Area Forecast Discussion
Issued by NWS Salt Lake City, UT
FXUS65 KSLC 301545
Area Forecast Discussion
National Weather Service Salt Lake City UT
945 AM MDT TUE AUG 30 2016
.SYNOPSIS...A ridge of high pressure over the Great Basin will
hold in place through today, before shifting east tomorrow. An
upper level trough of low pressure will move across the region
.DISCUSSION...High pressure currently in place (per morning water
vapor and H5 analysis) will slowly weaken and shift east over the
next 24 hours as an upstream trough nosing into the PacNW
continues to amplify and carve inland. An ejecting lobe riding the
southern periphery jet currently over NorCal will translate NE
through western Nevada today, this aiding to lower heights across
the extreme northwest, drive a slight uptick of cloud cover over
the north, and sharpen mid level baroclinicity across
central/western Nevada. The latter combined with some upper jet
influence will be the focus moving forward for introduction of
convective threats beginning late tomorrow as this zone noses into
In the mean time today will be dominated by the influence of the
high aloft and its attendant mid level subsidence. Outside of the
aforementioned uptick in high clouds in the north and development
of shallow cu over the highest terrain, looking at a very warm
and dry day today across the area with afternoon maxes pushing 10
degrees above climo. Feel the subsidence aloft and lack of
available moisture will limit deeper buildups over the terrain, so
have largely removed PoPs in this latest update. Similar temps
and only a net uptick of terrain based convection is expected for
Wednesday during the peak heating hours.
The aforementioned southern periphery jet and tightening
baroclinic zone will gradually nose into western Utah late in the
day Wednesday. Increased dynamic lift associated with this combined
with mid level moisture pooling within the zone does look
sufficient to support isolated high based convection along the
UT/NV border late day. Vertical profiles in BUFRs remain less
than ideal for deeper convection, but do support high based
shower/virga development beginning during the evening hours and
continuing overnight. With further eastward translation of the
trough overnight and through Thursday, and a continuation of
increasing moisture advection from the south, areal coverage of
showers and an increased threat of some storms will spread
southwest to northeast Thursday morning on through the day. With
a very dry subcloud layer in place at that time (especially in the
north), anticipate minimal rainfall potential but elevated outflow
threats aided by fast NE storm motions.
Synoptically driven southerly winds will also be trending up late
tomorrow through Thursday, and will likely remain elevated into
the weekend as the attendant cold front slowly shifts into
northern Utah, while sweeping the bulk of moisture/convective
potential over the east. CAA associated with this front and the
lowering of heights across the area will allow for a solid cool
down across the area (especially across the north/west) with temps
falling back to or below seasonal norms.
.AVIATION...Winds at the SLC terminal are expected to shift
to northwest between 20-22Z, returning to southeast after 03Z
tonight. VFR conditions will prevail through the TAF period.
.FIRE WEATHER...Yesterday`s ERC values were at or above the 97th
percentile across portions of northern Utah, while stations across
southern Utah remain below the 50th percentile, though ERC values
are trending higher.
A warming and drying trend will prevail today, plateauing for
tomorrow. Convection will be quite isolated, diurnal in nature,
and tied to the mountains.
Southerly winds look to increase along the Nevada border region
late today though critical fire weather conditions expected to be
isolated at best, with sub-critical gusts most locations. Dry
microburst winds may be supported due to high-based showers during
the late afternoon and evening hours in this area as well. Though
dont believe lightning will be much of a threat.
Better chance for critical fire weather conditions due to
combination of gusty winds, dry microbursts, and low RH Wednesday
through Friday across the western valleys.
A monsoon push will increase the coverage of thunderstorms during the
second half of the work week, supporting a cooling and moistening
trend and another round of lightning.
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