Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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FXUS65 KSLC 232159

Area Forecast Discussion
National Weather Service Salt Lake City UT
359 PM MDT Sat Jun 23 2018

.SYNOPSIS...An upper level low will graze extreme northern Utah
and southwest Wyoming late this afternoon through tonight with
cooler air spreading into the forecast area on Sunday. High
pressure aloft will return to the area to begin the work week
bringing a warming trend before another storm system approaches
the area late-week.


.Short Term (Through 00z Wednesday)...Southeastward translation of
the closed low over southern Montana continues per afternoon
satellite and H5 analysis. Mid/low level baroclinicity has sharpened
over northern Utah today associated with an accelerated surge of the
attendant cold front, but said surge has dissociated the front from
the upper support locally allowing for a dry passage thus far.
Further SE translation of the cold core into central Wyoming over
the next 12 hours will both drive the front further south across the
entirety of the area, and modestly destabilize SW Wyoming and the
Uintas where closer proximity to the mid level cold pool will enable
shallow/thin CAPE for a period this evening. Maintaining a slight
chance of isolated convection for those areas, but still feel the
weak lift/instability will primarily drive benign mid level CU
formation more often than not.

Downstream translation of the upper low tonight will allow for a
rapid building of heights by Sunday as upper ridging begins to
translate overhead. Sensibly, the primary takeaway from all this
will be markedly cooler temps across the north Sunday, with some
cooling across the south as well.

The upper ridge will remain oriented overhead through Monday
providing dry/stable conditions and rapidly warming temps within a
subsident and modifying airmass. This will hold true through
Tuesday, as all northern branch activity will remain well north of
the area during the early next week period. Have continued to
promote mid 90s+ temps along the Wasatch Front again by Tuesday,
with values down in the Dixie area ramping up to around 105F.

.LONG TERM (After 00Z Wednesday)...The area will be under
generally zonal flow at the start of the long term period as it
lies between the influences of a mid-lvl high over the desert
southwest and northern branch disturbances over the Northern
Rockies. The mean flow will begin to back more southwesterly
during the day on Wednesday in response to general troughiness
developing on the west coast. Given this warm (and dry)
southwesterly flow Wednesdays highs will likely be the warmest of
the long term period with maxes running 10-15 degrees above normal
(mid-upper 90s in northern Utah valleys, generally low to mid
100s in southern Utah valleys). A weak disturbance ejecting from
the large-scale west coast trough will graze northern Utah on
Thursday with a slightly stronger disturbance doing the same
early Friday. These disturbances may result in some mid-high lvl
clouds and slight (a few degrees on Thursday with 5 degrees or so
of additional cooling on Friday) cooling for the northern half of
Utah but given their glancing nature am not expecting much (if
any) chances of precipitation through late Friday. Southern Utah
looks to remain hot with breezy southerly winds through the end of
the week.

Guidance is in general agreement that a piece of the west coast
trough will amplify in the vicinity of northern Utah late Friday
into Saturday. The deterministic GFS is the most bullish of the
12Z guidance with this feature... bringing the edge of the cold
core to the UT/ID border with the resulting cold front being
intense enough to generate precipitation. Almost all other pieces
of guidance (EC/CMC/GEFS mean) depict the bulk of the system`s
energy/mid-lvl cold pool staying north of the area. Given this
seeming support of the less amplified/drier solution only went
with only slight chance PoPs over the far north on Saturday. That
being said guidance still seems to indicate that we will not
become decoupled from the northern branch (and associated cold
fronts) through at least the first couple days of July which is
good news for those who are not fans of the heat).


.AVIATION...VFR conditions with northerly winds are expected to
persist through the night at the SLC terminal. The winds should
weaken after 02-03Z. There is a 30% chance of 10K ft AGL cigs
between 05Z and 10Z.


.FIRE WEATHER...Dry and breezy conditions south and east of an
advancing cold front will continue to produce widespread Red Flag
conditions for most areas across southern/eastern Utah where fuels
have been deemed critical. The cold front will continue to advance
south tonight bringing cooler temperatures and decreased winds to
all areas Sunday. High pressure will build overhead for early next
week providing stable but bone dry conditions and light winds. At
this time, the potential of reaching critical fire weather
conditions once again will occur later in the week ahead of an
approaching pacific storm system.


UT...Red Flag Warning until 11 PM MDT this evening for UTZ482-484-488-



SHORT TERM...Merrill

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