Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Salt Lake City Utah
326 PM MDT Friday Mar 27 2015
Synopsis...high pressure overhead will move off to the east
Saturday ahead of a weak storm system. This system will send a
cold front into northern Utah Saturday afternoon and south through
the area Saturday night.
Discussion...strong middle level ridging centered across the Great
Basin this afternoon will shift east tonight...downstream from a
weak shortwave trough currently approaching the Pacific coast.
This wave will move onshore tonight before traversing the
northern rockies Saturday. The brunt of this wave will pass well
north of the forecast area...with the trailing surface front
forecast to cross northern Utah Saturday afternoon before stalling
across southern Utah Saturday night. Pre-frontal mixing should be
sufficient to once again push temperatures 15 or more degrees
above climatology Saturday...which would be encroaching on record
territory in a few locations (the record high for kslc Saturday is
77). With limited moisture and weak dynamic support only isolated
convection is expected as this feature crosses the north Saturday
afternoon through Saturday evening.
A portion of this wave is forecast to split as it moves ashore
tonight...then gradually cross the southern Great Basin during the
day Sunday. This feature will interact with the stalled surface
boundary across southern Utah Sunday afternoon into Sunday evening
bringing a somewhat better threat for convection...and have
raised probability of precipitation across the higher terrain accordingly. Meanwhile
somewhat cooler air behind this boundary will bring a modest
cooldown to most areas for the latter half of the weekend.
Middle level ridging is forecast to rebound across the region Monday
with perhaps a small threat for convection across the southern
mountains owing to lingering moisture.
Long term (after 00z tuesday)...ridging will be ongoing at the
start of the long term portion of the forecast as a Pacific trough
approaches the coast Monday evening. The 12z global models have
become fairly consistent with the evolution of this
system...bringing the associated cold front across the County Warning Area late
Tuesday through Wednesday morning. This is a bit slower than
previous runs...so warmed the temperatures for Tuesday for most
locations a bit.
A majority of the model guidance depicts this front as mainly
dry...but felt there was enough dynamics associated with this front
to at least increase the risk of precipitation across the higher
terrain into the slight category. Both the ec and the GFS depict
700mb temperatures falling to near -10 to -12c Post frontal
Yet another wave embedded in the northern jet will cross the state
Thursday. The models are considerably different during this time
period...so kept probability of precipitation near climatology for days 6 and 7. Confidence during
this portion of the forecast is fairly low.
Aviation...northwest winds will switch to the southwest at the
kslc terminal between 03z and 05z this evening.
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)