Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Salt Lake City Utah
431 am MST Monday Nov 30 2015
Synopsis...the cold upper low along The Spine of The Rockies will
continue east into the Central Plains states later today. High
pressure will gradually build over the region middle week.
Short term (until 00z friday)...the upper low centered along The
Spine of The Rockies early this morning will shift east into the
Central Plains states later today. The first of two vorticity
lobes rotating south along the west side of the low will cross
northern Utah first this morning...with the second to follow this
afternoon through early this evening. High pressure aloft
strengthening along the West Coast late tonight/Tuesday will shift
east into the region middle week.
The first of the two vorticity lobes currently sits along the
Utah/Idaho border. A still quite cold and moist air mass ahead of
this feature is fueling areas of light snow mainly to the north
of kslc at time. This snow will expand south along the urban
corridor with the advancing vorticity lobe early this morning...
then gradually dissipate as the vorticity lobe moves off to the
east and warming/drying aloft takes hold this afternoon. The
second lobe to follow for late this afternoon/early evening
appears to be a bit stronger than the first...but with the air
mass becoming drier and more stable would expect precipitation to be
somewhat less and confined mainly to the far northern and
northeast zones through early this evening. Any lingering snow
should end across the forecast area around midnight.
Stable high pressure aloft will strengthen along the West Coast
late tonight/Tuesday...then shift east across the Great Basin middle
week. Clearing skies and a stable air mass support patchy valley
fog late tonight and again Tuesday night. Low clouds could work
into the forecast Wednesday night as the subsidence inversion
tightens across the northern/western valleys.
The next upper level trough will advance on the West Coast
Thursday. An increasingly warm southwest flow aloft will work into
western Utah Thursday afternoon. High temperatures for Thursday will be
tricky as the rather stable air mass in place across the lower
western/northern valleys will be resistant to mixing. Have
trended temperatures upward cross the western valleys...but confidence
remains on the low side as to which valleys will mix completely
during the afternoon. The eastern valleys will likely not mix with
temperatures changing little from Wednesday.
Long term (after 00z friday)...the ridge continues to shift east of
the area into Thursday night...with the Pacific trough approaching
from the west. Models have generally slowed this storm down a
bit...with Thursday night looking to remain warm in the pre-frontal
While some models differences still remain with this trough...in
general this still appears to be a splitting and relatively weak
storm. Have kept fairly low probability of precipitation in place for Friday and Friday
night...as models are still depicting a brief period of
precipitation as the modest cold front pushes through the area.
However...the structure of this storm and the quick manner in which
it passes through the area do not appear conducive to significant or
A ridge returns to the region for the weekend...with valley
inversions likely to re-build. However...this stagnant pattern does
not appear to last long...as storms continue to progressively pass
through the west. The next weak trough in the train is currently
forecast to pass through the County Warning Area Sunday night or Monday. Details on
this storm differ a fair amount run-to-run...but would generally
lean toward the 00z European model (ecmwf) solution...which sticks with persistence
and tries to dig the upper level energy south into Arizona for the
beginning of next work week.
Aviation...there is a 30 percent chance of snow showers at the
slc terminal between 11z and 15z today...which could bring periods
of MVFR or high-end IFR conditions. Otherwise...ceilings should
remain below 7000ft before the lower cloud deck becomes
scattered...most likely between 14z and 18z.
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http://weather.Gov/saltlakecity (all lower case)
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http://weather.Gov/saltlakecity/general/afd_faqs.Php (all lower case)