Area Forecast Discussion
Issued by NWS Salt Lake City, UT
FXUS65 KSLC 211011
Area Forecast Discussion
National Weather Service Salt Lake City UT
411 AM MDT THU JUL 21 2016
.SYNOPSIS...The southwest flow over the Great Basin will maintain
warm and dry conditions across western Utah today. Moisture across
southern and eastern Utah will spawn showers and thunderstorms
again today. Drier air will move into Utah and southwest Wyoming
beginning late Friday...with dry and seasonally warm conditions
persisting into early next week.
.SHORT TERM (UNTIL 06Z MONDAY)...No significant change in the
large-scale pattern across the CONUS and eastern pacific today.
The strong and rather broad upper ridge remains centered across
the southern/central plains states, with an upper level trough
still positioned just off the Pacific Northwest coast. The
resultant southwest flow aloft over the Great Basin will maintain
warm and breezy conditions across western/northern Utah, with the
moisture plume across southern/eastern Utah spawning more showers
and thunderstorms this afternoon and evening.
Potential for stronger and somewhat better organized convection
within the moisture plume exists today across southern Utah, then
into eastern Utah this afternoon/evening. Model guidance continues
to indicate a vorticity max embedded in the plume over central
Arizona drifting into southern Utah this morning, then tracking
slowly northeast through eastern Utah later today. The deep slow-
moving convection that could develop in this situation would
generate locally heavy rainfall over southern through east-central
Utah, with the potential for flash flooding in some of the more
Over western/northern Utah some of the moisture associated with
the plume has broken away and has settled into area. PWAT values
are only running around .55 to .65 inches in this break away
moisture. The absence of dynamic support for lift along with the
limited moisture suggests more convective cloud cover, but little
in the way of precip this afternoon through early this evening.
A change in the pattern will begin Friday. The central CONUS upper
ridge become more west-to-east oriented across the southern CONUS
while the coastal Pacific Northwest trough turns east and tracks
across the Pacific Northwest/northern Rockies. The passing trough
will nudge a weak cold front into northern Utah late Friday, with
only a minimal impact on temps across the north on Saturday.
The rather dry air over the western Great Basin will spread east
across Utah behind the passing upper trough Saturday. This drier
air will dislodge the moisture plume from all but the four corners
region. Outside of a couple of terrain-based showers or storms
over the east, dry and seasonally warm conditions will exist area
wide late in the weekend.
.LONG TERM (AFTER 06Z MONDAY)...Globals continue to agree in large
that the low amplitude elongated ridge will reorient south and west
of the area early next week allowing a dry anticyclonic
northwesterly flow aloft to spread across the area. The deeper sub
tropical moisture will remain pinned well south of the area with the
only threat of convection remaining purely confined to the most
prone mtn regions across southern Utah early week, primarily driven
by remnant low level moisture in place from previous days. Hot temps
look to be the name of the game within this synoptic set up, with
max temps running 5 to 10 degrees above climo each day.
.AVIATION...Southeasterly surface winds are expected to remain in
place at the KSLC terminal into early afternoon. between 19-20z
winds are expected to switch to the northwest for the remaining
.FIRE WEATHER...Modestly deep moisture remains in place this morning
across central and eastern Utah, and with flow aloft trending more
southerly today expect this moisture to expand a bit more north
and west this afternoon. Wetting rain potential remains most
elevated across the east within the deeper moisture plume where
scattered thunderstorms are expected, but any development across
west central Utah will retain a drier nature due to the dry boundary
layer in place. The axis of this moisture plume is expected to
shift east for Friday as the trough over the PacNW states splits
ejecting the primary wave into the northern Rockies region.
Coincident with this a shallow front will work through northern
Utah Saturday allowing temps to marginally cool for the weekend
ahead. A drier near westerly flow aloft will spread across the
area this weekend and remain in place through the first half of
next week if not longer.
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