Area Forecast Discussion
Issued by NWS Salt Lake City, UT
FXUS65 KSLC 191647
Area Forecast Discussion
National Weather Service Salt Lake City UT
1047 AM MDT TUE JUL 19 2016
.SYNOPSIS...An upper level trough along the Pacific Northwest
coast will leave the Great Basin under a southwest flow through
much of the week, with moisture remaining over southern and
.DISCUSSION...Water vapor satellite imagery this morning shows a
broad trough over the Pacific NW while anticyclonic flow lies over
the southwestern US, advecting deeper moisture into AZ. Between
the two lies a much drier southwest flow over much of the Great
Basin. Our forecast area lies on the transition of the two latter
features. WV imagery also hints at a very weak impulse sliding
north across AZ. Satellite precipitable water products show 1-1.5"
PWAT (around 125% of normal) over the eastern half of Utah,
dropping off to < 0.5" over northwest Utah. Area radars show a few
light returns over the higher elevations of southern UT, but no
lightning activity has been detected thus far. At the surface,
a modest pressure gradient over the northern 2/3rds of UT and
southwest WY along with a weak 700mb jet brought breezy winds
overnight and this morning, which kept temperatures quite warm
overnight (e.g. a toasty low of 77 at SLC).
Models depict a similar situation this afternoon to yesterday,
with plenty of moisture available from around the central spine
mountains of UT eastward but relatively limited instability.
Cannot rule out a few stray buildups farther west, but nothing of
significance is expected given the dry airstream. Meanwhile, a hot
day is in store for the Wasatch Front, with deep mixing given the
stronger winds this morning. Currently, SLC is running 4 degrees
warmer than this time yesterday, where we topped out at 98. Thus,
current thinking is the mercury will eclipse 100 for SLC and other
Wasatch Front locations. The central and eastern parts of UT
should be cooler today with mostly cloudy skies this afternoon.
Have tweaked PoPs/QPF/Sky slightly to bring in line with latest
models, but only minimal changes. The majority of the previous
forecast is on track.
.Previous Discussion...issued 446 AM MDT...Not much change in the
overall pattern is expected throughout the short term period, with
moisture perhaps increasing just a bit and expanding a bit north
and westward, but convection remaining largely limited by meager
instability. Have maintained the highest POPs east of I-15 while
the west largely remains dry through the forecast period.
Temperatures will fluctuate little from day to day with KSLC
flirting with the 100 degree mark each afternoon through Thursday.
The mean ridge dominating the southwestern CONUS will continue to
build west into Friday as the previously persistent upstream
trough over the PacNW continues to split with remnant energy
retrograding west towards 140W. Resultant flow aloft locally will
trend more west-northwest aloft allowing a drier airmass to spread
across the eastern Great Basin beginning late week as a result.
Have maintained isolated coverage of convection over the central
mtn spines over central/eastern Utah due to evacuation of holdover
low level moisture from previous days, though as a whole the area
will transition into a drying trend into and through the weekend.
Bottom line outside of this isolated convection potential on
Friday, the area will trend drier and remain above seasonal
regarding temps as the influence of the high will promote modest
subsidence driving surface temps some 5+ degrees above climo into
early next week.
.AVIATION...southerly winds will prevail at the SLC terminal
through the TAF period. Winds will be the strongest through about
21Z with gusts over 25 kts, after which a gradual relaxation is
expected. There is a less than 10% chance of any outflow
impacting the terminal from a rogue thunderstorm developing over
the nearby higher terrain between 22Z and 02Z.
.FIRE WEATHER...Moisture which has worked its way northward
across southern and eastern Utah will remain in place today
allowing for elevated humidity values. despite this moisture the
airmass will remain quite stable with only isolated to widely
scattered thunderstorm coverage this afternoon and evening.
Meanwhile drier air will reside across western Utah. Little
change is expected through Wednesday before the airmass dries out
late in the week through the upcoming weekend.
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