Area Forecast Discussion
Issued by NWS Salt Lake City, UT
FXUS65 KSLC 310440
Area Forecast Discussion
National Weather Service Salt Lake City UT
1040 PM MDT SAT JUL 30 2016
.SYNOPSIS...High pressure extends from the southern Rockies into
southern California. Moisture rotating around this ridge will
remain across the region through early next week.
.SHORT TERM (THROUGH 06Z TUESDAY)...Area of the most active
convection remains across extreme southwest Utah late this
evening. A shortwave moving southeast from Nevada found plenty of
deep layer moisture and instability for strong and fairly deep
convection this afternoon and evening. Many storms produced brief
but very heavy rain, which has ended or moved south into northern
Arizona late this evening.
Up north scattered convection persists, with the most active area
south of KSLC along an old outflow boundary still moving to the
southeast this evening. This boundary will remain active to a
degree for a few more hours, then dissipate across central Utah
Convection could get an early start across the north Sunday
morning. A shortwave currently over northwest Nevada will track
east into northwest Utah early Sunday, then become more
convectively active as it reaches the moisture still in place
across the north. The most active period will likely period will
be late morning through midafternoon, with winds and brief but
locally heavy rain the main impacts.
Southern Utah will still be quite moist with deep layer moisture
covering much of the region. Terrain-based convection should fire
up during the late morning, followed by a expansion of convection
during the afternoon and early evening as the rain-cooled boundary
layer mixes out and instability increases.
Monday will likely be the least active day for convection as
modestly drier air spreads across the north and the deep layer
moisture is presses south closer to the Arizona border.
.PREVIOUS LONG TERM (AFTER 06Z TUESDAY)...Southwesterly flow
begins to increase a bit on Tuesday, as the next trough moves into
the Pacific Northwest. This draws a little moisture back into the
northern portions of the CWA, but in general the deepest moisture
will still be over the far south.
As the bulk of this trough moves through Idaho and Montana, it will
push a cold front into northern Utah on Wednesday. This will help
cool temperatures across the northern half of the CWA, including
perhaps ending Salt Lake City`s long string of 95+ degree days.
While this cold front will push some drier air into the northern
half of Utah, this looks to be short-lived, as deeper moisture
surges northward again Thursday and/or Friday. Have increased POPs
and lowered temperatures on both Thursday and Friday to account for
this deeper moisture and increased cloud cover.
.AVIATION...Lingering showers and isolated thunderstorms should
end across much of northern Utah between 06Z and 07Z. Light and
variable winds will exist through around 07z...then turn to the
south or southeast thereafter.
A weather disturbance moving into northern Utah from Nevada will
cross the area during the mid-morning through early afternoon
hours. Showers and possibly a thunderstorms could form near the
terminal by late morning, with impacts to the terminal through
.FIRE WEATHER...Primary concerns revolve around new starts due to
lightning. A Red Flag Warning continues for much of Utah through
tonight. Zones 478/492 have been added for tomorrow.
Yesterday`s ERC values were above the 97th percentile for many
stations across central and northern Utah, with areas greater than
the 80th percentile across southern Utah.
Storm coverage will have a noticeable uptick for the remainder of
today with a bit less coverage tomorrow.
The Red Flag Warning was added for 478/492 tomorrow based on storm
coverage expanding out of Nevada during the afternoon, while DCAPE
doubles vs. today, indicating deeper mixing with drier boundary
Some of the thunderstorms will contain little rainfall, but gusty
and erratic winds. This combination will not only support new fires,
but also lead to extreme fire behavior.
A slight cooling trend is forecast next week especially beyond
Tuesday. While many areas will remain more moist in the upcoming
week, single digit RH values are forecast for northwest Utah. Daily
convection is more likely east of Interstate 15, and across West
Central Utah each day than areas further northwest.
UT...Red Flag Warning until 4 AM MDT Sunday for UTZ479>484-488-489-
Red Flag Warning until 10 PM MDT Sunday for UTZ478-492.
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