FXUS65 KSLC 060245
Area Forecast Discussion
National Weather Service Salt Lake City UT
845 PM MDT Fri Jun 5 2020
.SYNOPSIS...The first in a series of Pacific storm systems will
cross the area from the southwest today into Saturday. This first
storm will be followed by a substantially colder storm system
Sunday into Monday.
.DISCUSSION...Afternoon convection begin to fill in from far
southern Utah where gusty winds were being realized with little to
no precipitation. The upper level low continues to track east into
Arizona this evening. An impressive cloud shield with nearly a
continuous stream of clouds can be seen from far northern Mexico
all the way into northwest Utah. Winds have persisted with
numerous locations seeing severe speeds of 55 mph or greater from
St George to Moab up to the Great Salt Lake. A very dry boundary
layer continues to be well mixed with a prominent inverted-V
sounding from the 00Z KSLC sounding. The well mixed layer extends
from the surface all the way to 500mb (13,500 ft AGL) where 50-60
knts of wind are being tapped into.
High-res model guidance is still mostly on track with the trough
ejecting northeast overnight bringing widespread moisture and
heavy rainfall to southern and eastern Utah during the overnight
hours. Updates made to the forecast this evening were mainly for
.PREVIOUS DISCUSSION (Issued at 137 pm MDT)...
When the moisture finally surges north, the next part of the story
will unfold. The moisture with the trough continues to look quite
impressive spreading northward. Widespread rainfall is expected
along and near I-15 in central and southern Utah later this
evening and will then spread into eastern Utah overnight through
early Saturday morning. Precipitation will continue spreading
north to near I-80 in the far extent of north and northeast Utah.
The going Flash Flood Watch was expanded into the far northeast
corner of Utah today to capture the numerous bands of convection
that may redevelop overnight into Saturday afternoon and bring
heavy rainfall. The synoptic scale ascent will help mix the
boundary layer increasing the available moisture. More high
resolution models today continue to advertise a redevelopment of
convection taking place from south-central Utah northeast through
Areas of concern continue to be normally dry washes and small
streams, slot canyon and slick rock areas, and locations near and
downstream of recent burn scars. Potential for debris flows off
any recent burn scars will remain elevated through late Saturday.
As convection begins to move off to the east late Saturday night,
the next weather feature will approach from the northwest as a
cold front bringing widespread precipitation to northern Utah this
.AVIATION...Gusty south winds are expected to persist at the SLC
Terminal through the rest of the valid TAF period into Saturday
evening. Wind speeds will taper off overnight tonight but remain
out of the south. Ceilings will begin to drop to 8k or 9k feet AGL
by 18z-19z Saturday with nearby showers and become more widespread
later in the afternoon Saturday.
.FIRE WEATHER (Issued at 137 pm MDT)...Strengthening southerly
flow combined with a very dry air mass will bring critical fire
weather conditions to most valleys this afternoon and evening.
Additionally, the leading edge of a plume of moisture centered
over eastern Utah will yield isolated to widely scattered dry
thunderstorms this afternoon for many locations. This moisture
will increase substantially overnight bringing widespread wetting
rains to areas east of I-15 through Saturday morning.
Thunderstorms will also bring a threat of locally heavy rainfall
during this time.
Southerly winds will once again strengthen Saturday afternoon
across most areas, however increased humidity should preclude
critical fire weather conditions. A cold front will cross northern
and central Utah Saturday evening bringing another round of
wetting rains, along with much cooler temperatures for Sunday.
Cool and unsettled weather is expected to persist into early next
week, followed by a rapid warmup midweek and another potential
period of critical fire weather conditions late in the week.
UT...Flash Flood Watch from midnight MDT tonight through Saturday
afternoon for UTZ009>013-021-517.
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