Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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FXUS65 KSLC 162133

Area Forecast Discussion
National Weather Service Salt Lake City UT
333 PM MDT Wed Aug 16 2017

.SYNOPSIS...A warming and drying trend will take place across the
area through Friday. Moisture will increase again from the south
over the weekend.


.SHORT TERM (THROUGH 12Z SATURDAY)...The large-scale pattern
this afternoon consists of a weak trough over Nevada, although the
latest RAP analysis indicates a 500mb closed low over southern
Nevada. Lingering moisture across western Utah combined with this
advancing low has led to a few showers across west-central and
southwest Utah this afternoon. Meanwhile, a few showers have also
developed along the higher terrain. However, instability parameters
are quite weak and as a result, only a few of these showers are
electrified, and most are only expected to produce light rain
before tapering off later this evening.

The low will shift into northwest Arizona overnight and is expected
to shear apart as the mean trough remains upstream but carving back
towards the southern California coast. Models indicate that a new
closed low will develop off the southern California coast tomorrow

Expect a continued drying and warming trend from the north and west
tomorrow into Friday, with a small potential for some terrain-based
showers and thunderstorms. However, there could be a bit of an
increase in convection by late Friday as the low starts to advance
and eject weak disturbances into Utah, with some of these showers
potentially lingering through late Friday night.

.LONG TERM (After 12Z Saturday)...The weak upper low along the
southern California coast will create a poorly defined deformation
axis across central Utah Saturday. This axis will be the focus for
convection, with the areal coverage running between isolated and
scattered with the peak period coming at max heating during the late
afternoon through early evening hours. A trailing vorticity lobe
Saturday evening will drive convection farther north into mainly
northwest Utah during the overnight hours.

The various global models show the coastal California low becoming
organized beginning Sunday, with a well defined upper low off the
coast for the early portion of the week. This feature will serve to
generate a steady southerly flow and bring moisture north across the
forecast area. PWAT values are expected to range between 0.75" and
1.00" during the first half of the week. A series of vorticity lobes
ejecting north from the coastal upper low will lead to periods of
convective precip through at least midweek. Locally heavy precip is
possible, especially in the upslope areas of far southern Utah.

Concerning eclipse viewing on Monday...some level of cloud cover
looks to be likely during the viewing period. Shortwave ridging
across northern Utah could create enough dynamic subsidence to limit
the expected cloud cover during the morning. Any shift to the ridge
axis will change the calculus, but for now it appears that impacts
from cloud cover will be on the low side across northern/central
Utah and southwest Wyoming.


.AVIATION...North to northwest winds will continue at the SLC
terminal, shifting to the southeast between 03-04Z.


.FIRE WEATHER...A warming and drying trend will continue across the
fire district through Friday. Although isolated showers and
thunderstorms will remain possible, especially over the higher
terrain of southern and central Utah, the chance of wetting rain
will be small. Winds outside of showers will remain light and
terrain-driven during this time.

A weak disturbance will lift north into central and northern Utah
Saturday into Saturday night, increasing convection across the area.
This will be followed by a moisture surge on Sunday which will
continue through the first half of next week.





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