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Area forecast discussion 
National Weather Service Salt Lake City Utah
633 PM MDT Sat Aug 30 2014

Synopsis...a cold front will push through northern Utah tonight before
stalling over central Utah tomorrow morning. A drier and more
stable pattern will return for the upcoming week.


Discussion...water vapor loop shows a trough has become
established across the west...with one disturbance lifting into
the northern rockies...while the next one upstream approaches from
Oregon. Amdar 400-250mb wind observations reveal a 75-130kt
cyclonic jet from the British Columbia coast over northern
California and into the central rockies. GOES/GPS/rap/00z radiosonde observation
indicate the precipitable water value ranges between 0.5"
northeast mountains and west central valleys to 1.0" most other

Convection late this afternoon and early this evening has been
fairly shallow being in between the two aforementioned systems.
Still...have quite a bit of shear (40-50kts effective sehar) across
the north...and dynamics of appraoching disturbance and left exit
region of the upper level jet. Therefore expect convective activity
to increase overnight...particurarly along and north of Interstate

Rap 850-700mb streamlines/saturated equivulent potential
temperature/thickness all indicate this mornings boundary near a
Wendover to Green River line. The cool front associated with the
upstream wave is across southwest Idaho...slated to reach slc around
08z. The southern baroclinic zone looks to ease southeast across
south central Utah overnight.

Gusty southwest winds in the warm sector will continue through the
evening but look to remain below advisory levels.


Previous discussion...cold front looks to be near a keko-ksun line
this afternoon and is making its way toward northwest Utah as the
associated storm moves across Idaho and Nevada. Shortwave energy out
ahead of the system brought widespread cloud cover and a few showers
to northern and central Utah but there are now only scattered clouds
over all but eastern Utah. There should be some increase in cloud
cover as the storm system moves through northern Utah this evening
and overnight.

Moisture is limited with the storm system and associated cold despite the instability coverage of precipitation will be
limited and confined to northern Utah. Based on the hrrr and other
short term guidance going probability of precipitation may even be a bit overdone but am
hesitant to lower them further given the expected instability. The
more noticeable impact from the system will be much cooler
temperatures behind the front as it moves through northern Utah this
evening and stalls over central Utah by tomorrow. Maxes are expected
to be around 10f below seasonal norms tomorrow over northern
Utah...compared to temperatures today that are hovering just below

Additional shortwave energy will move along the Utah/Idaho border during
the day Sunday but the airmass already starts to dry at that point
so the threat of precipitation looks to end Sunday morning. Behind the
exiting system...a drier and more stable airmass will build over the
forecast area through at least the middle of the upcoming
week...allowing temperatures to warm back near or slightly above
seasonal norms.

Global models now indicate that a Pacific northwest trough moving
onshore Wednesday will shift the ridge axis eastward...allowing
southwest flow to increase. By Thursday the system gets close enough
to bring some cooler air to northern Utah in the ec but it remains
well north of the area in the GFS. The passing system may provide a
bit of instability but it appears the airmass will remain mostly dry
through day 7.


Aviation...a cold front is approaching the slc terminal this
evening...and will most likely switch winds to the northwest between
06z and 09z. Winds could become light and variable or light
northerly before 06z...but speeds out of the north greater than 7
knots are not likely. There is a 20 percent chance of a shower at
the terminal through 12z...with ceilings below 7000ft possible under
the stronger showers.


Fire weather...a weak cold front currently over northwestern Utah
will continue to push south and east through two thirds of the state
by this time tomorrow. Dry and breezy conditions will remain across
the south with scattered showers and storms expected
overnight/tomorrow morning across mainly northwestern portions. High
pressure ridging will begin to build in tomorrow allowing a drying
and warming trend to take place Monday through at least Thursday of
next week.


Slc watches/warnings/advisories...


fire weather...Merrill

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