Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Salt Lake City Utah
734 PM MDT Thursday Aug 28 2014
Synopsis...high pressure will persist over the region tonight then
shift east late Friday. A cold front will cross northern Utah
Saturday...stalling across central Utah on Sunday.
Discussion...water vapor loop shows rising heights overhead as
the trough continues to drift east into the plains. A disturbance
is moving over northern California within the flattening flow.
Amdar 400-250mb wind observations reveal a 50-70kt westerly jet
from northern California into the central rockies. A stronger
50-90kt westerly jet was located along the Canadian border.
GOES/GPS/rap/00z radiosonde observation indicate the precipitable water value ranges
between 0.4" west central Utah to around 0.8" across the eastern
With mixing today...24hr dewpoint change is -5f to -10f where
pockets of fog developed this morning. Whats more telling is the
24hr dewpoint depression change is +20f to +30f. Its dried out
enough to be confident of good visibilities across southwest Wyoming
tonight. The Wasatch back should also behave though current
dewpoints are closer to forecast lows. Will keep mention out of the
A nice quiet evening for a change. Did lower cloud cover south of I-
80 as much of the activity looks diurnal per visibile satellte. A
little more in the way of cloud cover will reside closer to the
Idaho border ahead of the aforementioned disturbance. Minimal
changes to the rest of the grids overnight.
Previous short term discussion (thru 00z mon)...a drier and more
stable airmass has invaded the state in the wake of an exiting
trough...resulting in ubiquitous cumulus clouds over the higher
terrain across the region today. An upper level ridge centered off
the coast of Southern California will continue to advect warm air
into the region through tomorrow night. A trough blazing in from
the Pacific northwest will gradually flatten this ridge and shift
midlevel winds by Friday morning to west and then southwest as the
day progresses. A weak shortwave clipping northern Utah tomorrow
will encourage some convective activity along the Utah Idaho
border and the uintas...with little resulting precipitation.
Timing is still on track to usher a cold front into Utah beginning
Saturday as the initial 700mb baroclinic zone barrels into the
northwestern corner of the state early Saturday afternoon. Models
are suggesting the afternoon onset of precipitation with this first
push...but offer higher confidence of probability of precipitation coincident with a
secondary short wave entering Utah Saturday evening. This wave
nudges the colder air southward through the state...waning before
dousing southern Utah temperatures. Expecting northern and central Utah
temperatures to plummet 6 to 8 degrees from Saturday highs...with just a 2
to 3 degree drop in southern Utah.
Long term (after 00z monday)...the storm system exits the area
Sunday night/Monday morning...allowing a drier and more stable
airmass to move back in for the upcoming week. One last grazing
trough may initially limit warming on Monday...but maxes are
expected to approach seasonal norms by the middle to latter part of
the upcoming week.
Aviation...the slc terminal will see VFR conditions with mostly
clear skies through the taf sequence. Northwest winds are expected
to shift to the southeast between 03z and 04z.
Fire weather...high pressure is building over the area this
afternoon...resulting mostly clear skies and warming temperatures.
The ridge will remain in place through tomorrow before a storm
system brings a cold front through northern and central Utah on
Saturday. Moisture will be limited with this system...but a few
showers are possible...particularly over the higher terrain.
Southern Utah will continue to be dry with temperatures near
seasonal norms. Behind the trough a more stable airmass will build
over the district Sunday through the middle of the upcoming
week...resulting in generally dry conditions with warming
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http://weather.Gov/saltlakecity (all lower case)
For frequently asked questions about the area forecast discussion
http://weather.Gov/saltlakecity/general/afd_faqs.Php (all lower case)