Area Forecast Discussion
Issued by NWS Salt Lake City, UT
FXUS65 KSLC 290906
Area Forecast Discussion
National Weather Service Salt Lake City UT
306 AM MDT MON AUG 29 2016
.SYNOPSIS...An upper level low pressure system over the Four
Corners area will move slowly eastward today, as a ridge of high
pressure builds over the Great Basin. The ridge of high pressure
will remain over the region on Tuesday, before shifting east.
.SHORT TERM (THROUGH 06Z THURSDAY)...
Water vapor loop shows a closed low southeast of the Four Corners,
with ridging building in. MDCARS wind observations show a pair of
50-90kt southwesterly jets, one nosing into British Columbia, and
the second noising into northern California. GOES/HRRR/00Z KSLC
RAOB indicate the precipitable water value ranges from 0.20"-0.30"
northern mountains to 0.65"-0.85" southern valleys.
During the next several days convection will become more isolated,
diurnal in nature and tied to the higher terrain as anticyclonic
flow develops aloft. The pattern shift will support a warming and
drying trend across the region.
Moisture will begin increasing Wednesday on southerly flow ahead
of the trough easing into the West Coast. This will bring about an
increased threat of convection as well as cloudiness. Convection
should be high-based and pose a threat of strong dry microburst
.LONG TERM (AFTER 06Z THURSDAY)...
A fairly cold trough will approach the Pacific Coast late
Wednesday. While this system is largely oriented with the polar
jet, favorable jet dynamics from the southern jet with upper level
diffluence and modest lift should allow for convection overnight
Wednesday into Thursday morning. Additional convection will likely
develop Thursday afternoon, though this may be more correlated
with the higher terrain depending on the orientation of the jet.
As the upper level trough crosses the Pacific Northwest into the
northern Intermountain Region Thursday into Friday, sufficient lift
should continue, with at least a few thunderstorms along the higher
terrain and adjacent valleys.
Model to model and run to run consistency issues continue after
Friday. Continued to keep below climo pops in the forecast due to
the high level of uncertainty.
Southerly winds at the SLC terminal are expected to shift to the
northwest between 19-20Z.
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.
A warming and drying trend will prevail into mid week. Convection
will become more isolated, diurnal in nature, and tied to the
Southerly winds look to increase along the Nevada border region tomorrow
though critical fire weather conditions expected to be isolated,
limited by 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.
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 gradual cooling and moistening
trend and another round of lightning.
SHORT TERM/FIRE WEATHER...Rogowski
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