Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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FXUS65 KSLC 201736
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
1036 AM MST Fri Jan 20 2017

.SYNOPSIS...The active weather pattern will continue across the
region, with a series of weather systems crossing the area through
the first half of next week.

&&

.DISCUSSION...H5 analysis indicates a weak perturbation over
northern Utah lifting northeast attm, this in advance of a
progressive trough impacting coastal CA. This subtle feature
combined with favorable vertical profiles allowed for organization
of a narrow band of moderate snow and snow showers along the
Wasatch Front over the last few hours, and efficient crystal
growth yielded a quick half inch to an inch many areas in the
north. HRRR 1km suggests this band will continue to lift northeast
and dissipate through midday allowing a brief break from precip
and potentially a partial break in cloud cover. Earlier update
increased PoPs along the Wasatch Front this morning, and cancelled
the dense fog advisory (as visibilities improved quickly after
sunrise).

Upstream the next short wave of a series is currently tracking
southeast across CA and remains quite progressive due to being
coincident with a strong NW-SE upper jet poised to spread into
the desert southwest. A broad area of upper diffluence extends
downstream of this wave, and can be noted by expansion of a
mid/upper level cloud shield over Nevada in IR imagery. This is
currently just now nosing into the southern/western portions of
the state where clouds and light mtn precip are again filling in.

Models continue to agree that the track of this wave will carry
the bulk of the energy across the lower Colorado River Valley into
the desert Southwest late today through tomorrow morning, shifting
this broad diffluent area overhead. Deep moisture advection will
creep northeast within this sector overspreading the area within
modest SW flow aloft. Hi- res guidance suggests precip will expand
rapidly from SW-NE later this afternoon becoming areawide tonight,
with focused QPF areas south of the I-70 corridor. Passage of the
mid level trough axis tomorrow will likely enhance snowfall rates
along the Wasatch Front/I-15 corridor tomorrow morning into the
afternoon, with modestly unstable northwest flow in wake lasting
into the early evening hours. Will be addressing any need for
highlights this shift, as bulk of precip across the area will be
falling as snow, outside of modest rain potential across the
south/southwest...especially Dixie. Previous discussion below.

PREVIOUS DISCUSSION...As has been the case the last few model
runs, global models continue to indicate a lull in the action
Sunday morning. The next system will begin to impact the area
Sunday afternoon as a strong 160kt+ jet max takes aim on Utah.
Upper level diffluence combined with deep southwesterly flow and
associated warm air advection will provide more than sufficient
lift for precipitation across portions of Utah. The main locations
to see the highest precipitation rates will be portions of
southern Utah experiencing enhanced upslope flow and mountain
areas of Utah favored in southwesterly flow. Locations such as
Cedar City and the Salt Lake Valley will likely be shadowed until
the cold front arrives.

The cold front associated with the digging trough is expected to
cross the state Monday into early Tuesday. Expect an enhanced area
of precipitation near and behind this cold front.  A large and
somewhat diffuse trough will remain across the West through at least
Thursday. This will keep deep, moist and unstable north to
northwesterly flow in place. Expect at least mountain areas to
continue to see snow showers from Tuesday through Thursday.

Upper level ridging will finally build into the area by Friday
bringing a break to the action through at least the early part of
the weekend.

&&

.AVIATION...Ceilings at the SLC terminal have lifted above 3kft as
of 17Z, but there is an 80 percent chance they will remain below
7000 feet through most of the day. Visibilities will likely also
remain below 6SM through the day. Winds could be light and variable
at times today, but southerly is the only direction that winds
should exceed 7 knots through 03Z.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...None.
WY...None.
&&

$$

DISCUSSION...Merrill/Schoening
PREVIOUS DISCUSSION...Kruse

For more information from NOAA`s National Weather Service visit...
http://weather.gov/saltlakecity

For frequently asked questions about the Area Forecast Discussion
visit...
http://weather.gov/saltlakecity/general/afd_faqs.php



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