Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Salt Lake City Utah
435 am MDT Sat Mar 28 2015
Synopsis...high pressure overhead will move off to the east today
ahead of a weak storm system. This system will send a cold front
into northern Utah late this morning and south through the area
Short term (through 12z tuesday)...the ridge over the area is
starting to shift east ahead of a weak shortwave trough currently
over the Pacific northwest. Clear skies over the area this morning
will yield to scattered clouds as a cold front associated with the
trough enters northern Utah later this morning. This front is
expected to cross slc around midday and settle across central Utah
by late this afternoon. Despite the cold front...maximum temperatures
today will remain well above normal. This is due to decent mixing
ahead of and with the front and 700 mb temperature will remain
warm...for example near 4c at slc...at the time the cold front
The bulk of the upper support with the trough will remain north of
the forecast area...and not much moisture is expected to accompany
the front...with just a narrow band of clouds seen near the boundary
currently. As a result...this is not going to be a significant
storm. However...models do suggest some instability which could kick
off a few showers/thunderstorms over the northern mountains this
afternoon and central and southern mountains this evening...with any
precipitation that develops remaining very light.
The boundary will continue to gradually inch southward overnight
before stalling over southern Utah. Temperatures north of the front
will only see a modest cooldown for tomorrow. However...another weak
disturbance will approach the area tomorrow...offering enough
support to generate some showers/thunderstorms over the
southern/central mountains near the stalled boundary.
The progressive pattern will continue on Monday with yet another
weak disturbance crossing the area. Expecting mainly terrain-based
convection with this system as well...given the continued lack of
moisture and forcing to do anything more than that.
Long term (after 12z tuesday)...challenging to add much detail to
the previous long term forecast as run to run inconsistencies in
global guidance remain prevalent through the period. Global models
continue to portray two short wave troughs translating through the
eastern Great Basin/northern rockies states in the middle/late week
period...with the first Tuesday evening into the overnight hours and
the latter Thursday into Friday.
Have maintained warm temperatures Tuesday in a well mixed pre-frontal
environment and slight chance mountain probability of precipitation over the north coincident
with a cold frontal passage Tuesday evening into the overnight hours.
Models in fair bit better agreement west/this feature vs. The trailing
wave for late week but continue to waffle regarding breadth of cold air advection
Post frontal passage...700 mb temperatures at kslc now 2 to 4 degrees c warmer
in 00z ec vs. Previous runs and that current in the GFS. Holding pattern
west/a noted cool down focused across the northern half of the area in
wake of a mostly dry frontal passage...though model spread
diminishes confidence regarding extent. A significantly dry boundary
layer should limit/prohibit much in the way of any valley precipitation.
00z GFS trending more progressive west/the late week short wave vs.
Previous runs and the most recent European model (ecmwf). Standing pattern that said wave
will be a bit more amplified as upstream ridging ahead of a more
dominant eastern Pacific trough should allow for more amplified
curvature...and have retained near or slightly above climatology probability of precipitation
across the area...with temperatures running near or slightly below normal.
Confidence remains quite low however due to aforementioned run to
run and model to model inconsistencies.
Aviation...operational weather concerns will remain minimal at the
kslc terminal through the valid taf period. Southeasterly surface
winds are expected to become a prevailing northwest between 18-20z
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