Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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FXUS65 KSLC 251047

Area Forecast Discussion
National Weather Service Salt Lake City UT
447 AM MDT Tue Apr 25 2017

.SYNOPSIS...A low pressure system will cross the region today,
before high pressure temporarily builds across the region tonight.
a series of progressively colder systems are expected to continue
crossing the area through the remainder of the week.


.SHORT TERM (Through 12Z Saturday)...A longwave trough encompasses
the western and central CONUS this morning, maintaining a cyclonic
northwest flow across the forecast area. An embedded shortwave
trough is currently digging into the northern Great Basin, and
water vapor/IR imagery suggest an increase in large scale ascent
across northern Utah based on cooling cloud tops, while radar
imagery indicates an increase in precipitation across northwest
Utah. This feature is forecast to dig southeast through the
forecast area this morning maintaining valley rain and mountain
snow showers across much of the area from the ID border south to
Cedar City and points east. Shortwave ridging in the wake of this
wave is forecast to temporarily build into the region late this
afternoon through tonight, which should end any lingering precip
by early evening.

The next shortwave in the recent wave train is forecast to move
inland across the Pacific Northwest Wednesday morning, then dig
southeast through the forecast area Wednesday night. Ample
moisture associated with this wave will bring valley rain/mountain
snow to far northern Utah beginning Wednesday morning, then
spreading south across much of the remainder of the forecast area
Wednesday afternoon through Wednesday evening.

Another, colder wave is forecast to dig into the region Thursday
night through Friday as the longwave trough retrogrades a bit and
amplifies. This wave is forecast to be associated with much cooler
air, with 700mb temps Thursday night forecast at or below -10C,
which would lower snow levels to most valley floors excluding the
far south. A cold and unstable northerly flow will remain in place
through Friday.

.LONG TERM (After 12Z Saturday)...The trough will continue to push
southeastward on Saturday, with shower activity potentially
lingering in the eastern half of the CWA, but generally decreasing
as the best instability exits the area. A ridge builds over the
Great Basin on Saturday night, and the clearing skies should help
produce another cold morning Sunday, even with temperatures aloft
beginning to warm.

The ridge quickly flattens Sunday, as another shortwave ripples over
the Pacific Northwest. Most shower activity associated with this
feature is expected to remain north of the CWA through Sunday and
Sunday night, though there is a slight chance showers brush far
northern Utah. The associated low level cold front starts to push
further south on Monday, which is when northern Utah could possibly
return to the wet northwest flow pattern in earnest. There is still
a fair amount of uncertainty on how amplified this pattern will
become, and whether a strengthening trough Tuesday will have a
direct hit on Utah or miss us a bit to the northeast. Either way,
the cooler and unsettled weather that has defined much of the last
month looks to be a good bet to continue into the first week of May.


.AVIATION...Ceilings at the SLC terminal should stay below 7000 feet
through at least 18Z due to continuing shower activity; improvement
above that level is possible between 18Z and 22Z, but showers will
still be possible through 00Z. Showers will likely produce periods
of MVFR conditions and erratic winds, though northwest winds should
be most common through the day.





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