Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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FXUS65 KSLC 192146

Area Forecast Discussion
National Weather Service Salt Lake City UT
346 PM MDT Fri May 19 2017

.SYNOPSIS...High pressure will temporarily build into the area
on Saturday, before a weak trough enters Utah on Sunday. A ridge
will build into the west next week resulting in a warming/drying
trend through the middle of next week.


SHORT TERM (Through 00Z Monday)...A weak upper level disturbance -
seen on the high level water vapor moving southeast across northeast
Nevada - will help generate isolate showers across the higher
elevations of northwest Utah early this evening. The GFS shows a
weak 700-500mb Theta-E ridge across this area with a 700-500mb mean
wind flowing perpendicular into it through 00Z, but then the ridge
loses its identity by 03Z. A few showers have made it out into the
northwest desert this afternoon but the feeling is that the overall
trend is downward so only have PoPs in the mountains. The other area
which could see isolated showers late this afternoon and early
evening will be over the higher terrain of the northern mountains
including the Uintas from basically surface heating in a somewhat
moist air mass. Once the sun goes does all showers will dissipate.

Clouds have been thinning over southern portions of the CWA this
afternoon and this should continue as the jet aloft moves east and
warmer temperatures aloft settle in overnight. Look for clearing
skies over most of southern and western Utah late tonight. Despite
the clearer skies tonight, temperatures will not be as cold as last
night due to the warming of the air mass today.

Southern Utah will remain dry through the weekend with a continued
warming trend while another disturbance enters northern portions of
the CWA Saturday afternoon. Initially was not impressed with the
dynamic support for showers across the north Saturday afternoon but
after seeing the position of the jet and strengthening of the 700mb
warm advection by 21Z across the northern tier of Utah decided
isolated showers were not out of the question. Continued to increase
PoPs slightly through Saturday night as the jet is in a more
favorable position and there is 700mb convergence from the northwest
corner of Utah southeastward to SLC. By Sunday, the 500mb cold pool
moves southward across southwest Wyoming and northern Utah and this
will create better instability.  Consequently, boosted PoPs to
scattered along the Wasatch Front with likely PoPs in the mountains.
Isolated showers are possible over the west central valleys and
central mountains as well.


.LONG TERM (After 00Z MONDAY)...
The aforementioned system will continue to progress southeastward
through the fcst area Sunday evening and will at this time become
quite sheared with a significant chunk of it eventually pinching
off the California coast. Areas downstream of the wave axis in
Southern and Eastern Utah will likely see scattered showers and
storms persist Sunday evening before tapering off overnight as the
wave moves out and the diurnal stabilization occurs. Northern
Utah on the other hand should see a noticeable drying trend late
Sunday in the subsident northwest regime behind the wave.

Northwest flow aloft will become established on Monday as a ridge
over the west coast begins to amplify and progress eastward. An
upper level wave rotating on the periphery of the ridge may graze
northeastern Utah/southwest Wyoming late Monday/early Tuesday,
however outside of some cloud cover and slight chance PoPs in the
Uintas/Northern Wasatch this system will likely have little impact
for the fcst. area. The main weather story through the middle of
next week will be rising temps as the ridge axis progresses
eastward, with the center of the ridge becoming established over
Eastern Nevada/ Western Utah on Wednesday. Max temps rise from
near climatology on Monday to 5-10 degrees above climo on
Wed/Thurs. It is possible that Thurs. temps may be even higher
than what is currently forecast as H7 temps will potentially
exceed 10C over much of the state by Thursday afternoon. However
there appears to is sufficient chances of cloud cover/ precip
Thurs afternoon to preclude raising maxes significantly at this
time. Although the dynamic subsidence/stability associated with
the ridge should leave most of the area dry can`t rule out some
isolated convection developing over the higher terrain of
southwestern Utah on Wednesday.

Guidance begins to diverge in the Thurs/Friday timeframe although
there is pretty good agreement that the pattern will remain
progressive (at least by May standards) with an upstream wave
flattening the ridge Thurs-Friday. Although the dynamics
associated with this fairly low-amplitude feature are not
particularly impressive...cooling aloft combined with some
moisture advection should prove sufficient for scattered storm
development Thursday into Friday.


Little operational concerns at KSLC during the valid TAF period as
ceilings will gradually lift and scatter out this afternoon.
Can`t rule out a stray storm approaching from the northwest but
the chance of any storm directly impacting the terminal is quite
small. Northwest winds will persist through the afternoon before
shifting to the southeast around 03-04Z.


The storm system of the last few days will finally fully exit the
region tonight, allowing for warmer and drier conditions across
the area early Saturday. This break will be short-lived however,
as the next trough slides into the area by late in the day,
allowing for a few showers/thunderstorms over Northern Utah late
Saturday into Sunday. Wetting rains are possible over the Uintas,
Wasatch, and Bear Rivers, with only a minimal chance of
precipitation elsewhere.

A warming and drying trend is then expected through the middle of
next week and a ridge of high pressure build in, with
temperatures rebounding to near and even slightly above normal by
later in the week. The next chance of rain looks to be around next




SHORT TERM...Struthwolf

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