Area forecast discussion
National Weather Service Salt Lake City Utah
906 PM MDT sun may 19 2013
Synopsis...an upper trough will keep a cool moist and unstable
airmass over the region through Monday morning. High pressure
will briefly return on Tuesday then shift east Tuesday night. A
warm dry southwest flow will develop Wednesday.
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Discussion...a cold and unstable airmass across the forecast area
continues to allow for scattered showers and isolated
thunderstorms this evening. Small hail has accompanied the stronger
storms along with brief heavy rainfall. One last lobe rotating
westward across Wyoming is forecast to swing south through northern Utah
late tonight through Monday morning. This should enhance shower
activity once again...and with the cold airmass in place may once
again see convection develop over the gsl. Bumped probability of precipitation into the
likely category for overnight into Monday morning from roughly
Salt Lake County north and eastward.
Additionally...with the north to northeast gradient across
southern Utah localized downslope winds continue through the gaps of
Washington County as well as along the Highway 10 corridor in
Carbon/Emery counties. At this point do not anticipate needing a
Wind Advisory but will continue to monitor.
The upper trough which has lingered across the region all weekend
will finally pull east Monday afternoon...as a shortwave ridge
spreads over the Great Basin. This ridge will quickly slide east
Tuesday as a deep upper low develops over the Pacific
northwest...resulting in strengthening southerly flow along with a
considerable warming trend across the area during the midweek
period. The cold front associated with this low may spread into
northwest Utah at times from Wednesday through the end of the
week...although timing when this may happen is tough considering
the models are struggling a bit with respect to how this trough
evolves.
&&
Aviation...VFR conditions are expected at the slc terminal through
the taf period. Showers crossing the terminal should wane a bit
after 04z with ceilings rising above 7 kft...but are expected to pick up
again after 08z with ceilings once again falling below 7 kft. There is
a 20 percent chance of brief MVFR conditions and a 10 percent
chance of a thunderstorm during the 08-14z.
&&
Fire weather...a series of storm systems will keep a cool and wet
pattern in place through Monday. Downslope/canyon winds will gust
across prone areas across the state at times through Monday night as
reinforcing cooler air arrives. It could be dry and breezy enough to
present local critical fire weather conditions in Dixie on Monday.
The next system will bring another round of wetting rain (snow above
7.5kft) to northern and central Utah through this evening. The final
system will mainly affect eastern Utah Monday.
The pattern shifts as a ridge builds in Tuesday and Wednesday. A
warming and drying trend will take place with moisture recoveries at
night beginning to lag.
Southwest winds begin to develop Tuesday night as a large storm
system develops over the Pacific northwest. These winds increase and
become strong and gusty Wednesday through Saturday...except across
the northwest portion of the state where they will be gusty from the
northwest. At the same time...daytime humidity levels become very
dry...5-12% across most valleys...making for widespread critical
fire weather conditions with the only questionable parameter being
fuel status.
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Slc watches/warnings/advisories...
Utah...none.
Wyoming...none.
&&
$$
Seaman/rogowski
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