Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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FXUS65 KSLC 132131

Area Forecast Discussion
National Weather Service Salt Lake City UT
331 PM MDT Fri Apr 13 2018

.SYNOPSIS...High pressure will return to the Interior West for
the weekend. The next storm system will impact the region early
next week.


.SHORT TERM (Through 12Z Monday)...The strong, winter-like trough
that brought a return to cold, snowy weather to the state will
continue to pull away from the region this evening. Light snow
showers continue to impact mainly the higher terrain areas of the
Wasatch, mainly well above any roadways. Expect these showers to
end this evening due to the loss of insolation combined with the
subsidence behind the trough.

A welcome break in the active pattern will bring the state a
relatively warm and sunny weekend as upper level ridging build
into the West. Another strong, cold trough will approach the
western Great Basin Monday morning. Model guidance indicates 700mb
winds will be near 55 to as much as 65kts by Monday morning. This
should bring a period of high winds late Sunday into Monday (and
likely extending into the long term portion of the forecast).
Started increasing winds during this period...and winds will
likely need to continue to be increased on future shifts barring
some major change in the models. As was mentioned in AFDs earlier
this week, the longwave pattern expected over the next 7-10 days
has a higher degree of predictability than average.

.LONG TERM (After 12z Monday)...As the deepening trough moves into
the southern Great Basin early Monday, heights fall fairly rapidly
with a tightening baroclinic zone at 700mb. Translation: This has
many of the same characteristics as the storm that went through this
past week lending to strong pre-frontal and post-frontal winds and
widespread precipitation, both rain and snow.

Monday afternoon under a strong southwesterly flow, winds at 700mb
are nearing 50-65 knots. As the front pushes through during the
afternoon hours of Monday, there is potential for instability
showers (rain and snow) and can not rule out possibility for
thunderstorms associated with the strong front. The upper level
trough is positively tilted, bringing the colder air aloft right
along with the front. Steep lapse rates may lead to rapidly
developing showers. As temps drop to -10C to -12C snow will be
possible to valley floors once again; spring time in the
intermountain west.

Forecast models are in agreement with this system ejecting to the
east by late Tuesday and gradually building heights, although short
lived. The pattern through late next week continues to remain
unsettled and active. Differences begin showing up after 00z
Thursday with the next storm system. The EC wants to move the
deepening low through the Great Basin quicker than the GFS and thus
leading to precipitation across Utah under a southwest flow. The
models have been in great agreement up until now, so have low
confidence in the timing and details with this this system. As such,
have kept a broad brush approach to precip chances for late next


.AVIATION...There is a 20 percent chance of lingering ceilings below
7000 feet at the SLC terminal between 21Z and 00Z. Gusty west-
northwest winds should continue through at least 00Z. Winds are
forecast to switch to the southeast around 03-05Z, with a slight
chance that northwesterlies prevail through 06Z.





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