Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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FXUS65 KSLC 241553

Area Forecast Discussion
National Weather Service Salt Lake City UT
953 AM MDT TUE MAY 24 2016

.SYNOPSIS...A series of weak weather disturbances will continue
to cross Utah through late week, keeping unsettled conditions over
the area.


.DISCUSSION...The mean long wave trough in place continues to
stretch from the intermountain region west into the eastern
pacific, with two defined short waves rounding the base. The
closest upstream feature currently exists over central Cali and
is slowly churning east, and will trend northeast whilst lifting
across the area later this afternoon and evening. A defined
deformation axis exists over southern Montana west into eastern
Oregon on the southern periphery of a closed low spinning over
southern Canada. Weak convergence exists across the north due to
the proximity of these features, and scattered high based showers
exist across the northern mtns and extreme northwest. Made only
minor tweaks to PoPs and cloud cover this morning (in earlier
update) to follow latest trends regarding this.

Low/mid level lapse rates remain quite steep, with PWAT hovering
near a half inch. The combination of diurnal destabilization and
subtle forcing from the approaching wave will aid further
convection this afternoon/eve, though not unsimilar to yesterdays
and lacking organization potential. This said, potential for
isolated microbursts remains as a largely dry sub-cloud layer
is apparent below H6 in 12z KSLC RAOB and bufkit profiles.
Anticipating isolated coverage to occur largely over the terrain
in the south, but should be a bit more areally expansive and
scattered across the north within the convergent flow. Previous
forecast handled this well and made no changes.

PREVIOUS DISCUSSION...The second of the aforementioned shortwave
disturbances will develop into a closed low and track across
northern Arizona late tomorrow into Thursday morning. Meanwhile,
the Saskatchewan closed low is progged to elongate as a weak
disturbance rotates around it and grazes northern Utah tomorrow
afternoon. This northern feature will help drive scattered showers
for northern Utah tomorrow afternoon while portions of southern
Utah could see a few showers developing by tomorrow evening with
the closed low.

With the passage of the second shortwave disturbance, the mean
trough axis will start shifting east of Utah on Thursday.
Northwesterly flow will develop behind a weak boundary and
precipitation should become a bit more widespread over the forecast
area. However, temperatures will see only minor day-to-day changes
today through Thursday.

Shortwave ridging builds over the Rockies on Friday afternoon,
with Utah/Wyoming/Colorado generally between storm systems. This
will allow for warmer and somewhat more stable conditions for
Friday, though enough moisture looks to linger under the ridge to
allow for convection initiating off the terrain Friday afternoon.

The bulk of the next upper level trough remains north of the
forecast area Saturday, but models have come into better agreement
about bringing the surface cold front into the northern portions of
the CWA through the day Saturday. This front looks to be accompanied
by decent low level moisture, so have increased POPs for Saturday
afternoon across the north, and they will likely need to be raised
even more if models stand firm with the cold frontal timing. Sunday
is a little less certain, but looks somewhat similar to Saturday,
with the surface front hanging out across northern Utah and the bulk
of the upper low spinning off to the northwest.

The fate of this upper low becomes much less confident past Sunday,
with a fairly major divergence of model guidance; some push the
storm off to the east, while other models retrograde it a bit to the
west. Have kept the forecast temperatures and POPs generally close
to climatological normals in days 6 and 7 until models come into
better agreement.


.AVIATION...VFR conditions are expected at the SLC terminal today
with cigs generally above 6000 FT AGL. Southerly winds are expected
to shift to the northwest a bit later than usual, between 20Z and
22Z. However, there is a 30 percent chance of southerly winds
prevailing throughout the day. Showers in the vicinity of the
terminal may produce periods of gusty and/or erratic winds,
primarily during the later afternoon or early evening. There is a 20
percent chance of a thunderstorm directly impacting the terminal
later today.


.SLC Watches/Warnings/Advisories...



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