Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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FXUS65 KSLC 212150

Area Forecast Discussion
National Weather Service Salt Lake City UT
350 PM MDT Fri Jul 21 2017

.SYNOPSIS...Drier air will gradually spread back into the area
from the northwest over the next 24 hours. Moisture will start to
spread back into Utah Sunday night and Monday.


.SHORT TERM (Through 12z Monday)...A drying mid level airmass
continues to spread into the northwestern half of the area driving
largely clear skies and dry conditions namely west of the I-15
corridor this afternoon, while deep moisture coupled with modest
cape continue to support diurnal storm development across the
southeastern half of the area. With a net northwesterly flow aloft
in place as the mid level ridge circulation builds to our west,
storm motions across the south have tracked down-drainage
following weak outflows aiding flash flood potential for the prone
areas between Escalante/Lake Powell. Have had confirmation of
some of the stronger cells supporting 1.5" hourly rainfall rates
(spotter report of 1.23" in 40 min near Boulder), verifying
locally intense rainfall. Convection is expected to be maintained
through this evening, with a gradual decreasing trend from N-S
across eastern/southern portions.

The aforementioned high circulation will trend to become more
established over the area Saturday allowing the mid level drying
trend to spread into all but the extreme south over the next 24
hours. With a drying airmass and more subsident upper level
environment in place, do expect a net downtick of convection
Saturday, with largely isolated terrain based airmass convection
over the mtn spines outside of scattered potential across the
southern mountains. These conditions will be maintained into and
through much of Sunday, though a downstream shift of the high will
once again open the door for deeper moisture advection from the
south by early next week.

.LONG TERM (After 12z Monday)...Broad upper level ridge will remain
in place across the Rockies/High Plains early Monday. A weakening
trough will cross into northern California and move northeastward
into the northern Intermountain Region by Wednesday. This trough
will help to bring deeper moisture into the CWA from southwest to
northeast Monday through Wednesday. By Thursday, drier air will
begin to move into the CWA, decreasing the convective threat.  This
will continue into the weekend.

Main point: convection will be the main source of precipitation
Monday through Wednesday for much of the state.  A drier pattern
returns Thursday into the weekend.


.AVIATION...VFR conditions are expected at the SLC terminal through
the TAF period. Winds at the SLC terminal will continue to prevail
from the northwest, before shifting to the southeast this
evening between 03Z and 04Z.





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