag Warning from noon today to 8 PM MDT Thursday for
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