Scientific Forecaster Discussion
fxus65 kslc 260415
Area forecast discussion
National Weather Service Salt Lake City Utah
915 PM MST Sat Feb 25 2017
Synopsis...a weak weather disturbance will drift south across
central and southern Utah overnight. A stronger Pacific storm
system will impact the region during the first half of the week.
Short term (until 12 tuesday)...weak convergence in the old
west-to-east low-level baroclinic zone over southern Utah
continues to generate spotty light showers this evening. This
limited shower activity should persist along the boundary through
the balance of the night, then end as said boundary exist south
into northern Arizona early Sunday.
Up north a stable and still quite cold air mass will remain in
place tonight through much of Sunday. The next opportunity for
precip will arrive either late Sunday night or early Monday as
the next Pacific trough reaches the Great Basin.
This next feature, currently along the central britcol coast, will
continue to strengthen as it enters the Pacific northwest Sunday.
From there the trough will turn east and evolve into a trough
covering much of the western Continental U.S. Through Tuesday.
Significant snowfall potential exists with this trough, fueled
by the cold unstable air mass accompanying the trough, dynamic
features rotating through the mean trough position and the fairly
long duration of the event. Moisture appears to be a somewhat
limiting factor, but not enough so to prevent significant
mountain accumulations beginning Monday and continuing through
Will likely issue an update to remove pops across the north
tonight, and focus them along the previously mention boundary
Previous long term (after 12z tuesday)...the final cold trough in
this northwest flow aloft will move across the area Tuesday. The
thermal dynamics at 500mb look decent by both the GFS and ec but
the 700mb and below dynamics are rather weak in addition to a lack
of deep moisture as this feature has moved down across a land
trajectory from western Canada. Therefore have lowered the pops
for Tuesday. Cold temperatures will accompany this system and with
mostly cloudy skies and scattered snow showers over western Utah
have lowered the temps a couple from the previous forecast for
Tuesday. The southeast portion of the County Warning Area has the best chance for
some scattered snow showers Tuesday afternoon as the dynamics
aloft will be the strongest there.
The ec and GFS are in locked step Wednesday and Thursday with the
ridge building over the County Warning Area. After Thursday the operational GFS
becomes more of an outlier compared to the GFS ensemble which
remains in good agreement with the ec. Consequently have gone with
the ec through Saturday. The ec and GFS ensemble keep a Flat Ridge
in place over the County Warning Area which prevents the trough that the GFS from
reaching the northern portions of the County Warning Area. Have backed off on the
low pops across the north and kept the rest of the County Warning Area dry.
Temperatures will be on the warming trend from Wednesday forward
with the faster response occurring in the mountains as an inversion
will slow the warming in the valleys. Temperatures will be near
normal by Thursday and then go above normal Friday and Saturday.
Aviation...a stable west-northwest flow aloft behind the weak
weather disturbance that moved through early today will leave
mostly clear skies and light southerly winds at the terminal
tonight through Sunday morning.
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