Scientific Forecaster Discussion
fxus65 kslc 230910
Area forecast discussion
National Weather Service Salt Lake City Utah
310 am MDT Tue may 23 2017
Synopsis...high pressure will shift gradually eastward across
the Great Basin Tuesday into Wednesday then move off to the east.
A series of weather disturbances will impact Utah late Wednesday,
through the first half of the upcoming weekend.
Short term (through 12z thursday)...
water vapor loop shows a ridge along the West Coast. Amdar 400mb-
200mb wind observations reveal a 110kt-150kt anticyclonic jet
extends from western Canada and The Rockies. GOES/hrrr/00z kslc
radiosonde observation indicate precipitable water values range from 0.15"-0.30"
mountains to 0.40"-0.65" most valleys.
The warming and drying trend will accelerate today and peak
tomorrow as a ridge builds into the region.
The ridge breaks down tomorrow afternoon, allowing stronger
westerlies to build in. Gusty westerly flow will mix down to the
surface, though values look sub-advisory.
The other threat tomorrow afternoon are strong/erratic winds
associated with dry microbursts. Instability builds tomorrow
ahead of the next frontal zone. Most models, including high
resolution produce little in the way of precipitation tomorrow.
However, simulated reflectivity from convective allowing models
does show decent coverage of showers and thunderstorms across the
northern and portions of central Utah. They also indicate strong
gusts coincident with convection, due to the high-based nature of
BUFKIT forecast soundings.
Coverage of rainfall looks to increase tomorrow evening as the
cold front sweeps across northern Utah. Convection is expected to
last well into the night given dynamics and instability in place,
though will be on the decline late Wednesday night as the
boundary becomes more diffuse and stalls across central Utah.
Long term (after 12z thursday)...
NAM/GFS/Canadian all indicate decreasing coverage of precip
during the day Thursday as the front stalls and weakens over
central Utah. However, it should be noted that latest European model (ecmwf) is
noticeably slower with the boundary and keeps a fair amount of
convection going over northern Utah through Thursday afternoon.
Thus have kept in a large swath of isolated pops in the valley and
scattered pops in the mountains.
The initial wave associated with the cold front grazes northern Utah
during the day Thursday and is quickly followed by a slightly
stronger wave following a similar track for Thursday night into
early Saturday. There are some noticeable differences in the
guidance for Thursday night. 00z GFS lights up precip along the
boundary over central/southern Utah during this time while the ec
shows a much weaker boundary and thus little in the way of
Ec/GFS are in better agreement with the track of the main wave over
northern Utah Friday afternoon and evening. Think this period will
be a time of better coverage of convection with the best instability
from the wave and have raised pops a fair amount here. The wave
continues to hang around through Saturday morning before weakening
and exiting the area Saturday afternoon, so some precip should
linger. High pressure is expected to move in behind the wave for
Sunday, resulting in a warming and drying trend for the latter half
of the Memorial Day weekend. Ec keeps strong high pressure in place
through the end of the forecast period, while the GFS shows a slight
increase in instability for day seven.
the slc terminal will see VFR conditions through the morning with
some scattered high clouds. Southeast winds are expected to shift
to the northwest between 16z and 18z.
weak transport winds will limit clearing to the fair to good
categories across many valleys today. An increase in transport
winds will lead to excellent clearing Wednesday and Thursday
across the region.
Benign weather is expected through mid week as a ridge gradually
builds into the region. The warming and drying trend will
accelerate today, peaking tomorrow. A cooler and more moist
trough may impact the area during the second half of the work
week. A cold front will cross into northern Utah Wednesday night,
stalling across the central part of the state Thursday, before
finally passing into Arizona late Friday. This will spark isolated
to scattered showers and thunderstorms each day. Showers and
storms late tomorrow afternoon and evening will likely contain
Short term/fire weather...rogowski
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