Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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430
FXUS65 KSLC 191153
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
453 AM MST Sun Feb 19 2017

.SYNOPSIS...An elongated upper level trough will press east across
the eastern Great Basin today. High pressure aloft will develop
over Utah Monday, with a mild southwest flow aloft Tuesday. A
potentially strong winter storm could impact the region beginning
midweek.

&&

.SHORT TERM (Until 00Z Thursday)...An elongated upper level trough
extending from the BritCol coast southeast to an upper low over
Arizona will press slowly east across Utah today. The Arizona
upper low will create an expanding area of precip across south-
central through east-central Utah beginning early this morning.
Synoptic-scale lift will increase fairly quickly as the center of
the upper low cuts across the four corners region. Thermal
advection will also play a significant role as deep layer cold
advection will exist in the northeast flank of the advancing
upper low. Peak precip areal coverage and intensity will be this
morning, with this precip shifting off to the east during the
afternoon.

Up north the trough axis will turn the currently moist southerly
flow to the west this morning. Precip already is well aligned with
the trough axis through west-central Utah north through eastern
Idaho. Deep layer cold advection associated with the trough will
support deep synoptic-scale lift and help keep precip well
organized along the passing trough. Sufficient moisture and
instability trailing the trough along with orographic influences
will keep snow going along the Wasatch range this afternoon
through early evening. The greatest accumulations will likely
remain with the northern Wasatch, thus the reason for the winter
weather advisory through today.

Building heights tonight/early Monday should bring a short period
of dry weather later tonight/early Monday. Heights will lower
again late Monday as the next upper trough deepens over the
eastern Pacific. Shortwave ejecting out ahead of the deepening
trough could bring some light precip back into west-central
through northwest Utah by Monday afternoon/evening. This precip
should become better organized by late Monday night/Tuesday as
the near 700 mb baroclinic zone sags into northwest Utah. Would
not be too surprise if some heavy precip develops as this boundary
becomes frontogenic late Tuesday.

The now deep and cold upper trough along the west coast will turn
inland early Wednesday, then expand east into the western great
Basin late Wednesday. The associated surface cold front will sweep
south across northern Utah early Wednesday, then settle into
central Utah by late in the day. This feature will have most
everything needed to develop into a significant winter along and
to the north of the boundary. Solid baroclinic structure with this
trough will create strong synoptic-scale lift and widespread
precip along and north of the baroclinic zone beginning late in
the short term period and beyond.


.LONG TERM (After 00z Thursday)...The upper level trough depicted in
global models to begin the long term period will continue to slide
east-southeast into the eastern Great Basin Wednesday night through
Thursday. As this occurs, the near stationary mid level baroclinicity
in place across northern/central Utah will become more tightly
packed within a frontogenic environment, this becoming a cold
front focusing precip along and just in wake of passage. Globals
remain consistent in areal extent of precip initially over
northern Utah Wed night, then shifting south into central portions
Thursday. Have maintained likely PoPs most areas outside of those
downwind of the spine.

A combination of conditional instability in the post frontal
environment and some low/mid level moisture advection looks to
maintain largely orographically induced precip thereafter through
Thursday night. Focus being along the mtn spine/I-15 corridor within
a post frontal northwest flow.

Although valleys across northern/central Utah will see some rain in
the pre frontal environment, CAA with the front and in wake
continues to look to support snow to lower valley areas beginning
Thursday, with light accums possible into Friday.

Long wave pattern evolution thereafter maintains a cool but
relatively dry airmass across the area late week into the weekend,
with precip chances remaining tide largely to the mid level thermal
gradient across central/southern Utah and mtn areas.

&&

.Aviation...Periodic cigs below 7000 feet AGL are expected to impact
the KSLC terminal at times through early this afternoon. Light rain
showers are expected at times, though do not foresee much
operational impact outside of mtn obscuration locally. Southerly
winds are expected to switch to the northwest between 19-22z.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...Winter Weather Advisory until 4 PM MST this afternoon for UTZ007.

WY...None.
&&

$$

SHORT TERM...CONGER
LONG TERM/AVIATION...MERRILL

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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