Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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FXUS65 KSLC 220926

Area Forecast Discussion
National Weather Service Salt Lake City UT
326 AM MDT Mon May 22 2017

.SYNOPSIS...High pressure aloft will expand east across the Great
Basin through tomorrow then shift east Wednesday. The next storm
system will impact the region during the latter half of the week.


Water vapor loop shows yesterdays disturbance crossing Colorado,
as the next disturbance approaches the northern Rockies from west
central Canada. A ridge dominates the eastern Pacific. AMDAR
400mb-200mb wind observations reveal a 75kt-95kt anticyclonic jet
extends from Montana into southern California. GOES/HRRR/00Z KSLC
RAOB indicate precipitable water values range from 0.10"-0.20"
mountains to 0.40"-0.65" valleys.

Northerly downslope/canyon winds are breezy across southern Utah
early this morning thanks to a building northerly pressure
gradient, cool advection and 5mb pressure rises.

A disturbance currently crossing into Montana is expected to
reach Wyoming late today and tonight. This could bring additional
clouds but most all guidance including simulated reflectivity from
the Convective Allowing Models indicate that convection remains
to our east during this period.

A warming and drying trend is on tap into mid week as a ridge
gradually builds into the region.

A broad trough is expected to drop into the Pacific Northwest
during the day Wednesday as it splits. EC/GFS track the larger
portion of the system east along the US/Canada border but drop a
piece of the system and an associated frontal boundary into
northern Utah/southwest Wyoming Wednesday night/Thursday morning.
Moisture is not particularly impressive with the front but it does
have decent jet support, so expected at least some showers to
accompany it. The front should produce a rather noticeable
cooldown, however, with maxes dropping from up to 15F above
seasonal normals on Wednesday to near climo on Thursday.

The front is progged to stall over central Utah during the day
Thursday and wash out by early Friday as the initial upper wave
rotates east out of the area. GFS brings a second trailing wave
across northern Utah Friday into Saturday, which would enhance
coverage of convection. This feature is also present in the latest
EC, but is significantly weaker and thus produces much less in the
way of precip. The presence of the waves will also keep temperature
near or just slightly above climo, with only slight warming expected
through Saturday.

Global models indicate high pressure returning on Sunday, resulting
in a warming and drying trend. Latest EC keeps this going through
day seven, while the latest GFS flattens the ridge and brings in
enough weak shortwave energy by next Monday for an outside threat of
showers and thunderstorms. Have kept POPs well below climo at this


The SLC terminal will see VFR conditions throughout the
day with mostly clear skies. Light southeast winds are expected to
shift to the northwest between 16Z and 18Z.


Weak transport winds will limit clearing to the fair to good
categories across many valleys during the next several days.
An increase in transport winds will lead to excellent clearing
Wednesday across the region.

Benign weather is expected through mid week as a ridge gradually
builds into the region. The warming and drying trend will
accelerate during the first half of the work week. A cooler and
more moist trough may impact the area during the second half of
the work week.





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