Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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FXUS65 KSLC 240255

Area Forecast Discussion
National Weather Service Salt Lake City UT
855 PM MDT Thu May 23 2019

The upper level low pressure over northwest Utah will maintain
showers and thunderstorms across much of the region this evening.
Showers will linger across western and northern Utah through early
Friday morning as the low pressure exits through Wyoming.
Lingering showers and storms will follow for the weekend followed
by a new storm system early next week.


Mid/Upper level closed low feature currently over far northwest
Utah will begin to quickly propagate northeast out of the region
overnight due to the strong jet making its way downstream. As it
does so, the shearing tightens up a positively tilted trough axis
which makes its way across the area overnight and into tomorrow.

The trough is expected to bring another round of widespread
showers and perhaps a rumble of thunder to northern Utah later
tonight and tomorrow morning. Above 7500 feet several inches or
more of fresh snowfall will fall. Luckily any travel impacts
across the high elevation should be brief and spotty.

Height rises and warming aloft will stabilize the region from
south to north tomorrow into tomorrow night. The combination of
instability, steep lapse rates and proximity of the trough will
fire new convection tomorrow afternoon, with the best coverage
across the northwest portion of the state.


The now well-defined upper low currently centered across
northwest Utah will remain across northern Utah through mid-
evening. From there this feature will accelerate northeast through
Wyoming and leaving a mid-level trough extending back to coastal
California into early Friday.

Convective precip has been on a fairly steady increase across much
of the state during the afternoon. Increasing instability within
the core of the mid-level cold pool and increased dynamic support
from the upper low has spawned relatively deep convection with
brief heavy rain and small to medium size hail. This convection
should maintain it`s peak activity through around mid-evening,
then drop off as the center of the upper low moves into Wyoming.

The trough axis lagging back through Utah later tonight will
remain the focus of what should turn into generally light precip
through early Friday. Convective precip should fire up again
during the afternoon as the air mass remains moist and somewhat
unstable and a trailing shortwave moves across western/northern

For the weekend substantially drier and warmer air will move into
southern Utah and then spread quickly north as an increasingly
strong southerly flow aloft develops across the region. Still
looking at some terrain-based convection Saturday afternoon due to
stronger diurnal heating and lingering moisture. Sunday will see
even less convection due to even more limited moisture.

The upper low moving south along the west coast this weekend could
impact far western Utah later on Sunday. Anticipating at least one
decent shortwave ejecting out ahead of the upper low once it
settles in along the California coast. Diurnal heating ahead of
this feature along with increasing dynamic support for lift should
be able to fire up some convection near the Nevada border by late
in the day.

Global models in good agreement through early next week, ushering
in another low pressure system into the Four Corners region by
Monday morning. Moisture and instability spread northward
throughout the day, delivering precipitation to much of the CWA by
the afternoon and a weak cold front passage Monday night.
Expecting temperatures to drop 8-10 degrees by Tuesday and snow
levels near 8kft during this event.
southeast enhanced drainage flow with only a
remote potential of a vicinity shower. Winds will become gusty
late tonight and tomorrow from the south.
Though winds shift northwest after the trough passage, warm
advection and midlevel convergence promote renewed precipitation with
afternoon convection into Tuesday afternoon. Temperatures are
expected to rebound by midweek toward normals. At this point global
models diverge, as the ECMWF stifles the moisture tap while the GFS
keeps an unsettled pattern through the end of the forecast period.


Through the remainder of this evening at the KSLC terminal,
expect steady south-southeast enhanced drainage flow with only a
remote potential of a vicinity shower. Winds will become gusty
late tonight and tomorrow from the south.

Rain will become increasingly likely through the second half of
the night, lasting until mid morning. This will likely bring
reductions to visibilities along with ceilings, with the ceilings
obstructing the mountains overnight through much of Friday as new
convection forms during the afternoon.


Looking at somewhat drier and warmer conditions working into the
fire districts beginning Friday afternoon and continuing through
the upcoming weekend. Residual moisture will still be sufficient
to generate scattered afternoon and early evening showers and
isolated thunderstorms both Friday and Saturday. The next storm
system moving south along the west coast this weekend will turn
east and bring another round of widespread rain along with some
mountain snow and thunderstorms early next week.





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