Area Forecast Discussion
Issued by NWS Salt Lake City, UT
FXUS65 KSLC 302129
Area Forecast Discussion
National Weather Service Salt Lake City UT
329 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)...
Water vapor loop shows ridging over the southwest CONUS with
westerlies to our north. MDCARS wind observations show a 50-95kt
westerly jet across southern Canada and the northern Rockies.
GOES/HRRR/12Z KSLC RAOB indicate the precipitable water value
ranges from 0.35"-0.50" northern mountains to 1.00"-1.50" southern
Storm coverage will be on the increase today with a combination of
terrain driven storms and additional triggering due to weak waves
propagating across Utah from Nevada.
BUFKIT model forecast soundings show that the sub-cloud layer is
moistening somewhat compared to the last couple of days. So today
should be a hybrid day between dry microburst threat and locally
heavy rainfall threat.
HRRR and local WRF high resolution simulated reflectivity has been
indicating that a MCS may develop across southwest Utah this evening
into the overnight hours. This coincides with an increasing warm
cloud layer of 6-8kft with dewpoints in the middle 50s. The
evening shift will monitor convective treads late this afternoon
before deciding on a nocturnal Flash Flood Watch.
Tomorrow looks like the boundary layer begins to dry, as evident
by nearly double the DCAPE as today. This favors more in the way
of dry microbursts, but locally heavy rainfall cannot be ruled out
if clearing takes place early enough across southern Utah.
Convection Sunday and Monday appears to be more diurnal and driven
by terrain circulations.
.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...The wind forecast at the SLC terminal through this
evening is relatively low confidence, as additional showers and
thunderstorms could cause gusty erratic winds through 04Z. However,
away from showers, northeast winds are expected through 02Z,
switching to southeast around 02-04Z. The most likely timing for
additional thunderstorms is 00-02Z; in addition to winds, possible
impacts include lightning, brief heavy rain, and ceilings below 7000
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.
SHORT TERM/FIRE WEATHER...Rogowski
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