Area Forecast Discussion
Issued by NWS Salt Lake City, UT
FXUS65 KSLC 192142
Area Forecast Discussion
National Weather Service Salt Lake City UT
342 PM MDT Wed Oct 19 2016
.SYNOPSIS...High pressure will be over the area through the west
of the week. Southwesterly flow will develop over the weekend
with moisture spreading into the region by early next week.
.SHORT TERM (Through 00Z Sunday)...A drier and more stable
northwest flow has moved into the forecast area this afternoon
behind the exiting storm system. Lingering instability on the back
side of the system is keeping some scattered clouds over northern
Utah and southwest Wyoming, but skies are otherwise clear. The
airmass remains cool in the wake of the storm systems, with maxes
running around 10F below seasonal normals over northern Utah and
around 5F below climo over southern Utah. With clear skies
overnight, low temperatures will tumble quite a bit, reaching hard
freeze levels in some prone valley locations. Have issued a hard
freeze warning for the Western Uinta Basin, Southern Wasatch
Front, and San Rafael swell to cover this threat.
High pressure will build over the area tonight and during the day
tomorrow before flattening Thursday evening as a system moves over
the ridge in Canada. The ridge will rebound Friday with the axis
shifting east of the area, allowing a warmer southwest flow to
develop for the weekend. By Saturday, maxes will be up to 10F
above seasonal norms, with the warmest readings over southern
Utah. Warming will continue into Sunday.
.LONG TERM (After 00z Sunday)...Forecast confidence diminishes
rapidly Tue/Wed, but fairly strong confidence in the large scale
pattern evolution exists for the late weekend/early week period to
begin the long term.
Globals phasing more in line regarding trough evolution and track as
the next pacific long wave trough closes off the pacific northwest
Sunday into Monday, this driving an increasing southwesterly flow
aloft over the eastern Great Basin. Dry conditions with temps
running near 10 degrees above climo will remain the norm for Sunday,
but will be short lived heading into early next week.
A plume of modestly deep subtropical moisture pooling over the
desert southwest at that time will begin to get tapped within this
flow and a subtle return flow wave Sunday night and especially
Monday, driving strong moisture advection NE across southern/eastern
Utah by Monday afternoon. NAEFS mean PWAT values progged to be
running roughly 2 standard deviations above normal sets the stage,
and with slight diffluence aloft and the right entrance region of
the eastern periphery jet moving overhead, fairly widespread precip
can be expected across southern/central/eastern Utah by Monday
afternoon. Due to the convective nature of the expected precip,
maintaining generally chance PoPs until details come more into form,
specifically regarding the western periphery of this moisture
surge. This said, going PoPs very well could be well underdone.
Thereafter consistency wanes rapidly regarding evolution and track
of the upstream trough, and the significance of any ejecting energy
ahead of it. The GFS has trended more towards a consolidated trough
tracking east into the eastern Great Basin Tue/Wed, while the EC
splits the trough over the eastern pacific with the northern split
phasing east into the area. Both indicate a continuance of somewhat
unsettled weather and a gradual cooling trend, so have maintained
near or slightly above climo PoPs (especially north) for now, but
we`ll see how things shake out.
.AVIATION...Winds at the SLC terminal are expected to switch back
to the southeast around 03-05Z. VFR conditions should prevail
overnight under mostly clear skies.
UT...Hard Freeze Warning from midnight tonight to 9 AM MDT Thursday
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