Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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000
FXUS65 KSLC 261558
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
858 AM MST Sun Feb 26 2017

.SYNOPSIS...The next cold Pacific storm system will arrive
late tonight and impact the region through the first half of the
week.

&&

.DISCUSSION...
Water Vapor Satellite shows a positively tilted trough from the
Central Rockies into northern Arizona. The next storm is a closed
low along the Washington/Oregon coast. 400-200mb MDCARS wind
observations place a 110-165kt westerly jet from southern
California across the southern CONUS. A second 75-95kt cyclonic
jet was located over the Pacific Northwest. GOES/SLC 12Z RAOB/HRRR
indicate that precipitable water values vary from 0.05"-0.10"
mountains to 0.15"-0.25" most valleys.

Going forecast in great shape so just a couple of tweaks today.
Light snow continues at Heber out of a low stratus deck. Elsewhere
a sunny start with increasing high clouds as the day progresses.
Temperatures will modify on southwest flow ahead of tomorrow`s
storm. Updated the hourly temperature/RH curve based on
observations and latest model data.

Will be addressing tomorrow`s storm with the afternoon package.

&&

.PREVIOUS DISCUSSION...
The elongated upper trough that extends across southern Utah this
morning will continue to shift southeast out of the area. The few
snow showers that existed near the trough axis overnight have now
mostly ended. As a result, expect a fairly quiet weather day as a
more stable airmass settle into the area behind the trough. A
low-amplitude shortwave ridge will build briefly into the area
this afternoon with increasing southwest flow in warm advection.
This combined with mostly sunny skies underneath a thin veil of
cirrus advancing into northern Utah should lead to warmer
temperatures today.

The next trough is already moving onto the Pacific Northwest coast
and will carve into Utah late tonight through tomorrow. Snow is
expected to start filling in across northern Utah late this evening.
The midlevel baroclinic zone is then progged to sag into northern
Utah after midnight, which should bring a period of more intense
snow to the area. This baroclinc zone will then continue slowly into
central Utah by late afternoon. The baroclinc zone is expected to
tighten throughout the day as an increasing southwesterly flow
across southern Utah strengthens convergence into the boundary, so
there is a potential for heavier snow across Utah County and into
central Utah. The boundary will then slowly continue south overnight
while gradually weakening.

Precipitation will be widespread with this storm, and all areas but
the lowest valleys of southern Utah will likely see precipitation
fall as snow given the cold northwest flow that develops behind the
front. Significant snow is expected across the mountains with
accumulating snow in many northern, central, and western Utah
valleys as well as southwest Wyoming.

A brief lull in the weather is expected late tomorrow night into
Tuesday morning ahead of a second shortwave trough embedded within
the mean trough over the area. This shortwave will cross the area
Tuesday afternoon and bring a quick burst of snow to mainly the
mountains and adjacent valleys of northern and central Utah.

A cool and stable northwest flow remains over the area on
Wednesday, as an upper level ridge amplifies off the west coast.
The models have trended toward allowing the cold air to linger a
little bit longer over the CWA, so have kept temps fairly cold for
Wednesday. Have also cooled them down a little bit for Thursday,
though a 5-10 degree warming trend is still evident as the ridge
axis shifts inland.

A few weak ripples in the northwesterly flow generally pass north of
the CWA late Wednesday through Friday, though some light snow
showers cannot be ruled out across far northern Utah. A larger and
colder trough pushes into the Pacific Northwest on Friday, likely
followed by a decently strong secondary wave on Saturday. Models
have maintained decent agreement that much of this instability and
cold air remains north of the Utah/Idaho border, though the GFS
still has occasional runs that try to dig part of the trough into
the Rockies late Saturday through Sunday. Have kept some low end
POPs across the north over the weekend to account for this
possibility, but have otherwise favored the warmer and drier idea
for now.

&&

.AVIATION...
Southerly winds will prevail at the SLC terminal through
the remainder of the day and into the evening hours. Increasing
clouds below 10k feet after 04z this evening are expected with the
next round of showers during the overnight period into Monday
morning.

&&

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

$$

PUBLIC...Rogowski/Cheng/Schoening
AVIATION...Dewey

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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