Area Forecast Discussion
Issued by NWS Salt Lake City, UT
FXUS65 KSLC 260850
Area Forecast Discussion
National Weather Service Salt Lake City UT
250 AM MDT THU MAY 26 2016
.SYNOPSIS...Several weak disturbances will provide unsettled
conditions into next week.
.SHORT TERM (THROUGH 12Z SATURDAY)...
Water Vapor loop shows a compact closed low over Northwest
Arizona with the next system sliding down the British Columbia
coast. AMDAR 400-200MB wind observations place a 90-110kt
Southwesterly jet over Arizona into the Four Corners.
GOES/HRRR/00Z KSLC RAOB indicate the precipitable water value
ranges from 0.20"-0.40" mountains to 0.40"- 0.60" most valleys.
Short Range Ensembles indicate plenty of instability today to
support isolated to scattered showers and thunderstorms. The
greatest coverage should be in the deformation zone north of the
aforementioned closed low and in the mountains. Storm motions are
light out of the N-NW...thus Wasatch Front westward will likely see
Less instability in place tomorrow especially across the West. Flow
is stronger from the NW thus kept all areas along and West of
Interstate 15 isolated coverage with better coverage further east.
Could see some higher W-NW gusts across the Eastern Valleys due to
pressure gradient along with outflows from convection over the
terrain due to the drier conditions further East.
Snow level should range between 9-10KFT.
.LONG TERM (After 12Z Saturday)...
The bulk of the upstream trough is expected to remain north of
the forecast area through the weekend, but a weaker southern
portion of this trough is forecast to split off and slide over
California and Great Basin through the day Saturday. Combined with
a slow influx of moisture, this will allow isolated to widely
scattered showers to form Saturday, with current indications that
most of this activity will be over the southern half of Utah.
Moisture eventually pushes northward Saturday night and Sunday, and
shower activity Sunday/Monday could be somewhat aided by synoptic
forcing, as the northern and southern branch troughs phase and push
across the Intermountain West through 00Z Tuesday.
Tuesday is currently the least confident day of the extended
forecast, as models differ on how they eject the northern trough out
of the region. The least progressive solutions, including the 00Z
GFS, actually push another associated cold front into northern Utah
on Tuesday. The most progressive solutions, including the 00Z ECMWF,
generally keep this cold air on the other side of the Continental
Divide. All of this said, the primary impacts of these discrepancies
would be differences in temperatures and wind, as both still dry out
the airmass a fair amount heading into Tuesday. For now, the
forecast is a bit of a compromise, but primarily leans toward the
warmer EC solution, as it appears more in line with previous runs.
Either way, models agree that a high amplitude ridge builds over the
region on Wednesday and Thursday, leading to considerably warmer,
drier, and more stable conditions. Thursday currently looks to be
the warmest day of the week, and has the potential to approach the
warmest day of the year so far, depending on the evolution of the
ridge and the next upstream trough.
.AVIATION...Light and variable winds at the SLC terminal this
morning are expected to increase from the northwest after 15Z,
likely exceeding 7 knots around 17Z-19Z. Isolated to widely
scattered showers will again form across Utah this afternoon; the
most likely impact at the SLC terminal is gusty erratic winds.
Periods of ceilings below 7000 feet are also possible.
.FIRE WEATHER...Isolated to scattered convection can be expected
today and tomorrow across the region. In addition to the threat of
lightning, convection across Eastern Utah is more likely to contain
dry microburst wind gusts due to the drier sub-cloud layer.
Another weak system will graze Southern Utah during the weekend
keeping similar conditions in place heading into next week.
SHORT TERM/FIRE WEATHER...Rogowski
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