Area Forecast Discussion
Issued by NWS Salt Lake City, UT
FXUS65 KSLC 261045
Area Forecast Discussion
National Weather Service Salt Lake City UT
445 AM MDT TUE JUL 26 2016
.SYNOPSIS...Weak upper level trough will move across the northern
Great Basin today followed by dry westerly flow under a building
ridge for Wednesday and Thursday. The ridge shifts east Friday
allowing for moisture to return Friday afternoon through the
.SHORT TERM (through 06z Friday)...The combination of a trough
moving through the Pacific Northwest and a weak disturbance over
east central Nevada is drawing some moisture northward across
western Utah this morning. Satellite showing scattered clouds
developing as well as PW values increasing from near 0.40 of an
inch over DPG at 21Z Monday to 0.70 of an inch at 08Z Tuesday.
Have thrown in minimal threat of thunderstorms to northern Wasatch
Mountains today and scattered thunderstorms for the Uintas and
Tavaputs. May see a mixture of dry and wet thunderstorms and this
is addressed in Fire Weather portion of discussion.
Farther south and east remnant moisture will blossom into at least
isolated thunderstorms over the valleys with perhaps more over the
higher terrain. These storms should dissipate rapidly this evening
as a drier westerly air mass moves in in the wake the bypassing
trough. Temperatures will remain above normal through Thursday
with triple digits expected each day at SLC. Some moisture is
being hinted at returning as early as Thursday afternoon or
evening over the southwest Utah mountains so went with minimal
.LONG TERM (After 06z Friday)...High pressure centered over
northwest Arizona Thursday night will continue to allow midlevel
moisture to slowly seep into southwest Utah. While the GFS remains
a bit more aggressive with the moisture influx, expect the bulk of
any convection to remain confined mostly to southwest Utah and
produce high-based convection Friday afternoon. Meanwhile, a very
warm airmass will remain in place with H7 temperatures in the
18-20c range throughout the area.
The pattern is still expected to shift beginning this weekend, with
the GFS still a bit faster than the EC with the onset of this
evolution. This pattern shift will begin with a weak disturbance
developing under the ridge and lifting across Utah, thereby
flattening the ridge and shifting it east. Moisture will increase
across the area and showers/thunderstorms will increase in coverage
as a result. Although PWATs from the GFS are still not particularly
impressive at under 1 inch, this will be adequate for producing
increasingly wet showers especially as the lower levels gradually
moisten into the early part of next week. With the moisture along
with associated cloud cover, temperatures will start to slowly trend
downward during this time.
.FIRE WEATHER...Scattered dry thunderstorms moved across west
central Utah Monday with some gusty winds in excess of 50 mph.
This raises concern on the possibility of similar conditions today
over the higher terrain of northern Utah...specifically the Uintas
and Tavaputs where isolated lightning occurred yesterday but now
models showing a little more instability over these areas today as
a weak trough moves across for possible scattered thunderstorms.
Will let morning fire weather desk collaborate with GACC on
whether a RFW needs to be issued. Farther south and east the
moisture is a little deeper so concern for dry lightning is less.
In the wake of the trough moving by today a ridge will build in
across the Great Basin Wednesday into Thursday. Dry conditions
along with hot temperatures expected across the entire fire
district Wednesday with single digit RH values in most valleys.
Perhaps isolated thunderstorms return over the southwest mountains
of Utah Thursday but more likely this will occur Friday. The ridge
will shift east this weekend opening the door for moisture to move
up across the entire area. Elevated concern for a possible
dry/wet thunderstorm outbreak this weekend after this dry and hot
period across western and northern Utah/southwest Wyoming.
.AVIATION...Southeast winds will prevail at the SLC terminal
through about 19Z today, although there is a 30 percent chance
that winds shift as early as 17-18Z. There is about a 10 percent
chance that gusty outflow winds from high based thunderstorms
over the nearby higher terrain impact the terminal...mainly
between 19Z and 23Z.
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