Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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FXUS65 KSLC 191130

Area Forecast Discussion
National Weather Service Salt Lake City UT
430 AM MST Sat Jan 19 2019

.SYNOPSIS...High pressure aloft will settle over the area this
weekend. A new and potent storm system will reach Utah Monday and
bring widespread precipitation to the area early in the week.


.SHORT TERM (Until 00Z Wednesday)...A broad, low-amplitude upper
ridge will settle over the interior west this weekend. Moisture on
the upstream side of the ridge (PWAT values around 0.50") will
begin to spread across mainly the northern third of Utah this
morning. Could see some precip develop near the Idaho border
today as lift resulting from low/mid-level warm advection should
be sufficient to generate a fairly broad area of light precip
through early this evening. Precip will get nudged north of the
state for tonight through Sunday as the mean layer flow backs a
bit and sends the moisture more toward the northern Rockies and
Pacific Northwest.

The upper trough currently over the Gulf of Alaska will become the
next storm system to impact Utah to begin the new week. This next
trough will reach the Pacific Northwest coast by late Sunday, then
continue east across the Great Basin late Sunday night through
Monday night.

Strong southwest flow aloft and a somewhat drier pre-trough
environment will limit precip development over Utah Sunday night.
The one area that could see precip will be along the Nevada border
where moisture will increase quickly along the leading low-level
baroclinic zone late Sunday night. The strongest low-level cold
advection will surge into west-central and southwest Utah Monday
morning, followed by the mid-level cold pool and the best dynamic
support for lift from the upper trough late morning through the
afternoon. Anticipating significant precip due to the strong
synoptic-scale lift, with heavy snows over the central and
southwest mountains and adjacent higher valleys.

Across northern Utah favorable synoptic-scale lift will exist as
the trough moves through the area, though this lift may not be
quite as strong as that over central/southern Utah. Orographic
influences will likely be dampened a bit as the low-level flow
will be towards the weak side during the height of the event
Monday. May see a brief period of favorable northwest flow into
the northern mountains late Monday, though this will likely be too
late in the storm to generate much in the way of heavy snow for
the north.

High pressure aloft building over the eastern Pacific Tuesday will
produce a downstream anti-cyclonic north-northeast flow across
Utah. Any lingering snow showers will end quickly Tuesday morning
as the air mass dries and becomes subsident in the wake of the
exiting upper trough.

.LONG TERM (After 00Z Wednesday)...The long term forecast period is
largely monopolized by a building...extensive longwave trough across
the central and eastern portion of the US. Utah will remain largely
on the western flank of this developing trough. This will help to
keep northwesterly flow in place...with several relatively weak
waves embedded in the flow crossing the area through the end of next

Clearing behind the early week system will be in place to start
the long term forecast period. Expect the first northwest flow
wave to bring a period of snow showers to portions of northern
Utah Wednesday. Another weak wave will bring another round of
potential snow showers Thursday. Neither of these waves looks to
bring a substantial amount of snow to the area...but progressive
flow should prevent significant inversion conditions from
developing through Thursday/Friday.

As the central/eastern US trough deepens late in the week...upper
level ridging will amplify along the West Coast. The main impact of
this will be an end to the relatively moist...northwesterly flow
across Utah into next weekend. Given model to model and run to run
inconsistencies through this is too early to say whether
inversion conditions may develop during this time.


.AVIATION...Increasing mid-level clouds at the SLC terminal should
bring ceilings at or below 6000 feet AGL by 12-14Z. Expect southerly
winds to continue through the day. Showers are largely expected to
stay north of the terminal...but any showers that cross the terminal
may bring temporarily lower ceilings/visbys between 15-21Z.





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