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Area forecast discussion 
National Weather Service Salt Lake City Utah
338 PM MDT Friday Aug 28 2015

Synopsis...high pressure will bring a warming and drying trend
through tomorrow. A weak frontal boundary will cross the area
Saturday night...followed by a generally dry southwesterly flow
for much of next week.

&&

Short term...scattered convection that has developed over western
Nevada is expected to gradually spread east over far western Utah
this evening...though coverage trends will be decreasing as this
convection translates into a more suppressed environment. Latest
hrrr indicates full suppression by 03/04z this evening which fits
the conceptual model as updrafts have formed due to differential
heating and diurnal circulations over the higher terrain. Loss of
this will preclude further development during the overnight hours.

The previously deep closed low off the norcal coast has become
more progressive as a deeper low over britcol continues its
southward translation down the coast. Said progressive short wave
will lift through the pacnw over the next 36 hours displacing the
ridge and associated axis east of the area tomorrow. This will
allow a deep southwesterly flow to ramp up across the eastern
Great Basin. Associated with this wave...700 mb forecasts continue to
note a weak baroclinic zone translating east through northern
Nevada tomorrow afternoon that will then spread into northern Utah
during the evening hours. Ahead of and associated with this area
of weak lift...middle level moisture convergence should be enough to
form isolated to widely scattered high based convection across the
north...and a tightening S-north mslp will aid breezy southwesterly
winds focused across the western valleys. 700 mb temperature trends will
continue to climb in this deeply mixed environment and expect the
warmest temperatures of the period to occur tomorrow...some 5-10 degrees
above climatology.

Said baroclinic zone will shift over central Utah tomorrow night
through Sunday further suppressing the high south and east of the
area. Will have to monitor potential of moisture convergence along
and southeast of this boundary for isolated to widely scattered
convection Sunday...but expect a temperature drop to or a few degrees
back below climatology will be more notable sensibly north and west of
the boundary.

Long term (after 12z monday)...the 700mb baroclinic zone in far
northern Utah weakens and a dry subsident southwesterly flow
reinstates itself statewide by Monday afternoon. Global models are
in comfortable agreement with this pattern persisting through the
extended forecast...showing a mean trough over the Pacific
northwest remaining centered well to the north of the County Warning Area. By
Tuesday winds ramp up and temperatures in the northern half of the
County Warning Area climb above normals...while the southern half remains a few
degrees below norms. A modicum of instability may promote
convection over the highest terrain on Tuesday afternoon. Midlevel
winds increase further and remain elevated through the week.

A weak 700 mb baroclinic zone brushes northwest Utah on Wednesday
followed by an even drier airmass...thus shutting off the moisture
tap statewide for the remainder of the work week. GFS insinuates a
series of additional weak baroclinic zones nudging into northern
Utah after midweek...have thus bumped temperatures down a degree or two
each day.

&&

Aviation...north to northwest winds will continue at the slc
terminal before shifting to the southeast between 02-04z.

&&

Fire weather...isolated high based thunderstorms remain possible
through this afternoon across far western portions of the
district and along the mountain spines of central and southern
Utah.

High pressure will shift east overnight through tomorrow allowing
a strengthening southwesterly flow aloft to spread across the
area. A weak frontal boundary approaching from the northwest
coupled with the up tick in winds aloft will create breezy
southerly surface winds across the western valleys tomorrow
afternoon...and coupled with drying low levels will combine to
produce locally critical fire weather conditions across portions
of fire weather zones 478..492 and 495. This said fuels as
reported remain non-critical in those areas. As the frontal
boundary crosses northern Utah tomorrow afternoon/evening isolated
to widely scattered high based thunderstorms are expected to form
and linger into the overnight hours.

Deep southwesterly flow will remain in place through much of next
week allowing further drying across the district...and periodically
breezy conditions during the middle to late week period.

&&

Slc watches/warnings/advisories...
Utah...none.
Wyoming...red flag warning for wyz 277 from 17z Saturday through
03z Sunday.

&&

$$

Merrill/verzella/Kruse



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