Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Salt Lake City Utah
443 am MST Tuesday Dec 10 2013
Synopsis...high pressure aloft off the West Coast will produce a
stable and mostly dry northwest flow across the Great Basin
through midweek. The high pressure aloft will shift east over
Utah during the latter half of the week.
Short term (through 00z friday)...strong high pressure aloft
currently over the eastern Pacific will maintain a stable and
mostly dry northwest flow across the Great Basin through midweek.
The high will slowly shift east throughout the week...ending with
a low-amplitude over the interior west by the end of the week.
Shortwave energy embedded within the northwest flow will track
southeast along the Continental Divide...grazing the far northern
and eastern portions of the state the next couple of days. Low-
level warm advection with adequate moisture running over the top
of the entrenched cold air over the north could squeeze out
flurries or light accumulating snows across the far north through
late tonight or early Wednesday.
The steady warming aloft Wednesday and beyond Wills serve to
create rather strong valley inversions..especially throughout
central and northern Utah. Steadily building urban haze a given
this week. Fog may be a bit slower to develop with the very Cold
Valley air in place and no appreciable snow melt during the days.
Suspect that fog will begin to show up near open waters the next
couple of days...with a somewhat better threat for fog under the
tightening inversions late in the week.
Long term (after 00z friday)...by Friday morning...the ridge axis
retreats west enough to allow a weak storm system to move across the
state on the front side of the high. Moisture is somewhat limited
with this system...but have still kept in slight chance/chance probability of precipitation
over northern Utah as the system passes. 700 mb temperatures look to drop
from around -1c to so to -6 to -8c with the trough...which will
weaken valley inversions but may not be enough to completely mix
Relatively dry northwest flow is expected to persist behind the
trough through the weekend and into early next week. Models still
indicate a very weak system grazing northern Utah Saturday
night/Sunday morning which will increase clouds and likely do little
else. Models are noticeably weaker with the system than they were in
runs yesterday...and it was not all that impressive in those
previous runs. Have still kept some slight chance probability of precipitation in the
northern Utah mountains with the system. Otherwise...ridge
conditions are expected to build for early next week.
Aviation...the slc terminal will see VFR conditions through the
morning with some scattered clouds. Southeast winds are expected to
shift to the northwest between 18z and 20z.
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)