FXUS65 KSLC 202154
Area Forecast Discussion
National Weather Service Salt Lake City UT
354 PM MDT Fri Oct 20 2017
.SYNOPSIS...The strong cold front will exit the region this
evening with a ridge rapidly developing in its wake for this
weekend and the first half of next week. Another cold trough is
expected to impact the region by the end of the work week.
.SHORT TERM (until 00Z Tuesday)...Strong cold front continues to
race southeastward across central Utah this afternoon and is
expected to exit the CWA by mid evening. Strong west southwest
wind gusts in excess of 35 mph will occur in the prefrontal
environment across south and southeastern portions of the CWA
before shifting to the northwest at 20-35 mph then relaxing about
2-3 hrs after frontal passage.
GFS has been much better than the NAM with the idea of having
some rain showers across central Utah late this afternoon. Even
had a couple of lightning strikes near Richfield past hour so have
added thunderstorms to the forecast across central mountains for
this evening. The driving force for the thunderstorms is the cold
500 mb temps of -16 degrees C moving over the relatively warm
surface temps in the 60s. As the colder air mass works in at the
surface this temperature lapse rate will weaken and thunderstorms
will end as well as most showers across central Utah.
The cold trough axis will move across the state about midnight or
shortly thereafter, then warming aloft will occur in its wake.
Have kept a slight chance for showers in the northern mountains
beyond midnight until this trough axis passes, then dry it out.
The southern half of the CWA should see mostly sunny skies
Saturday, while a somewhat moist warm advection pattern at 700mb
will bring clouds across northern portions with the heaviest cloud
cover coming Saturday evening across the northern Wasatch Front
and Mountains when the warm advection becomes the most intense.
Temperatures will be about 5 degrees below normal across the
south and about 10 degrees below normal across the northern
portions of the CWA Saturday. However, as the ridge builds in
Sunday and Monday, temperatures will warm back to a few degrees
above normal with mostly sunny skies except across the far north.
.LONG TERM (After 00Z Tuesday)...Mid level ridging will remain
centered to the west of the forecast area throughout the long term
period, resulting in a northwest flow aloft across the Intermountain
Region. Initially this ridge will be centered along the west coast
maintaining dry and mild conditions inland across the eastern Great
Basin. However, by midweek this ridge is forecast to retrograde
offshore, allowing a potent but fast moving shortwave trough to
dig through the forecast area Wednesday night into Thursday. Have
increased PoPs for this period across the north, as well as
lowered temperatures for the end of the week.
.AVIATION...Ceilings are expected to rise above 7kft by 23Z as the
chance for rain comes to an end at the KSLC terminal. Northwest
winds will continue throughout remainder of the afternoon and
evening hours with gusts diminishing after 02Z.
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