Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Salt Lake City Utah
318 PM MDT Monday Sep 1 2014
Synopsis...high pressure will build over the region for the first
part of the week...resulting in a warming trend. A Pacific storm
system will move a cold front into northern Utah on Thursday.
Discussion...the forecast area is dry and stable this afternoon
with clear skies. Northern Utah maxes still running up to 5f
below seasonal normals in the wake of the front that moved through...but
temperatures have warmed a bit compared to yesterday. Southern Utah maxes
continue to run near climatology.
High pressure will continue to build through Tuesday...resulting
in quick warming of temperatures to above seasonal normals with
skies remaining mostly clear. By Wednesday...the ridge is prognosticated
to shift east as a Pacific northwest storm system moves onshore.
The resultant southwest flow should bring a bit of middle and high
level moisture into the forecast area...resulting in a bit of
afternoon convection over the higher terrain.
The Pacific storm system is expected to split during the day
Wednesday...with the northern piece moving along the Canadian
border. The southern piece is expected to move as far south as
southern Idaho Thursday and Friday. The vast majority of the
moisture and instability is prognosticated to stay north of the forecast
area. However...it is expected to bring a decent cold front into
northern Utah...resulting in maxes on Thursday that are 5 to 10f
below values observed on Wednesday.
Weak ridging is expected to develop over the area on Friday in
between the exiting trough and another low off the California
coast. This low is depicted in being stronger in the GFS than the
latest European model (ecmwf). The GFS slowly brings this system onshore over the
weekend...while it remains offshore in the ec. For now...have kept
temperatures near climatology for the extended period while keeping just
a bit of convection in the forecast over the higher terrain.
Aviation...winds at the slc terminal should Switch Back to the
southeast between 02z and 04z. VFR conditions will prevail through
the taf period under mostly clear skies.
Fire weather...strengthening high pressure aloft to the south of
Utah will maintain a dry/stable westerly flow across the area into
late Tuesday. A new and fairly strong upper trough will reach the
Pacific northwest late Tuesday...then slowly weaken as it moves east
across the northern rockies Wednesday/Thursday. Increasing southwest
flow ahead of this feature over the Great Basin will create breezy
and rather dry conditions for the western and southern fire
districts beginning late Tuesday. The expected low relative humidity along with
sufficiently strong wind speeds would indicate hazardous fire weather
conditions for Wednesday...and likely into Thursday across
southern Utah. Fuel moistures at last check were still high enough
that critical fire weather conditions are not expected. The caveat
to this is with a couple of days of lowering relative humidity values and
increasing winds fuels could dry out fairly quickly by Wednesday.
Thursday may be the day to keep an eye on ahead of a cold front
sweeping south across the state late Wednesday/Thursday. The
southern half of Utah may have sufficient dry fuels by that
time...and may see pockets of red flag conditions develop across
south-central and southwest Utah.
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)