Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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000
FXUS65 KSLC 292203
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
403 PM MDT Sat Apr 29 2017

.SYNOPSIS...The upper low over New Mexico will move slowly east into
the southern Rockies by this evening. A series of weak weather
disturbances will graze the area Sunday night through the early
portion of the upcoming week. Strong high pressure aloft will
finally reach the area around the middle of the week.

&&

.SHORT TERM (THROUGH 00Z WEDNESDAY)...The upper low continues to
track across New Mexico this afternoon while an upper level ridge
builds into the western CONUS. A few showers are noted on radar
imagery across far north-central Utah, but the airmass will be
trending more stable so these showers are expected to diminish
quickly this evening. Otherwise, northerly winds continue to gust
generally in the 20-30 mph range due to the near northerly MSLP
gradient and northerly flow at 700mb along the back edge of the
departing low. Winds near Washington County canyons actually
increased this afternoon, likely due to a more favorable gradient,
with occasional local gusts over 40 mph expected through the early
evening hours.

Skies will be mostly clear during the early part of the night, which
will lead to good radiative cooling. However, high clouds will start
to spread into northwest Utah after midnight. Although the airmass
in general is trending warmer, the radiative cooling tonight will
bring a risk of a hard freeze for some of the colder valleys,
including the Sanpete and Sevier Valleys, portions of southwest Utah
near Cedar City, and higher valleys of the western Uinta Basin. A
Hard Freeze Warning has been issued for these areas.

An unsettled northwesterly flow aloft will remain in place through
the first half of next week with weak troughs grazing northern Utah.
A fairly diffuse trough on Sunday into Monday will push a weak cold
front into Utah while a somewhat more consolidated feature on
Tuesday will lead to a stronger cold front. Even so, the airmass
behind neither of these fronts are very cold, with 700mb
temperatures down to -4C across northern Utah. A few showers are
expected to accompany both of these storms but significant
precipitation is not expected.

.LONG TERM (After 00Z Wednesday).....Medium range period begins with
a shortwave grazing northeast Utah as it drops southeast into
Colorado. Feature has some limited support in the form of weak upper
level divergence in the left exit region of an upper level jet
streak that intrudes into far northern Utah. With modest forcing
expected have included a slight chance of precipitation on Wednesday
night from the far northern Wasatch through southwest Wyoming and
into the Uintas.

This wave moves quickly to the southwest and a strong upper level
ridge builds over the Great Basin for Thursday and Friday bringing
much warmer temperatures and dry weather to Utah and southwest
Wyoming. Expect temperatures to quickly return to above normal under
sunny skies.

A splitting upper level trough moves over the west coast heading
into the weekend with an upper level low closing off in the southern
branch off the coast of central California on Saturday. The ECMWF
and GFS are in good agreement on this evolution although they differ
a bit on how far south the upper low dips with the GFS dropping it
to just west of far northern Baja California and the ECMWF keeping
it more off the central California coast. Meanwhile the northern
portion of the split moves through the Pacific Northwest and across
the northern Intermountain region over the weekend. Between these
two features a mid level baroclinic zone moves slowly southeast and
is poised just northwest of Utah on Saturday. Ahead of the
baroclinic zone the mid level flow increases to 25-35 knots over
much of western Utah, so it should be a windy day for many of the
western valleys with temperatures remaining above normal. On Sunday
moisture moves north into Utah ahead of the closed low off of the
southern California coast. With some instability in place have
expanded the coverage of slight chance PoPs a bit with both the
ECMWF and GFS indicating the potential for a little better coverage
of showers and thunderstorms.

&&

.AVIATION...Northwest winds will remain in place at the KSLC
terminal through 04z before trending back to a light southeast for
the overnight hours. VFR conditions will be maintained through the
valid TAF period under largely clear skies.

$$


.SLC WATCHES/WARNINGS/ADVISORIES...
UT...Hard Freeze Warning from midnight tonight to 9 AM MDT Sunday for
     UTZ011-014-016.
WY...None.
&&

$$

Cheng/Graham/Merrill

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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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