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Area forecast discussion
National Weather Service Salt Lake City Utah
250 am MDT Thursday Apr 17 2014
Synopsis...high pressure will spread across the region tonight
through tomorrow. The next weakening storm system will cross the
region late Friday through Saturday.
Short term (through 12z sunday)...
water vapor loop shows a ridge along the West Coast with the next
storm system approaching British Columbia. Amdar 400-250mb wind
observations reveal a 90-120kt anticyclonically curved jet from
British Columbia into the central rockies. GOES/GPS/rap/00z radiosonde observation
indicate the precipitable water value ranges between 0.12" and
Nice day on tap. Warm front lifts through the region from the
southwest this afternoon. Winds shift to the south and begin to
increase...allowing warmer temperatures considering 700mb
temperatures rise to about +4c.
Cold front slips into northwest Utah late tonight so introduced low
end probability of precipitation to the northwest corner of the state. Its noteworthy that
by 12z Friday...short range ensembles indicate 50 j/kg MUCAPE will
Best chance for showers Friday will be in the cool sector across
northern Utah...though enough moisture from an Arizona closed low
will allow convection in the central and southern mountains during
the afternoon. Copious clouds develop and thicken Friday and Friday
night. Lowered forecast high Friday due to clouds and likely passage
of cold front across the north. Increased winds ahead of the cold
front given strengthening pressure gradient and 30kt of southwest
flow at 700mb.
Frontal boundary settles into central Utah Friday night...with
further moisture advection occurring across southeast Utah. Bumped up
probability of precipitation ahead of slow-moving weakening Arizona low through Saturday
While the remnant of the Arizona low continues to weaken and lift
through southeast Utah Saturday afternoon...ridging begins to build
across western Utah. With thinning clouds and not a lot of
subsidence yet...believe fairly widespread convection will develop
especially south of Interstate 80 during the afternoon and evening
hours...given the ambient moisture in place.
Storm Prediction Center thunder guidance from short range ensembles indicate potential
both Friday and Saturday afternoons.
Long term (after 12z sunday)...
majority of the model guidance continues to indicate an active
long term forecast period. A quick moving wave will move across
the northern rockies Sunday into Monday. The associated cold front
is expected to move through the state Sunday. A few showers and
thunderstorms will be possible in the vicinity of this
front...mainly across the higher terrain.
A large Pacific system will approach the West Coast Monday. Deep
southwesterly flow will develop ahead of this system across the County Warning Area
Monday bringing a very warm day to much of the area. A few showers
or thunderstorms will again be possible across the higher terrain.
Model to model consistency begins to decrease as the Pacific system
begins to impact the western United States early next week. The 00z
GFS features a strengthening trough that swings through the Great
Basin Wednesday into Thursday while the ec is a weaker...more
progressive system. Continued the trend of increased probability of precipitation through
Wednesday and Thursday...though the GFS solution would warrant
higher probability of precipitation.
The biggest takeaways in the extended forecast are very warm
temperatures...exceeding normal temperatures for late April by 10
to 15 degrees Sunday through Tuesday. A dramatic cool down looks
to be increasing in confidence regardless of the model Wednesday
into Thursday...with temperatures falling to near to below normal
levels as an airmass reminiscent of early Spring moves into the
region. Confidence is still fairly low in the evolution and
resulting precipitation in association with the Pacific system at
Aviation...southerly winds will continue at the slc terminal
through the morning and into the early afternoon. A shift to
northwest winds is expected between 20-22z...though there is a 30
percent chance winds will remain southerly throughout the day.
For more information from National oceanic and atmospheric administration/S National Weather Service visit...
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)