Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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FXUS65 KSLC 141044

Area Forecast Discussion
National Weather Service Salt Lake City UT
444 AM MDT Sat Apr 14 2018

.SYNOPSIS...High pressure aloft across the Great Basin will bring
a warming trend to Utah this weekend. The next Pacific storm
system will impact the region early in the upcoming week.


.SHORT TERM (Until 18z Monday)...The low amplitude upper ridge
currently to the west of Utah will advance east into the state
later today. The axis of this ridge will remain progressive and
end up over western Colorado by Sunday afternoon. The warming
trend that will begin today and then pick up steam Sunday as an
increasingly warm southwest flow develops behind the passing upper

The moisture plume moving over the top of the approaching ridge
will begin to spill over into northern/central Utah today. This
moisture plume may be a little more than just mid/high level
moisture as PWAT values do show a modest increase across northern
and western Utah this afternoon through tonight. Various model
guidance does show some light precip working east along the Idaho
border late this afternoon through this evening. Other than weak
warm advection, not seeing much evidence for the necessary lift to
produce these showers. Will keep the current forecast dry, though
will maintain significant cloud resulting from the moisture plume.

The next cold core Pacific trough will reach the west coast Sunday
night, then advance east into the western Great Basin early
Monday. Ahead of this trough strong southerly winds and mild
temperatures will be the sensible weather issues impacting mainly
northern and western Utah Sunday night/Monday. Wind highlights
will likely be issued to address the strong winds, though these
highlights will occur beyond the current short term forecast

.LONG TERM (After 18z Monday)...Big picture: Expecting a high wind
event across at least the central and southwestern valleys Monday
afternoon, as model to model and run to run consistency has
portrayed enough consistency to lock into those areas. The cold
frontal push across the I-80 corridor may just limit impact along
that corridor, but those details will be worked out over the next
few forecast cycles.

A few hours makes all the difference for the high wind event
extending north into the I-80 corridor on Monday. This discrepancy
exists between the GFS/ECMWF in the 00z runs, though the overall
details of trough evolution remain quite similar. The GFS frontal
progression is just a touch faster than the EC with a midday frontal
passage at KSLC, which would limit maximizing the upper support. The
slower EC supports high winds across the I-80 corridor. The
potential for H7 winds in excess of 50kts coupled with a net MSLP
gradient of 10mb S-N and time of day supports this thinking. Time
will tell.

Yet another late season trough will be the driver of this cold
front, and outside of the subtle but meaningful details discussed
above, do expect a marked cool down come Tuesday. A brief period of
widespread precip is expected as the upper trough transitions
overhead late Monday night into Tuesday, but all guidance portrays
the trough becoming positively tilted very rapidly and lifting off
to the northeast limiting duration of precip. Temps support snow to
valley floors across the Wasatch Front Tuesday morning, but do not
foresee much impact from this at this time. Modest snow accums
expected in the northern mountains at best.

Upper ridging is expected to build into the region quite rapidly by
Wednesday within this progressive pattern, but it will be short
lived. Have higher than normal confidence that the next trough of
the wave train will begin to impact the area later Thursday through
Friday, but those details will be worked out at a later time.


.AVIATION...Southeast surface winds currently in place at the KSLC
terminal will remain so through 19-20z before switching to the
northwest per norm. Outside of this, operational weather concerns
will remain minimal through the valid TAF period.





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