Area Forecast Discussion
Issued by NWS Salt Lake City, UT
FXUS65 KSLC 202145
Area Forecast Discussion
National Weather Service Salt Lake City UT
345 PM MDT SAT AUG 20 2016
.SYNOPSIS...High pressure will move into the forecast area today,
resulting in a drying trend for much of the area. Moisture will
spread back into much of the forecast area Sunday into Monday.
.SHORT TERM (UNTIL 06Z TUESDAY)...Upper level ridge remains
centered over the Great Basin. This is placing Utah and southwest
Wyoming under a dry northwest flow aloft. Deep moisture is confined
to far southern Utah and anticipate isolated storms to continue to
drift south-southeast off of the higher terrain in far southern Utah
and over adjacent valleys. While storms will be drifting down
drainage in many cases...the flash flood threat remains low with
limited low level moisture in place...poor parcel acceleration at
the LFC and a very high LFC yielding high cloud bases.
Upper level ridge axis shifts east over the Rocky Mountain region on
Sunday allowing moisture to begin to return north on weak southerly
mid-level flow. This will bring increased coverage of showers and
storms across central and southern Utah on Sunday afternoon and
evening. With dry low levels in place an isolated dry thunderstorms
will be possible across west central Utah. Temperatures across
northern Utah should be a bit warmer as the thermal ridge slides
east across the area. Much of the south will likely be a bit
cooler due to increased cloud cover.
Moisture continues to deepen on Monday with precipitable water
values rising to .75" to 1" across portions of southern Utah.
Anticipate increased coverage of storms across central and southern
Utah with the potential for localized heavy rainfall. They will
also be a slight chance for storms in far northwest Utah as a weak
lifts northeast across Nevada.
.LONG TERM (AFTER 06Z TUESDAY)...Embedded disturbances within a
broad trough of low pressure will work across the forecast area
Tuesday and Tuesday night. Aside from across the northwest quarter
of Utah, adequate moisture will be in place with precipitable
water values of .75" to 1". Lift generated by the upper level
system and an associated weak cold front crossing the forecast
area supports going chances for showers and thunderstorms for much
of forecast region. With relatively low net storm motion, some
potential will exist for flash flooding across southern Utah
Tuesday afternoon and evening.
Northwest flow behind system will usher in drier air on Wednesday,
keeping all but higher terrain free from precipitation. With
cooling temperatures aloft, will see readings a couple of degrees
GFS and ECMWF in general agreement with sweeping another trough of
low pressure across the Great Basin late Thursday and Friday.
Ahead of this system, a return southwest flow should once again
spread moisture into the region, though northward extent of
moisture push is still in question. Thus, better chances for
convective activity indicated for southern and eastern portions of
.AVIATION...VFR conditions will prevail at KSLC through the TAF
period. Northwest wind will yield to a southeast drainage wind
.FIRE WEATHER...An upper level ridge remains in place over the Great
Basin bringing dry northwest flow to much of the area. With dry air
in place over much of the area thunderstorms will be confined to far
southern Utah this afternoon and evening. Moisture begins to spread
back north on Sunday which will bring isolated valley and scattered
mountain thunderstorms to central and southern Utah. There is the
potential for an isolated dry thunderstorm across west central Utah
on the leading edge of the return moisture...but confidence is low
at this time. Deeper moisture continues to spread north Monday
and Tuesday bringing the threat of storms to much of the area. A
weak storm passing north of the area will help spread drier air
back into the region during the middle of the week.
Winds will largely be terrain driven across the district on Sunday.
Monday will see an increase in southwest winds across southern Utah
although minimum relative humidity values will be trending up by
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